How can I check for a bent front pinion?

[BAs96XJ]

I have been trying to track down a front driveline vibe for years. After doing all the obvious stuff, rebuilt and rebalanced driveshaft, new ujoints, new yokes I still have the vibe. I have had this vibe since I switched to 4.10s several years ago. I bought the front r&p used so I think I might have gotten shafted with a bent pinion. What is the best way to check it? I am getting real tired of this vibe. I may switch to 4.56s to make it easier to tow my boat with 33s. Anyhow, help would be appreciated.

BA

 

[nate]

If you had a bent pinion, it would have made setting up the gears just about impossible.

 

[BAs96XJ]

Well if that is the case, where do I go from here? I am going to have the shaft checked by another driveline shop for a second opinion. Then what? I am out of ideas.
BA

 

[Wiley Coyote]

I’m thinking bent AXLE shafts. You would have to pull the inner/outer shafts and hub assembly, but it would be pretty easy for a machine shop to check if they were bent. Pulling the front shafts on a Dana 30 is not that bad. It took me about two hours, but most of that time was spent drinking beer with a buddy figuring out exactly how we should go about it.

 

[Beej]

I asked a question on here about used gears some time ago and a common theme in the responses had to do with the considerable noise associated with used gearsets. Since the vibes you describe occurred after changing in used gears, could this be the noise you are hearing/feeling as vibration?

 

[BAs96XJ]

If I take the front DS out it is smooth as a babies but. No vibes at all. So that eliminates the bent axles. I will get a second opinion on the DS and go from there.
Thanks for all the suggestions.
BA

 

[old_man]

If you pull the front DS and the vibes go away, you pretty much have isolated it to the DS. I can't tell you how many out of the box driveshafts I have seen that were not balanced correctly.

Yes, either the front or rear yoke could be bent, but I have never seen it. The other thing to do is to put the rig up on four jack stands, start it, put it in gear and carefully crawl under and watch the DS for wobble. I actually put the tcase in neutral and use a dial indicator on the shaft for reference. You would be surprised what a .020 out of line shaft can do for balance.

 

[IntrepidXJ]

how's the pinion angle and the driveshaft?

 

[BAs96XJ]

Dial indicator on the DS. I will do that tomorrow. I will post the angles for you also. Thanks
BA

 

[xj92]

Put in hubs so it all stops spinning. I'm still trying to find a cost effective way to do this myself, but it's what I'm planning. By hubs, I mean a hub conversion or an axle swap with hubs already on it.

 

[blackdogxj]

if i was you id just go to a DS shop and get the front shaft balanced. ive seen a lot of jeep front driveshaft slipjoints go bad, so that might be your problem.

 

[BAs96XJ]

I have already had it done. New slip joint, new ujoints, new center CV ball on the double cardan and balanced by the shop. Still have the vibe.

BA

 

[MaXJohnson]

so far, you haven't said anything that would eliminate excessive or incorrect u-joint angles as the problem

 

[sidriptide]

so far, you haven't said anything that would eliminate excessive or incorrect u-joint angles as the problem

what, if any, amount of lift do you have installed? lifting messes with D/s angles.. my front vibe went away when i retorqued the t/case front output yoke...

 

[nate]

How is your pinion angle?

Try home balancing the driveshaft using hose clamps.

 

[BAs96XJ]

Been working on some home balancing with hose clamps and bent washers. I found a sweet spot and welded a weight on. The vibes are much better. Still have a very small vibe that is more like a moan. I will use the hose clamp trick again to see if more weight is needed and where. Thanks again for all your help. BTW I have 4 inches of lift with heavily trimmed fenders, 33x10.5s, 4.10, auburn, SYE, custom front and rear bumper by me, custom tube flairs, home built gas tank and oil pan skids.

BA

 

[IntrepidXJ]

BTW I have 4 inches of lift with heavily trimmed fenders, 33x10.5s, 4.10, auburn, SYE, custom front and rear bumper by me, custom tube flairs, home built gas tank and oil pan skids.

That's nice...but tell us about your control arms...as it would be useful in this thread

 

[Digger87xj]

sounds like a pinion angle issue to me...

 

[BAs96XJ]

Stock control arms in stock location. I haven't checked the angles yet but it looks damn near no angle at all. I will check the angles in the morning. I'm at work right now.

BA

 

[BAs96XJ]

Get this, under very close inspection on my DS, I found a trace of a weld. It seems I thew a DS balancing weight at some point. This must have happened after I had it balanced. The shop must not have welded it very good. I will add a new weight and I should be good to go. Seems simple but it has taken me forever to figure this out. I just didn't think it would throw a weight off the DS.

BA