Odd thump

[Hasdrubal]

M1009, 4" lift w/blocks on rear. Its a thump that is more felt than heard. Seems to be coming from the rear. Its not the u-joint. Happens when starting from a full stop, not right away on throttle application but after a few feet of travel. Also occurs when coming to a full stop right at the end when truck rocks back. Does not occur on and off throttle while moving. Will have to get underneath and check all bolts for tightness. Thought I would throw this out there in case anyone has run into this symptom before.

 

[doghead]

I think it my be your gov lock differential.

Somewhat "normal" .

 

[tennmogger]

Try greasing the rear driveshaft slipjoint splines and ensuring the joint is not bottoming out. This is not a CUCV specific issue and typically occurs during acceleration and deceleration.

 

[Hasdrubal]

Interesting...that it might be the GOV LOC. Took a CUCV guy for a ride with me, first he didn't notice anything, then stated that it was normal for these trucks. With a 4" lift I'm pretty sure the slip joint can't bottom out.

 

[ZiggyO]

I had a similar symptom in my suburban with an rcd lift kit (spacer blocks between the rear axle and springs)--- it turned out to be the U-bolts not being tight enough which was allowing the axle to shift slightly during hard stops/ hard takeoffs. I confirmed this with chalked index markings on the axle, block, and springs. Tightening the U-bolts up solved the problem and it has not reappeared since........

Z

 

[Grega]

So ZiggyO, so where are you in Nebraska. I live a few miles south of St. Paul

 

[Hasdrubal]

I originally suspected the u-bolts or the leaf spring bushings. I mean, what else can it be back there that attaches the drive train to the truck. Will check the u-bolts for tightness. I asked another CUCV guy up here who has never felt this in one of his many Govloc equipped M1009's. As for greasing the slip joint splines..isn't that completely immersed with transfer-case oil?