Tonti drive pinion/coupler wear re-visited

[brider]

Last year I presented the worn pinion splines and coupler from my Cal 2 Auto. That discussion ended with me buying a new fine-spline coupler to reduce the wear-induced lash at the pinion end by 50%; and there were side-discussions about causes and remedies of this common wear:

https://wildguzzi.com/forum/index.php?topic=97853.30

I'd like to discuss a little further the method of welding the coupler to the drive pinion, and also the feasibility of using an industrial epoxy made specifically for this type of spline repair.

1. If tack-welding (I assume using (4) or (3) symmetrical "tack" beads around the coupler/pinion periphery), How is it possible to hold the coupler concentric to the pinion shaft without the first tack drawing it slightly out of concentric alignment? I haven't checked the axial "wiggle" play, but I assume there's SOME. Maybe a clever, big C-clamp clamping the open end of the coupler and the aft-end of the drive housing to inhibit "wiggle"? Maybe any slight mis-alignment will be absorbed at the driveshaft end, slightly accelerating wear on that end (ZERO discernable wear at the driveshaft end now)?

2. With a little research, one can find numerous industrial-strength spline-repair epoxies that apparently are designed for just this type of wear, and lots of testimonials from heavy-equipment and farm operators that have used this type of repair successfully. It is tempting to consider this type of repair because the driveline could be assembled before the epoxy has cured, assuring the driveshaft-side achieved alignment via the assembly process. The BIG downside is the possibility of the epoxy failing at some point without any warning, contaminating the drive box and eventually ruining it.

Let the suggestions and admonishments begin!

[RinkRat II]

   To answer your welding question the, easiest and most ideal way is to chuck it up in a lathe and a live center in your tailstock. Using a dial indicator to check runout while you tack it. If your a decent welder it won't move much as long as you alternate sides as you tack it.  As far as the epoxies go Devcon makes some good stuff in their Industrial line but not cheap.  Good Luck.

       Pau B.

[Chuck in Indiana]

It *will* move when you tack it. Just use your indicator and tap it back to zero with your copper hammer. Tack 180 degrees away. It'll move again, but not as much. Re indicate it, and tack again, 90 degrees away from the first two. Yeah, it'll move a little. Indicate it back to zero and tack the fourth spot. It's pretty much done moving, now..
I have no experience with the spline epoxys, so will leave that subject alone. <shrug>

[brider]

   ...chuck it up in a lathe and a live center in your tailstock.

At first you lost me after "...chuck it up in a lathe...", but this (and Chuck's method) assume the pinion assembly is removed from the rear drive, right?

[RinkRat II]

      Correct. Do you have a good friend who is a machinist or works for a machine shop?  It will save you much aggravation and be done correctly. Any fab shops in your area? Local welding shop?

      Paul B

[brider]

Yes, I know of a very good performance shop with zero glitz and a machinist that knows what he's doing. I'm a bit nervous of forever eliminating any way to re-build my pinion assembly, but how often does anyone need to do that? I imagine after a few thou of trouble-free riding I'll forget about it.

Thanks, I'll abandon the epoxy search, although I think that's a valid idea.

[RinkRat II]

   I would at least go talk to him and explain what it is you've got and are trying to do. He may have some ideas on the subject and steer you in the right direction.

     Paul B

[brider]

When welding the coupler to the pinion, is it a good idea to apply some Moly or other lube to the splines where they will forever be in contact? I can't see a downside to doing it, just wondering if I'm over-thinking this. Many people have reported rusty splines, so I figure if there's an opportunity for the spline interface to rust, this would be a BAD place for it to happen.

[Chuck in Indiana]

That would be an excellent way to contaminate your weld.  Let's face it. They are not going to slide again. Something will break before they rust away..