4 Speed Stud - Keyed Insert fix

I wouldn't call this fix a fail, but it was probably more time, energy, and money than really needed to be spent. I learned a few things and that's why I blog and share.

This stud is loose and I actually thought it was the source of my leak.


See it wiggle.

I decided to try key locking threaded inserts(keenserts) instead of my usually helical threaded insert (heli-coils). The goal was thinking that a keensert would be easier to seal than a heli-coil. I was also under the impression that keenserts have an OD thread in a standard pitch and can be installed with just a standard bolt. So no special tap or install tool would be needed. Both are true to a degree, but as I found, not completely accurate in this specific case.

I had some trouble finding a small batch of inserts in the size I wanted, but I did find 3/8-16 ID and 9/16-12 OD on ebay.


I had searched for the thin wall version with a 1/2-13 OD, but 9/16-12 is the best I could do on a budget. So I had to check to make sure I had enough case left for the oversized hole. That looked okay.


I need a work stand for my transmission and couldn't find the box I built last time. So I figured out a new way. Luckily, I already had some 3/4 inch plywood ripped to 4 1/8 inch wide and this was a perfect start.


Here are the rough locations of the bottom studs. This was kind of a hack job, but with the holes oversized it fit just fine.


I screwed two of the narrow boards together and then screwed that to a larger board for support.


It was pretty good, but still a bit cantilevered out so I slipped a scrap of plywood under the kicker end and I really liked the set-up.


Thinking this was a through hole, I began to step up the drill sizes and pack the bit with grease so that the chips wouldn't go into the transmission.


See how that holds the chips.


Well I figured out that the hole wasn't through and not the source of my leak, but I had to carry on at this point.


Did I say I wouldn't need a special tap? Well I didn't, but I still had to buy a tap because I didn't have a 9/16-12 and most stores don't carry anything over 1/2. So the no special tap really didn't have any advantage in this situation.


On to the no special install tool part, yes there are special tools but you can get by without them. The OD pitch is a very tight interference fit and using an allen bolt to install it was very tough. The dang thing wanted to cross thread extremely bad. Next time I will drill the hole slightly larger than normal spec for the given thread pitch. I wasted a couple trying to get them in.


Success. I got one in. It was so tight that I don't think the stakes were ever needed.


The hole is good now.


No wiggle and set with loctite.