I'm looking to upgrade my gears. I finished my LT1 install, and its running really good now. My car is the 91 RS and had the 305 v8. It has stock gears, which correct me if I'm wrong are 2.42 or something like that. And I think its a 1 wheel wonder... please let me know if I'm wrong on that too.

I will be driving my car on the highway a lot, but I LOVE off the line acceleration. Basically I want to be able to accelerate nice and fast, but I still need to be able to reliabily drive on the highway. I have the stock 700r4 trans.

I think I have 2 options for gear upgrades from what I found at yearone. 3.42 or 3.73. I'm leaning towards the 3.73, what do you all think? 4th gear in the 700r4 is like .92 or something small like that.

ALSO... Posi or Locker? I need to be able to manover and take corners, etc. so would a locer be better or posi?

Thanks for your input, Its greatly appreciated.

OH, if there is a cheaper place to get the parts other than yearone, that would be good to know too!

 

Just get a rear from a 4th gen car with manual trans. You'll get 3.42 gears and a posi. If you can find a rear from an LS1 car, you'll get bigger brakes and a zexel torsion posi. On top of all of that, a complete LS1 rear, with brakes, will probably be less than the price to swap gears in your current rear.

 

You might jerk the diff cover and look: numbers are stamped on the ring and pinion:

41 : 15 = 2.73
41 : 14 = 2.93
40 : 13 = 3.08
42 : 13 = 3.23
41 : 12 = 3.42
41 : 11 = 3.73

You'll be able to tell if it's limited slip as well. Limited slip is the way to go on a street-driven car. Year One is expensive. I'd look at a board sponsor, Summit or Jeg's.

JamesC

 

Do you want to convert from drum rears to disk braked rear? IF you've even considered that idea, or have that notion, then make that part of the action plan too. A complete rear end swap is the simplest way to get both a limited slip carrier and disk brakes. Just choose a (used) rear end equipped as you want it. Use the list that JamesC provided and go wrecking yard hunting.

 

I had thought about puting a 4th gen rear end in, but I thought I had read somewhere that they aren't the same width as the 3rd gen... So wouldnt' that throw the handeling off if the rear tires were off center from the front? And if I did find a rear end from a 4th gen LS1 would that be as dificult to get working as the LT1 was? I read so many times how easy the swap was. And I'm sure to a mechanic or someone who plays with this stuff a lot it may be easy, but this is all VERY new to me, its my first project. If I ran into problems would it be expensive for a shop to do for me? I would like to do it myself, but I was just thinking worse case senerio for cost.

Thanks everyone for your input, its really helpfull.

 

Though the fourthgen rear is 2" wider per side, it's a direct bolt in (just like the thirdgen would be). Many members have done the swap. You won't have any problems. A search will provide a ton of info.

JamesC

 

With it being 2" wider, wouldn't the rear tires then stick out past the sides of the car?? not very clean looking I wouldn't think. and I believe in MN isn't it illeagle to have your tires past the sides of your car?

 

If you have already done an engine swap, the rear end will be a piece of cake. I vote the same way everyone above does, get a complete 4th gen rear end and you won't regret it. If you are concerned about width, look for a 3rd gen rear from an early 90's car. I got one from a '91 Z28 and it was 3.23 posi with disk brakes.

 

What about this...

The stock rims I have are offset. The rear rims are made to push out farther than the front tires. If I got a set of front rims and put them on the back... would that help the offset? or would they not mount up??

 

That's what I did with my 91RS. Mine is a 9 bolt 3.27 limited slip w/disk brakes. Only must do drum to disk mod required is to change the brake proportioning valve.

 

I took the same route with my car. I bought a 3.23 posi/disc rear from a guy that was parting out a 91 GTA. If you do end up using a 4th gen rear, if you run 4th gen wheels on the rear, they have the correct offset to where your wheels won't stick out. The only catch to that is to run the same 4th gen rims up front, you have to buy a pair of 2 inch spacers for the front. Personally, I'm fond of my 3rd gen wheels, so I made it a point to find an 89-92, 3rd gen posi/disc rear for mine. Also, I agree with JamesC, stay far away from using a locker type carrier (i.e. Powertrax) if you like cornering fast. The Zexel-Torsen type carriers in the 98-02 f-bodies have no problem with corners. Same goes for an Auburn or Eaton, clutch style posi. Btw, if you decide to buy new gears and a new posi unit for your existing rear, go shopping on ebay. You'll save a ton of money. Even Summit and Jegs want about $500 for the Eaton posi. I've found them brand new from some of the ebay store sellers as cheap as $370. I've also seen Motive gearsets, which are great quality, for as cheap as $140 on there. Year One is great for body and interior stuff, but any of their hard, mechanical parts are outrageously priced.