2500 Sierra 6.0l Hard! Shifting

[2500sierra]

Truck info: 2000 Sierra 2500 4X4 4l80E and 4.10 gears. 265 75 16 tires about a 31 inch tire

 

Just got the truck about two weeks ago, when first started up from cold as long as i don't get on the gas too much i can go forever without hard shifts as long as i dont stay in OD too long. After being on the highway in OD for 7-15mins almost always shifts hard from that point on, after it starts shifting hard all the time i can turn off the truck for minimum of 10mins and it will completely cycle through this again. Its gettin kinda annoying and its probably not good on the rear end, u joints or anything behind the tranny.

 

My diagnosis: What i think might be wrong from reading on here and expierence. Is that my converter clutch is shot (i think this because i dont notice it locking up, and when brakes are applied while also on the gas i dont notice a sudden RPM spike) so as i read if the transmission senses your lockup not working or slipping it will tell the EPC soleniod to send MAX line pressure to the components, but i also know more line pressure=clutch plates engaging quicker therefore HARD! shifts.

 

I dont know too much about this so any info or suggestions on it are greatly appreciated. Sorry for the lengthy post, Thanks.

[superjim]

Pull the codes...see what codes are set, and report back.

That will point towards what is causing the problem.

[couch]

Pull the codes...see what codes are set, and report back.

That will point towards what is causing the problem.

 

Just had similar problem - dash light indicator for gear would not light up - caused by a broken wire which triggered a gear selector switch code (I think) wich in turn caused the transmission (Allison) to build more pressure resulting in a noticble hard shift.

The wire harness (2) had to be replaced - parts were cheaper than the diagnosis.

[silveradobobby]

The 4l80's had issue with trashing the convertors. How many miles? Any filter or fuild changes?

[Ranger]

Pull the codes...see what codes are set, and report back.

That will point towards what is causing the problem.

 

Just had similar problem - dash light indicator for gear would not light up - caused by a broken wire which triggered a gear selector switch code (I think) wich in turn caused the transmission (Allison) to build more pressure resulting in a noticble hard shift.

The wire harness (2) had to be replaced - parts were cheaper than the diagnosis.

 

 

He has a 6.0 though, gas motor...Which is mated to a 4L80E, not the Allison.