Driveline vibration heads up.

[TrailBeast]

Just wanted to get this out there in case someone can use it.
I had a driveline vibration coming in at about 45mph that blurred my mirrors and made my keys rattle in the ignition. (Not fly out bad, but irritating)
I could tell it was the driveline due to the speed of the harmonics, so I called a local shop and asked how much they charge for a driveline balance.
The guy told me $35 if thats all it needed, and $200 if he had to build another one.
The guy I bought it from said he just put new ujoints in it and it didn't have any odd noises like ringing the driveline or clunks when put in gear or shifting from forward to reverse.
The other day I figured I would pull it and give it a good visual inspection, and everything looked straight and solid. (0 play in the ujoints and they were nice and smooth and looked pretty new.)

Well,,,I had a thought.
Maybe the guy that changed them didn't know you are supposed to mark the line and yoke so they end up back in the original orientation.
So I marked the line and the yoke, pulled the ujoint then turned the yoke 180 and reassembled it. (I figured I could put it back the way it was in 20 min. if the vibration was worse) and take it to the balance shop.

Well, whatta ya know?
Vibration was gone.

Someone got the yoke back on at 180 off when they changed the ujoints.:violent1:

When changing ujoints you MUST mark the driveline and yoke and put it back together the same way.

 

[airwoofer]

Didn't know that, thanks. I had new U-joints put in my fish after I bought it cause it had the grease fitting joints and I wanted to eliminate that weak spot. guess they did put it back together the same way cause the previously balanced driveshaft was still balanced as far as I could tell from the seat of my pants.

 

[TrailBeast]

What do you mean by "weak spot" in the greasable ujoints?
Do you mean because of the hole where the zerk goes?

Didn't know that, thanks. I had new U-joints put in my fish after I bought it cause it had the grease fitting joints and I wanted to eliminate that weak spot. guess they did put it back together the same way cause the previously balanced driveshaft was still balanced as far as I could tell from the seat of my pants.

 

[Supershafts]

I have explained that here a few times how shafts are balanced and everything must always be the same as it was or the balance is off, and just changing joints can throw off the balance.

The greasable joints can be weaker than solids because the joint is drilled for the grease cavity thru the cross and between 2 bearing journals, you need a lot of power to break the joint there or you need a shitty suspension set up and no hp to break them.

 

[TrailBeast]

The only thing I could imagine the zerk ujoint might be weaker was the grease passage drilled out of the hub.
Thanks for your answer.

With as many members as thier are here, you could post it every day almost and it would be new to someone.

I have explained that here a few times how shafts are balanced and everything must always be the same as it was or the balance is off, and just changing joints can throw off the balance.

The greasable joints can be weaker than solids because the joint is drilled for the grease cavity thru the cross and between 2 bearing journals, you need a lot of power to break the joint there or you need a shitty suspension set up and no hp to break them.