shift fork bolt stripped

[audi]

As I was reassembling my 915, I noticed that the 3/4 shift fork bolt had stripped.

Seeing what I could of the threads in the bolt hole on the fork, I thought they looked pretty OK (it was the bolt threads that were chewed up). A fresh bolt met a little resistance when I tried to install it, so I carefully put a tap up from the bottom of the bolt hole in the fork to clean it out.

Should I be OK with this fix and a new bolt?

I should be able to get a helicoil in there, which I'm kind of leaning towards doing for peace of mind, just to make sure there's enough material in the bolt hole threads. I'd hate to replace the fork if I can make a good fix.

Any thoughts?

Thanks in advance.

[sc_rufctr]

Hmmmm... I'd get a good second hand one.

Maybe a helicoil would fix it but IMHO it's just not worth the added risk.

[dicklague]

helicoils usually are stronger than the stock situation. I have used them successfully many times. Not familiar with your application.

[john walker's workshop]

replace the fork. you would have to enlarge the unthreaded section too much to install a timesert/helicoil below it. risky.

[audi]

Thanks for the replies.

John, I know what you mean about not wanting to enlarge the unthreaded top portion, I wanted to avoid that as well; what if I drill up from below instead?

It looks to be a pretty short thread run, there appears to be enough material to do this, and I should be able to line up the fork straight on in the drill press to do this pretty accurately.

[john walker's workshop]

where are you at? i probably have a few extra forks.

[audi]

Hi John,

Thanks for the offer, I appreciate it!

I did a little sleuthing around, though...I just took the fork down to the local FLAPS, found a helicoil kit for an 8x1.25 bolt, looked up the appropriate drill bit (21/64) and it's just a light slip fit into the un-threaded portion of the fork.

I've had my heart set on getting this buttoned up for this weekend, and all that's in my way (knock on wood) is this fork, so I think I'm going to go with the helicoil on the fork - use the butt end of the bit to properly line up and position the fork in the drill press vice, then flip the bit and bore the hole.

I appreciate your generosity, John, about the fork offer - if I screw this up (I'll know tonight) I may well take you up on it! As an aside, I'm grateful for your help, through various 915 posts, with going through this 915 in the first place. Between your posts ("can't shift into first" thread, especially) and Pete's wiki article I'm getting more done than I thought I could, and have learned tons in the process.

Long live the second gear synchro!

[audi]

Well, the verdict is in:

Helicoils are not a viable alternative to obtaining a good condition, used shift fork. At least it didn't work for me.

All appeared to go swimmingly at first. Drilled through the top, didn't make the unthreaded part any bigger, so far so good. Tapped the bottom part of the fork for the helicoil, and inserted a short length in through the bottom of the hole, opposite the direction you install the bolt. And I think that's where my problem lay. There may have been a little rough edge or something where the tab got knocked off upon insertion of the helicoil, but whatever it was, it wouldn't let me insert a bolt up the "bottom" of the helicoil. From the same direction the helicoil was installed, no problem. Opposite that, the way the bolt needs to go, it wouldn't go without effort. Not the result I was hoping for.

Realizing at this point that this shift fork was otherwise a goner, I figured what the heck and put a tap in it, feeding it the same direction as the bolt would go. Tap broke off.

Feeling pretty humbled, John, I sent you a PM...

[john walker's workshop]

i'll get one overnighted.

[audi]

John is The Man.

Thanks again!

[callard]

I'm sorry, I cracked up here. Helicoils don't work backward as you found out the hard way. John is the Man!
Chuck

[audi]

Nope, they sure don't work backwards.

I have a long history of finding things out the hard way; oh well, now I know!

[sc_rufctr]

At least you had a go. Good luck for the rest of the rebuild.