changing u-joints on D30 disco axle

[NCSU90XJ]

I plan on changing out both driver and passenger side axle u-joints on my 90XJ this weekend. The shop I purchased the 5-260X Spicer joints from mentioned placing the vehicle in 4WD prior to starting the work so that when pulling the passenger side axle, the vacuum disco collar will not slide off and screw up the re-assembly. So my question is, is this correct? If the collar resides (when axle is disconnected) on the half shaft (axle between pumpkin and vacuum disconnect), then I should be OK. On the other hand, if it resides on the passenger side axle when disconnected, then I could see this being a problem when pulling this axle as it could slide off. Thanks for any feedback!

 

[CaliXJ]

Just a thought here..... putting it in 4WD without the motor running will only inguage the t case, The axle disco needs vac to inguage = motor running. Total guess on my part though. I don't have a vac disco D30 nor seen one work. :dunno:


I'm still such a noob and really don't know shizzzle

 

[NCSU90XJ]

If needed to be in 4WD, was going to shift into 4HI while engine is running so there is a vacuum available for the vacuum disco motor.

 

[CaliXJ]

Why not just get a Vac disco delete kit and upgrade the shafts to the better axles with 297/760 ujoints though?. I see no point in dealing with the vac disco crap IMO.

 

[8Mud]

Jack up just the side you are going to be changing really high, to keep most of the oil in the differential. I've pulled the short axle out before and gotten it back in again. I've also pulled the shift cover and guided it back in.

Anything is possible but IMO shifting into 4X isn't going to help much.

Pulling the shift motor isn't that big a deal, a little silicon seals it back up again. Just make sure the matting surfaces are clean, clean, clean.

I've had more issues getting the old joints out. I've actually bent the U-joint yoke trying to press them out. I've had to cut them out.

Just be careful of the vacuum lines, that old plastic gets brittle.

 

[8Mud]

Why not just get a Vac disco delete kit and upgrade the shafts to the better axles with 297/760 ujoints though?. I see no point in dealing with the vac disco crap IMO.

I never had any issues with shift motor, I sprayed a little oil into the vacuum openings periodically. It always worked.

 

[NCSU90XJ]

I agree w/ 8Mud. I have never had any real issues w/ the disco motor. I just make sure I shift in/out of 4WD every couple of weeks to keep anything from sticking up.

 

[garr]

I agree w/ 8Mud. I have never had any real issues w/ the disco motor. I just make sure I shift in/out of 4WD every couple of weeks to keep anything from sticking up.

No issues, Then one day you think you are in 4WD & end up stuck!
This just happened to one of my fishing buddies thursday (He called me & I pulled him out of the sand).

We went to the J-Yard, Picked up some late model shafts with the Bigger U-joints; eliminated the disco motor/2 piece shaft + upgraded the U-joints at the same time. Win Win, kill 3 birds with one stone situation! :thumbup:

Late model Dana 30 shafts with good U joints are all over the J-yards & inexpensive.
Good Luck!

 

[Matthew Currie]

I agree w/ 8Mud. I have never had any real issues w/ the disco motor. I just make sure I shift in/out of 4WD every couple of weeks to keep anything from sticking up.

You and 8Mud are lucky, then. When I had an 87 every possible thing went wrong at least once with mine. The Disco motor failed, the tubing connector rotted, the tubing under the battery got a hole eaten through it, the vacuum reservoir cracked, the metal part of the tubing rusted out, and the vacuum switch on the TC failed. All at different times of course. Between that Jeep and my 78 Mercedes (vacuum engine shutoff, heater and AC controls and door, trunk and fuel filler locks), I always knew where my hand vacuum pump was, and was tempted to make a little holster to carry it around with.

 

[souske]

The vac-disco is a relic of a bygone era

 

[8Mud]

You and 8Mud are lucky, then. When I had an 87 every possible thing went wrong at least once with mine. The Disco motor failed, the tubing connector rotted, the tubing under the battery got a hole eaten through it, the vacuum reservoir cracked, the metal part of the tubing rusted out, and the vacuum switch on the TC failed. All at different times of course. Between that Jeep and my 78 Mercedes (vacuum engine shutoff, heater and AC controls and door, trunk and fuel filler locks), I always knew where my hand vacuum pump was, and was tempted to make a little holster to carry it around with.

Some of us service and maintain our XJ's in an acceptable manner:cheers:.

When mine was having vacuum issues it usually made that ratcheting sound when I tired to engage it. The only real issues I ever had with mine was when I tore out all the vacuum lines to the shift motor on a fallen branch. Or like mentioned, when I'd let it set for six months and never used it.

 

[Matthew Currie]

Some of us service and maintain our XJ's in an acceptable manner:cheers:.

When mine was having vacuum issues it usually made that ratcheting sound when I tired to engage it. The only real issues I ever had with mine was when I tore out all the vacuum lines to the shift motor on a fallen branch. Or like mentioned, when I'd let it set for six months and never used it.

Har har. Of course that may be true too. Mine was well into its second hundred thou before I bought it, but I also drove it in Vermont, using 4wd a lot in winter. Most of the time I'd have no warning of failure until going up a hill in 4WD when it would suddenly clunk out near the top as vacuum was insufficient to hold it. Some things, like the switch on the TC, occurred from one day to the next.

I think it is a good idea, if you can, to get a good vacuum pump and test the system with that. Tiny leaks may not make a big difference for a long time, but they are trouble in the making.

 

[garr]

The vac-disco is a relic of a bygone era

And Good riddance to it