On my 86 22 RE 4x4 truck..a new gear on the speedo cable has failed.The latest one worked for two weeks and now works intermittantly.The plastic gear gets chewed up .Guess the fellow putting them in is doing something wrong.It's the right OEM part number.Any opinions?

 

Which end is failing: cluster end or Transfer case drive gear?

 

Not mechanical,but it's the yellow one with the splines

 

I just went through this. One of the needle bearings in my transfer case was gone and chewed up all the gears in the case... The output flange had a lot of wobble and the seal began to leak. I just swapped in another case. When I pulled the bad one apart to switch shift rails (top vs. front) The speed-o gear and the oil gear where pretty much ground down to nothing. They chewed up the tail housing too. All the movement inside of there kept eating the speed-o gears.