Loud thump in reverse ...

[Polaris bryan]

I have crawled under and looked for anything loose or broken don't see anything. The other day I was in low range as usual (just creeping around the woods on ranch) anyway I went to back up and let out on clutch a bit quick , and heard a thump on floor board area like you whacked it with a large rubber mallet..
Stopped and looked but do not see anything odd to me. Drove forward fine shifted up to 5th in low no noise. Stopped and put it in reverse again eased on clutch no noise , let out on clutch quickly and the came again. Anyone ever came across this before ? Maybe point me in right direction to check.
1969 m35a2 white multifuel , 11.00 Michelin x singles on all factory wheels.

 

[Mullaney]

I have crawled under and looked for anything loose or broken don't see anything. The other day I was in low range as usual (just creeping around the woods on ranch) anyway I went to back up and let out on clutch a bit quick , and heard a thump on floor board area like you whacked it with a large rubber mallet..
Stopped and looked but do not see anything odd to me. Drove forward fine shifted up to 5th in low no noise. Stopped and put it in reverse again eased on clutch no noise , let out on clutch quickly and the came again. Anyone ever came across this before ? Maybe point me in right direction to check.
1969 m35a2 white multifuel , 11.00 Michelin x singles on all factory wheels.

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Just fishing here... What about motor mounts - or based on the sound - it is possible that the mounts that hold your transfer case in place are missing or loose? Or by chance have the rubber biscuits that cushion it crumbled?

 

[ToddJK]

That is weird... I've never popped the clutch, always eased it, but I've never heard that from my deuce before. It could be like what Mullaney said, if you popping the clutch quickly, it could be coming up and hitting the floor board due to that rubber biscuit being rotted away. One way to test that is too pop the clutch with the engine off and see if that is repeatable, if so, it's that rubber bumper biscuit thingy, otherwise you'll have to look deeper and maybe be underneath looking while a helper pops that clutch, but be sure it's chocked and brake on for safety reasons.

 

[porkysplace]

Air shift or sprag transfer case ?

 

[Polaris bryan]

Air shift or sprag transfer case ?

Air shift

 

[Polaris bryan]

That is weird... I've never popped the clutch, always eased it, but I've never heard that from my deuce before. It could be like what Mullaney said, if you popping the clutch quickly, it could be coming up and hitting the floor board due to that rubber biscuit being rotted away. One way to test that is too pop the clutch with the engine off and see if that is repeatable, if so, it's that rubber bumper biscuit thingy, otherwise you'll have to look deeper and maybe be underneath looking while a helper pops that clutch, but be sure it's chocked and brake on for safety reasons.

Diddnt just "dump" the clutch , I'm pretty careful to not shock load the drive line after having to replace the torque rods out back (dogbones) but let out rather quickly.

 

[Mullaney]

Diddnt just "dump" the clutch , I'm pretty careful to not shock load the drive line after having to replace the torque rods out back (dogbones) but let out rather quickly.

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With a short pry bar - or maybe a crowbar if you have one handy... Crawl under the truck and see of the back of the transmission or transfer case will lift up off the cross-member that either of them rests on. You don't have to "dump the clutch" for them to move much to create a "thump" sound.

It could even be a motor mount if there were (are) oil leaks that would weaken the rubber supports.

Just looking for the cheap ideas to start with... Your post is in the "Deuce" forum. Can you give us any other details? Year model possibly?

You mentioned clutch meaning that it is a standard transmission? Have you just simply pushed up on the drive shafts to see if the universal joints are possibly tired ? And, maybe work that super short "jack-shaft" between the rear of a manual transmission and the front of the transfer case - with a short prybar? Does it wiggle? It shouldn't...

No insult to your driving skill. Just looking to offer suggestions.

 

[davidb56]

parking brake malfunctioning?

 

[Polaris bryan]

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With a short pry bar - or maybe a crowbar if you have one handy... Crawl under the truck and see of the back of the transmission or transfer case will lift up off the cross-member that either of them rests on. You don't have to "dump the clutch" for them to move much to create a "thump" sound.

It could even be a motor mount if there were (are) oil leaks that would weaken the rubber supports.

Just looking for the cheap ideas to start with... Your post is in the "Deuce" forum. Can you give us any other details? Year model possibly?

You mentioned clutch meaning that it is a standard transmission? Have you just simply pushed up on the drive shafts to see if the universal joints are possibly tired ? And, maybe work that super short "jack-shaft" between the rear of a manual transmission and the front of the transfer case - with a short prybar? Does it wiggle? It shouldn't...

No insult to your driving skill. Just looking to offer suggestions.

As stated in original post 1969 m35a2 white multifuel , 11.00 Michelin x singles on all factory wheels. Universal joints seem good no Play that I can find just greased them today. I have a few pry bars will try that route see what moves around.