Car starts out in 3rd gear when using foot brake off the line

[firebird_1995]

Turning on a buddys car this evening we notice that when hitting the throttle from a roll or even a dead stop it shifts fine, however from a dead stop when trying to use a line lock or foot brake to launch at high RPMs the transmission sort of goes into a limp mode and start out in a lower gear. If he shut the car off and restarted it it would then start taking off in first again. It does have a 3400 rpm stall converter on it but we don't have any issues with it shifting improperly which is what I've heard referred to as the stall wall problem before. are the two related or is there something in the tune that we are missing?

[popo8]

Cahall

[CPT]

Anything over 3200 stall will cause it to hit "stall wall". The complaint you're describing is exactly what it will do.

Frank

[firebird_1995]

This was actually only about 2k rpms. You can launch all day off idle or a roll but if you stall it up just a bit, immediately fails

[myltwon]

If the car is a 94-95 then the issue is stall wall. It is caused by tailshaft flex under hard launching causing the VSS in the rear of the trans to temporarily lose signal which sends the trans into limp mode. This was the cause years ago for a lot of guys swapping to TH350/400s because the fix wasn't well documented.

The fix for this is tuning the PCM to shift 1-2 only by rpm/map value, and setting the mph shift point to zero IIRC. I had to fix it a long time ago after I put a converter in it so my memory is a little fuzzy, one of the tuning guys on this site could likely give you more info.

[firebird_1995]

Interesting. I'll give that a shot. Thanks!

[myltwon]

No problem, let me know if that works out for you

[DMBlack]

That is the way I have done it also. Seems to work for me. I think I have the vss faults turned off also but don't if that makes a difference.

[SSlowBoat]

You only do that for the tps @ 100% and just below, I have done it just because since I'm using a 95 trans/Computer etc

[myltwon]

You only do that for the tps @ 100% and just below, I have done it just because since I'm using a 95 trans/Computer etc

yeah forgot to mention that part

[firebird_1995]

Ok good deal. Thanks for all the info guys!