My stock V6 2000 shifts REALLY hard when the engine is hot. (Like after driving on the freeway) When it is cool, it shifts hard, but not too far out of the ordinary.

I thought it may be my transmission mount, but that does not explain the difference when the car is hot.

Any idea what I should be looking for to solve my issue?

 

Invisible Bump

 

Maybe try a flush and new filter. Is the vacuum line hooked to the modulator.

 

I don't know, I will have to check. Can you tell me more about where I should look?

 

Maybe not the same, but I had an S10 once that did that, shifted really hard into second when it was hot (operating temp). Turned out to be a bad transmission.

 

The modulator would be at the end of the only vacuum line going to the transmission.

 

Daryl, let me clear up some mis-information here before you go barking up the wrong tree. Your trans is a 4L60E (Electronic shift).
It does not have a vacuum modulator, or any vacuum line going to it. The vacuum modulator is a feature that was phased out waaaaay back in the 80's when the 700R4 came out.
Is your check engine light on, any codes? How your trans shifts is tied to the TPS, VSS, the shift solenoids, trans line pressure, and likely some other things that escape me at the moment. Basically, the cause of the hard shifts could be a number of things, from electronic to an internal fluid pressure leak.

 

I used an Innova 3100c to read the codes. Nothing came up. After googling the 3100c on the internet, I see it isn't capable of reading transmission codes. I will have to see if I can get my hands on a different reader.

 

I could be a few things. Do a internet search for 1-2 accumulator see if you see anything that looks like what you are talking about. Piston sticking when hot is not uncommon.

 

Put a bottle of lube guard in it first