My existing 91 RS has a lazzy rear end. It has the GU2 code 2.73 ratio axel. I'm the original owner and its time to have some fun with this car. Thinking about upgrading the rear end to the SLP Zexel-Torsen posi in either the 3.03, the 3.42 or the more harry 3.73. Any suggestions? I noticed that Auburn gear makes a replacement as well. My understanding is that the SLP gear/carrier and installation kit will bolt right into my existing rear end housing.


Thanks Rezz

 

If SLP had any of those, then yes, it would bolt right in. However they ran out of them a long time ago. Been most of a year now I guess. They're gone forever.

There's no sense in upgrading from 2.73 to 3.08. That's a giant waste of alot of money, that will produce only a barely noticeable result.

3.73 isn't "hairy". It was the stock gear in ALOT of cars over the years, as in stock from the factory; for example, my 83 HO car came with it, as did all of the 70s Z28s I had back then.

But you've got a 305 TBI motor with auto trans it would appear. Basically as you know it has no real capability to rev. If you put 3.73s in it, what would happen, is you'd take off from a stop; the motor would wind up to 4000 RPM or so REAL QUICK, and then hang there for 2 or 3 seconds until the transmission decided to shift; then it would run through second real quick again, and hang at that RPM again while waiting for the trans to make up its mind; etc. You'd be cruising down the highway, and go to pass somebody, and the transmission would kick down; but the motor wouldn't produce any added power at all. In a word, it's too much gear for the rest of the setup. A mismatch.

3.42 is about as far as you should go. 3.23 might be OK too.

In either case, you would need a 3 series carrier, for 3.23 and up ratios. You have a 2 series now, for 3.08 and down. Whatever posi you buy, make sure you buy that and gears, that are the same series; most likely, that would be a 3 series posi, and your 3.23 or 3.42 gears. A 3.08 gear WILL NOT WORK on the SLP unit, or a stock one like it.

Having had a certain amount of experience with Auburn over the years, I would suggest getting something else. Either get a junkyard posi out of a 98-up Z28 or Trans Am (which is what the SLP unit would be), or an Eaton. And I mean a NEW Eaton, not an Eaton Gov-Lock ("Grenade-Lock") out of a S truck.

 

Great!! Thanks for the help. A little confused about the SLP parts. Their site still shows the gear and carrier to be available for third gens? Regardless, now that I'm educated, I'm armed and dangerouse.

Rezz

 

Yeah, what I did was get my hands on a '00 SS rearend for cheap, and pretty soon I'll be transfering the posi unit (which would be the same thing as the SLP unit like RB said) and LS1 rear disk brakes into/onto the stock 10 bolt in my 91 Z28. But I'm gonna be paying someone to install the posi unit since I've never done it before and I'm afraid I'll screw it up. I also wanna change out the ratio to something alot higher since the car will soon be 6 speed with 2 overdrive gears (T56). Just remember that the 4th gen posi units will only work with the 28 spline axle 10 bolts, so I think thats only the 91-92's, but not totally positive. Good budget way to go.

 

They still have the $400 torsens in stock, the $99 take-out units are all sold out.

 

I'm guessing you mean that one is the full carrier with the working componenets and the other is the internal gears, etc.

 

No, what he means is the Take-out posi is the ones that they took out of the cars they converted to Camaro SS's and Firehawk's. those are the cheap $99 ones, they had to sell them at that price because they were in the car for a whole 10 miles or so. cant be sold as new,

the $400 one is the same thing but BRAND NEW never been installed in a car ever.

 

Ok got you now. Thanks for the help.

 

Actually if I remember right...the $400 diff is the one that slp put into the SS's and Firehawks. It is a similar design to the take out version just a more heavy duty design. Too bad the take outs are no longer available. That was the best cheapest way to convert to posi.

 

yea your right, it was the cheapest way to convert, and i love it!

 

Just ordered a 3.42 carrier and ring and pinion from Trans Am Creations. The total with shipping was $200.00 US. The gear assembly is from a 1997 Z.