Have 2003 A4, 2.73. Want to swap in a 3.42. Cost to do the work myself would be: used diff-approx $600 plus tune $200, $800 total. If I take it to a shop the cost will be: new diff plus tune-approx $1800. I think my numbers are pretty close. About a grand difference, but with a "no worry" diff.
I am not familiar with Corvettes but have 40 plus years experience with sprint cars and late models. My race cars look a lot simpler under there than the Corvette does. Maybe a little intimidating, but pretty sure I could do it. Nice shop, no lift, but I do have pit. Is it worth it for me to do this myself or not. It's not like the grand would kill me, but a grand is a grand. I'm retired so I have the time to do the work. What do you all think?

 

Dang it!!!! meant to post this in c5 tech. Can some one move this for me. Sorry!!

 

I think you should ask in the Tech section... NOT the Parts for Sale/Wanted section.

 

yeah, sorry. I realized I was in the wrong section as soon a I hit the send button. Don't post much so still pretty dumb. Maybe a moderator could move it to c5 tech please. Thanks.

 

It is not that bad of a job. I did mine in my garage with just hand tools, and a transmission jack, on jack stands. It's a fun project that will keep you entertained for a few days.

 

It's not hard, but there's a lot of stuff that has to come off. I dropped the diff/trans and torque tube to change mines out. I don't know if there was an easier way. It was about 8 hours to take it apart and about another 8 hours to put it back together again. I would highly reccommend getting a factory manual for the job and have it book marked all over the place. Sometimes the tie rods are stubborn if the car has never been taken apart before. On my car I backed the nut off and it hit something on top. Keep backing the nut off and it popped the tie rod loose so I didn't need anything like joint seperator or anything other fancy tools for that matter, just a good selection of metric wrenches and sockets. Take care not to tear a CV joint boot so you don't land up having to replace any of them.

I don't know about a tune. I thought all you had to do was change shift points for the trans. I have a six speed so I didn't have to anything afterwards.

 

I've done three differential replacements. Two guys and a lift we can do it in a day easy, probably 6 hrs if we are really humping it. There are some nice write-ups with pictures available with a litte searching. Its really pretty straightforward, here is a quick summary of the procedure we use once the car is on a lift:
- Inside car, remove center console and all bolts holding the shifter in (I've only worked on a manual)
- Pop open hood and lift it up a few inches, prop it open
- Remove exahust mid pipe and tunnel plate. Leave mufflers in
- Unfasten the tops of the rear shocks and the upper A arms.
- Unbolt the calipers and E brake cable. The calipers don't need to be disconnected from the brake lines, they can just be tied up
- pop the axles out of the diff - they just pull out with a swift jerk
- 4 bolts hold the entire rear cradle on. Support the cradle on a tranny jack and unbolt it.
- We use a strap to hold the Diff/Tranny/TT in place in the car while lowering the rear cradle. The rear cradle and all suspension comes out as as a unit: swaybars, A-arms, rotors, knuckles, tie rods, springs, etc.
- Once the cradle is put aside we support the tranny with the tranny jack and then lower it a little so you can get your hands up on top. At this point you can reach up on top of the diff and tranny and disconnect all the wires. Also, on top of the TT is a big wire assembly that goes from the front of car to the rear. It sits in some brackets on the TT. This can be popped out
- Disconnect the clutch cable - there is a quick connect on it (again, this is manual)
- unbolt the TT bell housing from rear of engine. Make sure everything on the TT is disconnected
- lower the diff/tranny some more and then pull. Lowering the diff/tranny will cause the motor to tilt, thus the reason the hood is open. Pulling will pull the TT shaft out of the back of the flywheel (manual)
- the whole TT, tranny and Diff come out as a unit. Unbolt the diff and replace.

If you are only doing the Diff, then obviously no need to pull the whole TT free, you could just support the tranny and unbolt the diff in place. However, since you are in there anyway, taking everything out lets you check/fix TT bushings, transmission leaks, clutch, etc. The diff weighs somewhere around 100 lbs (guess) so its tough for one guy unless you have two tranny jacks or other way to support stuff.

The Auto shouldn't be too different. Good luck.