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Registered:
June 2003
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7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 02:40
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Which diff ratio's do you guys think would be best suited to me, if I want to hit around 90-100km/hr in second gear?
At the moment with the stock diff, I'm only making it to about 70 in second before I run out of huff, and the constant gearchanging at low speeds is pretty annoying. Lousy non-reving 7M!
Any particular makes/models of diffs you'd recommend, and rough prices for new/second hand items? And what ratio should I be targetting (more to the point, what's the ratio on my current diff?)
-J-
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Location:
c'town, NSW
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 02:45
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what ratio is in it now?
possible solution is 3.75 ratio in RA65 u can use.
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Location:
Brisbane
Registered:
November 2002
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 03:50
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i reckon a 3.9 would get you aout of trouble.
with a w58 in 2nd gear, the 3.9:1 diff and 7000rpm will get you 102kmh with stock wheels on the supra.
imho, the 7mgte is a beutiful, torquey motor, and youd be silly to over-stretch the ratios with a 3.5:1 and lose the 'grunt'. sure you wont go 'as fast' per rpm, but regular driving is much more fun. esp if you like corners 
fwiw, with the na 2j ill be dropping my ratio down to 4.5:1
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Location:
Sydney
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 03:55
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I recon a 3.583 which you guys are talkng about would be great for a 7m. I'm currently running that in my corona with a 1g and it's funny.. if you want to spice it up when driving you just find yourself down a gear. i can often find myself cruising at 70 in 2nd.
topspeed should be about 300
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 03:59
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i 'spose it depends what kind of driving characteristics you want to achieve...
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I supported Toymods
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Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:01
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| ed_ma61 wrote on Fri, 10 September 2004 13:50 |
fwiw, with the na 2j ill be dropping my ratio down to 4.5:1
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You better get a close ratio box and an 8000 rpm redline.
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:02
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I reckon a 3.73 diff would be a good compromise. The parts car we had had nice long legs with the 3.73, yet didn't seem to hamper the not-so-healthy 5MGE too much 
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:04
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| ed_ma61 wrote on Fri, 10 September 2004 11:50 |
fwiw, with the na 2j ill be dropping my ratio down to 4.5:1
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BTW, where are you getting that high a ratio in F-series from? Is it from the MA63 parts car you had?
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Location:
Brisbane
Registered:
November 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:07
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Having spent bulk time in a 2JZGTE MA61 originally fitted with 4.1:1 gears and later with 3.5:1 gears, I can say absolutely that the 3.5:1 gears are the way to go. Though the 2JZGTE is more powerful, it still gets wheelspin en masse with the 3.5:1 set so I can't imagine that the torquey 7M, despite the power difference, would suffer in any way.
Ed: 4.5's? You're a sick, sick man... it'll be horrible! 
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Location:
Burlington, On. Canada
Registered:
January 2004
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:08
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3.73 is the choice most US guys are using with a 7M-GTE. I think it was only available in the '82 model.
Joseph from Buffalo New York with his 7M-GTE engined '82 MA67 (North American MA61) ran two consecutive 12.9s quater miles at 109 mph. Video link below. Right mouse click and "save as..".
http://www.masupras.com/video/JosephSept3.AVI
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:12
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| gianttomato wrote on Fri, 10 September 2004 14:01 |
You better get a close ratio box and an 8000 rpm redline.
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thank you captain obvious
i have a sneaking suspicion the 4.5 will suit the square bore/stroke rpm character suprisingly well... (that and the 8000rpm redline). quick maths says 8000rpm in 4th should see 205kmh in the supra.
a close ratio box is debatable though - it depends what the power band of engine ends up being like. of course its an easy option if the power band ends up being only <--this big-->
also, with the shorter diff ratio, for a given increase in road speed the engine will move through its rpm 15% more quickly. which means: whilst the stock box still maintains a drop of say 1500rpm between gears, the time spent moving through that 1500rpm band is less (as a function of road speed).
surely i can make an engine that performs well from 6500-8000 
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Location:
Lost in the K hole
Registered:
May 2002
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:20
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| justcallmefrank wrote on Fri, 10 September 2004 14:04 |
BTW, where are you getting that high a ratio in F-series from? Is it from the MA63 parts car you had?
