will 3.42's out of an 2002 SS M6 camaro fit in my 1998 Z28 A4 with 2.73's. is there going to be any problems with the computer when i change?? Speedo or shift points?? are all rear ends the same in f-bodies from 1998-2002?? thanks

 

You are going to need tuning either through a handheld or a tuning program. I believe 98's are free on some programs so if you can find someone local they might hook you up.

Some shops will also do it.

The rear ends can be either Auburn or Torsen units and either 3 or 4 channel. Torsens are more common as Auburns were phased out after 98. 4 channels signify the car had traction control.

3 and 4 channels can be modified to convert to the other, but it is best if you just get the same type.

I believe all of this is in the stickys.

 

The speedo and shift point will need to be changed. The rpm for shifts will be fine, but you also need to change the shift@mph for WOT.

 

what do you mean free becuase my dad owns a dealership, not chev, do you think he could have it?? how would i tell what rear end mine and the car i got the gears out of has?? so are you saying theat auburns were only in 1998 and for 1999 to 2002 the rear ends came with torsens and that if my car has no ASR switch than it has no traction control???

 

It is not my area of knowledge but I believe one of the major tuning platforms like HPTuners doesn't charge users to tune 98 vehicles. So if you have a buddy with that tuning software, or can find someone with it, they could do your car without incurring costs for addtional licenses.

A GM dealership would be properly equipped to do what you need if you were going to 3.23's, because GM "stock" profiles existed for both 2.73's and 3.23's in autos. But using a set of 3.42's I'm not sure they could do it at a dealership.

Most likely you are staring down using:

- A handheld like a predator (buy used, limited flexibility, but cheapest way out probably)
- A local tuner (I would say the best value)
- Tuning software on your own (most expensive, most complicated, but best option long term and obviously flexible)

The only way to know for absolute sure what gears are in a given car/axle is to open up the diff and inspect them yourself. Autos only came from the factory with 2.73's and 3.23's, but swaps are very common so you can't fully rely upon build codes unless you know the car is a bone stock single owner and you trust that owner. 3.23's and 3.42's are close enough you wouldn't be able to tell just by driving the car, because there is no easy way to tell if the car has been programmed or not.

Again, assuming the car is 100% stock and you know this, then cars with ASR or traction control are 4 channels, those w/o ASR/traction control are 3 channels.

I believe all cars 00 on up were Torsens. I cannot say perfectly which one is better, but my general understanding is that Auburns have some risk to wear out, while Torsens pretty much work fine until they break completely, typically due to abuse or overloading.

Therefore for mostly stock and mild applications, Torsens are a safer bet. Behind an LS1 I wouldn't bet on a stock Auburn being worth much of anything once it gets up to 100k miles or so.

 

okay but i still dont know if the gears (ring and pinion) will fit yes or no?? 02 M6 3.42's i already have nbut not installed into my 98 Z28 A4 2.73?

 

they will not fit directly. you will need a series 3 carrier for the 3.42's, your 2.73's came in a series 2 carrier that fits the bigger gear.

 

Setting up the gears will typically cost as much as buying a complete used rear. M6 cars with the same ABS/TCS setup as your are what you want, as they come factory with 3.42s. Fair number of decent used rears go for a few hundred bucks, as low as 200.

IMHO, new 3.73 gears are the way to go for an A4, and a new diff at the same time. No, your dad won't be able to tune it, by 'tune' we almost always mean "with a programming tool like HPTuners or LS1edit".

So overall, based on your lack of experience and knowledge: Get someone who knows what they are doing to suggest a gear ratio for you based on your NEEDS, then either buy a complete used rear with those gears, and have the computer programmed for those gears, or buy new gears (200+ with install kit), and pay for install (about 200 right there), buy a new diff (100-1000 depending on needs), and have computer programmed for the gears.

Short answer: No, you can't just throw in used gears you got for cheap and have it work.

 

k thanks guys

 

All the advice is good so far except it should be noted that you can buy "thick" gears from any number of vendors that will allow you to keep your 2 series carrier and go up to a 3 series r & p. That will save a few bucks. As a side note, I drove around untuned for a few months after I did the swap. Speedo was off, but my tranny functioned ok. You do want to get it tuned as soon as you can, but it won't hurt anything to be untuned for a while if necessary.

 

Or if you are brave you can run a spacer and still use your stock carrier. Mines been in there for 3 months now and no problems or whining; gears were from a 70K mile car. She's still holding up after NUMEROUS passes at the track on slicks

 

what size spacers did you use if you can remember?

 

Look under GM/Motive Gear Sets HERE


Part # MOT75S $49.99

 

I have read about how weak the 10 bolt is, how much worse it this spacer kit than getting the "thick" gear.

 

It's all about tolerancing. You're adding another an extra source of variation to the gear by using a spacer. More variation equals less than ideal and less consistent setup, which means more chance for whine and premature wear.