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Discussion Starter · #1 ·
I have an 89 Jeep Wrangler and have recently discovered the vac lines coming from the front differential are broken. I have since pieced those things back together and still can't tell if four wheel drive is engaging. The light on the dash doesn't come on anymore(imagine that) but the front driveshaft is turning. I don't have a vacume pump to test the pressure coming out of the shifter motor to see if its bad at the front axle. Is there any other way to tell if this thing is engaging and pulling or just spinning the driveshaft and not engaging?

 

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First question...
Did you hook up all of the lines as I had described before?
If so....
Jack up one front tire. Run the engine and engage the 4wd from the shifter on the floor. Turn off the engine!! Spin the wheel that is elevated. If the driveshaft spins while doing this, you have 4wd. Make sure you can feel vacuum coming from the plugs that connect to the shift motor on your front axle. No vacuum, go back to my reply on your previous post to check if you hooked it up right.
Good luck.
Bryan/wwwthreads_images/icons/crazy.gif
88 YJ
 

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Pull off the vacume actuated shift motor on the passenger side front axle. While in neutral on the tranny shifter have someone engage the T case into 4 H and see if the actuator fork engages. Even though the front axle is turning you may not be in 4WD. With the stock open diff, if the actuator fork doesnt engage the axle coupler between the passenger side inner and outer axle the free side(unengaged passenger side) will spin with no output to either of the wheels. If the fork is engaging you should be good to go.
Jeff
89 Wrangler

 
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Discussion Starter · #4 ·
yea you guys are right on i'm sure/wwwthreads_images/icons/smile.gif
i know when i'm in 4wd just by feel.
how can you not know when in 4wd!
i am storing this knowledge with the vacuum lines if and when mine f$$$# up!
/wwwthreads_images/icons/tongue.gif
steve
 

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In reply to:

Is there any other way to tell if this thing is engaging?
Easy. First you need to remove the doors, and enlist a helper. Next, find a large mudhole and drive into the middle of it. Put it in 4WD. Lean out the door for a better look, and turn the steering wheel to the right so you're looking right down the wheel centerline. Now press the accelerator pedal to the floor. If your helper laughs hysterically, your 4WD is working./wwwthreads_images/icons/laugh.gif

-Dana

This administration is headed by someone who redefines what the meaning of "is", is, and what the meaning of "alone" is. Do you think they care AT ALL about the specific verbiage of the Constitution or Bill of Rights?
 
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Discussion Starter · #7 ·
When I first test drove my jeep, when it still worked, to test the 4wd I went around a cul-de-sac with out it on. Then I engaged it and went around the cul-de-sac again and the front shimmied/shaked. If 4wd is engaged you will feel the difference.

good luck

Robert87yj/wwwthreads_images/icons/tongue.gif
engine rebuild w/4.0 head done, now for the MPI
 

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Yeah,yeah,yeah
I can tell also, hell, either by the loud "SNAP" that usually preceeds it, or just the inability to turn the wheels on a hard surface with the front engaged and ARB activated. The helpful prodding was intended for someone not so familiar with the characteristics,especially with smaller tires,on pavement, with an open diff. You guys are a tough crowd.
Jeff
89 Wrangler(with four wheel drive,.... I think).

 

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Actualy to tell the truth I was out on trail ride a while back with the T case in 4 low all day and didnt realize the fronts werent locked until I needed the ARB and nothing happened. With the Detroit in the rear you dont need much help up front for most trail obstacles so the open diff(with the ARB off)is not very noticeable at all.
Jeff
89 Wrangler(4 WD...Im not sure anymore???)

 
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Discussion Starter · #10 ·
Yeah I hooked up all the lines as to how you had described them and nothing still. Your run down of the lines helped tremendously.

 
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Discussion Starter · #11 ·
Yeah I can always tell when I'm four wheel too and it feels like it in there but I can't seem to find either of the front wheels spinning like when crossing a tree that has fallen down. Whereas the back wheel will spin being open diffed. It just doesn't seem as if the front is working as hard as the rear but it definitely feels as if it is engaged and all the vac lines coming from the diff were broken three days ago. Now I'm thinking its in the shifter motor.

 

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The shift motor is just a rubber diaphram, if it's damaged it wont work well or at all or. Its easy to take it off(4 1/2" bolts) and see if its actuating, probably takes less time than typing another post. Open it up and test it, it sounds like your just looking for peace of mind, that should do it to you.
Jeff
89 Wrangler


 

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Well, if the shift collar is stuck on the axle splines the vacuum motor cannot overcome that ...er....stuckness. If you are going to remove the motor from the tube anyway to check it, then slather a good amount of axle grease on the splines, moving the collar back and forth by hand to work some grease under the collar itself. Don't worry about losing the differential fluid if you should remove the motor; the shift fork, collar and splines are in a sealed chamber. Some think the diff fluid lubricates the collar and splines but it doesn't. When you remove the motor from the tube, some old liquid grease will leak out so be prepared to catch it in something. Good Luck!!/wwwthreads_images/icons/smile.gif
 
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Discussion Starter · #14 ·
Only one sure way: Chain it to a tree on dirt or grass and put it in 4wd and press the gas: if you get spin marks front and back, guess what.

80 CJ5, 52M38
 

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Chain it to a tree? Get that tree protector out.

 
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Discussion Starter · #16 ·
OK, get the tree protector and keeper strap and strap it to a tree.
Tread lightly!

80 CJ5, 52M38
 
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Discussion Starter · #17 ·
I jacked it up and engaged it to see if the driveshaft would spin and nothing there. It just sits still. I have all the hoses hooked up as you described but no vacume from any of the at the actuator. Any other ideas or just break down and buy the wiring harness. I'll take the actuator off this afternoon to check the fork in it.

 

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There should be vacuum at the shift motor in 2wd or 4wd, as long as the engine is running. Vacuum holds the collar in the correct position, either locked(4wd)or unlocked(2wd). Trace the lines back to the transfer case switch and check there for vacuum. If it is not there , then there is a break in the vacuum supply line from the transfer case to the engine compartment. I think the vacuum supply line from the engine to the transfer case is red.

A check to see if the axle collar is working is to lift the passenger tire off the ground and engage the 4wd. Try to spin the passenger tire by hand: if it is locked and won't spin then the vacuum shift motor and collar are engaging and working correctly. Shift into 2wd and the tire should now spin freely. This will only work if there is vacuum to the shift motor in the first place. Good Luck!!/wwwthreads_images/icons/smile.gif
 
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