I called a performance shop about changing out my rear end gear, and he said to go from a 2.73 to a 3.42 that i would have to get a different carrier. Is this right or is the guy full of it? He's the only person that i have heard say this but i dont know too much about it. thanks

 

you can get aftermarket gears in a 3 series ratio to fit a 2 series carrier or you can use a shim. so the answer is no you maynot need to get a new carrier.

 

Like ede said, you can get the gears to fit in your housing, but there are 2 different series housings. I'm not sure of the exact difference between the 2 but I believe it has something to do with the location of the pinion gear from left to right in the housing.
It sounds like your car (with 2.73 gears) came with the series 2 housing. Summit or jegs sells gears that will fit this housing in the ratio that you want.

 

So i can just buy a used set off ebay that is a 2 series and use a shim? If so, where can i get the shim at? Thanks

 

The housings are the same. The thing that is different is the carrier.

Remember, the gear ratio is not only the ratio of the numbers of teeth; it is also the ratio of the diameter of the ring to the diameter of the pinion. The ring gear is a fixed diameter for every ratio in a given model of rear end; in these, it's about 7.5". So, if you imagine the changes in the gears as you step from one ratio to another, the lower the numerical ratio, the larger the pinion gear is.

So... if you're creating a model of rear end, and you're going to endow it with a wide range of ratios, you'd start out at the lowest ratio you planned on including in your product line, and locate the flange that the ring gear sits on as close to the pinion gear as practical, so that the ring gear would be as thin (cheaper to make) as possible. Then you'd step up one ratio, and the pinion would be a bit smaller, so the ring would have to be that much thicker; and you'd step up to the next ratio, and the ring would be thicker still; and so on. Eventually you'd get to a point where the ring would be so thick that it would be impossible to heat-treat it economically without it warping. At that point, you'd re-design the carrier, by locating the ring flange closer to the pinion centerline, such that the next ratio would again use the thinnest possible ring gear; and you'd step through some more ratios. If your range of ratios was really wide, you might have to do this another time or 2.

In this model of rear, the first and only step occurs between 3.08 and 3.23. The highest ratios you can get from the factory are 4.10 (41/10) and 4.11 (37/9), and 4.56 in the aftermarket (41/9). The 3.08 and lower ratios require a carrier with the flange moved about .4" farther away from the pinion centerline than the 3.23 and up ones do. We refer to the 2 types as "2-series" and "3-series".

It's impossible to put a 2-series gear on a 3-series carrier by any adaptation means, since AFAIK there's no way to make an adapter of negative thickness. However, it's possible to put a 3-series gear on a 2-series carrier, by one of 2 methods: either add a spacer (about .400" thick for this model of rear end), or get "special" gears with the extra thickness built in.

IMHO the "special" gears are a bad idea; not from any functional standpoint, since they work just fine, but rather because then you can't ever put them on a 3-series carrier. You're stuck with the 2-series carrier for as long as you keep those gears. The spacer is a better idea, because if you do ever happen to get the right carrier, you can then simply leave it out.

Most professional mechanics will refuse to rig a rear end that way, for warranty and similar reasons. So I'm not surprised that yours was not too enthusiastic about it.

Here's a place that has the spacers.

http://www.drivetrainspecialists.com...=28&cat=GM+7.5

 

ok, what spline is my rear end? It is a 91 rs. i found a performance shop the other day that has a posi unit carrier that he will sell me for 250.00, he said it was a 28 spline. He said that it is one of the better ones, he told me the brand name but i dont remember it. Im thinking about just doing that. Also i called another place about using a shim but he said that they had problems with them breaking, so i figure if im gonna spend the money i might as well do it right.

 

just get a Slp take out posi, and get some 3 series gears off of ebay. I just got my 28 spline axles today, got my zexel torsen from them last week. Well i already had the 3 series gear, swapped rears in my car because my stock one had a bent axle and couldnt find one at the time, i went to that guy in VA, then told jeff to go get him one there, the one i got from there was an 86 so it had 26 spline axles. I found someone on here that sold me a pair of 28 splined ones. so now im set to swap the gears from the old to the slp one, slap the 28 spline ones in and go.

If you are wanting a 3.42 talk to Jeff, i beleive he still has his, cuz he wants a 3.73

Kevin

 

Yea, i forgot about that, everytime i see jeff he's asking me about that. Where do i get the SLP take out posi? Is that what you got in VA? Also do you think mine is a 28 spline? Thanks

 

Oh what we got in VA was the rear ends with the 3.42 rear.
You can get the slp posi here http://www.slponline.com/view_produc...TNUMBER=64501T

And yes your rear has 28 spline axles all 90-92 has them.

 

Kevin, thats a really good deal. So that will fit mine right? And its a posi? Also will the gear that jeff has fit that, or if i get one on ebay, what do i need to look for? I was going to skip on the posi if possible but with that price ill probably buy it.

 

That is a zexel torsen posi, its kinda like a open diff, until you apply torque to it, hit the gas, and it locks up. Lots of people on here use it. Its a 3 series carrier, meaning it requires 3 series gears, which are 3.23 3.42 3.73, and so on.

Here are some gears :

http://cgi.ebay.com/ebaymotors/ws/eB...category=33731


The reason that posi is so cheap, its basicly the LS1 cars original posi, and people that bought a new LS1 upgraded to an eaton posi, so the Zexel torsen was took out and eaton installed. Therefore they are not new, have a few miles on them.

And if Jeffs are 3.42's then his are a 3 series gear, by the way he bought one of SLP takeouts too. Just has never installed it.

Kevin

 

Also read this it explains what a Zexel torsen is a T-2.

http://www.precisiongear.com/torsen.htm

 

Cool, ill end up buying that then. Thanks alot.

 

Anyone using those gm7.5 c-clip eliminators from PrecisionGear..... http://www.precisiongear.com/cclip.htm