No reverse occasionally (07 GMC Yukon Denali)

[jonathan_furman]

I have had the truck for about 1 year now and it has 148,000 miles on it, when we tow our small trailer (4,500 LBS) and utility trailer (1200 LBS) the truck will lose reverse. sometimes it will engage but most of the time it will not. it happens sometime when I'm not towing as well.

Truck will:
Act feel like it goes into reverse
Rev up and (some time s move)
Rev up and not move at all
All FWD gears work fine

I have a B&M trans cooler I added to the stock cooler setup.
Trans temp doesn't go above 140 normally.
I haven't towed with the new cooler.

What are some things that might be wrong and can I fix it my self.

 

[Warriorpluto]

Time to rip out the transmission and get rid of all the AWD crap

 

[lawfarm]

I have had the truck for about 1 year now and it has 148,000 miles on it, when we tow our small trailer (4,500 LBS) and utility trailer (1200 LBS) the truck will lose reverse. sometimes it will engage but most of the time it will not. it happens sometime when I'm not towing as well.

Truck will:
Act feel like it goes into reverse
Rev up and (some time s move)
Rev up and not move at all
All FWD gears work fine

I have a B&M trans cooler I added to the stock cooler setup.
Trans temp doesn't go above 140 normally.
I haven't towed with the new cooler.

What are some things that might be wrong and can I fix it my self.

You've checked trans fluid level and the color/smell of the fluid?

 

[67RS427]

You don't need to rip out the transmission to fix this issue... I actually have the same problem right now with the 2007 Yukon Denali I just picked up. It hesitates to go into reverse sometimes. Sometimes its a few seconds (5 or so) and I guess the guy I got it from said it's worse in the summer when it's hot or under a heavy load.

The actual issue is a cracked reverse piston usually. It'll crack right around where the pin is pressed into the piston. So fluid bleeds out and takes time for it to fill back up when engaged in reverse. It's usually not enough pressure drop to cause slipping in forward gears, just reverse. Lucky for you the transmission does not need to be removed for this to be fixed. Your mechanic can drop the pan and valve body and unbolt the reverse servo housing and remove and replace the piston. It's really not a hard procedure. Again, I have the same issue but I am choosing to pull the transmission and rebuild since I am rebuilding my 6.2L as well.

Good luck! It should only cost a few hundred, not much more...

 

[jonathan_furman]

You don't need to rip out the transmission to fix this issue... I actually have the same problem right now with the 2007 Yukon Denali I just picked up. It hesitates to go into reverse sometimes. Sometimes its a few seconds (5 or so) and I guess the guy I got it from said it's worse in the summer when it's hot or under a heavy load.

The actual issue is a cracked reverse piston usually. It'll crack right around where the pin is pressed into the piston. So fluid bleeds out and takes time for it to fill back up when engaged in reverse. It's usually not enough pressure drop to cause slipping in forward gears, just reverse. Lucky for you the transmission does not need to be removed for this to be fixed. Your mechanic can drop the pan and valve body and unbolt the reverse servo housing and remove and replace the piston. It's really not a hard procedure. Again, I have the same issue but I am choosing to pull the transmission and rebuild since I am rebuilding my 6.2L as well.

Good luck! It should only cost a few hundred, not much more...

yeah I was thinking the same thing as you. I asked a few guys who know the 6l80E in the Pontiac G8 groups and they said it might be the check ball feature. I was quoted $700 to do the job from a local shop but that s replacing the balls/ fluid/ filter/ gasket/ and all servos. I wish I could do it my self but transmissions are hard to find parts for and they can do it faster than me ( 2 kids/ project race car/ and rebuilding my bathroom) thanks a lot on confirming my suspicions.

 

[jonathan_furman]

You've checked trans fluid level and the color/smell of the fluid?

yeah fluid is okay and smells good a tiny burnt but not that bad

 

[Warriorpluto]

Thanks for the information. I'll keep the pin thing in mind if my truck starts to do it

 

[jonathan_furman]

so I took it to GM and they said 3rd, 5th, and rev were all slipping, So I'm getting a new trans tomorrow.

 

[67RS427]

so I took it to GM and they said 3rd, 5th, and rev were all slipping, So I'm getting a new trans tomorrow.

Probably a cracked 1-2-3-4 and 3-5-Reverse Clutch Housing. I just bought a new one for my rebuild. Very common failure point in these transmissions... New shell was only $170, crazy they don't rebuild and just install new transmissions instead...

 

[jonathan_furman]

Probably a cracked 1-2-3-4 and 3-5-Reverse Clutch Housing. I just bought a new one for my rebuild. Very common failure point in these transmissions... New shell was only $170, crazy they don't rebuild and just install new transmissions instead...

It was faster for GM to replace the TRANS, and it was only about 500 more to get a new one vice a rebuild...