What would cause a 99 4L60e to stack shift? Meaning, when put into D just like normal, and drive off, the tranny goes through all the gears to 4th within seconds. Like your in OD by 30mph? 1,2,3 literally dont last 500rpms? (this is with a TCI SSF3500, which it did the same with the last 2800 converter also)

anybody ever heard of this? ....FYI...the car is on a BONE STOCK PROGRAM.

somebody help???

 

are your gauges acting funny at all?

 

no, not at all. all the guages seem fine. it just does this type shifting.

 

My truck is doing the same thing. I have heard that it can be caused by the throttle cable being out of adjustment. Did this happen to coincide with putting your TB on?

Mine won't downshift at all when it does this, unless I manually select the gear myself.

I'm very interested to hear more info on this!!!

 

Well, i guess i could check the cable but it just seems weird.

Anybody else got anymore suggestions? at this point im open to anything!

 

Shifting is controled by the PCM, so something is telling it to control or not control the shifts. You might start with a tuner like LS1Edit or pay someone that can adjust it for you.

 

Honez, I have LS1EDIT but the program is STOCK right now. Being on the stock program, and tune, it still should not shift like this? it didnt shift this way before i got it rebuilt the first time? The only mods i didnt have was the cam and verter before the rebuild on the stock tranny with the stock program????

 

Try the output speed sensor. Maybe with ATAP you can see what the speed sensor is telling the PCM. Correct me if I am wrong (ATAP is new to me).


Kevin Steele
TCI
Product Engineer

 

TTT!!

 

i think its the pressure control solonoid

 

Did it happen right after rebuild? Check TPS for full throtlle sweep.

 

You're going to need a scan tool for this one.. Hook up your scanner, and monitor TPS, vehicle speed, and commanded gear.. As already suggested, make sure your TPS sweeps, then take the vehicle for a drive and verify the speed sensor works properly. See if the commanded gear coincides with the gear the transmission is actually shifting to. That should get you started.