1994 FJ80 Trnasmission/ECU problem (1 Viewer)

[rainbowrpk]

Newbie here, looking for some direction. Just picked up a 1994 FJ80 with 53000 miles. Body & interior are execellent with a little rust underneath. Here's my problem- Transmission works great at startup (starts in low & shifts through all the gears), but once she warms up (5 minutes of driving), no downshifting on acceleartion (with exception of overdrive on the highway). If I start from a dead stop, it won't downshift at all, jsut starts out in high gear. Replaced the shift solenoids, still no luck. Shifts great & runs strong manually. Transmission shop said no error codes, but said computer is sending funky signals to the transmission once it is warmed up. ECU problem? Any suggestions?

 

[80t0ylc]

Newbie here, looking for some direction. Just picked up a 1994 FJ80 with 53000 miles. Body & interior are execellent with a little rust underneath. Here's my problem- Transmission works great at startup (starts in low & shifts through all the gears), but once she warms up (5 minutes of driving), no downshifting on acceleartion (with exception of overdrive on the highway). If I start from a dead stop, it won't downshift at all, jsut starts out in high gear. Replaced the shift solenoids, still no luck. Shifts great & runs strong manually. Transmission shop said no error codes, but said computer is sending funky signals to the transmission once it is warmed up. ECU problem? Any suggestions?

First off welcome to MUD. You have chosen the best year, that said without bias.

At least 2 things point toward your tranny not being the problem. 1. Works when cold and 2. works manually. Plus the '94 tranny is the A442F, the stoutest of the 80s.

At least 2 things point at the Transmission Control Module (TCM). 1. Not working when warmed up, 2. No codes or "funky signals"(whatever that means). The Field Service Manual (FSM) chart lists closest symptom: "No down - shift when coasting". Possible causes in this order: 1. Valve body faulty, 2. Solenoid valve faulty, and 3. Electronic control faulty. It's possible the shop is not reading codes correctly which is why they say "funky signals".

Do you have a FSM? If not and you plan to do your own work, you need to get one. Do a search on FSM to find out how to get one (more than 1 way). There's a procedure in there for reading codes. And there's a Troubleshooting flow chart to help diagnose problems. A couple other pubs needed if getting deep into problems: 1. A442F Auto. Trans. Repair Manual and 2. Electrical Wiring Diagram.

 

[Drilldeeper]

Did you ever figure out what was going on? Mine (93) is doing a similar thing. PO said after some water crossings he started experiencing transmission throwing out of gear, then at the full stop it feels like it's in a high gear, then sometimes it will kick back in first gear when you give it gas. Also lost reverse. Everything defaults back to normal when you kill the engine and start again.
Thanks