86 Jimmy with transfer case issue

[kas11]

Greetings All,

Any ideas why a transfer case would randomly slip into neutral? It occurs predominately at a stop, but has occurred once at low speeds during a right hand turn. Not really sure that has any bearing, but...

I'm not much of a mechanic and have been learning with this project, but I'm now completely stumped. I have adjusted the linkage, which did seem to reduce the frequency, but it still occurs.

I have also noticed a "knock" type vibration, similiar to what I would describe as something catching then releasing. This occurs primarily in reverse with the wheels turned either direction, again, not sure this has any bearing.

Thanks in advance,
Ken

1986 GMC Jimmy
700r4 transmission
not sure on the transfer case np203/np208 maybe?

 

[Goose]

It should be a np208, aluminum case. My manual just talks about jumping out of 4-lo range, not 2-hi. As far as noise, it says low or incorrect lubricant, and specifies Dexron-II tranny fluid.

If the fluid check and linkage adjustment doesn't fix it, it may have internal problems.
There are alot of np208s out there, in my opinion the easy fix for internal problems is to replace it with a salvage yard one.

 

[Goose]

Oh yeah, welcome to the board!

 

[kas11]

Hey thanks for the reply,

The case is aluminum so I'll go with the np208. I couldn't quite tell what the last digit was - but I knew it was either a 3 or 8.

The fluid levels have been checked and are in the normal operating range - sorry, probably should've relayed that up front also.

it's only occurred in 2-Hi so far.

thanks,
Ken

 

[kas11]

Appreciate the welcome...

 

[udy2554]

I've had two 208s that lost either the fork or collar in the shift mechanism. Both times I lost 2wheel drive and the ability shift at all,(stranded). The second time, it actually happened in the tranny shop parking lot on the way to find out why I kept kicking out of 2wd. Be prepared!

 

[pauly383]

I've had two 208s that lost either the fork or collar in the shift mechanism. Both times I lost 2wheel drive and the ability shift at all,(stranded). The second time, it actually happened in the tranny shop parking lot on the way to find out why I kept kicking out of 2wd. Be prepared!

Bingo !! Well documneted on here too . You either get stuck in a single gear , or stuck out of gear . Time to swap it or rebuild it .

When I lost mine I was two miles from home , so I drove slow in 4lo , I had 3.08's and 33's at the time so I could at least do 15-20 mph clip

 

[Mike D]

The knocking sound in reverse may be the right front U joint binding. In forward 4wd the left front tire ahd the right rear tire move the vehicle. In reverse the right front and the left rear get the power. Check out the right front U joint. They have no load on them in forward.

 

[kas11]

"Well documneted on here too"

I searched around and found a couple of references to a fork issue but I wasn't sure if it was the same thing, so I figured I'd ask...guess I've got my answer...

Imagine I can give a rebuild a shot this weekend...worst case, I drop the pieces off monday...:-)

Thanks again

 

[resurrected_jimmy]

I've had two 208s that lost either the fork or collar in the shift mechanism. Both times I lost 2wheel drive and the ability shift at all,(stranded). The second time, it actually happened in the tranny shop parking lot on the way to find out why I kept kicking out of 2wd. Be prepared!

I read through the thread to see if this had been posted yet. I've had it happen on 208's and once on a 241

Rebuilding a 208 is not hard, the shift fork mentioned does not require total tear down, just start at the rear output and work your way forward until you can get the case halves apart.