Window Motor interchange between 87 and 88-91

[slack]

I couldn't decide if this would fall under electrical or interiors but I see a sticky for window motor related stuff here so I'm going here.

My driver's side window motor 'died' on my 87 and I have my old working ones from my 89 CV still.

I say 'died' because I pulled it out, hooked it up to a battery charger to test it out of the car and it spun fine in both directions. I'm guessing maybe the motor has gotten weak and doesn't have the 'umph' to pull the window up/down anymore though it looked and sounded okay..

Not wanting to throw a potentially bad motor back in and having a known working one on my bench from my 89, I decided to regrease it throw that one in instead. The 89 is the smaller motor housing vs the 87 with the larger motor. I took a quick look and they seemed to have the same mounting spots bolt wise.

After getting it into the door, it turns out that only 2/3 of the bolts line up to the mounting points (The ones at 9 & 3 o'clock). The bolt at 6 o'clock is off by maybe 1/2 an inch? I don't plan on drilling any extra holes in my door as good ol' mother nature is doing its damnedest already with that in rust.

The motor housing and assembly are completely different so there's no way to swap the 89 motor onto the assembly for the 87 so the mounting bolts line up.

The window seems to work fine with just the two bolts but I figured I could use some other opinions on running it without the 3rd bolt in there. The door is still apart for now as I'm also working on some rust treating.

Thanks!

[WagonMan]

Two bolts will work just fine. I have seen where the third hole is slotted to take both motors. Probably a mid year change-over. WagonMan

[friskyfrankie]

Are you sure the problem with the '87 motor was just the gear set being deteriorated? As you probably know, usually the plastic "pucks" break down and swapping them or the entire gear set fixes the issue.

[VicCrownVic]

The infamous gear plugs Frankie mentioned came to my mind as well.
I had a motor that was slow which turned out to be one of the brushes was stuck in a way that it wasn't making contact the way it should.

'89 seems to be a weird year for window motors. My '89 MGM had the large old style motors. My '89 CP has the large old style motors. I know for a fact that I can put a window motor from one of my '91 MGMs in the '89 CP and all 3 bolts line up with both motor types as wagonman suggested about the slotted 3rd hole. I'm not too surprised that '87 does not have that hole slotted.

Swapping motor parts between the large old style and new small style is definitely not possible as you found. But even worse is I have a couple different versions of the old big style that also do not interchange parts. That was neat to find out. Not sure if one is not stock or if there really was more than one variant of the old style big motors. Oddly they all use the same infamous gear pegs though. (Pucks, plugs, pegs take your pick on what they're called LOL.)

[gadget73]

Gear plugs are pretty obvious when they fail, the motor goes but the window doesn't and it makes clunking noises.

I have had the magnet detach and cause the motor to drag badly. That one is pretty obvious though, when you remove the motor from the gearbox it won't spin easily by hand.

Sometimes the end play gets too tight on them and they bind up, especially with replacement gears. Loosening the locknut and backing out the set screw a smidge usually sorts that out. Running the motor its obvious when it gets happy, it will speed up and sound less labored.

I've also just had trash in the gears from the gear plugs turning to dust, and once the center gear broke in the middle where it runs on that shaft and the thing would jam up in the worm because it wasn't staying in the center of the housing.

[friskyfrankie]

I would also suggest spraying a silicon lube, in the window channel, after repairing the window motor. Also lube up the internals in the door (regulator, metal channels, etc.). Works wonders!

[slack]

Thanks for the replies everyone!

Definitely not the gear being stripped. That was the case when I bought the car years ago now that I fixed. (The rear windows actually had the whole gear removed and were just empty casings with motors!). The driver's side motor just didn't have the power to pull the window down and up any more. For the gear of the motor I popped in there, I had a kit laying around with new bushings or whatever you call those three little cylinders and installed them on the gear. Honestly, whatever they supply in that dorman kit I'm pretty sure could snap an arm... with how tight they fit I might as well have just put metal in there...

I currently put it back together with the smaller 89' motor with just the two bolts connected. I might change it out and get the proper motor though as there's a bit of jitter rolling the window up which is maybe due to missing the 3rd mounting point.

While I had the door apart, I hit the inside with rust converter after cleaning it out and then painted it. Then I coated it with some fluid film and lubed all other components. The inside actually wasn't as bad as I remembered, the passenger's side door is next on my list for rust stuff though.