A Window Regulator Gear Replacement DIY for an E34 1988-1996 BMW 5 Series

Works For:
1988, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996 BMW 5-Series
5-Series Models includes: 518, 520, 524, 525, 230, 535, 540

Source: BimmerBoard

Not a hard job. A bit of a hack job but better than drilling out rivets and replacing the complete motor when there is nothing wrong with it.

Symptoms are a jammed window but you can still hear ‘clicking’ in the door. And/or there is a terrible ratcheting noise from the door but the window won’t move. And/or you hear the motor run but the window doesn’t move.

I bought the part here and it is of excellent quality and was shipped very fast:
http://stores.ebay.com/Auto-Parts-Professional

To remove the door panel you need a T20 and a Phillips driver. You can find this instruction in this forum or on Bruno’s site.

Once you have the panel off you will need the following tools:
Two number 8 screws and a screwdriver. A standard screwdriver, two pairs of locking plyers, a hammer, a punch, a small socket, some grease, and some form of glue.

Use the standard screwdriver to pop the cover off of the gearbox:

Once the gear is exposed:

Insert two #8 sheet metal screws into two opposing holes thus:

Lock a pair of locking plyers (Vice Grips) on each screw and start rocking the assembly out and off of the shaft. It can take a couple of minutes. Use force but not enough to pull the whole assembly apart.

Once the retainer mount is off you can remove the exposed gear. You nay need to use a locking plyer to pull it out of the housing.

Clean any detritus from inside the housing:

Lubricate the worm gear. I use silicone grease because it is inert to rubber and plastics:

Install the dampers into the gear and then install the retainer/lock ring:

You must assemble the gear first as above because it needs to be oriented correctly over the shaft when you insert it into the housing.
Insert the gear into the housing over the shaft:

Use a small socket over the shaft and tap with a hammer to begin locking it in place:

Once it is retained use the hammer and punch to press it to the correct depth on the shaft:

Use a plastic adhesive or a product like ‘Automotive Goop’ to reinstall the gear box cover: