Question about PCM and tranny

[meck]

I’ve just swapped a ’97 3.0 v-6 with 4r44e transmission from one ranger to another. The donor engine/tran was running and shifting great when I bought it (I drove it several times for quite a few miles). Now that it is in, the transmission is shifting late and shifts are hard. My question: does the pcm have to relearn the tranny shift points etc. the way it (the pcm) has to relearn the engine strategy? I’ve only driven it a few miles, and it did seem to improve some, but I wanted to check before driving more and maybe causing some damage.

 

[RonD]

Reads like PCM is in transmission "Limp mode", you don't have a Check Engine Light(CEL) on right?
And CEL is working?

PCM will go into Limp mode for a number of reasons, but you will almost always get a CEL and code for why.
Limp mode is actually better for the transmission, no slippage, hard shifts and higher RPMs so less Load

 

[meck]

The CEL is working, but it is not on. My scanner shows no codes, either set or conditional. I hesitate to start serious testing and tearing into the tran. when it was working so great when I removed it from the donor truck. I think I'm going to drive it some more and see if I can get a clearer picture of its symptoms.

Thanks for your reply.

 

[Craig0320]

Your throttle body might be really dirty and causing the hard shifts. Pull it and clean it real well. I have seen many of them needed to be cleaned after a new battery install or complete power loss. The pcm resets back to factory and the dirty tb screws with the air flow. I have seen both hard shifting and low to no idle conditions with a/c on after a battery swap out. Also, check your air filter for obstructions and dirt. My step-dad's buick started shifting hard and the air filter was dirty.