strange "bump" when decelerating quickly

[stampy]

Ok I have this problem on my m1009 that I had since I bought it, I already searched and found nothing. If I pull up to a stop sign and decelerate quickly there is a noticable "bump". I have new brakes all around and that didn't fix it, new shocks too, as well as a new to me driveshaft. If I approach the stop sign slow enough there is no "bump". It's annoying but I wanted to make sure it wasn't going to cause me trouble down the road. any ideas?

 

[MDSA]

Don't know if this will help, but I had a similar strange noise in my M37. Mine was a rattle. It developed after I had done some PM about 2 months ago. Took it for a drive, and it rattles!? Sometimes I heard it, sometimes I didn't. I tried to figure out what I had done when I changed oil, greased, etc, but couldn't find anything loose. Took me about 3 weeks to remember that I had put a can of brake fluid in the glove box. It was rolling around. No more rattle.

 

[BIG_RED]

I just started noticing something like that on my M1009 too.. It sounds almost like there might be movement in the calipers, so when they stop being dragged by the rotors (the truck stops), they move back to where they usually sit. I have given everything a wiggle and it all seems solid.

 

[tigger]

Check motor mounts! had similar thing and it was broken motor mount!

 

[stampy]

I will do that! Thanks! I know it isn't the junk in the truck as I removed everything from it one time just to be sure. I haven't checked the motor mounts. Is there an easy way to replace them? I chained up my Mercedes 300sd's motor and lifted (gently) with a forklift to replace the motor mounts on it without having to unbolt anything on the motor but I have never done a CUCV.

 

[BA232]

I have the same thing on my m1008, kind of a dull thud and only at higher speeds. I was thinking it was something in the drive line, I'll be checking my motor/trans mounts.

 

[jaymcb]

When I had the civvy version of the 1009 back in the early 90's, that thump was a worn motor mount on mine.....

and my wallet went thump every time I had to fill it up

 

[mikes47jeep]

are you sure the spare tire isnt moving around?

 

[stampy]

Yes checked the tire Thanks! I actually feel the bump I thought maybe the rear axle was moving slightly. I hope it is the motor mounts!

 

[M813A1]

Have you check the spring shackles the bushing may be worn and need to be replaced or grease in some way !!

 

[stampy]

No not yet. I will do that. I did check the spring to axle attachment. If it's not the motor mounts looks like it may be spring bushings. I hadn't even thought of that thanks!

 

[Pawnshop]

Check your transmission fluid. I had a leaky line on my M1009 and sometimes when the fluid was low and I would rapidly lift off the throttle the tranny would go into a neutral state for a moment, then give a noticeable "bump" when it re-engaged, sometimes after I came to a full stop. I am referring to a felt "bump" not an audible one.

 

[stampy]

Ok thanks...lots to do tomorrow! It has been normal, but I haven't checked it in a few weeks. It's possible, but I haven't noticed any "slop" in the drivetrain. It seems to be tight. I may have to mount a video camera (one of those reverse cameras) underneath to see if anything is moving around when I come to a stop if it is not any of the above stuff. Oh and I have both a felt and audible bump.

 

[cpf240]

While you are under there checking the motor mounts, be sure to check the trans mount! Third point of contact and all that...

 

[stampy]

Thanks will do!

 

[Goose2448]

I had a similar thing on my civy C20, and came to the conclusion it was the rear drums engaging. Only did it when I hit the brakes. I never did figure out how to fix it. My best guess was that the proportioning valve was sticking, or it had to do with the load level brake system. Never sounded too bad when I had a good load on. Just food for thought.

 

[O.D. Fever]

Hello Stampy, also check the tranny and case mounts, push up and down on the driveshafts at trans and case, also look for oil leaks at the seals, could be bad bushings for the shafts. Or it could be nuts and bolts rolling around in your head..

 

[moody]

I'm just getting educated in the CUCV world, but this complaint is a common one for owners of full size Broncos. The fix for Broncos is to lube the slip joint in the rear driveshaft. Although I've never seen a M1009 rear driveshaft, I imagine it's also a DC with a splined slip joint since both vehicles deal with a short wheelbase and a relatively steep rear driveline.

Anyway, there's one more thing to consider while your underneath checking bushings and mounts and what-not.

Good luck.

 

[Grega]

Someone here awhile back had your same problem, turned out it was the transmission mount. Also if you changed your driveshaft or other componet a while ago, recheck the bolts, something may have come loose.

 

[edpdx]

Stampy, when you figure this one out, please post the fix. I am having the same issue. It seems that when I let off the accelerator at anything over a moderate speed, I hear and feel a bump that feels like the rear axle or u-joint at the rear driveline. I don't know enough (yet) about rear suspensions to know what to look for; but I'll have a look at the topics that have been covered here.

What is axle wrap- is this possibly the start of this condition?