241C HELP!

[Swill2]

Hey guys, ive recently finished up a build. ive got about 1500 - 2000 miles on the truck now and just ran into an issue the other day. at 55 mph+ i will get a random, single THUNK every 30 seconds to a minute. I can feel it in the floor shifter and in the seat. Feels like a driveline shock. The curious thing is that i had driven the truck on the highway a few weeks prior with no issues, parked it, and the first time i took it out again, this issue popped up. A little background on the truck/transfer case: it has been solid axle swapped, everything in the drive train is new with high quality parts. Transfer case has been rebuilt with all new wear items including seals, bearings, chain, pump, i changed over to a steel shift fork with new pads, as well as a slip yoke eliminator. At the time of the rebuild all of the shafts, gears, bearing surfaces, planetaries were thoroughly cleaned, and inspected. Possibly related, the rear axle (sterling 10.5) also has all brand new quality internals including ARB locker, Yukon ring and pinion and all timken bearings and seals. im at a little bit of a loss here short of removing and tearing into the transfer case which is a HUGE pain with how tight everything is jammed in there.

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[Schurkey]

the rear axle (sterling 10.5)

Sterling?

Sorry, I can't help on the 30-second THUNK.

 

[DieselTech]

U-joints?

 

[Swill2]

U-joints?

I did do a quick check on the u joints - no binding all tight, thanks for the suggestion though!

 

[Swill2]

1 ton Ford rear axle

Sterling?

Sorry, I can't help on the 30-second THUNK.

 

[Keeper]

Sounds like a bind being released. No insult intended, but since it's newly built... rear diff has proper fluid level and/or friction modifier? ARB locker issue? Also, front driveshaft is not turning while in 2wd, right?

 

[Swill2]

Sounds like a bind being released. No insult intended, but since it's newly built... rear diff has proper fluid level and/or friction modifier? ARB locker issue? Also, front driveshaft is not turning while in 2wd, right?

None taken, thanks for the input. Yes, rear fluid is at the correct level, with the ARB it does not take friction additive (that i'm aware of fully mechanical, no clutches) so just straight gear oil. Haven't had time to pop the cover on the diff to look for any disco parties that i wasn't invited to. Front shaft should not be turning, i did check and make sure my hubs were unlocked.