Another 4l80e Problem

[TyeeMan]

Hi Everybody,

 

I read a gentlemans post with almost the same problem I am having only he had a 1993 truck, , I have a 2002 GMC 1500HD 4X4,6.0L, i would imagine there is a few differences which is why I'm kind of re-posting the question.

 

Problem - When I'm towing and the shifter is in 3rd, at times the the torque converter will lock up and unlock on it's own, with or with out cruise control. It seems more previlent at speeds around 55-65 mph on a flat surface. If I'm driving faster than 65, going up a mild hill or pulling into a wind it will largely stay engaged.

For test purposes I tried driving to work (84 miles round trip) in 3rd. For the first half of the trip (to or from work, trans fluid about 100-120 deg per gage) everything is just fine. Torque converter locks up and stays there until vehicle slows below 50 mph, , just like it always did/used to do. Second half of the trip, torque converter takes a long time to engage wether at 55 or 60 mph if it engages at all. If it engages it will likely cycle out a time or two by the time I get home. Trans temp is perhaps a little over 120 but still under 150.

Driving in OD the trans shifts perfectly, hits all the gears very nicely, drops into OD and stays there, it does seem however that it skips the tc lock up and goes dirctly into OD (when not towing) and fluid is warm. Cold fluid there seems to be a tc lock up.

Truck has 123,000 on it, transmission has about 25,000 on a new filter and complete fluid change, fluid is Amsoil ATF.

 

Could somebody please shed some light on this? I'm interested in the potential problem, , but I'm more interested in if this is a total tranny rebuild, tc clutch solonoid cleaning,sensor cleaning etc, etc.

 

Thank you very much for your input, it is greatly appreciated.

[TyeeMan]

Well that's the thing, there is no engine light on.

I know the 4L60E is a different tranny, but in a previous truck I had a thing where when driving in OD when the vehicle was warmed up the rpms would occasionally jump a couple hundred and then come back down to where they were. Long story short the problem was a (I hope I get this right) a proportioning valve in the valve body that controls line pressure. The ball in the valve sealed off on the aluminum case, the steel ball eventually peened out the aluminum mating surface, , , when the fluid was cold it worked just fine, I had full line pressure. After the fluid warmed up was when the problem started, the warm fluid would leak past the peened out valve/surface, I'd loose line pressure The dealership pulled th valve body, had a tranny shop ream out and insert a hard steel "sleeve" for that valve, , $400 bucks problem solved.

 

Where I'm going with this is, with my 4L80E it seems like the same thing is happening the difference is that it happens when I'm in 3rd and the TC locks and unlocks. Kind of the same thing as my other truck just in a different gear.

Is it possible the 4l80E has the same problem with the valve controlling line pressure?

 

Thanks again for any input.

[TyeeMan]

Thanks. Yeah it's going in deffinately, , when it comes to trannys, I know how they work but wouldn't even know where to begin working on one. I'd rather leave it to the profissionals to do the work.

I was just trying to get some feeling of what degree of badness I'm looking at when I take it to the dealership.

 

Thanks for your help.

[gmtech4]

get it scanned if the engine light is on and go from there

[gmtech4]

you need a master gauge to the test port and with a print out of pressures ,go from there ,or take it in .

 

in other words ,take it in,

lol