So I believe the 4l60e in the fiancee's 03 Yukon is on it's way out. It has roughly 260K miles on it. I haven't had any trouble out of the trans until now. I started on a 2 hour drive home pulling an empty 15' trailer @ 79mph (cruise on). I believe the 5.3 was turning around 2600rpm (3.73 gear). As I started up a small bridge, the trans attempted to downshift in order to keep me at my set speed. I say attempted, as I didn't feel the downshift, I only heard as saw the rpm jump to 6K. I immediately took the cruise off and everything seemed fine as far as the vehicle still being able to accelerate in OD. From there, I wanted to see how it would act if I requested it to downshift again. I eased into the throttle, and the trans attempted to downshift again, acting as it did the first time, going no where, only turning a ton of rpms. Being that I had at least an hour of driving ahead of me, I quit testing and kept cruising. Engine temperature looked good and no SES lights popped up. I finally came to my exit. Afraid that I wouldn't be able to downshift at all, I manually dropped into 3rd with success, then to 2nd, and all the way into 1st. From there I manually shifted to the next light. At a stop, I placed it back in Drive. Once the light turned, I applied throttle but no movement, just turning rpms. I quickly threw it back in 1st and moved on, having to let off the throttle throughout shifts in order not to turn high rpms. I made it to the house this way and checked the trans oil. It was slightly darker than I would have liked to have seen, with a slight burnt smell. The following day I checked for codes and attempted to see it acted any different now that it cooled down. Results were: still no movement in Drive, only being able to move when shifting manually.
I believe this occurred due to the additional load that was placed on the trans by the trailer, combined with the excessive rpm I was turning for a long duration of time. I have a fairly good size trans cooler, but it doesn't look like it stayed cool enough. I'm now trying to determine what to do next. Do I drain and replace the fluid and filter, hopeful that that takes care of the issue, or is it for sure gone, no need to throw any additional money at it, just needing to replace or rebuild it?

 

too late. find a low mileage junkyard replacement or take a crack at replacing clutches yourself.

 

Don't tell me this! Tell me that it just needs a new filter and fluid!
On a positive note, I should have the s10 rippin up the streets Thursday evening

 

you can waste money and time swapping the fluids and filters if you want. my experience is once 3rd gear slips once, it's down hill from there.

 

Yea, the more I dig, this is what I'm realizing. I just received a 1200 dollar quote from a local reputable builder for removal, rebuild and install. I'm now entertaining the idea to ordering a FLT unit and start throwing some power at the 5.3 (ls6 cam and 243's). I really struggle with spending money just to go back to stock. I'd rather spend a little more and gain something from it...

 

I have a small cam and ls6 springs i'd sell if you're looking to add a little to it. PM me if you're interested.

 

no movement in Drive indicates the forward sprag is gone

 

Where are you located? I'm about to swap out my 60e with less than 15K that has the usual - shift kit / vette servo / and deep Mag-Hytec pan - 3K stall as well. Going to let it go for around $900 but keeping it local most likely - located in NC.

 

Located near Savannah but have already had the trans rebuild and sold the 03 in order to get a 11 Denali. Thanks though!

 

That 6.2 and 6l80 suck, huh? ;-)