aw4 shifting issues

[coolwind57]

I've had limited time to look into this so far but I'd like to go ahead and toss this at you guys to see if I can quickly remedy this with your experience and knowledge for the next time I can afford a few minutes.

 

My 89 AW-4 Automatic (paired with 4.0L) began shifting erratically and within a few minutes stopped messing around and refused to budge past 1st gear.  I had to drive 3 miles back home in 1st.  This occurred only 2-3 minutes into the drive.  I parked and didn't look into it for a few weeks.

 

Today, I got into it and ran it.  Same thing, worked great for a couple minutes and began shifting funny--like it was searching or something, then it lost it's ability to leave 1st gear.    I got home and reset the transmission shift cable (using that little button reset method found near the throttle body).  I checked the fuse that likely goes to the TCU--yellow wires, in-line 10amp fuse at passenger foot well.  The fuse and wiring looked great, btw.

 

Next thing I did was pull the fuse and attempted to drive.  Without fuse, it reeeeaaaalllly didn't want to move at 1st gear and the truck crept along.  I replaced the fuse and it moved via 1st gear normally.

 

What's the next check?   Maybe TPS?  Should I swap in a new one?  Any other troubleshooting you can think of to narrow this down?  Sound like a bad TCU maybe?

 

It's my understanding that the AW-4 is overall pretty hearty.  Appreciate your thoughts.

 

 

 

[coolwind57]

I've got a Standard Motor Products TH67 (not the inferior TH67T) TPS on order that I found at a great price, so that's what I'll replace next to see if that'll take care of the problem.  Maybe I'll find some time in a few days to go test the old one.  If this is not the issue, then at least I'll have a backup TPS on hand for the future. 

 

just an update for those interested in following this issue with me.

[llhat]

22 hours ago, coolwind57 said:

Next thing I did was pull the fuse and attempted to drive.  Without fuse, it reeeeaaaalllly didn't want to move at 1st gear and the truck crept along.  I replaced the fuse and it moved via 1st gear normally.

 

What's the next check?   Maybe TPS?  Should I swap in a new one?  Any other troubleshooting you can think of to narrow this down?  Sound like a bad TCU maybe?

 

It's my understanding that the AW-4 is overall pretty hearty.  Appreciate your thoughts.

with the fuse pulled you 'should' have been able to manually shift the transmission to 1, then move toward D (it skips 2nd and goes to 3rd) you will not have overdrive or TC lockup...  I drove mine around for a good while manually shifting [it would try to start off in 3rd gear, then would 'go' when i moved the lever to 1]

 

According to a recent thread just down the way,  read it even though the title of the thread seems not related...

The TPS may be a decent trial, but you 'can' test the output ( I think analog meter is preferred to see sweep and any dropoffs)

 

otherwise look at an older thread i started..(it is about 7 pages back !) 

it had a LOT of tips from Ohm  and tests to wiring....

Ultimately 'my' issue was the TCU, but there were a LOT of red herrings along the way...  including the NSS... 

 

I do wish for you expedient repairs!

Edited 7 hours ago by llhat
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