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Transmission "hunting" for gear

C

cj5wagomando

NAXJA Forum User
Location
Livermore, CA
Hopefully I am not the only one to experience this.

1987 Wagoneer Limited 4.0 liter Auto Tranny 180,000miles

Tranny is full and filter was changed last year.

My Wagoneer does not seem to know what gear it wants to be in. It is jumping back and forth between second and third and is driving me crazy. I need to loan it to my daughter for a couple days but cannot with it acting like this.

I have readjusted the TPS.

Is there a "tranny sensor" ? that lets the computer know what is going on? (I seem to remember seeing something about at position sensor or something but cannot come up with anything in the search function)

Thanks to everyone in advance,

Dave.
 
Tranny sensor? Sort of. The NSS, neutral safety switch, acts as a mechanical/electrical input to the TCU as to what gear is selected.

Everything you need to know, and how to do it for the NSS: http://www.jpmagazine.com/techartic...eep_cherokee_neutral_safety_switch/index.html

I would, however, first unplug the TCU (transmission control unit) that is located under the dash, passenger's side, and drive it manually. You should have 1st in 1-2; 3rd in 3; 4th in D; reverse, neutral, and park. If you do, then your problem is electrical in nature; if not, the problem is mechanical/hydraulic.
 
Awesome Joe!

This is the article I remember seeing about a year ago....

I will do the unplug and manual test first.

Again, Thanks! I will follow up...

Dave.
 
Ok, post up what you find!
 
joe_peters said:
I would, however, first unplug the TCU (transmission control unit) that is located under the dash, passenger's side, and drive it manually. You should have 1st in 1-2; 3rd in 3; 4th in D; reverse, neutral, and park. If you do, then your problem is electrical in nature; if not, the problem is mechanical/hydraulic.
Click to expand...

Good info as always Joe...just for an FYI.....what models is this good for?? I would think all AW-4's??? I'm not experiencing any of the probs just would like to expand my VERY small knowledge on such issues. BTW i've completed the NSS fix already...no issues as of yet.

thanks Steve
 
Last edited:
DrRandy said:
Good info as always Joe...just for an FYI.....what models is this good for?? I would think all AW-4's??? I'm not experiencing any of the probs just would like to expand my VERY small knowledge on such issues. BTW i've completed the NSS fix already...no issues as of yet.

thanks Steve
Click to expand...

Works for all years of the AW4 in the XJ. In the later years the TCU was relocated from the passenger's underside of the dash to the driver's side, between the steering column and the air box.
 
I will be looking at it this evening. My daughter took it anyway last night and then complained that it scared her. I warned her not to take it but I find that at 19 years old she has a hard time listening to me.

Dave
 
cj5wagomando said:
I will be looking at it this evening. My daughter took it anyway last night and then complained that it scared her. I warned her not to take it but I find that at 19 years old she has a hard time listening to me.

Dave
Click to expand...

Ha! Yeah, I was just like that as a kid--Boot Camp knocked some sense into me. :twak:
 
took it for a 4 mile loop...top speed 50 _No "hunting for gear" obviously and it ran fairly well in "manual shift" mode with the TCU unplugged. So seems to be electrical.

I have a spare TCU. Would it be generally suggested that I try that before pulling open the NSS ?

Thanks,

Dave.
 
Nothing will be harmed. You could run like that till you junk the vehicle without damaging it.

You can try a spare TCU, I don't think it'll fix anything but hey, it's easy to plug in, easier than rebuilding an NSS, so try it first. If that and the NSS don't fix it, it's probably a wiring issue, fortunately the AW-4 is very simple to control and only really has a few wires going to it.
 
Cool, then I am driving it tomorrow. I have been trying to get the switch to come off the shaft but it will not come off. I tried some gentle prying, but nothing. so tightening up now and will try again in a day or two.

thanks,

Dave
 
as usual Joe, your reply is concise and to the point. I will follow up.

Drove it today for some bass fishin'. Manual shift. I think I could get used to that!!! worked better than it has in quite a while.

Thanks,

Dave
 
another question:

Does the NSS control the fuel pump signal from the ignition switch?


I am going to get the NSS off today, but now I am getting and intermittent fuel pump start. (cycle the gear selector and then it will pump, but then stop pumping)

Thanks,

Dave.
 
Well, it shouldn't interfere with the fuel pump "prime", the 3-second operation of the fuel pump when you first turn the key to ON--that power to the pump is supplied through the B Latch relay.

However, when you turn the key to START, then power is fed to the pump through the starter relay, and the starter relay won't operate if the NSS doesn't provide it a ground, so in that case it could be messing with the fuel pump.
 
Ok, got the NSS all cleaned and greased up per the JP Article linked above. So far so good (short test drive to work this morning). I will take it out some more at lunch but this seems to have solved the "hunting" problem.

I will be watching for the fuel pump prime....it is working so far, but I may have another issue....

Thank you,
Dave
 
Hope you got it!
 
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