Top Pull Down Motor Not Locking or unlocking

[mytc05]

Hey everyone. The top pull-down motor on my '90 is not working right. It's been like this for a while, and I've just been using the manual lock and unlock in the back trunk instead, but would like to be able to use my motor again. When I push the switch, I can hear something running (which I assume is the motor). So, I now it isn't a power problem. It just doesn't lock down or release the the prongs on the top. Hate to spend the money on a new motor if it doesn't really need it. I had read someone mention about the motor locking in one direction or something, but not sure how to correct this. Anyone ever have a similar problem and know how to fix it?

[Digger914]

This top pull down topic pops up a couple times every year and every question you can think to ask is probably answered somewhere in the old postings, wish these things were easy to search. As they're not; the gear and gear housing are made of plastic and these things do break, they are also available as new parts from GM and the numbers are listed here somewhere. Personally I go to the U-Pull yard and grab the trunk pull down assembly from big GM cars up to the mid to late 90's and get the whole deal for $5 then use what I need.

 

As you can hear the motor run when you hit the switch, odds are your big problem is the plastic gear. Unlatching the top could be a solenoid, but you won't know if you have that problem until you have the top pull down motor working like it should. Next time you have the top out of the way and the hatch open, push the button and look to see if anything moves when you hear the motor run.

[mytc05]

Hey Digger. I looked back on many of the threads some more tonight after you mentioned this. It led me to some possible conclusions, but still a little confused. So, I went out and double checked it. When I press and hold the down side on the "top" rocker switch, it makes noise and continues to do so until I let go of the switch. When I press the up side, nothing happens. So, I guess it is stuck in the down cycle, and unable to complete that, is not allowing it to go back to the up cycle. This leads me to believe that the gear is what is broken, though I couldn't find it to check to see. It stopped working on me a few years ago, and I just haven't gotten around to fixing it until now. Since the motor still seemingly works, I'd like to just try to get a new gear for the motor if that sounds like what is broken.  I found the old thread with the GM part number for a replacement gear. Just want to make sure that's what is probably what's wrong. Is there anything else that this would be that would make it not operate correctly but still make a noise? I appreciate the help on this. 

[Digger914]

Yes, the plastic housing could be broken and that would leave the gear flopping loose, more likely the gear is bad, but you should look before ordering parts. Six nuts and the entire pull down assembly comes off, give the whole thing a good visual inspection.

[mytc05]

Will do. Hopefully it's just that gear. Thanks Digger!

[Reaper1]

Yeah, I agree. The latch isn't moving in and out of the gear box. That latch also activates the limiter switch, which is probably why it doesn't go the other direction. I have personally successfully used the replacement parts that are out there available for the GM pull down motors as well as the Doorman replacement module (includes a new motor and gearbox). When you pull the mechanism out, it will be helpful to mark where the nuts are before you take them loose if you are happy with the way it latches as the whole thing is adjustable vertically, which also changes the latching height for the top pins. There are 5 10mm nuts that hold the assembly to the car, 2 on each side and 1 dead smack in the center near the top. Unplug the electrical first, remove the nuts, remove the assembly. Now you can see how it works. More than likely the latch from the motor is no longer engaged to the latch mechanism and that's due to you using the manual release and the fact that most likely the gearbox internals are probably shot. In order to remove the motor/gearbox you need to remove the limiter switch, then the 3 bolts that hold the motor/gearbox to the frame.

 

I personally cleaned the ever loving crap out of the latches because the old grease had gotten all hard and sticky and full of dirt. I then re-lubricated them with spray lithium grease. I ended up having to replace the whole motor/gearbox because when I replaced only the gearbox then the motor took a dump not too long after that. I believe I still had to take it apart to use the original TC latch as it is slightly different than the GM one because ours has a little tang on it that activates the limiter switch IIRC.

 

Putting it back together is the reverse. Make sure the limiter switch is oriented the correct way and that you have the latch pointed the correct direction. Don't tighten the screws too much as it will either break the gearbox plastic or simply strip it out.