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hole in one
came behind the MTE 2.0L 75x75mm b/s
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Registered:
June 2003
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Location:
Brisbane
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:38
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Speaking as an owner of an MA61 with a turbo 3 litre six, I can tell you the 3.5:1 gears are an excellent match for an engine like that. 3.7:1 would be OK as well; either one will be a huge improvement over 4.1:1, which is far too low for your torque-monster. Do it, you won't regret it!
Relaxed highway cruising is another bonus; at highway speeds the engine revs dropped from 3000 to 2500rpm when I swapped to the taller ratio. It makes a huge difference - less noise, less vibration, less fuel consumption. All good!
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Location:
Brisbane
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:39
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| joorsh wrote on Fri, 10 September 2004 14:37 |
So what ratio is my current diff? I guess that's a good place to start before I go looking at what to replace it with.
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If it's an AU-spec MA61, the diff will have a 3.9:1 ratio.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:40
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| Norbie wrote on Fri, 10 September 2004 14:38 |
less noise, less vibration, less fuel consumption. All good!
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??? buy an echo already 
***boring***
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:41
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why on earth are you hitting rev limit @ 70kmh with a w58 and a 3.9:1 diff ???
thats WRONG. even if you shift at 6000rpm you should still be hitting the 90's
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Registered:
June 2003
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:42
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I like your style there norbs. As it stands right now I'm up around 3 grand on the freeway, which is like half my peak rpm... so it's a little uncomfortable. I'd much rather have it down around 2500.
How does 3.5:1 ratio go in 1st and 2nd gear? Doesn't struggle? What sort of speed could I expect from second gear at around 6,000 rpm?
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Registered:
June 2003
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:45
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| Quote: |
why on earth are you hitting rev limit @ 70kmh with a w58 and a 3.9:1 diff ???
thats WRONG. even if you shift at 6000rpm you should still be hitting the 90's
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I didn't say hitting the rev limit - I said running out of huff
It still has more revs, but it's well past it's peak power according to the dyno run I did. Then again, I'm not too sure of the accuracy of my digi taco, and the dyno rev readings are based on that.
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Location:
Lost in the K hole
Registered:
May 2002
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Location:
Brisbane
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:49
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| joorsh wrote on Fri, 10 September 2004 14:42 |
How does 3.5:1 ratio go in 1st and 2nd gear? Doesn't struggle? What sort of speed could I expect from second gear at around 6,000 rpm?
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As 7M-Brisbane mentioned, this car has no problems breaking into insane wheelspin in first and second... not what I'd call "struggling". I also managed a 2.1 second 60ft on cheapo street tyres.
Ed: This is my daily driver, not a weekend racer. If you can have the best of both worlds (12.49 1/4 mile performance AND relaxed highway cruising), why the hell wouldn't you? Oh yeah and 
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Registered:
June 2003
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 04:58
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That's an old dyno run there. I've done a few mods since then, but nothing that should drastically effect the rpm.
Now when I saw that, the very first thing I thought was "hrmmm, that's pretty low rpm".
I queried Mark on it (the guy doing the dyno test), and he said it could be due to inacuracies in my taco. Now I'm not that up on dyno stuff, but from what I gather they have to calibrate the dyno to your car. I believe they do this by holding it at 2,000 rpm, and then going over to the dyno and effectively telling the dyno "this is 2,000 rpm". Then when you rev it out, the dyno knows what rpm you are doing. The only flaw with this is that if your taco is wrong when they calibrate it to your alleged "2000 rpm" (which I suspect mine is), it gives a bung reading for your rpm on the dyno chart.
The other alternative is that my car is just an anaerobic torque-monster. I believe the head has been off my car, but I have nfi what has been done to it. I know the 7M's are toquey beasts - but 600nm??? Do all 7M's put out this much at 9psi?
-J-
{EDIT} Does anyone else out there have a 7MGTE running through a W58 and a 3.9:1 diff... with dyno charts? Where was your peak power?
[Updated on: Fri, 10 September 2004 05:04]
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:03
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| Norbie wrote on Fri, 10 September 2004 14:49 |
Ed...Oh yeah and
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i wonder if this has a 3.5:1 diff for luxurious quiet driving and good economy?
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I supported Toymods
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Registered:
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:04
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Remember that is the torque as measured at the roller. It has been multipled by whatever gear that pull was done in, your diff and your tyre diameter. A better term might be "tractive effort".
