Long post alert!
My car is an US TT, automatic. I’ve destroyed this transmission several times, it was last rebuilt less than 5K miles ago.
I’m not looking for any real power anymore, it is a single conversion but I have the boost so low I doubt it’s much higher power than BPU.
The last couple of months I’ve been daily driving the car and it has a problem that I’m at my wits end over.
The transmission will NOT hold 2nd. If I leave it in D and accelerate normally, maybe 15% throttle, it’s a perfect, buttery smooth, at every 2500-3K RPM - 1,2,3,4,lockup. No slipping, no harsh engagement. You could not ask for anything better.
I can leave it in D, but then accelerate at a little more throttle, maybe 25-30%, still under no boost, sometimes it will almost instantly shift as quickly as it can 1-2-3-4, I can feel the box shift and watch it lug the RPM. It’s the equivalent of going to 1st to 4th gear with a manual at 3K RPM. I have to be careful and not lean in to much when pulling out in front of traffic.
I can let off the throttle or manually pull it down to L and it recovers under low throttle.
If I attempt to manually shift the box from a dead stop, light throttle or full throttle it will stay in 1st until I either shift to 2nd, hit rev limit or let out of the throttle. But the instant I shift up in to 2nd, it instantly shifts to 3rd. Even while the selector is still in 2nd. If I’m going slow and low throttle it will do this every time at 3K RPM. Even while it’s still in the 2 position.
If I have it under load (boost) its even more odd, it does not feel like it’s in neutral but almost like it’s in between gears, engine is doing what it should be but the transmission pretty much checks out at this point. I can coast till I fall to around 3K RPM and it will select 2nd.
As most of you know, this transmission is 100% electronically controlled. It’s going to do, within its capacity, what the ECU tells it to do.
I replaced both of the VSS’s on the trans, the two sensors that look like modified cam position sensors (magnetic). Calling them VSS’s is kind of wrong because one measures the forward drum speed (input?) and the other measures output shaft speed. There is a third sensor that is a driven shaft and I guess it’s a backup to the speedometer if one of the other VSS’s fail. I have the new third sensor but it’s not really used for a signal to the ECU to determine transmission control. I’m going to install it but I don’t think it will help.
Replacing the two VSS’s did appear to make the shift points more exact and the transmission shifts smoother. None of the hard engagement when going from park to reverse anymore but the refusal to stay in second is still there.
I pulled the throttle body and calibrated the TPS’s, I still have factory TRAC on the car, still works. The TRAC TPS (sub) was replaced years ago because I broke it pulling the engine but the main TPS is 26 year old Toyota. Checking it with a meter, it checks fine. Throttle response and idle are perfect.
I’ve found that TPS, at least on OBD1 MKIV’s, as long as it knows idle and a reasonable amount of change, it’s good enough for these cars. The ECU will compensate for a lot. But according to the TSRM mine is spot on.
Since this is throttle/RPM related even though it checks good, could this be a TPS issue?
ECU is stock. Had swollen caps but none were leaking, they were all replaced. I still wonder though if the ECU could be screwy since it’s telling the trans what to do.
Wiring (ground) issue? Could it actually be a problem in the transmission? Valve body? Solenoids? TRAC?
I’ve taken any piggy back ECU’s, etc. off the car to get it back to stock as much as possible. I will likely never sell the car, I just want to drive it and enjoy the targa out days and let anyone who wants to race, drive by and wave.
I’ve always needed to buy a built A340e and I don’t mind doing it but for what, if I get it, install it and it’s still stupid because it’s doing what it’s being told to do, I’m no better off because I’m not making any real power at the moment anyways.
What am I missing? I’m open to any ideas and I’m hoping someone has seen this before.
My car is an US TT, automatic. I’ve destroyed this transmission several times, it was last rebuilt less than 5K miles ago.
I’m not looking for any real power anymore, it is a single conversion but I have the boost so low I doubt it’s much higher power than BPU.
The last couple of months I’ve been daily driving the car and it has a problem that I’m at my wits end over.
The transmission will NOT hold 2nd. If I leave it in D and accelerate normally, maybe 15% throttle, it’s a perfect, buttery smooth, at every 2500-3K RPM - 1,2,3,4,lockup. No slipping, no harsh engagement. You could not ask for anything better.
I can leave it in D, but then accelerate at a little more throttle, maybe 25-30%, still under no boost, sometimes it will almost instantly shift as quickly as it can 1-2-3-4, I can feel the box shift and watch it lug the RPM. It’s the equivalent of going to 1st to 4th gear with a manual at 3K RPM. I have to be careful and not lean in to much when pulling out in front of traffic.
I can let off the throttle or manually pull it down to L and it recovers under low throttle.
If I attempt to manually shift the box from a dead stop, light throttle or full throttle it will stay in 1st until I either shift to 2nd, hit rev limit or let out of the throttle. But the instant I shift up in to 2nd, it instantly shifts to 3rd. Even while the selector is still in 2nd. If I’m going slow and low throttle it will do this every time at 3K RPM. Even while it’s still in the 2 position.
If I have it under load (boost) its even more odd, it does not feel like it’s in neutral but almost like it’s in between gears, engine is doing what it should be but the transmission pretty much checks out at this point. I can coast till I fall to around 3K RPM and it will select 2nd.
As most of you know, this transmission is 100% electronically controlled. It’s going to do, within its capacity, what the ECU tells it to do.
I replaced both of the VSS’s on the trans, the two sensors that look like modified cam position sensors (magnetic). Calling them VSS’s is kind of wrong because one measures the forward drum speed (input?) and the other measures output shaft speed. There is a third sensor that is a driven shaft and I guess it’s a backup to the speedometer if one of the other VSS’s fail. I have the new third sensor but it’s not really used for a signal to the ECU to determine transmission control. I’m going to install it but I don’t think it will help.
Replacing the two VSS’s did appear to make the shift points more exact and the transmission shifts smoother. None of the hard engagement when going from park to reverse anymore but the refusal to stay in second is still there.
I pulled the throttle body and calibrated the TPS’s, I still have factory TRAC on the car, still works. The TRAC TPS (sub) was replaced years ago because I broke it pulling the engine but the main TPS is 26 year old Toyota. Checking it with a meter, it checks fine. Throttle response and idle are perfect.
I’ve found that TPS, at least on OBD1 MKIV’s, as long as it knows idle and a reasonable amount of change, it’s good enough for these cars. The ECU will compensate for a lot. But according to the TSRM mine is spot on.
Since this is throttle/RPM related even though it checks good, could this be a TPS issue?
ECU is stock. Had swollen caps but none were leaking, they were all replaced. I still wonder though if the ECU could be screwy since it’s telling the trans what to do.
Wiring (ground) issue? Could it actually be a problem in the transmission? Valve body? Solenoids? TRAC?
I’ve taken any piggy back ECU’s, etc. off the car to get it back to stock as much as possible. I will likely never sell the car, I just want to drive it and enjoy the targa out days and let anyone who wants to race, drive by and wave.
I’ve always needed to buy a built A340e and I don’t mind doing it but for what, if I get it, install it and it’s still stupid because it’s doing what it’s being told to do, I’m no better off because I’m not making any real power at the moment anyways.
What am I missing? I’m open to any ideas and I’m hoping someone has seen this before.