We got a program/tune for a '99 Z28 loaded into the '99 SS PCM to fix the
shift points after the rear end swap (3.23 to 2.73). It still has a strange
shifting issue I havent seen before. It does not take manual input for any
up shifts, is late to do manual downshifts, though pedal driven downshifts
are immediate and strong, up shifts are late, or non-existent under load. No
slipping, when it shifts it is solid and firm. Very odd. Does not matter what
gear - 1st to 4th. It also will hit the rev limiter before shifting when floored.

Tom

 

still sounds like you have a tuning issue of some sort, Any issues before the gear change?

 

Thats the problem, we bought the car with a blown rear end, so we only
limped it home, never could tell if it shifted poorly. The trans was rebuilt
by a shop in San Pedro, on the receipt it lists a V6 converter.

I dont see how the tune could be wrong, since its a tune for that rearend.

Is there any accumulator springs, solenoids, or perhaps a defective sensor
that could cause this?

Tom

 

You have the ability to load the tune , do you have the ability to monitor data

 

I found a very nice individual with the ability to mod the tune, he has a
TunerCAT from what I understand. He should be getting a Datalogger in
the next couple weeks (or may have it already).

I guess thats what you are asking about.

I was reading a post on another forum about the shifter linkage causing
the no upshift on WOT, sounds weird, but I guess if its loose ..... ?

Tom