Dorman is the bottom of the barrel. They are a lowest bidder reseller. Use Aisin or OEM.

 

Now that I look on the RockAuto site I see several suppliers including Aisin, but also ACDelco Gold which should be pretty good for $73. No idea where the auto parts guy came up with a price of over $300 for the ACDelco part. Should have gone to RockAuto.

I have some 3-in-one/WD40 RVcare window and track dry lube, I will give that a try. Good suggestion.

 

My suspicion would be that all of the window moving components need to be well cleaned and lubricated. In particular the window channels that the glass slides up and down against and the glass itself needs to be super clean to its edge and lubed (hard if not impossible to clean and lubricate the glass to the edges with the door panel on as you can't get to the front\rear window edges otherwise). Use silicone spray lube. On a related note, the reason your front windows don't have the same issues (or as much of an issue) is because you are likely lowering and raising the front windows much more often, similar to many household windows where the windows easiest to open and close are those you open and close often so in this case the motors are likely all similar in strength, but the rear windows in particular are the hardest to open and close.

 

Dry Lube is ok and best for certain situations, in this case though the silicone spray with a straw into the channels and rubber wipers provides the best and longest effect. For your slow window and even without pulling the door panel, try spraying silicone spray into the tracks and I suspect you will notice the window is not slow anymore. Removing the door panel does allow for you to clean the glass edges and spray more areas, but the tracks themselves are a common sticking point which I spray lube every so often.

 

GM Genuine at Rock Auto is about 2X the ACDelco price. Unless you do a hell of a lot of rear window movement, I'd go for the Delco. Make sure you are getting power to the window motor connection before you buy. I know you will.

 

Guess I should have clarified. I have already replaced the two back window motors (one inoperative and one slow). They both work fine, nice and fast now. Just expecting since I replaced Dorman with Dorman that they could fail again in two years. If they do fail again I will likely go with the ACDelco Gold rather than exercise the Dorman warranty.

 

I haven't had motors go bad but both back regulators had the cable housings go bad at the motor. I replaced one and haven't gotten to the other one yet. I'll see how the Amazon one lasts.