1989 YJ not engaging the front axle

[rholbrook]

My friend just picked up a really low mileage 89 YJ. He went to put it in 4 wheel drive and had nothing. Does this use vacum to engage the hubs and if so, what is the most common issue with this? He claims the front driveline was turning and that the transfer case seems good.

 

[DOSS]

There is a Vacuum actuator on the pass side of the axle (2 pc shaft on that side). Most common is that the Vacuum actuator is disconnected or broken and not actuating.. Most common fix is to clean it and hook vacuum back up.. otherwise you can go 1 pc shaft (seals etc involved) or a Posi Lock cable engagement

 

[STAG]

yeah the passenger side is a 2-piece shaft. I'll tell you a little secret and its what I did on my XJ and it worked great.

-locate the vacuum actuator (can be found about 1 foot inboard from the
passenger side knuckle on the axle tube. it has 4 bolts holding it in.

-undo the four bolts, some gear oil will come out, it's stinky.

-you will see there is a "fork" that slides on a rod, and a slider, that connects the two pieces of the passenger axle.

-look at the fork on the rod, you will see a retaining "E-clip", undo this clip, and you should be able to slide the rod out of the side, then flip the fork 180 degrees so that the bend in the fork is going the opposite direction, and re-insert the rod and the retaining clip.

-now look at the axle again, move the axleshaft engaging "slider" over to the drivers side of the housing, which will engage the 2-piece axleshaft together and will work as one piece.

-now reinstall the vacuum housing cover, with the inverted fork, (the fork should line back up with the slider) and this will give your friend his 4wd back without messing with vacuum actuators anymore.

-don't forget to add more gear oil to compensate for the amount that dripped out.



*this mod is not recommended for D30 axles that have a locker in the front end.

 

[RockMonkey]

In my experience the problem is usually the vacuum switch that's screwed into the transfer case. The driveshaft will spin, but the vacuum switch gets stuck, and doesn't ever send the vacuum to the actuator on the axle. I fabbed up a more reliable system using a bike shifter last time I owned one of these axles (it's been a while).

 

[MikeGyver]

I flipped my actuator and have had no issues since.

 

[Mope]

Does flipping the fork just keep it engaged all the time?

 

[DOSS]

yes

 

[rholbrook]

Thanks for all the suggestions. My TJ's axles are always moving so I don't know why it would hurt to flip the fork to make it engaged all the time. Am I wrong in thinking this way? The front is open and I doubt it will ever get locked.

 

[eatrocks]

There are some thoughts that lockouts and such on the front axel will change miles per gallon. They will. This vacuum dis on the YJ and the XJ are along the same thought. But since everything still turns it’s very little of a change. It also is a weak point and prone to failure. As you pointed out your TJ does not have this. Does it change wear maybe does it fail more often then what it does seams too. Do lockouts change MPG yes enough to offset their cost Maybe?

 

[mesha]

I swapped my shaft on the YJ out for a TJ shaft and never had anymore problems.

 

[MikeGyver]

Does flipping the fork just keep it engaged all the time?

I forgot what all I did but mine is not engaged all the time. The 4x4 dash light is backwards but it never disengages randomly anymore.
I think I just flipped the housing, rotated the diaphragm 180degrees so the vac ports are still aiming up, and flipped the shift fork on its shaft.