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Need help! AW4 stays in 4th when stopping

P

pancake

NAXJA Forum User
Location
Seattle, WA
I took it to a couple transmission shops for their "free" diagnostic service and neither could help. I don't know what to look for. I've searched and found the TCU might be bad. I bought a used one on ebay and I 'thought' it started to work again but acted up almost immediately.

I've also seen people say the "governor pressure/thermistor sensor"?? could be bad?

Please help. I really don't want to take this to a dealer. I can drive it by shifting manually.

FWIW it's a 1998 XJ, AW4 (of course), NP242, D30/D35, 4.0, 166k miles.
 
xjwest said:
just so you know my aw4 blew up at 172000 miles. yours might just need a rebuild.
Click to expand...

Ugh...I hope not. That would depress me. What did that run?
 
You could buy a repair manual from an auto parts store and start adjusting things like the transmission shifter cables and such. I adusted my throttle cable to make sure when I depressed the throttle all the way I was at wide open throttle. I also cleaned out around the air intake to the top of the engine, and between all of that something helped. I think you should start with all the easy stuff and then start thinking about a new transmission. You may be able to fix it with something simple, which would save you lots of money.
 
What fluid is in there and is it burned? You should make sure dexron 3 is used in the tranny. When was the last time the filter was changed? It sounds like the solenoid is sticking and may just need a good cleaning. I'm no trans expert by any means but I had other vehicles do the same. As long as it is not slipping then I would go the new fluid and filter route.
 
Do all the test in this link....... before you start throwing any money at it.
http://www.transonline.com/transdigest/magazines/1997-10/Shift%20Pointers/index.html
My problem was a cut wire from the TCU to the TPS.
It could be a power issue "to" the TCU as to it being unplugged from the harness, you could manually shift it as you stated.
Do the function test in the link above for a good starting point.
There are many threads covering this particular problem on this board ....... you will just need to be patient and work thru it to find your particular problem by process of elimination, that's what I did with the help from this board and a couple of pointers (from Ecomike and others) as to where to start looking.
 
Last edited:
Ok, I might give those a shot.

I did call the Jeep dealer and they told me basic diagnostic is $105 plus tax. I don't know if that is per hour or a flat rate (I need to call them back). Would the dealer be able to find the problem in a reasonable amount of time?
 
More than likely the TC Lockup is not releasing. Send me your email address if you want access to the factory manual.
 
Agreed the above link is a good place to start. Often it's simply the TPS sensor has worn out. It's very rare for the trans computer itself to go bad. Can you clarify what the problem is? Does it feel like it's going to stall the engine when you stop, or is it feeling like it's in 4th gear when you go to takeoff again?
 
lawsoncl said:
Does it feel like it's going to stall the engine when you stop, or is it feeling like it's in 4th gear when you go to takeoff again?
Click to expand...

Feels like it's in 4th gear when I start driving and it won't shift automatically (or doesn't seem to) while driving around in "D". I replaced the TPS not too long ago when this started. It was doing this a little (every 1-2 weeks) in the beginning but now all the time.
 
CheapXJ said:
the OBDII AW4 has two internal speed sensors. one of them is bad.
Click to expand...

Usually a bad output speed sensor results in the TCU thinking you're not moving and thus it never upshifts from 1st gear. No power to the TCU results in 4th gear with the shifter in (D), 3rd in (3), and 1st in (1-2).

Is your check-engine light on? The 98+ AW4 and TCU are much better at self-diagnosing primarily due to the added input speed sensor. It will notice when the solenoids are not responding correctly and at if the front speed sensor is bad. This is why doing the manual shifting mod causes the check engine light to come. I don't know if it will notice if the rear speed sensor is bad, but the symptom for that is no upshifting out of first. You should also get a check engine light if the TCU doesn't have power.

Have a look at http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html and check for power and the solenoid resistances.
 
lawsoncl said:
Is your check-engine light on? The 98+ AW4 and TCU are much better at self-diagnosing primarily due to the added input speed sensor. It will notice when the solenoids are not responding correctly and at if the front speed sensor is bad. This is why doing the manual shifting mod causes the check engine light to come. I don't know if it will notice if the rear speed sensor is bad, but the symptom for that is no upshifting out of first. You should also get a check engine light if the TCU doesn't have power.
Click to expand...

I took it to Autozone and they pulled two codes (yes, the CEL is on).

P0700 Transmission Control System Malfunction
P0758 Shift Solenoid B Electrical

Does this help?
 
Yup. The P0700 means there is a tranmission related code set, which is the P0758 code. The trans computer thinks the shift solenoid B is not working, which fits your symptoms. First step I think would be to measure the resistance of the solenoid at the trans computer wiring harness, which will check the wiring harness as well as the solenoid. It should be 11-16 ohms I believe. The good news is that it's easy to get to and replace. You drop the pan off the bottom of the tranny, and remove the filter to get to them. They are held in with a single bolt and come right out. The bad news is that they can be expensive to buy new. EBay or a pull-it-yourself style junkyard are viable options.
 
Check craigslist in your area. Sometimes folks get rid of the aw4 thinking it was bad when it wasn't. I have seen them sold in my area for $25.00 dollars a piece. There is a guy on Sacramento craigslist selling two for $25.00 each right now.. wealth of parts on there. Hal :scottm:
 
copper204 said:
Check craigslist in your area. Sometimes folks get rid of the aw4 thinking it was bad when it wasn't. I have seen them sold in my area for $25.00 dollars a piece. There is a guy on Sacramento craigslist selling two for $25.00 each right now.. wealth of parts on there. Hal :scottm:
Click to expand...

I don't see any positng for the Sacramento area. My cousin lives there and could pick them up for me.
 
pancake said:
Oh...doesn't sound good. How much is the solenoid?
Click to expand...
My parts list shows two solenoids as part number 4797402 and one as part number 479403. I believe that corresponds to the two shift and one lockup solenoid (someone confirm this?). Looking those up at http://www.chryslerpartsdirect.com shows 4797402 is superceded by 5016120AA and costs $165. For comparison, the lockup solenoid for a Chrysler 42RE tranny is $29.
 
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