Hi. I have a 98 Legacy outback 2.5. I just rebuilt the transmission on this car, so I know its not transmissions related. I'm having trouble with a harsh 1-2 shift, and late upshifts after. It doesn't do it all the time, but i have discovered its because of a voltage drop to the transmission that causes it.

 

I have tried all the following: New MAF, dropping resister, NEW TPS, used TCM and I have traced all the wires for HOURS, and see nothing grounded or cut.

 

I have no idea what could be causing this. Any ideas, no matter how crazy, are appreciated.

If you are sure that the trouble is due to a problem with the power to the transmission area then you need to trace back the wiring that ties to the problem area and look for a connection problem.

ALWAYS replace one part at a time, if that does not solve the issue, put the original part back on, otherwise it can make it impossible to diagnose properly.

 

Go back and unplug then plug all the connectors in again. Do you have the VSS operating properly and the MAP sensor working?

Well I found it. The ground on top of the intake manafold was causing my voltage drop. Not sure how it got loose, but I could wiggle it with my hand. I tightened it up and no more problems.

Good job. Bad grounding can cause all kinds of strange issues. Thanks for the update.