I have a new to me 2012 GT MT82 manual car with a Roush supercharger with a custom tune and a factory 3.55 rear end. 1st and 2nd gears feel way too short, with the wheels spinning with just throttle (sometimes in 3rd as well). I don't really care about the drag strip, but want to make gears 1-5 more useful, instead of ending up in 4 or 5th while trolling around in the city. With respect to parts, is it just a 3.15 ring, pinion, and seal kit required, or does some other material dimension change?
What is needed to switch from 3.55 to 3.15 rear end?
- Thread starter Resinears
- Start date
delroy
Junior Member
You probably don't need much else and you will find the difference very dramatic. Changing the ring and pinion is not as simple as it looks. You need pinion bearings and a crushable sleeve. The preload on the pinion bearings is very important. You may need to shim the ring gear to get a good pattern, maybe not. I had a '69 Dart with 3.91 gears and I switched it to 3.23. I loved the change. Don't throw away the stock gears though. You may want to switch back.
bullitt1011
Member
Personally I think you should keep the 3.55's for a Supercharged car it's the perfect gear, but if you feel it's too much my opinion like everyone else's which will be varied I would look at 3.31's. Get a reputable shop to do it for you ring & pinion not a DIY job. DaSilva Racing in Pickering are awesome all they do is Mustangs. Good luck and enjoy the car.
Gladams
Member
To bad we don’t live closer, we could swap out the rear differentials. You could have my 331 and I would get the 355 I have been wanting.
skwerl
tree hugger
I had 3.73 gears in my 643hp Bullitt 13 years ago and the gears were perfect. But if you want taller gears then the 3.31 ring and pinion will fit perfectly in your axle.
I had 3.08 gears in my 1988 F150 with a 170hp 5.0 engine and 5 speed manual. I could hit 35mph in first gear! Was miserable because I bought the truck for my lawn business and pulled a trailer 90% of the time. I swapped in 3.55 gears but didn't know anything about the shims so I tossed them. Worked great for a year until the rear end exploded one day while I was making a u turn. I ended up buying another stock 3.08 rear axle from the junkyard.
I had 3.08 gears in my 1988 F150 with a 170hp 5.0 engine and 5 speed manual. I could hit 35mph in first gear! Was miserable because I bought the truck for my lawn business and pulled a trailer 90% of the time. I swapped in 3.55 gears but didn't know anything about the shims so I tossed them. Worked great for a year until the rear end exploded one day while I was making a u turn. I ended up buying another stock 3.08 rear axle from the junkyard.
I have very little experience with the net results of changing the gearing in a car. What I can say is that with the MT82, I can easily start in 2nd gear, and overall, 1st is useless. I wonder if going to 3.31's would be a dramatic enough change to achieve what I'm looking for. I'm worried that the increment between 3.55 and 3.31 won't be noticable enough to warrant the headache of doing the swap.
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Thanks! I was pretty smitten when I saw it and bought it last year with only 32,000 km on it. I've since had a custom dyno tune (night and day from the Roush provided tune), and somewhat sorted out the factory suspension. Interior smelled like new. You don't want to know what I paid for this, (far, far too much!) but hey, it makes me happy.
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