Won't engage 4 wheel drive. No light on dash either.

[Dogote]

My new to me 2.5 liter 5 speed 1986 (edited,sorry, not an 85) Comanche X won't go into 4 wheel drive.

 

The are no noises from the Transfer case, it does engage low range, but does not drive the front wheels. A couple times I got a neutral in 4 low, but other times it engages low but does not drive the front axle. There is no indication in the dash as to if it is in four wheel drive. I assume the indicator would be on the right light cluster where the up shift light is. 

 

I have read a bit about the vacuum lines having something to do with engaging the front axle. I have searched this forum and else where and have not found a good guide on the subject.  I have not figured out if I have an NP 231 or NV 231 transfer case, or what the difference is.

[gogmorgo]

The vacuum stuff slides a collar to connect two pieces of the front passenger side axle. This prevents the front driveshaft from turning in 2wd. It doesn't make much difference to anything much if it spins, though. Locking the collar over is a pretty simple task. See the link.

http://comancheclub.com/topic/17377-cad-fix-1/

There's a lot of thread there that should answer most of your questions.

[Eagle]

My new to me 2.5 liter 5 speed 1985 Comanche X won't go into 4 wheel drive.

 

The are no noises from the Transfer case, it does engage low range, but does not drive the front wheels. A couple times I got a neutral in 4 low, but other times it engages low but does not drive the front axle. There is no indication in the dash as to if it is in four wheel drive. I assume the indicator would be on the right light cluster where the up shift light is. 

 

I have read a bit about the vacuum lines having something to do with engaging the front axle. I have searched this forum and else where and have not found a good guide on the subject.  I have not figured out if I have an NP 231 or NV 231 transfer case, or what the difference is.

 

If you can get to low range, the transfer case is functioning. And you're wrong on where the 4WD light is -- it's in the status light cluster to the left of the primary gauges.

 

As already pointed out, your MJ has a vacuum-controlled axle disconnect. If you don't have good vacuum, it won't engage. The 4WD light is also actuated by a vacuum switch, so that's a second hint that you have a vacuum leak. You could try to track it down (which would be a good idea, since it probably also affects your cabin heating/ventilation distribution), or you could just permanently lock the axle in the engaged position.

 

{Edit to add} I overlooked the fact that you said you have an '85. That's interesting, considering that there is no such thing -- the MJ was introduced in the 1986 model year. What transfer case does your MJ have? There should be a label on the driver's side sun visor that will say either "Command-Trac" or "Selec-Trac." The operation of the 1986 Selec-Trac was very different from the MP242 Selec-Trac of later years. The '86 would not have an NP231. If it's Commend-Trac it would be an NP207, IIRC. The 231 didn't come in until 1987 or possibly 1988.

 

http://jeep.wikia.com/wiki/List_of_Jeep_transfer_cases

 

http://www.4x4review.com/jeep-transfer-case-identification-guide/

[Dogote]

Thanks. Checking this out today. My Comanche is an '86, not sure what I was thinking when I typed '85. 

I suspect vacuum leaks due to the fact I can't get hot air to blow out the heater vents either. De-frost is fine, it just won't switch to vent.

If it wasn't freezing out, and with 4 inches of snow, I would de-grease the engine and under the body. It's pretty messy fro years of leaks. I like clean stuff.

I may leave it parked for a few days until I get some stuff done in my hangar and can pull it in there to work on it. 

[cruiser54]

Do the CAD elimination no matter what.

The vacuum to it is only ONE of it's troublesome parts.

 

As for the heat, look under the front bumper on the passenger side for the vacuum storage ball. It holds engine vacuum to operate the vents.

[Eagle]

I suspect vacuum leaks due to the fact I can't get hot air to blow out the heater vents either. De-frost is fine, it just won't switch to vent.

 

Yes, that there is what we call a "clue." Vacuum leak.

[mvusse]

 

My new to me 2.5 liter 5 speed 1985 Comanche X won't go into 4 wheel drive.

