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tfranzone 09-05-2012 05:23 PM

Front End Yoke Extension?
so.. after my 2" BB Daystar lift, i've been experiencing the phantom knocks from under my jeep quite often since... mostly on turning, over bumps, and going from drive to reverse quickly..

I've read multiple threads and checked all the possibilities that different users said bushings, joints, tie rods... and had a few more knowledgable people take a look... everything appears to be in good shape so the assumption of the person who looked at it who has owned lifted XJs said it appears the culprit is ujoint related.. I'm getting some pitch from the stress the 2" lift is putting on.. and I was told that it isnt terrible bc my jeep only has 40K on it.. but its a nice jeep and should be fixed to avoid puking a ujoint over time.

I was told a front end yoke extension in order to lengthen my driveshaft 2" would be the trick...i would not need to drop the transfer case.. just extend the front slip yoke so the ujoints arent pitched... does that sound right? it seems right to me...I have no good knowledge of this kind of stuff.. he wasnt trying to say to have them do it so he wasnt trying to sell me on anything and he seemed to be pretty certain this would be the fix...

can anyone tell me about this?
he said it was relatively inexpensive.. like 80 bucks.. but that seems like a trickier fix than 80 bucks.. help please?

Valpacer 09-05-2012 05:43 PM

Re: Front End Yoke Extension?
A Daystar lift doesnt change the front driveshaft angle at all, the differential doesn't move. Only on a SL does the front diff drop lower.

I think the 4.7 hve a uni in the fonrt of the front drive shaft, and a CV style joint at the xfer case end, which may also be on the way out, but they are very easy to see and feel if they have movement in them.

I would almost guarantee that the front diff isolator bushings are shot, especially the one on top which you cant see. Get the car on a hoist and have someone in the car putting it from revers to drive and have someone under the Jeep watching the front diff to see it moving around.

Even after a SL diff drop the factory front driveshaft is still fine.

tfranzone 09-05-2012 08:40 PM

Re: Front End Yoke Extension?
thanks valpacer... maybe I will bring it in and have them take a look at that isolator bushing... is it an expensive fix? the knocking sounds like a cause for concern and it only started after the daystar lift. Would that isolator bushing be shot from the lift? what exactly causes that? like i said my jeep is fairly young, 40K. and i would also like to get this taken care of so it stays in top shape. thanks.

Valpacer 09-05-2012 09:49 PM

Re: Front End Yoke Extension?
I have done 3 sets of front diff bushes in 100,000 km. (63k miles) If they get used offroad they will kill those bushes regularly. There is a how to on youtube or JF i think, you can do them all in the car, but is easier on the bench. Its only around an hour and a half to drop the front diff out (if you know what you are doing!). Bushes are only around 100 bucks for the set of 3 i think.

Doing the reverse to drive test in the air and seeing the movement is the best way to check, usually the diff will hardly move, but if any of the bushes are gone you will easily notice.

tfranzone 09-06-2012 10:36 AM

Re: Front End Yoke Extension?
Thanks for the help. I will bring it in somewhere and have them put it in the air and take a look at it exactly how you mentioned.

tfranzone 09-10-2012 05:21 PM

Re: Front End Yoke Extension?
just wondering.... would a trac bar or sway bar have anything to do with issues to reduce the stress on parts causing knocking?

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