4+3 manual trans
Thread Starter
Pro
Joined: Jul 2002
Posts: 703
Likes: 0
From: Milwaukee Wi
4+3 manual trans
Does anyone know how and if the ECU commands the 4+3? I see in the Haynes shop manual a comment made that OD is controlled by the ECU or by a switch. Mine is a 1984 and I have the switch on console.
Reason I ask is that I use EBL-ECU and it has torque coverter control based upon TPS-coolant temp-MPH. I do not see MAP? Not sure if those settings affect 4+3?
Reason I ask is that I am seeing the OD rapidly move in and out occasionally. Totally intermittant and infrequent however it is more often when car is under a load 70+ MPH at cruise high MAP.
It happened a couple years back by was a result of insulation on wires in OD being deteriorated but that was repaired and sealed well. In that case the OD light would blink but today it says on solid when in OD.
I also have highway mode enabled to enlean the A/F so possibly it is too lean and is misfiring. I enrichened a tad today. I am seeing the leanest at 16.8/1 on WB.
Fluid in OD is topped off and that did not help. It was about 80% full on inspection B4 topping off. It does leak a bit. I top off in spring.
when OD unit is failing what is symptom? Does it fail all at once?
Past week it is working fine?
Reason I ask is that I use EBL-ECU and it has torque coverter control based upon TPS-coolant temp-MPH. I do not see MAP? Not sure if those settings affect 4+3?
Reason I ask is that I am seeing the OD rapidly move in and out occasionally. Totally intermittant and infrequent however it is more often when car is under a load 70+ MPH at cruise high MAP.
It happened a couple years back by was a result of insulation on wires in OD being deteriorated but that was repaired and sealed well. In that case the OD light would blink but today it says on solid when in OD.
I also have highway mode enabled to enlean the A/F so possibly it is too lean and is misfiring. I enrichened a tad today. I am seeing the leanest at 16.8/1 on WB.
Fluid in OD is topped off and that did not help. It was about 80% full on inspection B4 topping off. It does leak a bit. I top off in spring.
when OD unit is failing what is symptom? Does it fail all at once?
Past week it is working fine?
Racer
Joined: Sep 2011
Posts: 400
Likes: 5
From: Bakersfield Ca
Does anyone know how and if the ECU commands the 4+3? I see in the Haynes shop manual a comment made that OD is controlled by the ECU or by a switch. Mine is a 1984 and I have the switch on console.
Reason I ask is that I use EBL-ECU and it has torque coverter control based upon TPS-coolant temp-MPH. I do not see MAP? Not sure if those settings affect 4+3?
Reason I ask is that I am seeing the OD rapidly move in and out occasionally. Totally intermittant and infrequent however it is more often when car is under a load 70+ MPH at cruise high MAP.
It happened a couple years back by was a result of insulation on wires in OD being deteriorated but that was repaired and sealed well. In that case the OD light would blink but today it says on solid when in OD.
I also have highway mode enabled to enlean the A/F so possibly it is too lean and is misfiring. I enrichened a tad today. I am seeing the leanest at 16.8/1 on WB.
Fluid in OD is topped off and that did not help. It was about 80% full on inspection B4 topping off. It does leak a bit. I top off in spring.
when OD unit is failing what is symptom? Does it fail all at once?
Past week it is working fine?
Reason I ask is that I use EBL-ECU and it has torque coverter control based upon TPS-coolant temp-MPH. I do not see MAP? Not sure if those settings affect 4+3?
Reason I ask is that I am seeing the OD rapidly move in and out occasionally. Totally intermittant and infrequent however it is more often when car is under a load 70+ MPH at cruise high MAP.
It happened a couple years back by was a result of insulation on wires in OD being deteriorated but that was repaired and sealed well. In that case the OD light would blink but today it says on solid when in OD.
I also have highway mode enabled to enlean the A/F so possibly it is too lean and is misfiring. I enrichened a tad today. I am seeing the leanest at 16.8/1 on WB.
Fluid in OD is topped off and that did not help. It was about 80% full on inspection B4 topping off. It does leak a bit. I top off in spring.
when OD unit is failing what is symptom? Does it fail all at once?
Past week it is working fine?
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I have a 700r4 but I have heard some things...
The way I understand it, when you push the OD button that signals the ECM that you want overdrive. The ECM decides if the conditions are right for overdrive. It turns on the OD light and puts the OD unit into overdrive. One part of this is that you can't get OD in 1st gear. That's why it's +3 instead of +4. I vaguely remember reading somewhere about somebody who modified something to get a true 4 + 4, but I don't remember the details.
The way I understand it, when you push the OD button that signals the ECM that you want overdrive. The ECM decides if the conditions are right for overdrive. It turns on the OD light and puts the OD unit into overdrive. One part of this is that you can't get OD in 1st gear. That's why it's +3 instead of +4. I vaguely remember reading somewhere about somebody who modified something to get a true 4 + 4, but I don't remember the details.
