Question about shift coupler cone set screw

[NONO5.0]

About once every month and a half or so, I have to get back under my car and tighten up the cone set screw (pic below) and I was wondering, is this a common issue? If so, how do you fix it so you don't have to re-tighten it so often?





that goes into:



Thanks for any advice!

[Oh Haha]

Lock-Tite?

I changed my cone style screw to a machine bolt. The bolt head is 13mm so you can get a decent amount of torque on it versus a set screw. While I had the coupler on the bench I used a drill to make a "dish" where the set screw meets the coupler rod. A little red thread locker and it's been just fine.

[Eagledriver]

How do you get to this under your car? Is it a 914? I would try cleaning it real good and using red loctite on it. Make sure you have a good fit with your allen wrench before you use the set screw or get a new one first. If that didn't work you could try to find a longer one or grind a cone onto a bolt of the correct size and use a locking nut to keep it inplace.

-Andy

[Oh Haha]

I missed that. Why do you have to get UNDER the car to get to it? On a 911, it;s right between the rear seats.

[911pcars]

Red Loctite is a more or less permanent type of solution. Requires intense heat to loosen its grip, and since your upholstery and fuel supply line are inches away, I'd avoid the potential hazard. If you must use a lesser sealant, try Blue Loctite.

I suggest drilling the bolt for safety wire, then safety wire it. If you wrap the wire properly, it won't back out.

Sherwood

[911quest]

What I do on the 914's is No loctite but tighten the set screw then put a hose clamp over the screw and the tighten it keeps it from backing out

[NONO5.0]

Originally Posted by Oh Haha

I missed that. Why do you have to get UNDER the car to get to it? On a 911, it;s right between the rear seats.

Actually, I've got a '72 915 tranny installed in my '81 DeLorean pushing a Chevy Vortec 4.3 engine. I found out what the problem was though....I wasn't the one who originally set the cone screw in place in the tranny....I was in the car making sure the linkage was ok...my friend just tightened down the cone screw which was just sitting on the shaft, but not in the hole in the shaft. I was reading other threads and came across that info! I feel really stupid now! I've had the tranny in there for about 3 years now with no issues whatsoever. Its really a good transmission...however, I know I just jinxed myself and it'll grenade later today knowin my luck Thanks to everyone for all the help!

[dvkk]

The screw from a VW Beetle has an 8mm square head that you can really tighten. It also has a hole for some lockwire. That should fix your problem.

[PSJoyce]

The new cone screws that you referenced from Pelican have embedded plastic that acts to lock the screw. I used these last week for an installation of a WEVO PSJ, and they worked well.

Paul

[pmax]

So, the H4 set screw came loose.

Bentley says it's 17 ft lbs, seems like a lot for a 4mm hex. With Locktite, I can see how some needs to be drilled out. I went to half that. Will check again after a few drives.

[Mahler9th]

I have a friend that had his back out in a race at Sears Point. He did not finish the race. Another good friend that has probably 40+ years of experience and co-owns a highly regarded shop suggested Blue Loctite.

[911pcars]

Originally Posted by dvkk

The screw from a VW Beetle has an 8mm square head that you can really tighten. It also has a hole for some lockwire. That should fix your problem.

+1
Suggested. The square head set screw and safety wire avoids having to crank in excessive tightening torque and/or using thread lock compounds that inhibit mechanical disassembly.

[RWebb]

Purple Loctite (low strength) will work great - everybody needs some

[crazy997]

Originally Posted by pmax

So, the H4 set screw came loose.

Bentley says it's 17 ft lbs, seems like a lot for a 4mm hex. With Locktite, I can see how some needs to be drilled out. I went to half that. Will check again after a few drives.

I rounded out my set screw trying to torque it to 17.

[pmax]

Thanks for all the feedback.

I am now more inclined to believe the torque suggested by Bentley is too high and given the more robust and bulkier (heavier) VW version, suspect Porsche optimized this design as they often do. Though rereading the OP's last post, I'm not sure I haven't made the same mistake as he did (13 years ago!) the last time by not having aligned the cone properly. If it still backs out easily, I would lean towards converting to the 8mm VW "upgrade", with apologies to the Porsche overlords ! However that screw appears to have a different cone design so there's that consideration. Sounds like the blue (purple?AC) Locktite suggestion will hold but that can make disassembly more challenging which is something I rather not do.

When it started backing out, I couldn't change gears easily but 2nd worked fine on the streets. Even shifted to 4th by mistake and that "worked" too though lugging the engine some. Another interesting 915 experience !