94 W900, 3406 Cat, 15spd: Vibration 30-34mph?

Had some time to go to the shop after work and mess with the truck somemore. I won't start full time there until July. We jacked it up. Narrowed it down to somewhere in the drive line or power divider. No tires out of round, everything nice and smooth. We did find one odd thing though. The previous mechanic had welded the rear yoke back on at some point. Using a stick welder and puddled a little thick in a couple places, and had the yoke off balance by a little bit. We both took trips up the road standing on the headache rack watching. Hanging on tightly of course. Didn't get over the suspect speed. Topped at 40. But you can see that the yoke is just a hair off center. Although this has been done for a while now. And the problem has just arose recently. Although I know you can run for a while like that and there not be a problem until something finally gets a little loose. We didn't have a spare laying around. So we'll probably have it sent to be balanced. Seems to be quite a bit of slack in the power divider...although no shavings could be found and everything seems smooth up on blocks and on the road. Except for the vibration. I guess it could be a Ujoint still even though they look and feel fine. There is no slack in any of them. There may be some flattened or bad needle bearings in it and we just haven't gotten slack yet...just the vibration. I wish we had another drive shaft to try out. We have 10 laying around probably but all either do not slip on the right side, are to short, or are solid. lol. Go figure. Will keep you updated. Thanks again.

 

Thanks will do that.

 

good thoughts...it was really welded. we have another w900 setup the same way with an intact driveline and no vibration. I"m going to drop the driveline out of it and put it in the one with the vibration and see if we can narrow it down to the driveline or not. Like the thought of checking the ujoints with one wheel up...that will give you ALOT more leverage to try to see if the ujoints have any slack. Will do that before dropping the other one. Will make sure to get grease from all caps also. They are well greased...but the hands stop when they see one of the caps push out grease...not all four.

 

Got it fixed. Finally slowed down enough we could get it in the shop. Dropped the driveline from an identical W9 that we have and swapped them. Vibration gone. Left that driveline in the truck. Took the suspect and laid it on the shop floor flat. All ujoints in excellent condition. But, where the previous mech had cut and rewelded the rear yoke, it was slightly out of time. You could lay the driveline on level floor across the covers where the bolts go in and get wobble back and forth. The four bolts should be lined up and when you lay the driveline on the floor it shouldn't wobble. The yoke was out of time probably 10-15 degrees.

Anyways, cut the yoke back off and spent about an hour with a tapemeasure and a square and got it back right. Welded her up and she is smooth as silk now. He had done quite a few yokes that way and never had a problem...boss thinks he got in a hurry on this one. I don't think that was a good job to get in a hurry on.