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:05
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J,
forget about the dyno and whether the tach figure is wrong... if you say its actually run out of puff by 70kmh, and you can actually feel it has - thats as much evidence as you need.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:09
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probably also runs a 3.5:1 diff...
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:10
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yes, im bored
i should be studying vaginas
sorry J ...
/end hijack
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Location:
c'town, NSW
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:10
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my bad with the RA65 call, looks like its 3.5 soz
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Location:
Brisbane
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:20
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Ed did I mention my car is considerably faster with the 3.5:1 gears? Oh and did I also mention my car runs a 12.49 @ 117mph... and what does your car run again? Oh that's right you were too scared to take your girly NA car to the track and put your money where your mouth is. I nearly forgot about that. 
Run along now.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:24
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| Norbie wrote on Fri, 10 September 2004 15:20 |
Ed did I mention my car is considerably faster with the 3.5:1 gears?
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because we all value the opportunity to drive at 300kmh
as for the drags? meh, no skin off my nose
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Location:
Brisbane
Registered:
June 2003
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:27
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yeah as per diff ratios i was going to go and buy a new gearset for the ma70 diff going into ma61..then i bought myself some 18's the other day, and thought i might need to think twice and do some calculations first
just like the 235/65/14 in an ma61 manual was 3.9...
In ma70 with the 235/45 or 50?/16 the gearing was 4.3... to get the same RPM achievemnt!
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Location:
Adelaide, SA
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:32
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Ed,
FWIW I had a 4.3:1 diff (G285) behind a 1jz-gte/r154 combo and it was very good for driving in the hills - hold 3rd from 45 km/h to 150km/h no worries. It kinda sucked on the highway with fuel consumption, but had damn good acceleration when it counted. I loved the diff ratio for real driving. My 1jz was dead stock and had about 152 rwkw - probably similar to what you're aiming for with a worked N/A 2jz (OK, maybe lower than a "GT" style 2jz )
Plus you could drop in the clutch in 2nd from a standing start and light the tyres for 100m up the road (not that I ever did that often).
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Registered:
June 2003
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 05:33
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| Quote: |
Remember that is the torque as measured at the roller. It has been multipled by whatever gear that pull was done in, your diff and your tyre diameter. A better term might be "tractive effort".
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That's actually re-calculated torque at the engine (only an approximate - note "S_Nm"). The tractive effort for my car was about 7100 newtons.
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Location:
Lost in the K hole
Registered:
May 2002
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I supported Toymods
Location:
I renounced punctuation
Registered:
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Location:
Brisbane
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 06:00
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| ed_ma61 wrote on Fri, 10 September 2004 15:24 |
| Norbie wrote on Fri, 10 September 2004 15:20 |
Ed did I mention my car is considerably faster with the 3.5:1 gears?
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because we all value the opportunity to drive at 300kmh
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I wasn't going to insult you by explaining myself, but since you insist. I was talking about making full use of the engine's power band, I said nothing about top speed (which I don't care about; 200km/h is more than enough for me). With the 4.1:1 gears I was unable to develop full boost in 1st gear, at all, ever - it would be time to change into second before the turbos got a chance to spool up! The 3.5:1 gears load up the engine much better though, which means the car is considerably faster in real world conditions. The lower highway rpm was a bonus but it was not the reason I did the swap.
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as for the drags? meh, no skin off my nose
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I don't care much for the drags either, but if you can come up with a better way to measure straight-line performance objectively and consistently, I'd like to hear about it.
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Registered:
June 2003
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 06:12
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Well, after this gargantuan rambling diatribe, I think I'm going to look into a 3.5:1 diff. Is there a car out there I can pinch these ratio's from, or do you think I'm better off going for a new set? And what am I looking at price wise?
And Norbie - where did you pinch your diff from and how much did it cost you (If you don't mind me asking)? I presume it's LSD?
-J-
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Location:
Brisbane
Registered:
November 2002
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Registered:
June 2003
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 06:34
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Thanks 7M-Brisbane!
Can the RA65 gears handle punishment? Read: buttloads of torque.
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Location:
Brisbane
Registered:
June 2003
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Location:
Brisbane
Registered:
November 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 06:47
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They are exactly the same diameter, so they will be basically the same strength (of course allowing for the fact that due to different gearing the teeth differ slightly in number and thickness).
