So recently in the past month or so i noticed that if i hit the brakes while going slowly (<5 mph) in reverse my jeep makes a jerking/play sound from underneath and I thought it was one of my lcas. I asked my friend who's also a mechanic to take a look while i made the sound and he said that my whole axle's pinion was moving out of place when i would hit the brakes. My lcas didn't move and are solid. My lcas are RE superflex with great bushings but my ucas are my 25 yr old factory ones with the old bushings. Is it possibly that the bushings are going bad on them and just need to be replaced or is there something else I may be overlooking? My jeep is an 88' a 3.5" lift and 31s with a HP30 and an aw4 transmission and a np242 transfercase if anyone was wondering.

 

What does he mean
"the pinion was moving out of place" ?

Thats very general!

 

I mean the top of the axle is moving so the angle of the pinion is moving, it's hard to explain at least for me. The pumpkin's angle shifts as thought there is some play somewhere so it's not solid

 

So no one?

 

Well I would think step 1 is to wiggle around your control arms.
Shouldnt be really any play to speak of in those.

Ball joints maybe?

 

If your pinion angle changes when you brake it would be control arm related, if i were you id look the upper bushings over

 

I have the same symptoms and it is, indeed, the UCA axle-side bushings. OEM Part# 52088214 or NAPA part# 267-1450

If you re-do the check (rolling in reverse then applying the brakes) but have your friend watch the UCAs you can see the UCA axle mount pitch back and forth as you apply/release the brakes.

 

I will, i'm going to tighten everything tomorrow as i was going to do it today but other things got in the way. But thanks for the info i'll make it a summer project

 

Not sure tightening will help. If the rubber in the bushing is shot tightening the bolt only makes the UCA clamp harder onto the bushing sleeve but the sleeve will still be able to move independently of the outer bushing shell (and, therefore, independently of the axle).

The only thing you can do at this point is replace the bushings.

To further complicate matters, you will see that the replacement bushings are actually a poor fit. The inner sleeve has an ID of 12 mm however the bolt specified and used by the factory is a 10mm x 75mm bolt. There are little tabs inside the sleeve that are supposed to centre the 10mm bolt but there is still a great deal of play between the bolt and the bushing sleeve.

I've checked on other forums and it seems that the best solution is to get UCA axle-side bushings for a WJ (1999-2004) Grand Cherokee as the sleeve's ID is 10mm. OEM part number is 52088214. They are available from Quadratec

 

I know that tightening won't help much if at all but still would be good to check, as for the bolt size bleepinjeep on youtube made a how to video on replacing the bushings but used a RE superride bushing part number RE3784 instead and on their website it's a 10mm bolt size and is easier to install/replace yet longer lasting than the factory bushing and still the same price so i'll probably go that route

 

Does this same poor UCA busing / bolt fitment also apply to the LCA or for that matter any other CA bushings other than the UCA axle side bushings?

....

 

I have an 01 with a 4.5in lift and I have the same thing, the whole pumpkin shifting on braking in reverse. Did you solve the problem. My bushings look good but maybe it's the disparity in the bushing size vs the bolt size. Any suggestions would be great. Thanks.

 

took it to the auto hobby shop on base today, looks like it's the lower control arm bushings, the whole arm/axle moves about a quarter inch when braking in reverse, any suggestions on bushings, should I go with the BDS or does anyone know anything about the bolt/bushing size difference?

 

my xj used to do it. after swapping all of my control arm bushings it went away. until they wore out and it came back.....damn rough country bushings