Hey all, just pulled my old trans that was slipping and not wanting to shift out of first a few weeks back.  Got a brand new rebuild with a shift kit, raised pressure, redone VB, the works (not a full race trans but warrantied to as much power as I could add on a single turbo) and put it in.  At first, it wouldn't run well, so I figured "what the heck, I'll replace output speed sensor and try."  After that, It ran fine for about 5 miles until suddenly, it started slipping and wouldn't shift out of first.  Same exact issue I had with the old one.  The other day, it started up and went through the gears no issue but the problem has since come back.

 

Now I've got the fluid level perfectly dialed in, adjusted the TV cable all around, cleaned all contacts, and put in a brand new output speed sensor.  The issue is still there.

 

Any common issues?  I know it could possibly be TPS related, but I don't have any dead spots on the pedal and none of the other weird tps issues.  I was told it could be an internal harness, but I have one that was tested before installation and was found to be good so I doubt that.

 

Could it be TCM or a bad ground or something?  It seems like it must not be making enough pressure because of the slipping and no shift, but I'm not sure what would cause that.  Not enough power to the pump maybe?  Air in the system somehow?

 

Any wires/grounds I need to check before bringing it in for pressure testing?\

 

I installed it myself so I know it was done right, the one mistake I made was overfilling it at first, but I never turned the truck on or even connected the battery until I had drained out the excess fluid.

 

I've got all sorts of time and money tied up in this now and it still won't work right, starting to get super worried.

 

Thanks.

Alright, I've got a few things to investigate.  Thanks a lot guys, helped me sort through the issues.

Like was mentioned already locate a scan tool and see if any codes come up. If you have the EXACT same symptoms before and after I'd suspect the PCM or possibly a wiring/ground issue. When the PCM went bad on my truck it would not shift properly at all and also started in 2nd gear every time.

Being as the issues are almost identical with the new transmission as they were with the old, I would almost say you can rule it out. I would definitely be looking at the PCM, and wiring in the truck. Just a quick question, what does your AC voltage look like coming out of the alternator? If it is high enough it could be messing with the computers and such. Just something else to look at.