4r100 tranny slippage after shift kit???

[kegcrawler]

so I installed a Sonnax shift kit in my transmission last weekend, and it drove and shifted fine all week. I am about to leave town this past friday and it starts slipping when it is supposed to be going into second gear. the only thing that i can think of that would be wrong is that the guy i bought it from changed the transmission fluid to Mercon V and i (since i didn't know he had done that) put 8 quarts of DextronIII/Mercon in it.

i am thinking about draining all the fluid and replacing it with the straight Mercon V (it was working fine before) and if that doesn't fix it then i guess i will remove the shift kit, and if it still slips then i guess i have bigger problems...

Could the fluid be what is causing my problem? Is this a good plan of attack to try to fix the situation before i just let a mechanic look at it? Please i need to figure this out asap!!!

[Cody77]

Yes the wrong fluid in a tranny can cause problems. Always make sure you have the correct fluid in your tranny before you jump to conclusions.