Np 231 tcase noise

[mtbxj87]

I've had a grinding rumbling noise coming from the tcase for a few months now. It does it in 2wd and 4wd. I have the cad axle so front shaft isn't spinning so that rules out chain. It does it at above 30mph while maintaining speed and coasting. Here's what I've done to combat it: overhauled tcase, new bearings seals, new mode shift fork, output shaft bushing. 6-pinion planetary gear and oil pump.
Yj slip yoke and tried angling the axle both ways to rule out drive line. Also t case drop. It's not drive shaft issue. I have recently put in a 8.25 rear still have noise.
I'm kinda lost on what it could be. It's definitely the tcase. I've been in it twice and everything looks great, fluid is always clean and it shifts great.
What am I missing?
Thanks

 

[TravelsWithRalph]

That's a tough one with you already ruling out chain stretch, a) no metal in the fluid, b) no marks visible in the case during overhaul. My 231 was clearly the chain. It sounded like someone shaking a sleigh bell, but holding their hand around it to muffle the ring.

 

[mtbxj87]

I wish it was the chain! I think it could be the mode hub. When im maintaining speed and I let off the throttle then kinda snap it I hear a clunk from the t case that sounds similar to the rumble/ grind. Like too much play between the input gear and mainshaft. Today I disengaged the tcase linkage to verify that its not linkage related. The fluid has always looked great. Im looking around for another tcase.

 

[mtbxj87]

I found a problem! I was getting a clunk/ click when i would rotate the driveshaft back and forth in the tcase. I pulled the speedo gear out and looked in there. The oil pump housing had free play in the case half, this caused the pick up tube to fall off! So I took the back case half off and put a bend in the pick up tube using a tubing bender and pushed a piece of hose over the bend so it would rest against the case and more pressure in to the pump. Put a o ring on either side of the tube flare and made nylon spacers on the pump housing tabs so it cant rotate in the case. Bueno!

 

[1stDeuce]

So you were driving it with the oil pickup not plugged into the pump? If so, you may have done a bit of damage to the bearings or bearing surfaces where of the mainshaft... Time will tell!!

 

[mtbxj87]

Luckly not very far, probably 10 miles. Ive taken a sample from the drain plug since, It looked great.