I know there's a lot of metal magicians in here. When I ran into this problem, this was the first place I thought of to seek advice. My "Project Phoenix" '52 F-2 is getting a ZF 5-speed this winter in the course of its resurrection. I tore the transmission that I'm going to use down for a rebuild and all has gone well except for one little detail:

This transmission has an aluminum case with an integral bellhousing. Some knuckle-dragging neanderthal has overtorqued the starter bolts at some point. One of the holes just had the threads pulled out. That one was an easy fix - drilled, tapped, and heli-coiled. The other one is a mess. Said neanderthal broke the bolt off in it and proceeded to drill it out - off center. He just jammed a bolt through from the back side and attached the starter with a nut. I was able to get the remains of the bolt out without causing further damage, but now I have an oval hole with part of the original threads on one side. The ovality of the hole makes it too big to heli-coil as the insert would not contact the enlarged side of the hole - not to mention it would be hell to try to get it drilled out on the center of the original threads now. The only solution I see is to drill it way oversize and tap it, sink in a short bolt with thread locker, and then cut the head off flush with the face of the housing. Basically I want to put a steel plug in in place of the mess. Then I could redrill the hole from scratch in the correct location in the steel plug and tap it. Thoughts or opinions? Whatever I do, there's no room for error. If I screw up, the tranny case is scrap!

 

I would try to drill it out way oversize and buy a threaded bushing to thread in that will hold the bolt as well...You know, like a tube that is threaaded bothinside and out side.

You tap the big hole, screw in the bushing, then screw in the bolt.

Or you could take it to a machine shop, have the hole filled and redrilled/threaded.

 

I would have the hole welded full, pull the helicoil and fill that hole, and then mark, drill, and tap new holes.

 

Something I have done in similar cases is probably not looked favoribly on by many but it has worked every time.

Clean out the hole, put the starter on with the good bolt. Put a piece of soft threaded rod (not grade 8) with the threads greased in the other hole and nut it on both sides (starter side and back of bell). Mix some JB Weld and work it into the missing hole with a tooth pick being sure to fill the voids around the threaded rod. Once it sets, screw the piece of threaded rod out. Drill and put in a heli-coil so you have metal threads again. I have done this several times over the years and it has always worked. If I have any voids around the repaired area after drilling for the heli-coil, I put it in with JB Weld, too.

Permatex also makes a thread repair kit that does this same thing. It sets hard enough that you have to use a tap and clean the threads. Have done this on some big truck repairs and they held fine. Same principle.

Good luck,
SPark

 

First thing that came to mind, ………was an lock-tightened oversize threaded aluminum plug, bushing, or bolt cut off and then re-drilled and tapped correct size?

 

IMO, weld it up first, if that's not possible, try this: http://www.bollhoff-china.com/web/ge..._twinsert.html

Lastly, some type of JB Weld or similar compound. (I've used it to hold aluminum T-case housings together)

 

Another vote to fill with weld. Then redrill and tap and install a heli-coil to prevent it happening again. It may not have been totally the Neanderthal's fault.

Dissimilar metals will cause galvanic corrosion.

 

Always put antiseize on any steel bolt, sparkplug etc that screws into aluminum! I would drill it out as far oversize as possible. thread and install an aluminum bolt with locktite red. once the locktite has set cut and grind off the bolt flush with the case. Drill and tap for the original sized bolt. If there is clearance on the back side you could leave the head on the plug bolt and screw it in from that side (pointing towards the starter) then drill and tap it. The head would prevent the plug from ever backing out since the starter mounting bolt would be pulling it in against the head.

 

I have had good luck using this type of a threaded bushing.
See this link for an example.
http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=68131506
Hope this helps

 

Thanks for all the replies and ideas. While welding the hole up and retapping it would obviously be the best and most logical fix, it is unfortunately not a viable option in this case. There is only one shop around capable of welding aluminum that is willing to do it and they wanted to handle the entire repair for $150. Um, I don't think so. I only paid $75 for the whole transmission in the salvage yard. Not only that, my parts source has good used housings for $175. I'll go get another one with a good housing and start over before I'll pay that. I really want to save this housing if possible because I've already got the bearing preload set. It's a pain in the butt to set and I'd have to start all over with a new housing. I think I'm going to try the JB Weld method first. I'm going to try filling the ovalled side of the hole in and then I'm going to build a drilling jig to redrill the hole on it's original center and put in a heli-coil. If it doesn't work, then at least I haven't really removed much more metal from the hole and I can still try something else. Good or bad, I'll post my results.

 

BACAgrizz - Yeah, after removing the remains of the original bolt, it is clear that galvanic corrosion was the root cause of the problem here. I'll cut the knuckle-dragger some slack for that. He has no one to blame for drilling it out off-center, though! Farmerized and cootie-bobbed for sure!

 

I guess I'm too late but I thought you could use one of these:

 

bushing.jpg

 

That is very true. He is still a knuckledragger. Ignorant is as ignorant does.

By the way, do you know the difference between ignorance and apathy?

I don't know and I don't care!

 

LOL.....I like it!

Bob, that's a great bolt chart. I think I'll print it out and take it over to my local True Value and see if I can ge them to start stocking some of those.

Bobby