87 AW4 TC unlocking issue

[cruiser54]

So then it's a TPS problem.

Does the Snap-On RENIX scanners just tell you what's on the ECU side of things?

Not necessarily a TPS problem. I don't know about the Snap-On scanners but the DRB I have reads the engine side of the TPS whwn checking the engine and trans side when checking the trans. Does it give a percentage reading? If so, compare that to my instructions and you'll see where it's reading from. 17% would be engine side. 83% would be trans side.

 

[bigalpha]

I don't think that the Snap On could switch between each side. It wasn't my scanner, so I don't know exactly what it was reading.

I will check it with a DMM though, to verify.

 

[cruiser54]

I don't think that the Snap On could switch between each side. It wasn't my scanner, so I don't know exactly what it was reading.

I will check it with a DMM though, to verify.

Excellent idea. But, I don't think the TPS could fool the TCU into engaging TC lockup in 3rd gear.

Ever refurbish your NSS?.

 

[bigalpha]

Ever refurbish your NSS?.

I have never touched it.

 

[cruiser54]

I have never touched it.

Just curious. Wondering how the TCU could get the idea that you're in OD and lock the TC in 3rd. Just thinking......

 

[bigalpha]

Not sure, but it sure is annoying when I'm trying to accelerate onto the interstate.

 

[cruiser54]

Not sure, but it sure is annoying when I'm trying to accelerate onto the interstate.

I think that's why they dumped that TCU program at the end of 87. How about getting the part number off your TCU?

 

[bigalpha]

I can do that. Won't be until later, though.

 

[cruiser54]

I can do that. Won't be until later, though.

I'm in no hurry. My Jeeps shift fine. LOL. I've got one or two later model TCUs in my garage. We could compare part numbers.

 

[bigalpha]

That must be a nice feeling

It'll give me something to do today.

 

[cheapcherokee93]

lol i almost forgot about this thread :gee:

i will be checking the TPS adjustment, i also have a spare TPS that i might try
gonna check the connecters

if all this checks out i'll try swapping TCUs. its really odd though, like said it will lock up in 3rd while shifter is in D. i also found it will lock up 2nd gear with shifter in 1-2. never heard of that happening stock. wouldn't be surprised if its the TCU

 

[kastein]

Are you sure it is locking up with the shifter in 1-2 while it's in 2nd? Engine braking is somehow enabled when the shifter's in 1-2, not sure how but it's hydraulic in nature, I need to look at my AW4 FSM valve body flow diagrams and figure out what the difference is before I can answer that very well.

 

[bigalpha]

This is what I got

 

[cruiser54]

Both my 89 spare TCUs are 8953005305.

 

[bigalpha]

Hmm. Do you know if the #'s changed between 87, 88 and 89?

 

[cruiser54]

I just googled them and yours cam up 87 to 89 but I know they're different between the years. 87 shifted 1,2,3, TC lock, OD, OD lock.

 

[Ecomike]

Yeah. I'm almost positive it was only in 87 that it locked in 3rd with the lever in OD.

I think my 89 also locks up the TC the same way my 87 does. They both first lock up in 3rd gear (while set to D, which I assume you are calling OD), at about 37-38 MPH. And they relock in 2nd or 3rd after downshifts to 2nd or third, while the shifter is in OD as well. They unlock the TC at about 1200 rpm engine speed in 2nd gear, and unlock for about 1 second during any downshift to a low gear, then relock the TC on my 87 and 89. Both are all stock, OEM ECU and TCU (as far as I know).

 

[Ecomike]

I just googled them and yours cam up 87 to 89 but I know they're different between the years. 87 shifted 1,2,3, TC lock, OD, OD lock.

That is how my 87 works, and I am 90% sure the 89 is currently locking the same way.

 

[Ecomike]

That white switch also definitely affects TC lock up.

I did a 96 booster swap and my TC was not locking up because the switch was not adjusted properly. After adjusting it, I now get lock up, though my TC locks up all through third gear too.

Did you ever verify this, if so how and what did you find?

 

[cruiser54]

That is how my 87 works, and I am 90% sure the 89 is currently locking the same way.

Unless someone swapped the tCU, I doubt it. My 88 and 90 do not lock in 3 before shifting to D.