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[scrw]

Okay, new DC propshaft now in & getting front end vibes. New pinion, crush sleave & seal also fitted. I have checked the pinion angle & it lines up with the prop. Is this looking like I fooked up the front diff fitting the pinion? Any easy was to check? vibes only happen over 55mph, going to take the prop off now & see if it cures it, thinkig it won't

[scrw]

 

[scrw]

Right, getting no where with this.


Fault is vibrations (seem to be at the front) over 55mph while on the gas, off gas the vibes go. Without the front prop, no vibes.
I have an IRO DC front prop with 3.5" lift on the front.
I was running for 6 months without a front prop, after fitting the prop I had vibes (despite setting the angles correctly on the diff). After some head scratching I thought I had an issue with the front diff. So a tested front axle has been fitted & I left the yoke fitting to a Jeep dealer, still the same problem.
I have just had the front prop inspected & rebalanced, same problem.
Tonight I took off the rear prop to see if I was having an issue with the rear prop (maybe some odd phased balance issue with the front prop) go for a drive and still the same problem.

Before I scrap the jeep anyone got any good ideas? It all points to the front prop but it has been checked out and is okay. Front diff was checked out at a dealers and was okay. Transfer case appears to be working okay. One has given up on the jeep now.

[Bishops Finger]

Have you tried removing the LPG?

[scrw]

 

[JamesH]

OK, back to basics - I assume when you say DC front prop you mean what I found quickly on the IRO site and the same as fitted to most lifted Jeeps, one UJ at pinion yoke and a double cardan joint with two UJs and a ball and socket thingy at the transfer case.

It sounds most likely to be an angle at the diff yoke issue to me if everything else is balanced and has been checked as you say.

I had to mess around with my angle (XJ) to balance vibes from the prop against getting some caster angle for alignment on the front steering. It ended up being a lot of adjusting control arms to find where I could just about get away with no vibes, any more adjustment to reduce vibes made it handle like a shopping trolley.

If you've got the time, adjust it all the way back so the pinion is pointing at the DC joint, take for a drive and be prepared for no return to centre on the steering. hopefully this will eliminate any vibes.

If not, sell for peanuts to a Birty 

[warp]

From what you've said it sounds like the pinion bearing have started to wear

[scrw]

From what you've said it sounds like the pinion bearing have started to wear

How do I prove this either way without pulling the diff apart? I did ask the jeep dealer to check the diff out when they fitted the yoke and they say it was okay. Would be unlikely 2 axles have shot bearings that cause vibrations at the same road speed though.

[warp]

Not really any otherway, what you could do though is make sure the large nut on the outside of the diff in between the UJ and diff case is tight.

Another thought occurred to me is that it could be a imbalance on the prop shaft, as you go faster the prop shaft will vibrate more. I had a look in the FSM and the way they resolve this is by putting some jubilee clips on the prop shaft between the uj and the telescopic joint. Just have to rotate the nut around to see if it makes it better or worse.

Worth a try

[Dave69]

I had a look in the FSM and the way they resolve this is by putting some jubilee clips on the prop shaft between the uj and the telescopic joint. Just have to rotate the nut around to see if it makes it better or worse.

Worth a try

Be carefull on what sized nut(weight) you use for this, i have destroyed the drive line of a vehicle measureing prop out of balance vibration with only an additional 7gms of weight.



check the UJ's on the front prop for movement and smoothness in operation, most likely already checked.
look at the front diff nose alignment with the prop as the same rules apply when aligning the rear. the diff nose uj should be a straight line to the double uj at the transfer box.
this then leads to adjustable control arms to get the correct angles or cut and shut the arms to get the correct length and reweld with bracing

[scrw]

prop is in balance & joint have been checked out. Will have 1 more go at setting the pinion to inline with the prop, then who knows.