I did my A4 swap w/ a 3.42 and kept the stock converter. It was very nice, but I do regret not getting a 2800 or 3000 stall converter put in for a bonus effect.
I was able to reprogram my pcm shifting w/ a Predator programmer, but it was painful. I bought it a couple years ago when I did this and at that time the Predator didn't have the right software to reprogram my pcm accurately. I ended up having to go to Radio Shack to buy an adaptor and power source to download from my computer a custom tune emailed to me by Diablosport. Once I downloaded that info I was able to program my pcm properly and it worked fine after that. However it took a little time trying to call them/email them to get it for free (as it should have had this software already in it).
I don't know now if they are any better w/ the new Predators, but if I were to do it all over again, I'd definitely have either a tuner do it for me +/- dyno tune at the same time (which adds $$ to your costs), or last choice would be buying a programming tool in which hp tuners seems the best bang for the buck and likely effective the 1st go around. I'd rec u contacting hp tuner 1st before buying to see if their software will accomodate u.

 

I had a tuner shop do this. It only cost $75.00, they also took out TM, and changed the temp that the fans turn on. I didn't want to pay $400.00 for a new programer.

 

If you're changing gears anyway, the extra for a torque converter changeout is very minimal. And, in any event, you're planning on,a torque converter switchout anyway. If you think the 3.42s are something, hang a Yank SS3200 in there. It's a very mild, very tight, converter. It's not loose like the older ones used to be. It will drive like stock and you won't believe the performance difference. Find someone who has one and go for a ride. Good luck with whatever you decide to do!
Ed

 

Love your comment , mild and thight, not like the older ones. This is what I just ordered along with a 342 . I was reloctent as I know how loose the old ones were if you did not have an realy low gear. Thanks.

 

i have 3.42's and a 2800 stall and drive my vette all over the place, in town, up to my boat, yada yada. there's no added temp and the tranny doesn't slip, the converter slips.

 

I have a 224/224 cam and idles at 800 RPM and don't have a stall converter with 3:42 gears..no problem car runs great.
Just have a tunner to change for the 3:42s.

 

You are going to love it!
Ed

 

I've got an A4 w/3.42 and stock TC. Driving is great and I don't feel like I'm missing much on performance. I have a H/C with headers (423 rwhp, 391 rwtq) and the tires spin too much as it is. But, even with just a very mild cam and headers (367 rwhp and 356 rwtq) the tires were spinning quite a bit. Below is a video that might give you a better idea of the performance.

http://www.comp-soln.com/Chips_C5-lowres.mov

Anyway, I'm completely satisfied with the stock TC and 3.42 gears.

 

have same set-up,runs and acts fine on street

 

I just put a 3.42 rear-end in my '02, with automatic. What a change! (I cannot believe Chevy puts 2.73's in these things!) I'm very happy with it, and did not do the higher-stall TC. DynoTech (Fort Wayne, IN) did the work, by the way. Top notch people. Phil saw no need to change out the TC, for my kind of driving (just an everyday guy having fun with my Vette).

 

I have a 98 A4 with 3.15 gears. What performance difference will it be to change to a 3.42 or should I go to another gear ratio?

 

IMO, not enough for the price. The difference from a 2.73 to 3.42 is a 25%. From a 3.15 to 3.42 is only 8.5%.