has anyone here swapped a LT1 rear end in their 3rd gen. 10 bolt with 3.42's.....i wanna know how much work is involved and if it'll even bolt in right....thanks_

 

 

Yes it will bolt in and yes it is very commong. A few searches will yeild you many threads to read through. There are some certian issues that need to be addressed. Such as, e-brake, and wheel backspacing issues.

 

yea nevermind it's gonna cost a bit more money to do that than just get 4 spacers lol

 

spacers arent cheap though, i think i spent 300 on my set of 4 2 inch spacers. you can find a used 4th gen rear for around 500.

 

If you spend $500 you have been ripped off. A good 4th gen rear should go for no more than $350. LS1 rears are often more expensive than LT1 rears due to the larger brakes.

 

Any reason you guys are swappin or is it the mistque of the 4th gen's power? Gears are no stronger ya know! Same wimpy 7 5/8th's rear. The torsen is an improvement. The big torsen is a bit better. The improvement is ony a fraction of what it is reality. Don't be fooled. If you need a 12 bolt then buy one. Don't waste your money rebuilding 10 bolts.


what tranny you running, what gears, what short times and what MPH?

 

how fast can you go on a 10 bolt? my car runs mid 11's on spray, but rarely sees spray. i flog it occasionally, lot of hard 1-2 shifts and getting sideways around corners every now and again. last week my richmond 4.10's came apart on me, having some precision 3.73's put in, ought to have the car back tomorrow. i think i have around 370 hp at the wheels, maybe 440 lb ft of torque. is my 10 bolt going to last?

 

Often times a used 4th gen rear is cheaper than buying aftermarket 10 bolt parts that accomplish the same thing. Upgrading a 2.73 open 10 ten bolt to a 3.42 posi can cost upwards of $600+ by the time you add in parts and labor. This cost is greatly reduced if you can do the work yourself but that is a rarity for most modders. If you are planning on running different wheels than the idea of running a 4th gen rear becomes even smarter. You can then buy two wheels with 4th gen backspacing.

People also go with 4th gen rears for the brake upgrade. Spending $300 on an LS1 disk rear saves money in the long run if you want great disk brakes. LS1 rear brakes perform nearly the same as any aftermarket 10 bolt disk brake kit. That same $300 gets you these brakes without having to spend $700 for an aftermarket drum to disk conversion later on.

 

Not cheaper at all when you count in the wheel spacers needed to keep the wheels in line it gets out of hand.

Grab some axles from a 89.74 up to a 92.
Throw a 3 series take off torsen on it and you got your self a cheap good rear. As good as 10 bolts get anyway. Pushing anymore than 1.5 short times and you need some more meat in the ring/pinion. A 12 bolt will sufface.

 

You don't need spacers in the rear with a 4th gen rear. You only need spacers for the front should you choose to c0onvert to 4th gen wheel specs. You can run the stock wheels on a 4th gen rear but they will stick out roughly 1.5" or so more.

Throwing used parts at a rear end is the worst way to build one. You also need a $100 rebuild kit that comes with new bearings shims and such. Some people don't have the means to do it themselves and they can often times get the same outcome (even better because of the brakes) for less money if they go with a 4th gen rear.

 

so if I swap in a rear end out of a 93 LT1 I can reuse my wheels I already have on my 91 firebird?

 

So just to make sure...the lt1 bolts up and the ls1 bolts up. I plan on upgrading my brakes to the c5 brakes...so it would be smarter to go with a ls1 rear, right?

I'm also wanting to lower it with eibach's 1" pro kit, then putting new LCA's and panhard bar...all of this will bolt up??

 

Yes but they will stick out roughly 1.625" or so per side. To some people this looks bad. This is something you have to consider when running a 4th gen rear.


Yes it will.

 

cool thanks for the info!

 

i found a 4th gen rear with posi and disc brakes for 200 so in my opinion it was a cheap upgrade to posi and disc brakes, my wheel spacers were also $150 locally for a set of 4 and my WS6 wheels were free. i've also seen local yards say they want 600-800 for a 4th gen rear... out of a v6 car. so keep looking the deals are there, you just have to find them.

 

I can't beleive how much people pay for wheel spacers. I just bought a pair off Ebay 1.25" thick for $67 shipped to my house. They are solid billet AL with studs & nuts.

 

What do wheel spacers actually do?
Do you need them if you are going to swap in a 4th gen rear?

 

you need the wheel spacers if you are putting 4th gen wheels onto a third gen. the offset from 3rd to 4th gen is different, about 2 inches. if you put in a 4th gen rear end you dont need the wheel adapters on the rear , but if you still run 3rd gen wheels they will stick out a little since the 4th gen rear end is wider. do a search and you will learn a ton

 

For a street car making under 400hp and running street tires (not slicks), the 7 5/8" is more than strong enough. Even if you do break it, you can buy 4th gen rearends all day long for 350.00 or less. Going to a 12 bolt or 9 inch would cost a minimum of 17-1800.00. It SHOULD actually be more; if you're going to sink that much into a rear end, it's not very smart to buy the cheapest one available. Might as well go ahead and sink another 3-400.00 and get one that's truly bulletproof.

If you do the math, though, the 4th gen rear makes more sense. you'll go through 5 of them before you'll spend as much as you would for a single low-end 12 bolt.

I used to see 4th gen guys break their rearends at the dragstrip pretty regularly, but, every time I can remember, they were shooting nitrous and running slicks. I know a number of guys with LS1s making well over 400hp who run them regularly and have never had a problem with their rearend. If you're on street tires, you're going to spin the tires before you're going to put enough strain on that rear to break something.