Selec-Trac Problems / Questions

[Rootehound]

I recently purchased a 1987 Cherokee (Wagoneer) to use as a winter car. It's my third Cherokee, but my first with Selec-Trac.

The other night, during a heavy rainstorm, I decided to try out the 4WD system. I put the lever into 4WD, but it went into 4W High, and took about 10 minutes to go into 4WD. Is that normal?

After moving the lever back into the 2WD it seemed to take another 10 minutes or so to go back into 2WD. The 4WD light went out right away, but I could still hear the whine from the transfer case or diff. When it finally did go back into 2WD it did so with a BANG.

This morning, while driving to work in 2WD, it seemed to partially engage 4WD again (without me touching the lever) as I could hear a whine again. When I backed into the parking space at work, I heard another BANG and it seemed to disengage again.

This never happened in my other Jeeps. Anybody have any idea what the problem / cure is?

Dave

 

[bjoehandley]

What do you have the airpressure in your tires at? My Dad has found that can have an effect on the Selec-Trac's performance if you don't have the pressure the same at all four corners. It seems to be affected by tire diameter. Dad has had to either drive backward ot find a way to get the front and rear tires to spin at separate speeds to disengage. Short of gravel, wet grass, and muddy contruction siters there are few places aound here to do that.

 

[Neil]

Check the fluid level! Low fluid will cause the 242 to do some strange things. Shifting should be smooth, no bangs. Low fluid will also cause excessive whine from the t-case.

Neil

 

[sjx40250]

I had a similar problem early in my ownership of my 90. Took it to the stealer under warrranty. He said the vaccum line was faulty.

Since then I have gotten into the habit of shifting into 4HI while accelerating and then letting off the throttle, max vaccum. Same when shifting out of 4HI. I listen for a slight clunk which tells me the shift actually happend. It won't when your are accelerating and have min vaccum. Same story with my 92.

 

[Flyfisher]

The guy suggesting tire pressure was right on the money. It's differental wheel speed that's causing the gears to bind and not disengage. From my experience (with my 242), shifting in and out on slippery surfaces at low speed is good. Also, try turning right, then left (at slow speed). The turning allows the wheels (front and rear) to turn at different speeds and relieves the pressure on the gears.

As always...make sure fluid is full...and let off of gas to help the system shift.

Good luck.

 

[bottleworks]

I had a similar problem early in my ownership of my 90. Took it to the stealer under warrranty. He said the vaccum line was faulty.

That's funny because the NP242 does not use a vac disco axle. No vac control at all.

 

[Rootehound]

Thanks for all the advice...

All four tires (215/70/15's) are at 32 psi, so I doubt the tires are a factor. All fluid levels are where they should be.

That leaves me thinking it's a linkage problem (fairly easy to check) or a vacuum problem (not so easy). The manual I'm looking at shows a vacuum switch, but it doesn't show where the vacuum originates in the engine compartment. Can anyone tell me where that is?

On another note, I was in a junkyard last week and spotted an '86 2.5 with an instrument cluster that included a tach. How tough would it be to swap that to my car (an '87 4.0 with guages, but no tach). Does the tach need to be recalibrated? Are the sending units the same in a 2.5 and a 4.0? Speedo cable?


Thanks!
Dave