Engine runs rough RPM's jump like it want to downshift

[rminiger]

I have a 96 tahoe that has been running rough off and on. Traveling @ 45-55 light on the accelerator with little to no load/strain the engine "bucks" and the RPM's jump a couple hundred then returns back down to where it was. Occasionally the service engine light comes on. Sometimes it doesn't. Been to the dealer 3 times for a diagnostic. Nothing identified.

Almost acts like it is trying to downshift.

Any advice?

[ARNIE]

Some of these issues are hard to daignose online, especially when you cannot get a code. My first thought though is a tranny issue. I would suggest you go to a good transmission shop and let them have a look at the prindle switch. As well, a bad torque converter and several other things could cause that. I would hate to see you just start replacing parts at a big cost and still not have the issue resolved, that is why I am suggestiong a tranny shop.

[Steve]

Just curious if there is an update for this issue?

[Robbiev]

I had a similar problem in my 02 yukon. Tranny shop put a shift kit in and it fixed the problem. Some to do with the lockup gear not holding because the piston is aluminum and the case is steel. SHift kit installs a steel piston.

[Steve]

How hard does the shift kit kick in when shifting?

[Robbiev]

It does not seem to bad to me. I have driven other tahoe's and yukon's and it feels pretty much the same.

[Steve]

Well, they are smoother than they used to be. My Suburban has a shift kit, and it kicks hard if the RPMs are up high enough. Like getting kicked by a mule.