"U" joint question

[chunk]

So, hi all. This is my first and new to me gw. 1981, gl1100I

This is how it sits today, I've stripped off lots of bling and the running boards. This was given to me by an older guy who couldn't ride any more. It has about 200K on the chassis and 60K on a replacement motor. Belts were changed when the shop did the engine swap.
To this point, I've changed all the fluids including a proper flush and fill on the cooling system. Adjusted valve lash, synced the carbs, and went through the forks with new seals and bushings. It runs fine now, but sometimes i will feel, for a lack of better term, almost a tapping feel through the foot pegs when rolling the throttle on from a low rpm, think slightly lugging for a moment. I'm wondering if this is a "u" joint going bad. No vibration and the "tapping" i feel through the pegs is random not regular. I've looked at the"u" joint and from what i can see it looks okay other than a little grease at the joint. I expected it to be free of grease, being it's sealed. Anyway i thought I'd ask about what it feels like when the joint goes south, if anyone has some experience. Thanks, scott.

[ride dont hide]

You will get an audible chatter (and feel it through the foot pegs) if you are in the wrong gear and the rpms are to low while accelerating. Its like taking off from a stop in second gear. Does that sound like it? This will happen in any gear if it is short shifted. Hope this helps.

[chunk]

Thanks for that, but i know what you mean and it's not really that. It's more like someone is striking the underside of the pegs with an end wrench, sounds silly i know, but that's what i think of when i feel it. It happens so quickly it's hard to diagnose. I'll keep investigating and will appreciate more imput, especially from anyone who has had joint go bad. Thanks, scott.

[RBGERSON]

Slipping splines?? have yoiu checked teh rear spline at the shaft and in the wheel..properly lubed with moly?? and the teeth still "square". rare to have a knuckle fail

[chunk]

I haven't looked at the splines in the rear drive area yet, but will do soon. It came with brand new tires front and rear so i didn't have a need to remove the rear wheel. I guess i do now. I always have hope that the independent shop where this was always serviced would have looked at, and lubed the splines with a tire change, but you never know. Thanks, scott.