But yes, no different to the ones you currently have.
Norbie has ~300rwhp through his with no problems...
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 06:50
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| 7M-Brisbane wrote on Fri, 10 September 2004 16:22 |
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if you can come up with a better way to measure straight-line performance objectively and consistently, I'd like to hear about it.
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It's called "Roshamboe"
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oh dear, more picures...
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 06:58
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| Norbie wrote on Fri, 10 September 2004 16:00 |
With the 4.1:1 gears I was unable to develop full boost in 1st gear, at all, ever - it would be time to change into second before the turbos got a chance to spool up! The 3.5:1 gears load up the engine much better though, which means the car is considerably faster
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i hadnt considered that. im not used to taking turbo spool into consideration. my bad.
you cannot disagree though : different ratios are suited for different driving styles/purposes and expected engine performance characteristics (given the desired driving style). there is no 'ultimate' setup that is a cure all.
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I supported Toymods
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Perth
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 06:59
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Ed, go study vaginas already
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 07:02
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im trying...
ive just done 2hrs of reading on '7 different types of bleeding'
YAY!!
not
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 07:14
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Actually, dude, thats just not cool, take ALL the time you want talking about diffs and stuff that is only vaguely related to diffs.
On that topic, what centre are you planning to use with the 4.5 ring gear?
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Location:
Brisbane
Registered:
November 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 07:28
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Now now frank, don't teach Ed to be a vagina decliner
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I supported Toymods
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Perth
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 07:29
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I'm not, but all this nasty shit hes reading about them is bound to put him off them! Just doing it for his own sake
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Location:
Lost in the K hole
Registered:
May 2002
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I supported Toymods
Location:
Perth
Registered:
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 08:03
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Not cool dude! Will be interesting to see what you choose, and pit the Torsen cars versus the clutch-LSD's...now, to get my damn car back and have it driving at all
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Registered:
June 2003
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 08:24
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Bad Ed, BAD!
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Location:
Brisbane
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 10:02
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| ed_ma61 wrote on Fri, 10 September 2004 16:58 |
you cannot disagree though : different ratios are suited for different driving styles/purposes and expected engine performance characteristics (given the desired driving style). there is no 'ultimate' setup that is a cure all.
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I couldn't agree more, but since his setup is very similar to mine I figured what works for me will likely work for him also.
As for the Torsen issue, admittedly I haven't taken mine to the track but it rules in the tight'n'twisties. And exactly how do you plan to lift a wheel in a fat-ass Supra with IRS? Have you ever done this?? I know I haven't, but if I did I'd promptly fix my suspension to make sure it didn't happen any more! This sort of behaviour is acceptable on small FWD's, but not a Supra.
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Location:
Lost in the K hole
Registered:
May 2002
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Location:
Brisbane
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 11:16
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When you said "track work" I envisioned circuit, not hillclimb. No I've never done a hillclimb (I'm itching to give it a try though) so I can't comment on the best setup for that. If you decide to stick with a clutch LSD, you should consider getting a beefier aftermarket jobbie... I suspect the stocker will only cop so much abuse before it turns itself into diff soup.
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Location:
Brisbane
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 11:18
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| ed_ma61 wrote on Fri, 10 September 2004 21:13 |
yes, it may be setup like yours, but where is the indication that he wishes to drive it like yours?
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What do you mean by that? How do you even know how I drive mine? You've only been in it once and that was a sedate trip to the shops! (Which apparently was "unimpressive") 
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Location:
Brisbane
Registered:
June 2003
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 11:21
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no no no ...dont get me wrong norbs, not implying anything...
im just saying, theres 2 factors to tak into consideration. one is what the engine/driveline set up is, the other is intended use.
weve established that ok, the set up between yours and his is similar, but we're missing pt2 of the equation.
what kind of driving does he value? fuel economy, rpm, 1/4mile trap speed, etc etc
thats all i meant
btw: unimpressive by my own value system, not generally
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Location:
Brisbane
Registered:
May 2002
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Re: 7M-GTE MA61 rear Diff choice?
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Fri, 10 September 2004 11:24
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Bah! I should have cracked the throttle open at 4k rpm, I'd like to know how your value system would have responded to that!
It would almost be worth the loss of license and massive fine...
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