I live in the Seattle area and I own a 2011 Sierra 1500 sly with a 5.3l 4x4. It has the 6l80 transmission with 130,000 miles on it. The transmission feels like it is starting to have a difficult time shifting and finding the correct gear. My question is does anyone know of any good transmission rebuilders in this area? It will be for everyday driving.

I’m in the Seattle area and looking to get my transmission rebuilt. Does anyone have any recommendations?

Merged duplicate thread from General GM Chat into this thread. Duplicate post is Post #2.

Please do not start multiple threads for the same issue.

I would look for a shop that is an ATRA member and has good reviews to diagnose it first. Has it had any services (recently)? Has it been through any trauma? Is the check engine light one? Is the fluid in good condition and full? A shop would be able to look at this. We can help you with it as well if you're interested.

I bought the truck used but it looked like, according to carfax, that it was serviced regularly at the dealership. I change the filter once and the transmission fluid twice with a 500 miles between the changes. No codes. No trauma. I’m adventurous enough to try it on my own, but I don’t have the space to do the work.

What did you do to determine it needs a rebuild? Many things can cause shift issues that do not require tearing it down.
What exactly is it doing?

When in third going into fourth at lite RPM’*, there is a sound of metal rubbing on metal. In my head it sounds like that high pitch noise that trains wheels make on the talk but muffled. Another thing is, and I’m not sure if this is normal or not, but when I’m driving and coasting, I’ll push the gas pedal down and it’ll go to about 2000 RPM’*, and then drop drop down to about 1400-1500 and makes a sound of needing to down shift. Again, I’m not sure if that’* common or not with Sierras. I had 1999 f-150 that had only four gears and I think I’m just used to that. Another thing it does is when I get onto the freeway, it’ll stay in a high heat with low RPM’* and when I try to go faster it’ll either just stay in the high gear and slowly build up speed, or jump a couple gears down and be up into the 4-5000 RPM’*. Like it couldn’t down shift one great, it had to go two or more.

Based on that, I think a diagnostic is in order by a reputable shop. It could be that bad, but it could be a bad accelerator position sensor or some other thing like that. Could also be that there is an update available for the PCM that would solve some or all of this. The screeching noise like train wheels is a bad sign though. Since you just bought it, I suspect someone started having problems with it, then poured some magic juice in it to get it to run well enough to sell. Changing fluid would undo some of that.

As a summary: With the shift performance, I wonder what is being commanded, what is actually happening, and why the PCM doesn't notice that bad things are happening. All of these would be easily diagnosed by an experienced transmission tech.

I just looked around out there for a couple of minutes. If I were stuck there with your car and issues and restricted ability to diagnose and repair myself, I'd probably try George'* Transmission, and then if that wouldn't work for some reason I'd try General Transmission next.

Disclaimer: I don't live in that area. I only looked for a few minutes. Ultimate decision is up to you. Actual mileage may vary. Professional driver on a closed course. Past performance doesn't predict future results. Yada. Yada.

I am curious how this turns out!

I'd drop the pan and see if there'* any metal in it and take it from there.