A while back I posted a question on how best to adjust the door window regulator on my '89 744 because the glass when up had a 1/4" gap at the top-rear vertical edge that allowed an amazing amount of air and wind-noise to blast into the drivers head.

The answer I got was confirmation that this is a reasonable common problem, but that there is no provision built into the regulator system to adjust the tracking of the window.

I've come up with what fixes the problem with what I consider minimal effort and for zero cost.

Basically the problem is that the front regulator arm no longer goes as high as it is supposed to because play develops in the hinge/pivot point, resulting in a condition where the window is slightly tilted down at the front, allowing the top rear to no longer be inside it's felt track (resulting on the aforementioned gap).

One has two choices: Lengthening or altering the shape of the front arm, or shortening the rear arm. I settled on the rear-arm solution because it's quite accessible through the opening in the inside door structure and because shortening an arm is easier then lengthening it.

I cut the arm about 3" from the top (where it is held in the nylon "tuning fork" guide bushing) and raised the front of the glass with one hand, while holding the now severed rear arms together to see how much would need to be removed to get the window level, which in my case was about 1/4" at the rear, and 1/8" (width of the cutting disk) at the front edge, essentially removing a pie-piece shaped piece zero" at the front and 1/4" at the rear (see diagram 1). To get the top of the arm to not run out of room in the tuning fork in the full-up position, it was necessary to not only cut away the pie shape, but also to slightly mis-align/offset the two pieces when welding them together (see diagram 1).I held the two arm pieces manually with a pair of Vise Grips while welding the arm sections together. It is easier to access/weld the sections with the window halfway open.

The window is very stable with the rear arm cut, and will, in fact, operate normally with the rear arm cut/detached.

The result is that the window operates perfectly as-new, sealing well at the top. The front of the glass is still slightly low when opened completely, though this is of zero consequence.

I have posted photos of the revised arm, as well as components involved in retaining the interior door panel. Unlike so many vehicles, the 740 does not use clips that release the inner panel when pried away from the door frame. I am sure there are removal instructions elsewhere on the Brickboard, but basically, the panel comes off by gently lifting after two white nylon clips are withdrawn downward from under the bottom of the panel (they engage the red posts that stay with the door frame), and the rear red door-open light is withdrawn aft. Of course, the locking knob must be unscrewed and lifted off, and the screw (under the plug in the plastic opening knob) and knob are removed, as must be the plastic excutcheon under the lever.

If the post seems worthy, perhaps someone with posting ability would consider replacing the links I posted with actual images?

(Copy and Paste Links)

Diagram 1 Showing Necessary Rear Regulator Arm Modification
http://screencast.com/t/Db5BibC4BBM

Photo of Actual Modified/Welded Rear Regulator Arm (Notice Offset)
http://screencast.com/t/MU1bPAvBSg

Door Panel Retaining Hardware and Knob Screw Access
http://screencast.com/t/QNqilDsdt0r6