warn universal joints

[Dix]

Mehanic Foram

I have a Bush Hog brand front deck mower (ZT22). The universal joints that power the mower deck (two) seem to be wearing out quickly. The first time I noticed they were warn was at around 200 hrs. I had them replaced, and later checked them at around 90 hrs. Again the amount of vibration seemed to indicate that they were warn and needed replaceing. I have been told to try another type of grease & to grease them every day ( the book saies every 50 hrs.) I have also been told that I would must have an alighnment problmen for the joints to ware that fast. Note: after the joints were replaced, there was still a noticable amount of vibration in the drive shaft, although it was less. (the shaft is not bent) I check the vibration by watcing the drive shaft spin and can see the "goast immage". How long should I expect the joints to last (if thats the real problem). Does it sound reasonable that it is an alighment problem? What about ware in the juick connect or the splined shaft?
Thanks,
Dix

[khouse]

Your telescopic may be worn. The yoke bores may be loose. You may have knocked off a balance weight. Take it to a driveshaft rebuilder and they will find the problem.

[Dix]

Khouse - I can't feel any play in the joints when I grab the driveshaft & twist it. When you say the telospic may be worn, do you mean the fit between the male splined shaft & the female drive shaft housing? This unit is still under warrenty and only has between 400 & 500 hrs. total time. What would you expect is an abvrage number of hrs. I should get before having these type troubles? What do you think of the idea of an "alighnment problem" I was told about? I am trying to go forarmed for any runaround treatment I may get.
Thanks

[khouse]

Yes, the male and female sliding part (telescopic). That's what I call it anyway. I would think that thing should go 2k to 3k hours. I assume it was fine when new. If I remember right the driveshaft connects way in the back and is a two piece shaft with a carrier brg. in the center? If so, maybe the carrier bearing is bad? Not the shaft itself. Tell me if I'm mistaken.

[Dix]

Khouse-The drive shaft has a u-joint where it attaches to the deck gear box. It also has one towards the rear past where the male & female shafts unite. Just behind this u-joint is what I call a quick connect (a collar that is spring loaded & has ball bearings inside it). This connects to the PTO shaft. So what I have is a u-joint at each end of the drive shaft with no support in between. What I thought was strange is the amount of play I feel when I grab the drive shaft and yank on it, as if there is too much play where the male & female shafts fit together. Eather that or excessive wear in the quick connect. But that is mearly a guess from me. I have been told that some vibration of the drive shaft is normal because of needed clearences between the male & female sections. Strange, I never notice any vibration of truck or car drive shafts. Your thoughts? I'll ck back tomorrow. Thanks Dix

[khouse]

You shouldn't have any play in the splines. Or at least very little. It sounds like the splines need to be replaced and the whole shaft balanced. This can be done by a pro. Look in your Yellow pages under "drive shafts" and let them do thier thing.

This would tie in to you ghosting effect.