Like others before me, my driveshaft/pinon shaft coupler didn't get lubed adequately and chewed up itself and the pinion shaft splines too. Replacing the final drive and and coupler is pricey even with used parts. Has anyone had any success or has attempted to operate a bike after carefully welding a bead along the inner coupler/pinion shaft circumference to make that a solid unit? It would mean not having to use the coupler external circlip any more and making the driveshaft/coupler part the "movable" side instead of the downstream coupler/pinion shaft side. The driveshaft/coupler portion on my unit is almost like new and it would seem a fairly easy, inexpensive way to remedy the situation. Does anyone see any reasons it wouldn't work?

I don't think it's a good idea. It has something to do with allowing flexing when going over bumps and such.

I think that lancer is right. It is a slip joint.

Yep,I agree with lancer and niterider.
If you do that I bet you'll destroy the Universal.

Yeah, it's a slip joint, but the way he's seeming to explain it, it's gonna slip on the front side of the coupler instead and be permanent to the rear drive unit.
With the torque that's there though, I'd make sure it's a really good weld, which may be a little tough to get, depending on the material of the parts.

I can get two pieces of metal welded together, but I don't have much knowledge in welding properly.
But it does (IMO) sound like it could work.

The other end is not designed to slip back and forth. It is in a fixed permanent splined connection. It is like a car drive line that has a slip joint for when the drive line, like shortens and lengthens for the uneven road.

The coupler is held onto the shaft with a snap ring.... ( sliding on the final drive ) if you remove the snap ring and weld the coupler to the final drive then it will slide at the drive shaft side.. I think that is how he is thinking.... and if you put the spring back in also it should keep the drive shaft in the same place it has always been..... interesting

I can't see it because I have not as yet checked my splines for lube. Very likely, once I open it up I will understand what he means.

I like it! This is a simple and elegant solution, provided it works. I haven't examined the parts in question to see if the forward joint can slip, but I can't imagine why it wouldn't.

Please try it and report back.

The forward joint really doesn't slip tha much which is why it only takes a good spray of the lithium grease. The other part of the driveshaft to consider is the Universal joint and how it sits in relationship to the swingarm.
Tolerances here are a bit touchy. I know when I put my driveshaft back in and didn't have the swingarm tightened down correctly, the rear wheel wouldn't spin freely. I'd hate to see someone go out for a test drive and find out that 4th or 5th gear is where the tolerance is met and the wheel locks up.

Just something else to consider.

I noticed that my shaft splines were worn more than the coupler so... How about having a machine shop filling in the shaft splines with weld and cutting new splines to match the worn coupler? Do they mill or grind the hardened shaft material? I too believe the link must remain a slip joint to compensate for the movement of the swing arm. My shaft was dry and I'm riding on luck now.

I noticed that my shaft splines were worn more than the coupler so... How about having a machine shop filling in the shaft splines with weld and cutting new splines to match the worn coupler? Do they mill or grind the hardened shaft material? I too believe the link must remain a slip joint to compensate for the movement of the swing arm. My shaft was dry and I'm riding on luck now.

I'd guess (and that's all it is, a guess) that they roll the splines on the shaft.
That'd be the quickest way to do it, and would harden the splines in the process (and it's cheaper to make that way)

It'll still slip, just on the opposite side that it is now (or was).

THE COUPLER IS RELATIVELY CHEEP (AND SOFTER THAN THE SHAFT) IT IS DESIGNED TO WARE OUT INSTEAD OF THE SHAFT, SO YOU 'SHOULD' ONLY HAVE TO REPLACE IT NOT THE SHAFT(WELL THATS THE THEORY ANYWAY). I WOULD TRY REPLACING THIS FIRST AND SEE IF IT GIVES YOU ENOUGH DRIVE TO GET YOU BACK ON THE ROAD. BUT ON THE WELDING SIDE i WOULD WORRY ABOUT WEEKENING THE DRIVE BOX SHAFT WHEN WELDING IT,BUT IF IT WAS PRE HEATED THEN ALOWED TO COOL SLOWLY THIS CAN BE AVOIDED,BUT YOU WOULD PROBABLY DESTROY YOUR OIL SEAL AT THE SAME TIME.BUT IF YOU HALF FILL YOUR SWING ARM TUBE WITH GREASE IT WON'T MATTER! ALSO I SUGEST THE CLIP BE REMOVED AND THE SPRING REPLACED SO THE FRONT END STAYES FIRM AGAINST THE BEVEL BOX SPLINE AND THE MID SPLINE CAN SLIDE. ON MY HARDTAIL I EXPERIMENTED WITH SHAFTS AS I EXTENDED THE BACK END 5" THE SHAFT HAD TO BE 5" LONGER i EVEN HAD ONE PROFESIONALY LENGTHENED(SNAPED) FOR THE PAST 17YEARS IT HAS RUN ON ONE STANDARD SHAFT WITH TWO COUPLERS WELDED ON EATHER END OF A MACHINED THICK WALL TUBE, FITTED THE SAME AS A STD. COUPLER WOULD BE. SHE HAS BEEN WHEEL SPUN DOWN SANTAPOD DRAG STRIP QUITE A FEW TIMES SINCE THEN WITH NO TROUBLES.
GOOD LUCK.
P.S. IF IT DOES'T WORK YOU WOULD HAVE HAD TO REPLACE THOSE PARTS ANY WAY, GO FOR IT.

I checked the slip joint (splines) on my bike. Every thing is good and well lubed. The design works great the way it was made and no need to modify it.
The problem is that some got past the assembler and did not get lubed. My opinion.