Shift Diaphagm linkage- fixed

[peteinjp]

Just wanted to post a followup to a post i made a long time ago:

https://forum.ih8mud.com/40-55-series-tech/390194-whats-point-behing-vacuum-activated-tc.html

The deal was that I could not get 4wd. There is nothing- I mean nothing worse than getting stuck in 1" of mud in a 40 series.

The truck is a BJ44 1981. It has a vacuum activated transfer case. I checked for vacuum and I had it on both lines so I assumed incorrectly that the diaphragm was shot. I began to dismantle the unit only to find that both the chassis manuals I have downloaded contained different vacuum units. I'd be interested to know what other truck share this type.

The biggest difference that i can see is that the early one as well as the later one- presumable common on a 60 series- both unbolt from the side of the transfer case. In taking off the 4 bolts the whole unit can be pulled off to the right side of the truck which simultaneously separates the linkage from the shaft that engages the front axle on the transfer case.

Well in my case there is no way to remove the whole unit without taking off a cover and then taking the linkage that connects the shaft driven by the diaphragm and the 2wd/4wd shaft on the transfer case. However that did not prove to be so easy. So I thought I'd post this for any others who may have this setup.

As it turns out the diaphragm was fine. I pulled the tranny cover and took the diaphragm cover off from above- revealing its perfect condition. The issue turned out to be the pin which supports the connecting linkage. Here you can see the cover that has to be removed. It looks to have 4 bolts but there is actually 5. ( sorry for the bad pic!)

 

[peteinjp]

In my case I could not get this cover to budge- not even a little- with all the bolts out. I figured I found my problem as it must be a pin- there is no way a bolt or circlip could be fitted without access to the back and 2 of the 4 bolts that hold the entire unit to the TC can not be removed without first removing this cover- so it must be removable. I hit that little protruding bump in the cover with a torch and rotated it back and forth. It would barely more- so I torched the living daylights out of it and sure enough I got it to rotate and then was able to pull it off. This was after going at it with a 2# hammer and chisel. That thing was on there.

 

[peteinjp]

After the cover is off and I finally wrestled the interim linkage out- which took a lot of work as well- I could remove the 4 mounting bolts and pull the thing out. I should say that the switch has to be disconnected though the vacuum lines are actually better left on until this point- unless your planning on replacing them in which case you should cut them. They get hard and can not be easily compressed. I pulled them off once the unit was free. Here you can see the the problem area:

 

[peteinjp]

So there you have it. I have to say that I think the design is flawed in that there is bound to be condensation in there and rust will form. I didn't check it out but if the fill level of the transfer case is below the level of the breather on this vacuum shift I might consider leaving out the seal on the shaft to allow this area to be filled with lube as well. Of course if I did this I would not be able to drain this area withouth removing the cover. However if there is no water entry I can't see needing to drain it- its not like the oil is getting lots of wear in there. If I were to do a rebuild I would consider this idea. Another consideration that should be taken is that since this has a breather it will take in water in the event of submersion during a crossing- and there is no way to get the water out without taking off this cover. If I ever pull this TC then I'll consider leaving the seal out. Either way I'll be routing the breather to a filter- probably T-ing it to the transfer case and transmission breather. And when i do so I may just fill a little oil in there.

The funny thing is that the guy I bought the BJ from swore that the 4wd worked. But I know that it did not and has not for many many years. In fact I wonder if it has ever been used.

The first thing I did was go down to the river and splash around in the worn out muddy roads with all that 4wd glory! And so now for the first time I feel like I have actually driven this truck- i kinda like it.



(I freakin love it)

Best!

Pete