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Reverse braking thump

S

SgtJCJ

NAXJA Forum User
Location
Tacoma, WA
I have searched for a few days without success. I have found some probable issues, but they proved to be not. Here is the issue. When backing up I hit the brake and there is a thump. It ONLY happens when backing. It sounds like it is coming from the right side somewhere. It is quite loud from the cab but not from outside when I have someone else in the drivers seat and I am right next to the jeep.

Things I have found here on the forum and tried.
Front breaks including calipers, pads, abutment clips and rotors,
Control arms, lower and upper,
motor and trans mounts,
u-joints and ball joints,
all spring mounts
shock mounts
steering and track bars and bushings

The reason I am posting here on Mod forum, It has RE 3.5" front, bastard pack rear, unknown adj lower control arms, RE track bar.

Any help would be greatly appreciated.
 
Are you sure you cranked on the LCA bolts?

I know mine did the EXACT same thing...only a loud thump on the right side when braking in reverse.

Either that or could be worn LCA bushings?
 
both me and my dad had this issue and turned out to be lower lca bushings.
 
dgrigorenko said:
both me and my dad had this issue and turned out to be lower lca bushings.
Click to expand...

I will check them again. I know they are good. I tightened them yesterday just to make sure, but, I'll do it again.
 
I would be willing to bet 50 bucks its your LCA bushings... I had the same problema it turned out to be them.

What was happening on mine was :

The force of the spring wanted to push the top of the axle forward which put most of the stress on the back side of the LCA bushing. Which wore out that side of the bushing. When you hit the brakes the whole LCA assembly jumps that gap and slams into the other side. I would suggest poly bushing for the LCAs.

I fixed it by buying the RK 3- link. lol
 
SgtJCJ said:
I will check them again. I know they are good. I tightened them yesterday just to make sure, but, I'll do it again.
Click to expand...

Did you tighten them to spec? I had a similar issue, I knew for a fact it was my LCA's but I didn't realize that I wasnt tightening them enough. IIRC spec is 110lbs.
 
Let me start by saying the LCA are second hand. I don't even know what brand they are. Here is a pic. If someone knows the brand, please tell me.
100_1160.jpg

I have tightened it to spec. And the poly bushings are fine. However, There is about 1/16" gap between the poly bushing and the center metal sleeve. And the center hole through the sleeve is about 1/16" larger than the bolt that goes through it. Anybody know the brand so I can at least make sure that the bushing and sleeve are the right ones that go with this LCA?
 
I have no idea on the brand but I promise that's the problem. Switch those out and it'll go away... I promise. I've got some for sale in fact. :)
 
lowrange2 said:
I have no idea on the brand but I promise that's the problem. Switch those out and it'll go away... I promise. I've got some for sale in fact. :)
Click to expand...

X2, those are probably a custom job as I havent seen a design like that before. But from what you described to us that is your problem.
 
They look like Tera-flex arms to me,I have yet to see any arms that pivot on the threads that REALLY work in the long run! TF arms were known for tearing mounts off(frame and axle side)!
 
Rusty's fixed 30 bucks plus shipping... They need new LCA bushings! lol They use stock rubber bushings or poly bushings (which I suggest). If your LCAs use stock sized bushings then I wouldn't buy any other arms... I would just replace the LCA bushing with a poly.
 
lowrange2 said:
Rusty's fixed 30 bucks plus shipping... They need new LCA bushings! lol They use stock rubber bushings or poly bushings (which I suggest). If your LCAs use stock sized bushings then I wouldn't buy any other arms... I would just replace the LCA bushing with a poly.
Click to expand...
I'm still in the research process. But if I do decide to buy, are the LCAs you have stock length?
 
You all were right. It was the Lower control arms. I finally was ably to get back under there and work on them. I ended up putting the stock ones back in and just shimmed them back to the equivilant length of the after market ones. Thanks for the help.
Question though, Why do people go with adjustable LCAs when going with a 4" or less? The reason I ask is, there is enough adjustment in the lower bracket to adjust for this. And second, the stock I put back on is a much softer ride than the poly ones I just took off.
 
SgtJCJ said:
You all were right. It was the Lower control arms. I finally was ably to get back under there and work on them. I ended up putting the stock ones back in and just shimmed them back to the equivilant length of the after market ones. Thanks for the help.
Question though, Why do people go with adjustable LCAs when going with a 4" or less? The reason I ask is, there is enough adjustment in the lower bracket to adjust for this. And second, the stock I put back on is a much softer ride than the poly ones I just took off.
Click to expand...

when i went with RE SF adjustables, i felt less shake and better control when turning or hitting a bump. the stock arms just flexed too much. i also planned on going up to 4.5"
 
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