Questions About Borg Warner Transfer Case on 1978 Cherokee Chief - JeepForum.com
 
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post #1 of 6 Old 06-03-2020, 06:20 PM Thread Starter
MackReed
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Questions About Borg Warner Transfer Case on 1978 Cherokee Chief

Hey Everyone,

Just picked up a 1978 Cherokee Chief with an Automatic 400, first Jeep ever! Was delivered from out of town and upon driving it realized the 4WD was engaged when I would go around corners. Set the transfer case linkage to 4WD Hi (It was in 4WD Low), shifted into neutral, unlocked the front hubs and rocked it back and forth a little, then went to put it into gear which it wouldn't do. It just hums and sometimes sounds like it's grinding and does not move in forward or reverse.

I got under there and can see that the front driveshaft is rotating when the hubs are unlocked which makes sense because the Borg Warner transfer case is a 4WD all the time. So basically when I am driving it is only with front wheel drive and the rear setup is never engaging. I also notice that the 4WD/ EDrive modulator was removed from the transfer case and the two vacuum lines were capped off with screws just hanging next to the transfer case. So basically the previous owner probably had problems with the EDrive and eliminated it just deciding to not have a fully front and rear locking differential.

Wondering if anyone knows whats wrong with the transfer case that makes only the front driveshaft work correctly? Again, when the hubs are locked which puts the front driveshaft under tension, it will drive. When the hubs are unlocked it just hums. It may still be shifting into gear but the driveshaft isn't engaged in the transfer case so nothing is happening and the hum noise is probably coming from whatever is wrong in the transfer case.

Any thoughts? Thanks in advance!


Last edited by MackReed; 06-03-2020 at 07:34 PM.
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post #2 of 6 Old 06-03-2020, 09:24 PM
jeepdaddy2000
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So, the t case(BW1339) has a Limited Slip differential in the middle of it, which allows for full time operation. The E drive mechanically locks the front and rear driveline through the diff. With the front end unlocked (It isn't supposed to have hubs), the diff simply spins. This is especially bad, as the unit is wearing out the cones.



I'm guessing that the vacuum motor on the t case went bad. Someone moved the engagement fork to lock the LS, thereby giving the rig the ability to move. In order to repair the existing t case, you will have to replace the motor in order to operate the rig on hard dry surfaces. I'm pretty sure vacuum motors are a hard to find item. You may want to post in the CJ section (CJ7's with auto's came with the same t case). Someone may have an extra one lying around.

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post #3 of 6 Old 06-05-2020, 09:47 PM
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Lots of good info here: http://www.jubileejeeps.org/quadratrac/
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post #4 of 6 Old 06-06-2020, 09:05 AM
jeepdaddy2000
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Just reread my post and found it needed to be corrected.



So the front driveline spinning with the hubs disengaged is a good thing, as that tells us the E drive is disengaged. This means you can engage the hubs and operate the rig normally (unless you have a MM part time kit, I recommend dump the hubs and switch back to drive flanges). You still have traction to all four wheels, not front wheel drive, as the t case diff is providing power to both the front and rear drivelines. The downfall to this is if you loose traction to any tire, you may stop moving. This is partially overcome by the use of a limited slip diff in the t case which still biases power to the driveline (tire) with traction.



The downfall is you have no way to engage the E drive, which will be an issue trying to negotiate anything more than ice and packed snow.



That being said, in order for the t case to operate properly, you will still need to replace the vacuum motor.


Sorry for the mis-information.

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post #5 of 6 Old 06-06-2020, 02:45 PM Thread Starter
MackReed
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Quote:
Originally Posted by jeepdaddy2000 View Post
Just reread my post and found it needed to be corrected.



So the front driveline spinning with the hubs disengaged is a good thing, as that tells us the E drive is disengaged. This means you can engage the hubs and operate the rig normally (unless you have a MM part time kit, I recommend dump the hubs and switch back to drive flanges). You still have traction to all four wheels, not front wheel drive, as the t case diff is providing power to both the front and rear drivelines. The downfall to this is if you loose traction to any tire, you may stop moving. This is partially overcome by the use of a limited slip diff in the t case which still biases power to the driveline (tire) with traction.



The downfall is you have no way to engage the E drive, which will be an issue trying to negotiate anything more than ice and packed snow.



That being said, in order for the t case to operate properly, you will still need to replace the vacuum motor.


Sorry for the mis-information.

Thanks for the information! I locked the front hubs again and verified that the rear drive was working by doing a turn on some gravel and I watched the driver side rear tire grabbing during the turn.

So with this model I am fine driving on normal roads in the 4WD? The part time kit would just disengage the front to safe fuel correct? Thanks again!
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post #6 of 6 Old 06-06-2020, 05:08 PM
jeepdaddy2000
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Quote:
So with this model I am fine driving on normal roads in the 4WD? The part time kit would just disengage the front to safe fuel correct? Thanks again!

An aftermarket part time kit, which includes hubs, is installed in the t case, which converts the Quadratrac system to true part time operation. Not sure why your rig has just hubs, since they are useless without the rest of the kit (which you don't seem to have due to the front driveline spinning).


So, you aren't technically in "4WD" with the hubs locked in. With the E drive disengaged, you are actually operating the system as it was originally designed. Think of the Quadratrac system as an AWD (full time) unit that can be locked into 4WD with the E drive engaged.



Your front axle originally came with drive flanges, not locking hubs, which were not selectable.




Sorry about the confusion in my earlier post.

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