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Discussion Starter · #1 ·
I had an assumption that the electronics were mostly the same for most Toyota Automatics(in the 80's and 90's at least), since Jim King had put an A340(forget which one) into his black MA60.

Last year my 84 Cressida's ECT funked up and was causing the Trans to always go into second with the TQ converter locked. As per the manual, unplugging the ECT gave me 1st in 'L', 3rd in '2' and 4th in 'D', meaning the Trans itself was fine.
During that time I got an Auto Turbo 87 Supra for a motor swap to my Supra and I kept the ECT from it and some other bits.

I finally got tired of manually shifting the now 3 Speed Auto Cressida(it would still chirp from 1st to 3rd :duh:) and got to thinking. I busted out the 87's Wiring diagram book and the Trans Diagnostic book for the 83-85 Supra/Cressida Autos.

As far as I could tell, the wiring all used the same names, and worked in the same way, except for the mode switch. So a few days ago I wired it up, plugged it in, and it works great. Only issue is that it shifts early, but I think thats because the mode switch is not hooked up and its in the Norm mode(or it could be the speed sensors, but I think it runs off the one in the dash primarily).

I wrapped it up in a rag and tape, since the mounts are way off, and its been great ever since!

Just something I thought you all should know! A340 and A43DE's all work the same!
(make sure you check your wiring diagrams and such, as I'm not liable for any damages caused by this info!)
 

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So if I understand this correctly...

7m auto + 88 Cressida auto driveshaft + wiresplicing = A340 trans swap?

Does this mean no more custom driveshaft....?
 

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by wiring I meant replacing connectors so the old harness can connect to the new trans, unless they used the same clips.. What about a driveshaft? Will that one mentioned work?
 

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A3xx solenoids will work off A4x electronics(other than 82!), but will not work "correctly". The early shifting is because they use different control strategies and solenoid types(later solenoid = pwm?). Otherwise, you could retrofit A3xx solenoids into a4xs-you cant. The a3xx solenoid shares design elements with other 86ish on Toyota trans solenoids, and some vendors sell a "universal" type that works in a14x, a24x, a34x, and a54x. None will work in a4x. The 3xx expects to see a speed signal, and you are not supplying one. You can use the a34x ECT and shifter with an automatic 7m ecu, or buy an aftermarket control unit to correct early shifting if it bugs you. Have no clue how this affects solenoid life long term. Saying the a340 works with early electronics is like saying a ct26 will just bolt on.....:zzzzz:
 

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Discussion Starter · #8 ·
It does get a speed input. The one from the trans and the one from the Cluster, just like in the Piggy. However I was thinking a few days ago, that the frequencies of the signals might be a bit different, hence the shift points being pushed back as speed increases. But the solenoids aren't PWM, http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=AT&P=12.
 

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Yeah, thats right, the freakin GM crap was PWM-sorry. Its been a while, now. If you were to scope the signal, you would see difference...
 
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