Unusual AW4 Issue

[Tactical Bacon]

This is my 1992 Eliminator. I got back from Florida in October and noticed a distinct lack of 2nd and 3rd gear. Put it in Drive, starts in 1st, shifts to 4th. Move the shifter to 3rd, downshifts to 3rd. Pull the fuse, starts off in whatever gear the selector is in, so I know it's electrical. 

 

I figured it was a bad solenoid but found some service data in Mitchell's that said to check for continuity, 11-15 ohms, between the ground wire and the solenoid wires at the connector near the dipstick. Did that and I had no continuity between any of the wires on the transmission side of that connector.

 

I crawled under it Thursday and found some chewed looking wires. Fixed them with heat shrink butt crimps and then when I test drove it, it never shifted out of 1st gear but it seemed like the TCC was possibly engaging at higher vehicle speeds when the shifter is in 3 or D. I say that because when I'd move the shifter from 3 to 1/2 at 20-25 mph, the rpms would jump up about 300.

 

Got back to the house and went back up top, still no continuity at the connector near the dipstick between the solenoids and the ground wire or the OSS signal wire and ground wire, but the solenoid wires now have about 0.3 ohms between each other. Verified continuity of the ground and OSS signal wires between the connector at the transmission and the plug for the OSS.

 

If I apply 12V to the solenoid wires, I can hear them engage. Tried swapping back to the original TPS from the aftermarket, no change. Following the service data, I used wire piercers on the wires for solenoids 1 & 2, connected my other multimeter lead to a known good ground, and swapped the leads from the wire piercers at my multimeter and it was showing -0.31V when in D and it should have been sending 12V to the solenoids. 

 

Lastly, I jacked up the rear, put my meter in diode test, hooked it to the OSS leads, and spun the driveshaft. No beeps, never changed resistance. So I'm thinking it's a bad OSS.

 

I still need to check at the TCU but wanted to ask in case I'm missing anything obvious or I'm making a testing error I don't see. 

[Pete M]

oh man, if I found those mangled wires and fixing them didn't fix the issue, I'd be bummed.  

[Tactical Bacon]

2 hours ago, Pete M said:

oh man, if I found those mangled wires and fixing them didn't fix the issue, I'd be bummed.  

That's the best part, fixing the wires honestly made it worse. Before, I could take off with the shifter in 3 and it would (by some witchcraft) start in first, shift to 3rd, and then I just bump it to D. Now it stays in 1st all the time if I plug up the TCU. 

 

To add to the strangeness, I measured resistance between D7 and C14, 15, and 16 for good news. I don't know why there's still no continuity between ground and solenoids at the 7 pin connector, but Solenoids 1, 2, and 3, gave me readings of 15.0, 14.8, and 14.8 ohms at the TCU connector. I went through some more tests to verify all the wiring up to the TCU connector and when I left work tonight, I had my test leads in C3 and D7 and still no changes in resistance. So, everything I'm seeing is just re-confirming my diagnosis that the OSS is bad and I'm still just driving it around in full manual shift mode.

[Tactical Bacon]

Jumping the OSS pigtail with a wire doesn't change anything. Hoped it would do something different but nope, still stuck in 1st gear with the TCU hooked up.

[75sv1]

Might check the speed sensor. Should be one. The latter 98+ have two. I had a failure like yours. I replaced the shift solenoid. Did a Transgo shift kit. Nada. Neighbor did a scan test. Couldn't check the speed sensor, but everything else checked good. Replace the rear one. Trans worked. 

[Tactical Bacon]

7 hours ago, 75sv1 said:

Might check the speed sensor. Should be one. The latter 98+ have two. I had a failure like yours. I replaced the shift solenoid. Did a Transgo shift kit. Nada. Neighbor did a scan test. Couldn't check the speed sensor, but everything else checked good. Replace the rear one. Trans worked. 

Yeah, that's what I think is the issue, the Output Shaft Speed Sensor (OSS). The problem is it's out of stock everywhere.