dragander

I just finished up doing a 5.3/4L60E swap into a 1955 chevy car. The swap went smooth and was very easy. Now with that being said I am having issues with the trans. The trans wants to short shift through the gears but only in drive or overdrive. I can hold the gears if i manually shift. Ideas??? The harness was built as a stand alone for my application. The computer as well was tuned for my application. I know the computer is good because it works perfect in my C-10 that has the same swap. Sooo assuming its in the harness... I traced both harnesses and every thing looks to be the same. I must be looking over the obvious??? any help is greatly appreciated. Thanks LS1 TECH

mrvedit

The shifting is completely controlled by the PCM. I cannot think of how even a few mixed up wires could give you "short shifting". You say that you have even swapped the PCM, but did both vehicles have the same rearend ratio?

dragander

One had 3:73 and the other had 4:10. I'm thinking maybe its not picking up reference signal from the TPS and can't tell how far the throttle is open??

mrvedit

Good deduction - the TPS, MAP and MAF are all part of the formula the PCM uses to determine the load and shift points.
I understood that you swapped PCMs; if true you also need to be sure both vehicles have the same MAF. You might try disconnecting the MAF to see that if that improves your shifting. (To be safe, don't go WOT with a disconnected MAF unless you are sure your PCM was tuned for that.)

dragander

Good News! Fixed the problem. It had two wires crossed at the TPS connector. Runs like a champ!

mrvedit

Thanks for the update and glad you got it figured out and working.