possible T-Case or tranny prob

i installed a new (well used) t-case (np 231) a while back. but when i put it in drive, it's in 4th gear, i have to unplug the lil box behid the dash under the glove box (maybe the TCU) and then i can shift it mannually. but why is it not shifting on it's own. any help would be great. oh yeah its the AW4(?) auto tranny and a 4.0 thanks

So with the TCU connected and in (D), it's starting it 1st gear and not upshifting? Did it shift correctly before the swap? Your profile says 92, so I'll assume it's a 92.

Here's a quick primer on the AW4 electronic controls. The trans computer uses the throttle position sensor (TPS) and the output shaft speed sensor to determine when to shift. 1996 and later also has an input shaft sensor. It controls the shifting and lockup by sending power to three solenoids in the tranny (accessibly by pulling the pan). The tranny cable from the throttle body only controls the hydraulic pressure in the tranny and does not affect shifting.

Since you mentioned changing the xfer case, I wonder if you damaged the wiring to the rear output speed sensor. As I recall there is a connector for it about mid-way up the side of the tranny. The sensor itself is under the shift linkage plate bolted to the drivers side of the tranny.

To diagnose this, I would pull unplug the connector and put a meter on it. With the xfer case in neutral, put the tranny in drive. The sensor is basically a magnetic switch that closes once per revolution as a magnet goes by. With the meter on a resistance scale you should see a brief connection once per revolution. Newer sensors are not reed switches, but hall-effect sensors and you'll see a voltage spike 4 times/revolution.

You can check the solenoids by unplugging the TCU connector and checking their resistance to ground. They should be around 10-15 ohms.

well when it's in drive it stars in 4th, but now that you mention the speed sensor, i do know the nut that holds it on is cracked, perhaps that would keep it from being tight or whatever. i'll have to get a new one and i'll let you know what happens. thanks a lot! that probally will make a difference. and yeah it's a 92

lawsoncl said:

They should be around 10-15 ohms.

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11-15

xjndmud said:

well when it's in drive it stars in 4th, but now that you mention the speed sensor, i do know the nut that holds it on is cracked, perhaps that would keep it from being tight or whatever. i'll have to get a new one and i'll let you know what happens. thanks a lot! that probally will make a difference. and yeah it's a 92

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That doesn't sound like a bad speed sensor. If the speed sensor was bad it would stay in 1st and not want to shift up.

xjndmud said:

well when it's in drive it stars in 4th, but now that you mention the speed sensor, i do know the nut that holds it on is cracked, perhaps that would keep it from being tight or whatever. i'll have to get a new one and i'll let you know what happens. thanks a lot! that probally will make a difference. and yeah it's a 92

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Is the nut cracked or the piece that the nut bolts through cracked? I think I have on in the Ghost, not sure if it will work. But you are welcome to it or any of the ones I have laying arround. Did you and Rich do the tcase swap? Did you plug everything up that you unpluged? Is this the same problem you had b4 going to Iraq?

nah i did the swap my self, and think i got everything hooked back up. yeah the nut is cracked, i did that durring the swap. so it's really been dangling since. but i havent driven it but a few times since that happend. but im ready to get it back on the trail. and yeah same problem i had since before iraq

I forgot to ask, what's it do in (1) with the TCU plugged in? If it shifts manually with the TCU plugged in, I'd check that you have power to the TCU connector. Maybe check and see if you're getting power to any of the solenoids. I'm not sure if your TCU is the problem, but I happen to have one up on eBay if that's the case. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=8072698598
No-ones bid on it and there's an hour left, so I'll probably stick it on the for-sale section here.

in 1st with the tcu plugged in i cant shift mannually i have to unplug the tcu to make it work.

I had a similar problem, the difference is that my tranny didn't lower the gears, it just go from 1st to 4th, no matter if you where WOT or cruising, my problem was the TPS.... New TPS and problem solved... HTH

xjndmud said:

in 1st with the tcu plugged in i cant shift mannually i have to unplug the tcu to make it work.

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Looks like it's time to probe the TCU connector and see if its sending voltage to the solenoids. Check the resistance on the solenoids too. It's possible it's the TPS, but if that's a problem I would think it would still start in 1st and either refuse to upshift (thinks its floored) or immediately upshift (thinking you're not on the gas).

ok y'all i the rain finnally stopped so i got to go wrench a lil today. ok here's how it stands now. with tcu connected it's stuck in 1st gear no matter what i put it in besides reverse, neutral, or park. and it's not shifting. with it unpluged i can shift manualy. Ghost, that TPS didnt fit, but i found another and going to try it out tomorrow. i'll let y'all know how that does then. thanks for the help guys.

xjndmud said:

ok y'all i the rain finnally stopped so i got to go wrench a lil today. ok here's how it stands now. with tcu connected it's stuck in 1st gear no matter what i put it in besides reverse, neutral, or park. and it's not shifting. with it unpluged i can shift manualy. Ghost, that TPS didnt fit, but i found another and going to try it out tomorrow. i'll let y'all know how that does then. thanks for the help guys.

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That was the speed sensor I gave you. lol! Finally no more rain!

opps yeah that's what i ment :confused1