older axle, "newer" cherokee

[bluejeepkid]

ok, so i have to get a new axle, my dana 35 took a crap on me...i have an 89 4.0 on 33"s and i can get a set of stock axles with 4.10 gears out of a v6 cherokee for free....my question is, the 4wd enhgages by vacuum on mine but not on the other axle....how do i make it work??

 

[Matthew Currie]

On vacuum disconnect models, the transfer case shifts into 4WD and while doing so switches vacuum to the axle to engage it. Later Cherokees of all types dispensed with the vacuum disconnect, and many people prefer this, since the vacuum setup is unreliable and can be expensive to repair. If you like the ratios, I'd say go for it. It will go in and out of 4WD just fine. Your only concern will be that the indicator light will not light unless you replace the vacuum switch in the transfer case with an electric one, or rig the vacuum switch to actuate the light directly (it is presently actuated by vacuum from a third line on the axle disconnect motor).

I'm guessing that your prospective new axles come from a model with full time 4WD, which did not have disconnecting axles. The only thing I'd be cautious about here is if it is one of the earliest V6 models that had constant velocity universals in the axle. Nothing wrong with that per se, but I think they could be expensive to repair, so if you see boots on the universals in the axle, make sure that they're in good shape.

 

[Mr_Random]

On vacuum disconnect models, the transfer case shifts into 4WD and while doing so switches vacuum to the axle to engage it. Later Cherokees of all types dispensed with the vacuum disconnect, and many people prefer this, since the vacuum setup is unreliable and can be expensive to repair. If you like the ratios, I'd say go for it. It will go in and out of 4WD just fine. Your only concern will be that the indicator light will not light unless you replace the vacuum switch in the transfer case with an electric one, or rig the vacuum switch to actuate the light directly (it is presently actuated by vacuum from a third line on the axle disconnect motor).

I'm guessing that your prospective new axles come from a model with full time 4WD, which did not have disconnecting axles. The only thing I'd be cautious about here is if it is one of the earliest V6 models that had constant velocity universals in the axle. Nothing wrong with that per se, but I think they could be expensive to repair, so if you see boots on the universals in the axle, make sure that they're in good shape.

It may not have CV shafts, but if it does, they will be perfectly compatible with normal non-disco shafts (I would suggest pulling the 297[?] shafts from either non-disco ABS pre 96[quite rare], or ANY post 96 shaft). CV shafts aren't necessarily weak, but are finnicky when it comes to dust getting inside their boots/rocks or twigs ripping them off...

 

[bluejeepkid]

say i have the axle in my jeep.... will the vacuum lines under the passenger seat be used? or should i just cap them or what??

 

[Mr_Random]

say i have the axle in my jeep.... will the vacuum lines under the passenger seat be used? or should i just cap them or what??

Cap them and figure out how to get the light to work. check your current axle to find which tube goes from the t-case to the axle, then which one from axle to the switch (pretty sure the switch is in the furthest rearward left corner of the engine compartment). Run one piece directly from the t-case to the switch and I think you're good! If this is wrong... well finding out shouldn't be too hard... I'm just too lazy to go outside and check it out...

 

[scottmcneal]

Do you have the same gears front and rear? If not i would not use the 4x4.

 

[Mr_Random]

Ha said front and rear 4.10's for free... so I assume He'll be getting both...

 

[bluejeepkid]

yes im getting both...............duh

 

[lawsoncl]

Cap them and figure out how to get the light to work. check your current axle to find which tube goes from the t-case to the axle, then which one from axle to the switch (pretty sure the switch is in the furthest rearward left corner of the engine compartment). Run one piece directly from the t-case to the switch and I think you're good! If this is wrong... well finding out shouldn't be too hard... I'm just too lazy to go outside and check it out...

Doesn't the non-disco setup have an electrical switch instead of the vacumn switch in the side of the xfer case. I think you can simply swap that out and do a little extra wiring to it for the light.

 

[Matthew Currie]

Doesn't the non-disco setup have an electrical switch instead of the vacumn switch in the side of the xfer case. I think you can simply swap that out and do a little extra wiring to it for the light.

It should work fine if he wants to buy a switch and find or make the wiring harness plug for it.

On the other hand, I think the vacuum should work. I don't remember colors, but there are four connections to the switch on the TC: one is vacuum from engine, one is vent to atmosphere, and the other two are vacuum to the axle for engaging and disengaging. All you'd need to do, I think, is run the "engage" line to the light switch on the inner fender, and plug the "disengage" line.

 

[bluejeepkid]

well i hope i can get it to work if not ima be bummed

 

[Matthew Currie]

well i hope i can get it to work if not ima be bummed

The TC and axle will work just fine assuming the new axles aren't broken. The worst case scenario here is that you won't have an indicator light, though I'm guessing you'll get that working too.

 

[bluejeepkid]

i think i should be able to get it

 

[bluejeepkid]

anybody know of an actual write up on doing this??

 

[Matthew Currie]

anybody know of an actual write up on doing this??

I don't know of an actual writeup, but here's how I would do it:

1. buy a vacuum gauge if you don't already have one. You ought to have one anyway, because it's a very versatile diagnostic tool that has come into undeserved neglect in recent years.

2. Find the harness with vacuum lines, which goes between engine bay and transfer case. There will be 4 lines.

3. Start the engine.

4. Find the vacuum line that goes from engine to switch. This is the one that has vacuum whenever the engine is running, no matter what. Leave this one alone. Also leave alone the line that ends with a little filter (I think that one is blue)

5. Of the two remaining lines, find the one that has vacuum when engine is running, and the TC is in 2WD. Cap or plug that one.

6. The remaining line should have vacuum only when the TC is in 4WD or neutral. Connect that one directly to the vacuum operated switch on the right inner fender.

If my theory is correct, you'll get a working 4WD light.