Thread: Fixing the front window regulator on the P38

P38s have a problem with the front window regulator mounting cracking,



which allows the the rack to be forced outwards near the end of the regulator's travel upward, allowing the teeth on the pinion to wear away the teeth on the rack:




Which necessitates two repairs. The mounting has to be fixed and the rack has to be fixed. You could buy a new one at about three hundred bucks ... and you'd have the problem back some time later, because of the design weakness in the mount.

The traditional repair has been to try to weld the fracture, but this seemed to me to be deferring the problem, because the metal being welded was too thin. So I thought that transferring the stress elsewhere would work OK. I did this by using a bracket I happened to have lying around the shed - I think it originally was from a Jag throttle cable mounting - and using a short piece of pipe to hold down the spindle mount:




I found a part of the mount that was sturdier than where the crack was and riveted the bracket there, using high strength rivets and a backing plate.

The bracket I used is actually too high. You only need one that just clears the spindle mount, and then you can use a shorter piece of pipe to hold the spindle mount down. As it was I had to give it a bit of extra clearance when I fitted it back to the car:



Nothing a ball pein hammer couldn't fix! Using a lower profile bracket would mean you don't have to do this bit.

Next I had to repair the rack itself. First I welded up the broken bit:



Then I ground it down using a 5 inch angle grinder:



Then I had to file the new teeth. I made a paper template by getting a piece of white paper, holding it up to some good teeth and rubbing my by now slightly greasy thumb over it. That gave a good outline which I cut out with scissors and then used as a template for the new teeth.

Filing out the new teeth was easy. A triangle file fits exactly, and its only a matter of careful patience to get the shape.




Then, just reassembly and refitting. Once I had it refitted I noticed that when the window wound up there was a fair bit of flexing in the mount, so I adjusted the stop by undoing the bolt half a turn or so and moving it backwards by about a millimeter:



This meant that there was much less flex when the window came to the up position. The window has worked faultlessly since.

I wonder if it is this excessive flex that is causing the problem in the first place, and if it could be prevented by correctly adjusting the stop?

Willem

Wow you really went to town.

I did this exact same job 3 weeks ago, but I found a new (non genuine) replacement part for $80 from a local LR part supplier.

I drilled out the rivets and when I put the new unit back in I used bolts with Nylon lock nuts.

I do not have access to any welding gear, but I didn't think $80 was too exe.

Dave