I have an 06 6.0 and when its the engine is cold the tranny runs like crap, or at least I think its the tranny. This started last summer and its gotten worse through the winter, but until the engine warms up, it doesn't like to shift. It'll hold the gear until 3000+ RPMs then it'll sit in the higher RPMs then when it finally does shift it slams real hard like the converter isn't engaging. But once the truck is warmed up, it shifts just fine. What could be my problem? Im not throwing any codes and the dealer has had it 3 times now and each time it comes back to me with the same shifting problem.

 

When was the last time the trans oil was changed. I just had this and it is supposedly that the oil is running to thick unil it gets flowing as stated by my mech. also need to change the filter under your front bumber for trans. mine is fixed now after doing that

 

Thanks! Ill have to give that a shot over the weekend and see if that fixes my problem

 

its probably the tranns my buddys truck didi that and he got bigger gears and had it rebulit

 

Update: I changed the fluid and both filters on the tranny and it help a little, but last week when cold, it wouldn't shift out of 1st and when it finally did it started slamming through all of the gears until the tranny is warm, and after the fluid change, it feels like the top end is missing. When I get on the freeway it hits 65 then it takes its sweet time getting up to 80

 

Have you tried plugging in to the OBDII and checking if the TCM (Transmission Control Module) or TPS (throttle positioning sensor) are AFU? I fixed a Jeep once that had a malfunctioning TPS that was giving bad info to the TCM causing erratic shifting.

If these two are not the issue, your transmission may have deep rooted emotional issues.

 

Mine's doing this as well, but I dont think as severe as you. Mine will only do this if its colder than 20 degrees F out. I usually let it warm up a little before driving in that cold anyways. I have a reman tranny with less than 10k miles on it too.

 

I haven't checked any of that or so I don't think... I have the Edge Juice Platinum and it isn't pulling any codes, but I should probably take it to Auto Zone and have them check...

 

I don't know if a diesel even has a TPS, but if it does, an Ohms meter will tell if it is working properly. If you hook up and simulate useage there should be an even/linear increase in Ohms, not a jerky/spiking read out.

However, with all of the electronic, there has to be a TCM and it has to get its input from somewhere.

 

There are TCM's on these, but the Edge can't do anything for programming it, so I don't think it's going to do anything for reading it. An SCT would let you data log what is going on since it can actually access the TCM.

Are you positive it's actually the transmission. It could also be injector related as well, which is far more common.