Hi there,

Some background: I have a 2011 Ford E250 with a 4×4 conversion. It’s a 4.6L engine mated to a 4R75E transmission and an NP271 transfer case. The transfer case only “jumps” when I’m in reverse, in 4LO or 4HI, on uneven ground and under load—like when I’m trying to get unstuck from mud or a stand. It does not jump on level ground.

Initially I thought the transfer case had too much slop and that the chain might be worn, so I pulled the TC down and inspected the internals. The chain and sprockets look fine. There’s about 1/2 inch of play between forward and reverse rotation only in 4LO or 4HI, but that seems to be within the normal range. The play appears to be coming from the hub drive sprocket (NV25552 F81Z7W060BA – 62) and the clutch gear / mode‑shift component (NV25524 F81Z7C215AA – 61), which have roughly 1/2 inch of clearance between the teeth.







I also have some slight rubbing on the transmission crossmember where the front driveshaft sits, even on level ground. I’m not sure how much worse it gets when the front suspension flexes in certain conditions. I’m wondering if this rubbing could be causing the front driveshaft to bind enough to make the transfer case “jump.” Oddly, though, the jumping only happens in reverse—you’d think the same thing would occur going forward if all other conditions were the same.

I’ve checked all the U‑joints and the center joints on the cardan joint; there’s no binding or slop there either.

Any ideas what might be going on?

Have a look at video IMG_9695 first!

Thank you

 

Both shafts are not being supported and therefore, the chain will be slightly loose, but that picture is way too loose.

Take the chain off and check the links. Push the links towards each other and there should be no play. I bet there is a lot. At a minimum, I would put a chain in it.