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AW4 only goes forward

X

XJ.Atticus

NAXJA Forum User
Location
Portland, Oregon
:confused:

just picked-up a jeep (89 wagoneer).

Was told the trans was slipping and after seeing the sludge under the valve cap,i figured the guy i bought it from may not have taken care of it.
So I drained the trans fluid (which wasn't much) and replaced the pan gasket and the main pump seal. No leaks, i thought something had gone right...

The Problem: Now every gear seems to move the jeep forward.
After reading alot of NAXJA forums I disconnected the TCU... Still Same Problem
Also realized that the jeep only started in what should be the P (park) and N (neutral) Positions.

I am by no means a mechanic, nor know much about transmissions. So i am hopping someone can point out a mistake or something obvious i have missed.

I would really like to take this jeep out this season and have removed an installed this trans twice this week. So i am desperate for any help.

AW4 (aisin 30-40le) mated to a NP242
:confused:
 
Last edited:
kinda awkward.
 
So, with the new TCM and the shifter in P the jeep doesn't move... But in R,N,D,3,1-2 it still wants to move forward.

I'm still confused...

While i wait for more ideas, I am going to change the fluid again and probe the TCM.
 
Another update...

P seems to work
R feels like it is neutral
N Jeep moves forward
D Jeep moves forward
3 Jeep moves forward
1-2 Jeep moves forward

Is there any way to adjust linkage?
Could it be a solenoid?

Thanks for any help
 
I would disconnect the shifter cable at the tranny, and shift it by hand into all the gears. That would eliminate the shift cable as a problem. Carefully pop the cable off the shift lever on the drivers side. I don't recommend trying to remove the arm itself as the threads on the shaft tends to twist off before the nut yields.
 
Will try the "linkage bypass."

Update:

1. Tested TPS voltage. Everything checked out (B-D,output, is 85% of A-D,input)
2. Manually activated all three solenoids
3. Probed TCM plug with DVOM to the "shift pointers" specs. Everything checked out... Except C8 and C9 did not show any voltage. C8-C9 are affected by the shifter position being either in 1-2 or D (Hoping this is a clue to the problem)

All for now... off to more AW4 fun

Thanks again to everyone for taking time to help me out.

P.S. i have noticed alot of people using the knowledge of NAXJA members to solve their problems, But once the problem is solved they vanish and never post what / how they fixed the problem.
So I will follow this trouble shooting to the end and post my full results for others to use
 
Linkage Bypass done. Nothing was different. Did notice that between the first position (P) and second position (R) there is a spot where it wants to go forward. This is happening with and with out the linkage.

1st position (P) - jeep seems to be in park
1.5 position - Jeep wants to move forward
2nd position (R) - Jeep feels like is in neutral
3rd - 6th position - Jeep wants to roll forward
 
Good idea and i have drained it, cleaned the pan, cleaned the filter, and refilled it. I realize there may be sludge in the cooler or elsewhere that may be clogging it again. But i am delaying changing the fluid again or dropping the pan, until i can more or less rule out electrical stuff, or anything else, as the problem.

I have an Aisin 30-43le with a 23 spline output and am flirting with the idea of changing the input shaft on my NP242 to match. Has anyone done this? is it feasible?
 
To eliminate the TCM, simply unplug it. WIth the TCM unplugged you definitely should get reverse in (R). You'll also get 4th in (D), 3rd in (3), and 1st in (1-2).
 
That's just it. I'm not...
i guess i should have said that i have had another XJ that had problems shifting gears. So i went online and found out how to make it shift with toggle switches controlling the solenoids. I drove that around for a while until the jeep got impounded...

all that to say with either: TCM plugged in, TCM unplugged, linkage bypassed and manually shifted at the trans.

the shift is still
1st position (P) - jeep seems to be in park
1.5 position - Jeep wants to move forward
2nd position (R) - Jeep feels like is in neutral
3rd - 6th position - Jeep wants to roll forward

I figured with the TCM unplugged it should go into P R N D. As far as i know reverse isn't controlled by a solenoid like 1-2, 3, D...

I could understand the trans being bad and it slipping in/out of gear. But the fact that I have 4 gears moving forward and 2 not moving anywhere, leads me to think the problem might not be solved by simply putting a different trans in.
if i haven't fixed the problem by the time I round up some money for a new trans, then i will try a new one. Till then i want to fix this one or atleast understand what the problem is.
 
Possibly when you drained out the old fluid you might have done some wrong to it.. I am not an expert with the AW4 but I know with most autos when it is older and poorly taken care of when you go ahead and just drain out all the old fluid and replace it with new you sometimes have a bigger problem on your hands because some of that dirt in the old oil is keeping your tranny in check oddly enough.
 
lawsoncl said:
To eliminate the TCM, simply unplug it. WIth the TCM unplugged you definitely should get reverse in (R). You'll also get 4th in (D), 3rd in (3), and 1st in (1-2).
Click to expand...

lawsoncl,

how does the TCM gets its signal as to which gear has been selected? I am guessing the NSS, if that is true shouldn't he be working on it too, or does the TCU not care, and only looks at the VSS? I am thinking for some reason the NSS in Park, Reverse and neutral talks to the TCU, but I have not looked it up.
 
You mentioned impound, did they tow it and damage the tranny in park, or was it in neutral during the tow?
 
Ecomike said:
lawsoncl,

how does the TCM gets its signal as to which gear has been selected? I am guessing the NSS, if that is true shouldn't he be working on it too, or does the TCU not care, and only looks at the VSS? I am thinking for some reason the NSS in Park, Reverse and neutral talks to the TCU, but I have not looked it up.
Click to expand...

The NSS had two versions, and I believe it changed in 97? The earlier version just had switches that close when the shifter was in either (D) and (1-2). I think the 97+ added another contact for (3) as well. The switch for the Park/Neutral only went to the starter relay. The contact for reverse just went to the backup lights.

You can unplug the NSS on a 89 entirely and it should shift normally. Reverse is entirely mechanical and I don't think the TCM flipping solenoids would affect anything. Getting forward motion in reverse, assuming its really in reverse, is likely a mechanical problem.

For a 4WD, the tranny has its own output sensor and doesn't use the VSS. Makes sense as the tranny doesn't know or case if the xfer case is in 4-lo or not.
 
FSM says solenoid #1 is on for reverse and first gear.

lawsoncl, I am starting a new emergency AW4 thread for me, please comment it!
 
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