TR4/4A TR4A Overdrive

It's really great now that it's rebuilt--except for one nagging problem.

The pinch bolt on the operating shaft slips every 2 weeks. Is there a trick to this?

I used an Allen screw and a nut shaped so it won't loosen. But it sure must be coming loose.

Maybe it needs to be tighter? Mine only slipped once, just before I installed the SHCS, but I did reef down on it pretty hard. I suppose some low-strength Loctite or a lockwasher between the bolt head & flat washer couldn't hurt, but I don't use anything on mine.

I haven't seen the operating shaft on the bench before but if there is no relief cut out in it perhaps you could solve your problem by drilling a small dimple in the shaft and finding your self a bolt with a pointy head to keep it in place!

The problem with that approach is that the lever position on the shaft is a fairly critical adjustment. Really tough to get the dimple in just the right place. On top of that, the lever is just folded sheet metal, not really thick enough to take threads. The other end of it curls into a 'J' shape around the shaft of the operating solenoid.

I did toy with the idea of making a new lever in two pieces, so part of it could be pinned or otherwise positively located to the shaft, and a screw between them to allow fine adjustment. I might still do that if I run out of better things to do. But for now, I'm happy with what I have:

Experienced the same problem when I installed my OD. The clamp might be slipping even though you tightened it aggressively. Over the years the clamp gets deformed and bottom and top half touch before a tight clamping action is made. Are the tabs on the clamp making contact with each other?

You can make the shaft larger or make the clamp smaller.

Two approaches, 1. wrap some aluminum tape, or a strip of beer can around the shaft then reinstall ....making the shaft larger.

Better, use a grinder to take off some material between the ears that the bolt passes through...this will allow for more "travel" and make the clamp smaller

Let us know what works

I think you guys are right. I just don't have it tight enough. I thought I had a setup like Randall shows, but my fabricated nut isn't nearly as stout, and I do believe the ears of my clamp could be a problem. Off it comes again. Thanks.

FWIW, TRF has new levers on sale for $17 (instead of the usual $20). P/N 502568

My "nut" is probably much heavier than it had to be, but I knew the steel I used (an old broken lathe bit shank) wasn't very hard and wanted to be sure it wouldn't strip. Here's another view, showing the tab that fits into the lever.