 

Even though you *can* bench test the unit, I like to lay it in the car and hook it back up to the car to test it. I run it up and down many times to make sure things are working freely and nothing is binding. Then, I re-install it back in the car. I like to get the center nut back on and *slighty* snug to hold the unit in whatever height position I put it in, then go to one side and get a nut on that side with the unit positioned where I want it...then the other side. Double check it, tighten the nuts down. Run it a few more times, then give it a true go at latching the top. Clean the pins of the top off with some fine sand paper or Emory cloth. Make sure it pulls the top down and seals it the way it is supposed to, and that you can actually get the pins to catch the first lock. If the mechanism is too low, you won't be able to push hard enough to get it to catch. It should also release both sides at the same time.  Once it's all back together...enjoy!  Only use the manual release if you have to. While it *should* be possible to reset the mechanism using only the switch, I found that in order to make absolutely sure it is reset, that you have to remove the whole thing....again.

 

I hope that helps!

[mytc05]

Thanks Reaper. Probably going to be a few weekends till I can get to it, but the info. you guys provided should make this a lot easier to figure out!

[Guest p38nut]

Not trying to hi-jack this thread but,  I know my mechanism is broken.  Replaced parts 2 years ago because of a broken housing.  This leads to a bad gear.  Same thing this time.  Right now I would like to use the top, by using the hand method of the 3/4" socket wrench.  But it wouldn't latch tightly.  The prongs on the top pop out each time I go to set them into the holes and push down.  Does it take 3 people to get this thing to work?  When I took the mechanism out of the car, minus the motor and such, it will latch up properly.  Could the grommets in the fiberglass hatch be throwing the alignment.  I know that this worked 2 years ago.  Any suggestions would be appreciated.  Thanks.  Mike

[Digger914]

Mike, you have a couple of good questions and first question first;

Yes, if you're attempting to adjust to the hard top, it might just take three people to get this thing to work. The soft top is easier to move in and out of position and that can be done by one, faster with two.

No, the grommets in the hard tonneau are where they are and if your pins aren't lining up with the latch you need to adjust the latch.

Suggestions for manual latching;

Make sure your mechanism is in sync and if I remember correctly directions for this and manual latching are in the owners manual, when I get near my car later this afternoon I will look to make sure.

If your mechanism is in sync and you're still not latching, you're way out of adjustment, or you have more than one broken part.

[Guest p38nut]

To make myself clearer, I'm working with the soft top.  I have removed the motorized mechanism from the rod-latching bracket.  All of it.  I then re-installed the long metal plate with the 5 nuts onto the studs in the trunk.   I'll go through the owners manual again to see if I am missing something in the hex nut mode.

 

Thanks.  Mike

[Reaper1]

So when I first got my TC and I attempted to put the top up the first time I had one heck of a time getting things to latch and stay latched. The problem was twofold. #1...the top itself had been down so long and it appears to be a new installation of the top, but not used much that the material wasn't stretched out enough. I had to leave it up in the sun to let the material relax. #2...the mechanism wasn't adjusted corrected in the vertical direction basically making it almost impossible for the top to be pulled down all the way without the pins coming out.

 

Now, I repaired my motor stuff, so I was already adjusting and synching the mechanism.

 

One tip is that make sure that you not only have released the mechanism, but also got it in the fully "up" position so it can accept the pins.

[mytc05]

Finally got around to fixing this. Turned out it was indeed just the gear that had went bad. Had a few broken teeth on it. Ordered a new one from GM, put it in today, and it works great now. Thanks again for all the help with this guys. That made this whole repair process much easier!

[Vet4TC]

What was the GM part number for the gear?

[mytc05]

14 hours ago, Vet4TC said:

What was the GM part number for the gear?

I don’t remember the part number for sure, but I found it here in the TC forums. I think I just searched for posts about the top pull-down motor and someone has the exact part number stated in one of those posts. Hope that helps!

[Reaper1]

The gear can also be had from Doorman as can the entire assembly and the gearbox.

[Vet4TC]

Found the part number in old post .

20160587



 

Edited August 18, 2018 by Vet4TC
Forgot number (see edit history)