 

The are no noises from the Transfer case, it does engage low range, but does not drive the front wheels. A couple times I got a neutral in 4 low, but other times it engages low but does not drive the front axle. There is no indication in the dash as to if it is in four wheel drive. I assume the indicator would be on the right light cluster where the up shift light is. 

 

I have read a bit about the vacuum lines having something to do with engaging the front axle. I have searched this forum and else where and have not found a good guide on the subject.  I have not figured out if I have an NP 231 or NV 231 transfer case, or what the difference is.

 

If you can get to low range, the transfer case is functioning. And you're wrong on where the 4WD light is -- it's in the status light cluster to the left of the primary gauges.

 

As already pointed out, your MJ has a vacuum-controlled axle disconnect. If you don't have good vacuum, it won't engage. The 4WD light is also actuated by a vacuum switch, so that's a second hint that you have a vacuum leak. You could try to track it down (which would be a good idea, since it probably also affects your cabin heating/ventilation distribution), or you could just permanently lock the axle in the engaged position.

 

{Edit to add} I overlooked the fact that you said you have an '85. That's interesting, considering that there is no such thing -- the MJ was introduced in the 1986 model year. What transfer case does your MJ have? There should be a label on the driver's side sun visor that will say either "Command-Trac" or "Selec-Trac." The operation of the 1986 Selec-Trac was very different from the MP242 Selec-Trac of later years. The '86 would not have an NP231. If it's Commend-Trac it would be an NP207, IIRC. The 231 didn't come in until 1987 or possibly 1988.

 

http://jeep.wikia.com/wiki/List_of_Jeep_transfer_cases

 

http://www.4x4review.com/jeep-transfer-case-identification-guide/

 

He did say "where the upshift light is".  That light is in the same cluster, maybe he has left and right mixed up?

[Eagle]

He did say "where the upshift light is".  That light is in the same cluster, maybe he has left and right mixed up?

Ya got me. Brain freeze.

 

The upshift light has been disabled on all my Renix-era vehicles for so long that I forgot. On the 2000 XJs it's located above and to the right of the speedo.

[cruiser54]

My 2 cents.

 

Forget the stupid lights. Do the CAD fix in the link below.

Rely on transfer case shifter position rather than lights. We did it for decades.

 

http://comancheclub.com/topic/17377-cad-fix-1/

[Dogote]

My 2 cents.

 

Forget the stupid lights. Do the CAD fix in the link below.

Rely on transfer case shifter position rather than lights. We did it for decades.

 

http://comancheclub.com/topic/17377-cad-fix-1/

I don't care much if the light works or not. I mentioned it because I would have expected to see some indication and was not sure where that would be since I have never seen it work. I may do the CAD fix to see that everything does actually function in the axle, but I will buy the cable set up as a permanent fix. I would rather not have the drive line always engaged. I also like the fact that with the cable, I would also have a 2 low option. It is a nice thing to have for stuff like precision trailer backing or pushing aircraft and helicopters in and out of my hangar.

[Eagle]

My 2 cents.

 

Forget the stupid lights. Do the CAD fix in the link below.

Rely on transfer case shifter position rather than lights. We did it for decades.

I agree. Even in high range the transfer case makes a bit of a whine in 4WD. If you can't tell you're in 4WD fromt that and the shifter position, you should probably be driving something with full-time AWD rather than an MJ.

[Dogote]

 

My 2 cents.

 

Forget the stupid lights. Do the CAD fix in the link below.

Rely on transfer case shifter position rather than lights. We did it for decades.

 

http://comancheclub.com/topic/17377-cad-fix-1/

I don't care much if the light works or not. I mentioned it because I would have expected to see some indication and was not sure where that would be since I have never seen it work. I may do the CAD fix to see that everything does actually function in the axle, but I will buy the cable set up as a permanent fix. I would rather not have the drive line always engaged. I also like the fact that with the cable, I would also have a 2 low option. It is a nice thing to have for stuff like precision trailer backing or pushing aircraft and helicopters in and out of my hangar.

 

 

 

Not my first old school 4WD. And like I said previously, not really caring if the light works, but may fix it anyways because I usually fix broken stuff, even if it is not very useful. I also will be loaning this to my mom sometimes, and it may be driven by others too.