Different Diff problem

[ChrisG]

For a couple of weeks my trooper has been making a cluncking noise in the rear and I couldn't trace the problem. It wasn't until I removed all of my extra parts and rear cage to do further troubleshooting that I realized where the problem was. The nut had come off the rear diff mount on the rear diff and the bolt was hanging half out. This raised my concern because my dealer double checks, re-torques and puts his own mark on every bolt on his PVI. Looking at the mounts on the trooper, it appears that they drilled the same hole twice right next to each other elongating the hole. I figure it came from the factory like this because there is the exact same problem on both sides and there is no crushed metal from a sloppy bolt. I've already established with my dealer that it would be cheaper for me that I weld a "washer" (his suggestion) to reinforce this area. I plan to drill the appropriate hole in a steel tab and weld these tabs in shortly to correct this issue. In the mean time I have replaced the bolt with the same grade couse thread M12 (fine threads are hard to come by). There is still movement in my diff though. Should I be increasing the bolt size to take up the play where the bolt goes through the diff? I know a few thousands more I would be able to accept a standard bolt and have no slop whatsoever. Do others have the same movement in this connection and is it enough to raise concern? I am not worried about shearing a bolt or losing another nut but I want to reduce the chance of problems in the future. I figured while some of you have the diffs on the bench you could check and let me know what you think. I appretiate it, thanks.

[Kinarfi]

One of my concerns brought on by something Lenny said is that the threaded part of the bolt is also the support part like the shank. My feeling, developed from when I had my airplane, is that the shank should go all the way through with a washer and nut so the shearing forces are all taken by the shank and not the threads. I have been thinking of looking or longer bolts to make this happen for me, and since there is no warranty and no reason not to, I just may be doing some drilling myself, as you can see by this foto, there is room for a larger hole. The main disadvantage to switching to easily found, easily replaced American Standard Bolts is you may have to use 2 sets of wrenches, metric and standard, WAAAA

It's too bad bolts are sold like AN hardware, for instance, A breakdown of a typical bolt AN number follows:

AN4-8A

* AN means the bolt is manufactured according to Air Force-Navy specs.

* 4 identifies the diameter of the bolt shank in 1/16" increments

* 8 identifies the length of the shank in 1/8" increments

* A means the shank of the bolt is undrilled (no letter here means a drilled shank

and the threaded part is always the same length.

I think the two holes are from the stamping operator not getting the part out of the press and it got double stamped and never rejected.

I think welding on a good thick washer and using longer American Standard Parts is a good way to go. That's my 2 cents worth.

Kinarfi

[FlyCanadianGuy]

One of my concerns brought on by something Lenny said is that the threaded part of the bolt is also the support part like the shank. My feeling, developed from when I had my airplane, is that the shank should go all the way through with a washer and nut so the shearing forces are all taken by the shank and not the threads. I have been thinking of looking or longer bolts to make this happen for me, and since there is no warranty and no reason not to, I just may be doing some drilling myself, as you can see by this foto, there is room for a larger hole. The main disadvantage to switching to easily found, easily replaced American Standard Bolts is you may have to use 2 sets of wrenches, metric and standard, WAAAA

It's too bad bolts are sold like AN hardware, for instance, A breakdown of a typical bolt AN number follows:

AN4-8A

* AN means the bolt is manufactured according to Air Force-Navy specs.

* 4 identifies the diameter of the bolt shank in 1/16" increments

* 8 identifies the length of the shank in 1/8" increments

* A means the shank of the bolt is undrilled (no letter here means a drilled shank

and the threaded part is always the same length.

I think the two holes are from the stamping operator not getting the part out of the press and it got double stamped and never rejected.

I think welding on a good thick washer and using longer American Standard Parts is a good way to go. That's my 2 cents worth.

Kinarfi

Fellow Mechanical Engineer?

[Kinarfi]

Nope, just good with mechanical stuff, electrical stuff, electronic stuff, you know your basic all around genius type person with a very well rounded assortment of jobs and experiences.

Kinarfi