1986.5 Automatic Shifting High (and sometimes low?)

M47R1X · 03-19-2014, 02:34 AM

My wife's 1986.5 Supra with an auto trans has a weird issue. It decided out of the blue to start shifting up at about 4500 RPM during normal acceleration. Putting the ETC into sport mode changes that to about 5000 RPM. It kinda feels like it's shifting a bit hard as well. I ran through the tests in the repair manual and it passed all of them (it was a few years ago, so I don't entirely remember them. I used a jumper wire at one point, definitely. The car has spent a lot of time rotting away in a shop since then). Unplugging the ECT (down by the passenger's foot) allowed manual shifting, which works fine.

Today, something weird happened, though. I replaced the battery last night (not sure if it's related, but I thought I'd mention it) and on my way home from work today, I thought I'd give it a shot and plug the ECT computer in, and it shifted at about 2500 RPM. I had thought it was "fixed", or at least somewhat. Flooring it didn't cause the Supra to downshift at all and it really didn't seem to affect shifting whatsoever. I stopped the car when I got home, did some work on the steering wheel (damn indicator needed cleaning like none other), and it was back to 4500 RPM shifts after.

What the heck is going on? Would it be the speedometer cable? I've searched and haven't really found anything. It does this between ALL gears, not just a few. I'd think it'd be something electrical rather than mechanical, but my experience with automatics isn't so great.

Any cheap fixes? Ripping out the auto and replacing it with a manual isn't an option, sadly. Thanks in advance

03-19-2014, 02:34 AM	#1
M47R1X Stock Join Date: Jul 2012 Location: OKC, OK Posts: 5	1986.5 Automatic Shifting High (and sometimes low?) My wife's 1986.5 Supra with an auto trans has a weird issue. It decided out of the blue to start shifting up at about 4500 RPM during normal acceleration. Putting the ETC into sport mode changes that to about 5000 RPM. It kinda feels like it's shifting a bit hard as well. I ran through the tests in the repair manual and it passed all of them (it was a few years ago, so I don't entirely remember them. I used a jumper wire at one point, definitely. The car has spent a lot of time rotting away in a shop since then). Unplugging the ECT (down by the passenger's foot) allowed manual shifting, which works fine. Today, something weird happened, though. I replaced the battery last night (not sure if it's related, but I thought I'd mention it) and on my way home from work today, I thought I'd give it a shot and plug the ECT computer in, and it shifted at about 2500 RPM. I had thought it was "fixed", or at least somewhat. Flooring it didn't cause the Supra to downshift at all and it really didn't seem to affect shifting whatsoever. I stopped the car when I got home, did some work on the steering wheel (damn indicator needed cleaning like none other), and it was back to 4500 RPM shifts after. What the heck is going on? Would it be the speedometer cable? I've searched and haven't really found anything. It does this between ALL gears, not just a few. I'd think it'd be something electrical rather than mechanical, but my experience with automatics isn't so great. Any cheap fixes? Ripping out the auto and replacing it with a manual isn't an option, sadly. Thanks in advance Last edited by M47R1X; 03-19-2014 at 02:37 AM.