Went to pickup my boat at LCM this past week to spend the weekend at Lake Cumberland. My tow vehicle is a 2007 Yukon Denali XL with a 6.2L and 6-speed auto. Never had any trans issues and the truck usually pulls the 4000lbs boat/trailer like it is not even behind it.

On the first day I hit Lee's Ford and got a weird grind noise down the hill for less than 10 seconds (didn't sound like brakes and all 4 corners are brand new). Truck seemed to struggle getting the boat up the ramp, but made it to the top. I don't usually put in on that steep of a ramp; however, I was surprised to see the truck struggle considering the power to weight ratio.

Day two towed the rig over to Grider Hill and started to head down the lodge ramp by mistake. When I went to backup on the hill with the trailer, the trans kept slipping out of gear and I couldn't move it. Just before we stopped to back up I once again heard the grinding noise. Had everything towed to flat ground and I disconnected the boat. With the boat off I was able to drive the Yukon back to Ohio (5 hours) with no issue and no slippage even on some larger grades.

Anyone had a similar issue on one of these trucks? Is this simply a worn transmission, or likely another issue (electronic control, etc.)?

Also, any recommendations for a less steep ramp at Cumberland? Regardless of if I get the truck fixed, I managed to scare the crap out of out my wife so if I want to hit Cumberland again I am definitely going to need a less steep ramp. Thoughts? Thanks.

Conley is the best marina ramp I've used. Burnside island if no marina services are needed.

6L80E trans problems
The 1234/35R clutch drum cracks and can cause slipping. I'd guess that certain torque loads/temp would expand the crack and let it slip at times.
The stator support/pump also have updated sealing rings to help a poor seal/slip/flare problem.
The noise could have been a clutch chatter and/or valve buzz from a pressure instability due to a leak.
There are also valve problems and a few other things.
http://c.ymcdn.com/sites/members.atr...6L50-80-90.pdf
Even if it's something totally different, get the lates trans computer program installed. It helps a lot.

Put in at the damn. Much easier.

Might be a good time to trade it

This...

yup

Thanks everyone, great information. Turns out the truck had a bad MAP sensor and it was freaking out electronics under load. Manifold was dumping the power making it feel like slippage under load. Dodged a big bullet on this and got away with a quick sensor replacement.

I'll definitely check out the dam and Conley for launching going forward. After the last experience it's going to take some convincing to get my wife back on a launch ramp.

I hope the launch was not a deal breaker for your wife. It is a great lake, and water is very clear.

Tell her that her bikini's will be much cleaner there than in a river somewhere! :-)

My wife loves that lake, but nerves/tensions do get high around the ramp. (she drives the truck / trailer and I handle the boat).

As long as you dont get the dreaded P0010 or P0011 code. That code can be worse then the ex.... Man I have heard some horror storys with that. Crossing fingers it dont happen to my 6.2 esky.