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4.27 Gears For Auto Supra...

2047 Views 5 Replies 3 Participants Last post by  BLK-SP64
Although I started this thread already, I want to get some feedback on the Powerhouse Racing 4.27:1 Gears vs. the stock 3.72:1 gears for the Automatic Supra. I happen to be using the HKS T04R Kit without a stall so this would definitely help my getting out of the hole and even more so when I get the 4K stall. In my past experiences, the vehicle with the lower gear ratio dominates when it comes to acceleration whether it be getting good 60' times or roll ons from 60 mph. Granted, wheelspin will be a factor with the 4.27 gears, I know this thing will pull a ton harder. In my world, there's no need for 180 mph gearing. All I want is quarter mile times. Why aren't guys using this setup? This is probably one of the best bangs for the buck in the Supra Performance Arena. Why aren't guys speaking of this mod?
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There are TOO many 9-second auto Supras running stock gears. I will not change mine. Most of the fast Supras are almost shifting in to OD crossing the finish line. 4.27 gears would only be worse. I actually would like lower numerical gearing in my diff. I think 4.27 gears would help out of the hole, but not help pull on the big end. Shorter gears are best left for cars with 28" or taller rear racing slicks.

FWIW, turbo cars run harder with a load on the engine, which helps the turbo spool faster. For example, many nitrous V8 Mustangs run 28" tall tires and 4.10-4.56 gears. The turbo V8 Mustangs run 28" tall tires with 3.25-3.73 gears.

Also, I tried 3.70 gears in my 11-second 1989 Turbo T/A. My car went SLOWER in the quarter, so I had the original 3.27 gearset reinstalled...
I have completed a project car, not supra-7, but supra-z. Yes, 2jzgte into a 1991 300z. It runs the 300z na gear ration of 4.08. Wheelspin is terrible. Have since lowered it to 3.69. It may have a better 60' time if you deal with the wheelspin. I have since lowered it to 3.69 and intending to go lower. I would stick to your present setup if i were you.
An invite to Ianong

Ianong, may I invite you to visit and post about your car at HybridZ ? We would love to hear all about your Z and I think you'll find yourself in good company - not a bunch of purist zealots ;)

Having said that - a couple of our turbo members on HybridZ have run into this same issue. Gear ratio in back too low forcing a shift into O/D at the 1/8th mile mark. A 'Vette rear is fixing that problem (3.08:1). I also ran into a problem like this when my Mustang had twin turbos - switching from 3.08 to 3.73 caused the car to slow down AND I ran out of gear before the lights! switching to a 3.27:1 gear seemed to be a good compromise.

I'd bet that more than a few turbo folks have fouond that they pull more boost in higher gears than they do in the first couple of gears off the line. Longer pulls in a gear, within reason, build more boost and keep the area under the HP curve broad.

I can't speak from Supra experience, I've not got any, but I've seen more than a few people lament switching gears to a shorter ratio in a turbo car. More than one GN guy has regretted such a change I know. If you still feel this is a good way to go I would at least urge you to figure out your max RPM\MPH in each gear and at what RPM you expect to be at in the lights. Don't make the mistake I did and run out of gear!:eek:
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A lowered numerical gearing certainly packs better top end power, at the expense of some mid range torque. I think that "lost torque" is dispensible though, coz it accounts for most of the unwanted wheelspin.
Visit the HybridZ forum? Why not? Wouldn't at all mind on sharing some stuff on extreme ZXmods.
Rear gears:

turbo 6spd-- ~3.13
turbo Auto-- ~3.72
Na Supra---- ~4.2

Sure, 4.2 might slow you down at the track a little, BUT, you don't drive on the track 99.9999% of the time. For a auto with a big turbo and a small stall, it will really improve the driveability of the car. Btw, why don't you call the local salvage yard for a rear out of a turbo/NA car, Im sure you could get both for the price of the phr kit.
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