Biggreen99

I recently had my rear end in my 99 A4 changed from the stock 2.73 gears to a 3.42 & had the shop that did the upgrade re-tune. Less than 500 miles later, my car is upshifting very harshly. You can really feel it slamming on the 1-2 change. The 2-3 change is not as bad, but still doesn't feel right. Any ideas what's wrong?

BudgetPlan1

They probably have the line pressure too high for your tastes; take it back and they can adjust the firmness of the shifts.

ALVETTE00

Is this at WOT or Part? I have mine set tamely for Part and high pressure at WOT.

biggreen54

It's happening at partial throttle. What's concerning me most, it did not behave this way when I picked it up. At first there was new sound, like a hiss, during the shift but fairly smooth shifting. Now it's shifting so harsh it feels almost like someone is rear ending my car. It's hitting that hard.

If it's something straight forward like a line pressure change, I will definately go back to the shop for a tweak.

Mike Mercury

this kinda hard shifting may be the pre-cursor for a Check Engine light and the4 setting of the P1870 error code.

Check your error codes and see what comes back.

If this is the case, then the reprog (done after your rear ratio upgrade) was incomplete. Did the person doing the reprog have specific experience and knowledge with the C5... or was he just a "book expert" type of tech ?

biggreen54

I'm inclined to say they know what they're doing. The shop is Corvette Specialties of California, and vettes is all they work on. That said, I was not there to oversee the programing & verify it wasn't a new tech. The code you reference is for trans component slipping. I'll try pulling the codes when I get home after work. I hope that's not it..That sounds bad...like a mechanical problem in the trans versus a software change. That would really have me upset because there was no shifting issues before the rear swap & reprogram.

bobc997615

When my A4 was overfilled, it would shift HARD from 1-2.

Biggreen99

You called it...P1870 is the code that came up. Is the next course of action to reflash the trans, or does it indicate actual mechanical damage?

BATM4N

yaonttwo

It needs to be reprogrammed. Mine did the exact same (moron forgot to adjust for the ratio change).