trans shift issue

[kastein]

If it drives the same with the TCU unplugged, then the problem is not the TCU!

not quite... if it drives the same with the TCU unplugged it means the TCU is doing nothing. Which means either it's toast or it's not getting power.

 

[Ecomike]

not quite... if it drives the same with the TCU unplugged it means the TCU is doing nothing. Which means either it's toast or it's not getting power.

I guess the question then is what is it doing with the TCU unplugged? Does it shift to 1 in 1-2, shift to 3 in 3, and shift to OD in D?

Also does it down shift to 2 from 3, when shifting to 1-2 at about 35 mph. Since he mentioned thread jacking, and seems to be new, seems prudent to ask, what is it doing with no TCU?

 

[Ecomike]

not quite... if it drives the same with the TCU unplugged it means the TCU is doing nothing. Which means either it's toast or it's not getting power.

Or the wires leading to the AW4 have a problem and so on!

 

[lawsoncl]

Might but I'm not all that sure if his info is correct for it fitting 87-90.

I really need to test this all out at some point... I've got enough random parts hanging around it wouldn't even take that much, just have a million other things on the list.

87-90 didn't have OBDI, but the pins that would normally go to the obd diagnostic lines just go to the yellow diagnostic connectors under the hood. The problem would be the TPS signal is reversed on the Renix (hence the need for the dual output). I suppose you could rewire that to tap into the 'normal' output that goes to the ECU.

 

[kastein]

87-90 didn't have OBDI, but the pins that would normally go to the obd diagnostic lines just go to the yellow diagnostic connectors under the hood. The problem would be the TPS signal is reversed on the Renix (hence the need for the dual output). I suppose you could rewire that to tap into the 'normal' output that goes to the ECU.

yeah, I dunno which one changed though - did the TCU stay the same and the ECU was changed to use the same signal, or vice versa?

 

[Ecomike]

If I designed it, I would have just flipped the 2 signal wires to the TCU from the TPS in 91. The 87-90 TCU to TPS signal voltage is reversed (goes from high to low, Idle to WOT), the from the TPS to ECU (it goes from low to high, idle to WOT)

 

[lawsoncl]

yeah, I dunno which one changed though - did the TCU stay the same and the ECU was changed to use the same signal, or vice versa?

The ECU was always normal. The input that the TCU expected switched to match the ECU. In the HO engines, the TPS signal is just Tee'd off the signal going to the ECU.

 

[lawsoncl]

If I designed it, I would have just flipped the 2 signal wires to the TCU from the TPS in 91. The 87-90 TCU to TPS signal voltage is reversed (goes from high to low, Idle to WOT), the from the TPS to ECU (it goes from low to high, idle to WOT)

Except you can't just flip the ground wire....

 

[Ecomike]

Except you can't just flip the ground wire....

Yep, that was too simple to work, LOL.

 

[kastein]

You could flip the 5 volt and ground lines going to the variable resistor TPS though.

Really all they had to do to change it was add a couple instructions to the function that read the TPS input, not sure why they didn't simply do that instead of adding more wiring and doubling the hardware in the TPS. Oh well.

 

[Squirly]

I guess the question then is what is it doing with the TCU unplugged? Does it shift to 1 in 1-2, shift to 3 in 3, and shift to OD in D?

Also does it down shift to 2 from 3, when shifting to 1-2 at about 35 mph. Since he mentioned thread jacking, and seems to be new, seems prudent to ask, what is it doing with no TCU?

I tried a TCU off of a '90 & it didn't do anything, as said '96 is different! With TCU unpluged tranny won't downshift unless you do it manually then under acceleration it skips 2nd and the converter doesn't lock up! I did hold it in 1-2 with the TCU unpluged pedal to the metal & it would not shift to 2nd, when the TCU is hooked up it would shift to 2nd when floored, I'm going to re-test that today! I'm also going to read the solenid test article & try to get the test done to verify solenoids! Thanks for all the input I know I'm a newb on this site but I've been in the sport a long time!

 

[Squirly]

Well I ran the test with a DVOM per article here are my findings! Speed sensor is supposed to be 5- Volts mine are 0, this is a little confusing because article says pulse per 1 revolution which to me says you need to be moving but intructions say key on eng. off, solenoid #1 had 0 ohms resistence should have 11-15, and TPS voltage input was the exact opposite of article! So should I start with a shift solenoid and where is the speed sensor? Thanks, Troy

 

[lawsoncl]

The TPS voltages in the article are for the older Renix setup. They are indeed opposite for the later models. If the speed sensor is bad, it won't upshift out of first. I don't think that's your problem

The solenoid reading points to damaged wiring or a shorted solenoid. This would cause your symptoms and needs to be addressed. Next step would be verifying the wiring and perhaps dropping the tranny pan and measuring the solenoid resistance directly.

Oh, and if you need a source for the solenoid, check this thread. http://www.naxja.org/forum/showthread.php?t=996259

 

[Squirly]

ok thank you I read the other thread on solenoid replacemaent and ordered the solenoids! Hope it's the prob.! Thanks, Troy