Transfer case jumps out in reverse

[bcoutdoor]

I have a 1980 BJ 40. Owned it for about 2 months now and still working out the quirks.
We were backing up down a gravel road in 4wheel low and the transfer case kept jumping out into neutral. My buddy had to hold it in place to keep it in.
Doesn’t do this in 2wheel drive. Thanks in advance if you can help.

 

[roscoFJ73]

I would start by checking the T/case shifting mechanism. Make sure nothing is bent or has slop in the connections and joints.

There seems to be 3 different shift mechanisms in the parts manual . Two of them rely on small metal balls with springs that hold them into the correct t/case mode. These are labelled "direct type" and the other is the "magnet type". I couldn't see a magnet in the parts diagram, but I'm guessing one is used to hold it in gear somehow.
You may get some owners in the 40/55 section who are very knowledgeable on the t/cases.
Some pics may help to identify it. They also have some gearbox/t/case info on the aluminium tag on the firewall (on most cruisers)

Is yours a vacuum shift or manual type?

 

[bcoutdoor]

I would start by checking the T/case shifting mechanism. Make sure nothing is bent or has slop in the connections and joints.

There seems to be 3 different shift mechanisms in the parts manual . Two of them rely on small metal balls with springs that hold them into the correct t/case mode. These are labelled "direct type" and the other is the "magnet type". I couldn't see a magnet in the parts diagram, but I'm guessing one is used to hold it in gear somehow.
You may get some owners in the 40/55 section who are very knowledgeable on the t/cases.
Some pics may help to identify it. They also have some gearbox/t/case info on the aluminium tag on the firewall (on most cruisers)

Is yours a vacuum shift or manual type?

Ok, thanks thanks for the advice. I believe it’s manual.

 

[stevebradford]

A bj40 1980 would be manual. I think it would be the split transfer case rather than the one peice case. But either way the place to start is to check the shifter linkage throw. The linkage is threaded and adjustable by lenghting or shortning. There will be a little lever on top of the case. it has three positions high, neutral and low.

This is a split case if yours isent the one peice is similar The lever is circled on top.

Reach up under the truck make sure that lever is on there tight (mine fell off at the worst time) shift the truck into low range and make sure that lever is all the way to the right or left I can't remember. Also make sure your lever isent hitting the body where it comes threw.

If that checks out there is a detent ball and spring here under this plug.

That detent ball holds the shifter fork in high or low. Sometimes that spring isent strong enough to hold the fork in place on a sloppy gear. You can add a shim or stronger spring to get more life out of it.

This was for a fj40 I believe but function is the same. Some reading for fun. T-Case hi/low detent spring

 

[bcoutdoor]

Thanks Steve