sclarkfam

Hello, newbie hear.

2006 G3500 6.0L with 4L80E transmission and 69K miles. Check engine light came on during interstate driving. DTC P0894 code: TCC slippage detected. I also noted an abnormal ryhthmic roaring sound that begins around 25 mph and gets louder until 45mph. Sound may continue beyond 45mph, but road and engine noise may be masking. I drained and flushed the transmission as well as changed the filter. Reset the code and drove on the interstate. Check engine light returned and I noticed hard shifting from 1st to 2nd and 3rd. Hard shifting goes away after recyling the ignition key, but that seems a normal function of resetting the computer. I then added some Lucas transmission treatment and quickly noticed that the previous rhythmic roaring sound went away, however the check engine light returned during interstate driving as well as the hard shifting. In reviewing the alldatadiy.com diagnostics, I read where if slippage occurs in 3rd, it is isolated to the torque converter, but if slippage occurs only in 4th, it can be either the torque converter or 4th gear clutch band. On a whim, I drove the interstate in 3rd gear and NO check engine light came on and the shifts from 1st thru 3rd were smooth as normal. Any thoughts on what the problem is?
Thanks in advance,
sclarkfam

EinST

Welcome to the forum. It sounds like you're on the right track on the 4th gear clutch pack. The hard shifting is the TCM commanding maximum line pressure once the DTC is set.

sclarkfam

Thanks for the insight. Took another 400 mile trip on the interstate today and left the tranny in 3rd. Check engine light came on about 30 min into the trip--no other abnormal indications. Haven't pulled the code yet (need to get a code scanner and stop bothering autozone). Unlike previous times (always in 4th) in which the hard shifting occurred when accelerating from 1st to 2nd and 3rd after the check engine light flagged, when I exited the interstate this time and cycled through the gears, the transmission shifted smooth as normal. Quite confusing at this point. Looks like a trip to the transmission shop next weekend.

sclarkfam

After further driving in 3rd gear, a new code p0741 flagged which once again indicated torque converter slipping. Changed out the torque converter and problem fixed. Just like new again.

EinST

Ouch, that must've been a lot of work. Thanks for the update.

tlstickel

I am having the same problem. At highway speeds it shifts down to 3rd and then hard shifts from 1st to 2nd until I turn off the engine and turn it back on, everything returns to normal, only that it downshifts again at highway speeds again. The code I'm getting indicates transmission component slipping. After a lot of research, I decided to replace the torque converter. This improved it some in that it takes longer for the failure to occur, but I still have the same problem. I've replaced all electronic shifter parts in the pan plus the speed sensors on the outside of the case. Lastly, I replaced the torque converter. (6 hour job). Can anybody tell me if I need to look at the valve body or the 4th gear clutch band?

gsferraro

Hello,
Usually with converter codes, you may want to look at the pump area, you may have a problem with the o ring on the input shaft, could be a worn pump bushings, or even a worn pump pocket will limit converter charge oil. Gary

tlstickel

Thanks Gary. Since I have to pull the trans again to work on the pump, I think I'll just go through the whole thing. At least I have a lot of the parts already new. With 216K miles, an easy fix was more hopeful than realistic.

gsferraro

Your welcome, pay close attention to all the bushings, the 4l80e transmissions love to wear out the bushings. What year is your truck?

tlstickel

2000 c3500