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Discussion Starter · #1 ·
How should I go about checking if my shift motor is locking my hubs on a stock 88 Wrangler front axle? Will I need to drain fluid? How do I tell if it works? Also, I thought I had hooked up my 4wd right, but I might not have.
Which of the two vacuum lines coming from the vacuum harness(ones that go into the engine compartment) is supposed to have a constant vacuum. There is a blue one with a "valve"(i think) of some sort on it and also a black one. I hooked up the blue one and am getting some vacuum to the axle.
In checking the vacuum at the axle:
1: I get vacuum from the hose on the side of the shift motor when I engage the 4wd.(Green hose)

2: I get vacuum, when looking towards the front of the Jeep, from the right side of the top vacuum plug.(double plug that goes into the top of the shift motor).

3: I get no vacuum to the indicator on the tub, which tells me "4wd" on my dash. Most of the time I get the light no matter what I'm in(2wd or 4wd), when the Jeep is warming up after sitting a few hours.

4: The vacuum source that I am using comes off of the manifold and has five ports for vacuum on it. It is located under the carb and air cleaner.

I want to make sure that I have the vacuum harness hooked up right. So if anyone can take a look at their setup for their 4wd vacuum harness and tell me which color hose gets the vacuum, I will have a few beers and a big ol' strip steak for them./wwwthreads_images/icons/tongue.gif

Please help, I need to go off road and I can't do it in 2wd(safely).
Thanks
Bryan/wwwthreads_images/icons/crazy.gif
 

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Re: Checking a shift motor on front axle?

your light should be accurate. if it's lit, the collar has the shafts locked together. one way to tell would be to lift the passenger front tire off the ground and see if it turns. if it spins without spinning the driveshaft, it's not locking. if it spins the driveshaft, the transfer case is not locked. if the tire does not turn, the axle and transfer case are engaged. you can feel for vacuum on the lines. vacuum applied to the driver's side of the diaphram will slide the collar to the lock position. vacuum applied to the passenger side will unlock it.

79/CJ-7/AMC360/TH400/Q-TRAC/d30/d44/33's/RS9000s/Herculiner/Pro-jection 2D
 

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Discussion Starter · #3 ·
Re: Checking a shift motor on front axle?

There are actually three hoses to the shift motor. One on the pass. side of the ,motor and two on the drivers side. The passenger side one has vacuum when I engage 4wd.(far right hose). In 2wd the one in the middle (it is connected to the other one on drivers side by a two-holed plug) has vacuum. So does that mean that I somehow have the vaccum source hooked to the wrong hose?
Bryan/wwwthreads_images/icons/crazy.gif
 

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Re: Checking a shift motor on front axle?

Dont trust the light, the indicator light is actuated by the shifting forks on the NP231 T case. there is a small switch taht is activated when the forks move into the either one of the 4 wd modes. It does not detect it at the axle. i have removed all of that stuff on my 89 Wrangler, so i dont have anything to reference for propper connections,but my 89 used to indicate 4 WD whenever it felt like it,untill the lamp burned out. Check it physically like the other post suggested then see if you can get the lamp to work when its on then off. You can follow the wires to the T case and remove and clean the sensor also.
Jeff,
89 Wrangler
 

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Discussion Starter · #5 ·
Re: Checking a shift motor on front axle?

I need to find which color hose, blue or black, is supposed to have the vacuum.
Blue has a little disc shaped plastic piece on it about the size of a quarter. the black one is the soft type of vacuum tube.
All of the tubes on the harness are hard plastic, except for the black one that goes somewhere in the engine compartment.
I hope I'm not being to repetative.
I just want some input before I jack it up this weekend to spin the tire.
Thanks
Bryan/wwwthreads_images/icons/crazy.gif
 

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Re: Checking a shift motor on front axle?

Bryan,
The blue tube with the plastic check valve on the end of it is a vent and it shouldn't be connected to anything. The black one to the engine compartment might be the branch to the vacuum/electric switch for the dash 4wd light.

That 5 port harness on your engine block is the Dual Coolant Temperature Override switch and it is supposed to be used for the emissions control circuit, not the 4wd disconnect. You might not be getting vacuum to the axle all the time. Find a vacuum source directly from the intake manifold, like the one the cannister is connected to. The red tube is the supply to the transfer case from the intake manifold.

If you decide to remove the shift motor from the axle, you won't lose the diff fluid. The collar is in a sealed chamber. It will ooze out some old liquid grease, however, and you need to catch that in a container.

Good luck!!/wwwthreads_images/icons/smile.gif
 

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Discussion Starter · #7 ·
Re: Checking a shift motor on front axle?

Thanks,
I have it all hooked up wrong. I have the red going to the firewall indicator, the blue hooked to the emissions, and the black hooked up to something(who knows). I will try it reroute it tomorrow and see. Could I put a tee in the vacuum source to the carb and use that as my constant vacuum source without really screwing up my performance?
Bryan/wwwthreads_images/icons/crazy.gif

BUT, the red seem to attach perfectly to the indicator switch since it has a little rubber boot on the end of it. I could still be wrong though.
 

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Re: Checking a shift motor on front axle?

By and large, carburetor vacuum is not constant; it will fluctuate with throttle position. Try to find a source from the intake manifold directly.
 
G

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Re: Checking a shift motor on front axle?

If you are hooking up a constant vacuum to the shift motor, the shift motor will always be locked. Normally, when you shift to 4WD, the switch in the T-Case routes vacuum to the shift motor. Once the shift motor activates, vacuum comes from the shift motor to the vacuum switch mounted on the firewall, next to the battery. The vacuum switch will then apply a ground to the 4WD indicator, which then will light the bulb. The bulb always will have 12v on one side, waiting on the ground to complete the circuit. Oh, the little plastic valve is a one way valve so that the colored side is pointing away from the shift motor on the vent. Been there... good luck!

Wayfarer
79 CJ7 Golden Eagle, 304, T150, D20
Experience... knowledge gained too late! /wwwthreads_images/icons/laugh.gif
 
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