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View Full Version : vacuum shift...piece of shift...:)


FJBen
09-11-2007, 10:26 AM
Ok, in the seemingly endless minor issues that are occuring ( my cruiser is pissed) this one has popped up. It won't shift into 4WD(engage the front axle) and then sometimes it will. Then when it's locked in, it won't disengage. Like it is right now.

I pulled the hoses off the actuator and there is vacuum so I'm wondering what can be bound up in there? thoughts?

Uncle Ben
09-11-2007, 10:45 AM
Ok, in the seemingly endless minor issues that are occuring ( my cruiser is pissed) this one has popped up. It won't shift into 4WD(engage the front axle) and then sometimes it will. Then when it's locked in, it won't disengage. Like it is right now.

I pulled the hoses off the actuator and there is vacuum so I'm wondering what can be bound up in there? thoughts?

The vacuum shifter are actually very good IMHO! I totally prefer them to the "passenger kick it out of 4wd sloppy because of 100 pivot point" mechanical linkages. The problem could be one of three things, the lever is gunked up because of badly maintained T-case, the diaphragm is cracked or the most probable cause is the sleeve or splines are buggered up on the front drive assembly.

FJBen
09-11-2007, 11:14 AM
The vacuum shifter are actually very good IMHO! I totally prefer them to the "passenger kick it out of 4wd sloppy because of 100 pivot point" mechanical linkages. The problem could be one of three things, the lever is gunked up because of badly maintained T-case, the diaphragm is cracked or the most probable cause is the sleeve or splines are buggered up on the front drive assembly.

I really like the vacuum shift setup as well, I took the nosecone off to put a new seal on and gasket. It was kinda hard putting the vacuum shift assembly on. I suppose it's highly possible I didn't line up the shift fork correctly? But it did shift a time or two. it just doesn't work smoothly like it used to.

maybe I'll pull it off and verify i did it correctly.

SteveH
09-11-2007, 12:25 PM
Be sure the flip-flop valve (That's the technical term) under the hood is operating smoothly and allowing the vacuum to un-vent out of the other side so that the diaphram can move easily in both directions. It's possible you're seeing vacuum to the diaphram but not letting air pass out of the 'other' side, when engaging/disengaging.

FJBen
09-12-2007, 08:07 AM
checked vacuum, working correctly for both sides. Took it all apart, the fork slides and I can here it changing vacuum. The collar slides easily over the the nosecone and back.

my only thought is maybe i didn't line up the fork on the slot in the collar? It was hard to see looking up in there to check. I guess I could pull it apart again and take the nosecone off to make for sure.

it's frustrating the crap out of me, all the little things that are going wrong right now.

PS: hey uncle ben! you don't by chance have or can make a serial to ALDL cable? I tried making one according to some online directions at some fuel injection places and have failed.

SteveH
09-12-2007, 10:37 AM
Realize that if you're on the gas, you have little or no engine vacuum to work with. So when you used the FD knob, it would likely be a good idea to let off the gas to allow max engine vacuum to work on your shifter. Unlike a brake booster, there is no reservoir of vacuum for the xfer shifter. Having said that, my '65 shifter bolted to an '80 xfer case shifts readily in and out of 4WD under all conditions - I'm surprised at how well it works, given that I didn't rebuild the ancient shifter.

FJBen
09-12-2007, 01:41 PM
Realize that if you're on the gas, you have little or no engine vacuum to work with. So when you used the FD knob, it would likely be a good idea to let off the gas to allow max engine vacuum to work on your shifter. Unlike a brake booster, there is no reservoir of vacuum for the xfer shifter. Having said that, my '65 shifter bolted to an '80 xfer case shifts readily in and out of 4WD under all conditions - I'm surprised at how well it works, given that I didn't rebuild the ancient shifter.

I noticed when I tool it off last night, it moved pretty freely, but then there was a spot that was really hard to move back...i wonder if it's just gunked up and occasionally sticks?

SteveH
09-13-2007, 09:01 AM
Perhaps the rubber diaphram in the shifter unit isn't too pliable any more? Time for a complete rebuild of that unit?