4+3 OD Shift

[Achilles]

I've had a problem with my '86 in that the 4+3 automaticaly shifts into OD when it's cold. And it only does this once. I was wondering if this is a chronic problem with these models or is there something wrong in the system. Is there a standard number of turns for the T-Rod for the OD button? Also, can the OD be deactivated?

It's not much of a problem, just annoying.

 

[c4cruiser]

The OD will not activate until the coolant reaches 122 degrees.

Check this site out for the 4+3 basic operating characteristics:
http://www.5speeds.com/dne.htm The "OD Comparison Chart" link has infor on how the different years operate.
There's a message board from that page here: http://www.5speeds.com/archive/27.html that may be of some help

The ECM controls the OD so deactivating it so that it defaults to OFF may require a custom chip in the ECM. Not too sure if that can even be done.

 

[nyernga]

Theres a little trick you can do to make the ecm think the transmission is always in 2nd thereby making the od completely manual. That's what they say anyway. I did it almost 3 years ago and it works fairly well. The only time mine goes into OD by itself, high speed notwithstanding, is when the temp hits 122 as stated before. Once I hit the button it goes back to 4th and never happes again until the cars left overnight. These 4+3 are tempermental to say the least.

And yes, there are a certain number of turns for the "T" rod. The problem is it's the exact number of turns it took to remove it so if you didn't count them coming out......trial and error is best for putting it back in. The other side effect of the mod I did is that if I so desire, I can have OD in first gear as well. Given my car is used mainly on weekends and not my daily driver, I'd do as much research as possible before monkeying with it. The 4+3 is actually what caused me to join the CAC 4 years ago. Check with Ken here as well. He can steer you to a wealth of info on these puppies...

Len

 

[rrubel]

Unfortunately, you can't do the 'full manual' mod on an 86 - that year lacks the extra connector that has to be jumpered.

I wonder if someone tried this with the original poster's car?

Remember, too, that if you hit the button once each time you start the engine, then it'll turn off overdrive until next restart.

Also, you probably don't want to completely disable it - over 124 mph (varies with year) or so, the car has to go into OD to keep accelerating.
[RICHR]

 

[nyernga]

Unfortunately, you can't do the 'full manual' mod on an 86 - that year lacks the extra connector that has to be jumpered.

I gotta pay closer attention to the model year.

Len

 

[Achilles]

Unfortunately, you can't do the 'full manual' mod on an 86 - that year lacks the extra connector that has to be jumpered.
[RICHR]

I don't know about that. Mine will not go into OD automaticaly at all, except for when it is cold and I get a about a block or two from home. It will automaticaly shift into OD one time. Once I push the button back into direct drive, it stays in direct until I manualy push the OD button. Also, I have drag raced this car and reached pretty high RPMs and the car never shifts into OD by itself.

I do know that this car has had alot of work done to it over it's life, (not all of it quality work either), so maybe something has been done to the ecm that is affecting the OD. Because I also have OD in first gear. Not that I need it. If the 4+3 is designed to shift into OD automaticaly at a certain RPM, maybe I should leave it alone because I don't like that feature....Must be a control thing.

Hmmm, Maybe I have a 4+4 tranny!:eyerole

Thanks for the info...

 

[rrubel]

Is it possible you don't have the original transmission in your car? If someone did a swap for a later year, then you'd have different behavior... If you read some of the articles that Ken's collected on the 4+3, you'll see that 86 is listed as the one year without the extra connector... I spent a long time under my car once, trying to find it.

The ECM on 86's does control the OD behavior (again, the only year for this much control); if you have a new ECM then that might also explain it. I do know that you can't program the OD out by using the MEMCAL - Jeff and I looked into it, although you CAN change the shift points.

Oh, and the car staying in direct once you've pushed the button is normal - you've turned off the OD and it will NOT go back on unless you either turn the engine off or go over 124 mph.

[RICHR]

 

[Achilles]

Oh, and the car staying in direct once you've pushed the button is normal - you've turned off the OD and it will NOT go back on unless you either turn the engine off or go over 124 mph.

[RICHR]

That explains it. Maybe I should try to get an owner's manual that might explain how to operate the OD correctly. You could be right about the tranny swap. Like I said, quite a bit of work has been done on this car over the years.

 

[c4cruiser]

I've run my 87 at track days where the speeds I have reached on the straights was just over 126 and the OD never did engage. :confused This was a full-throttle condition where I would hit that speed and then have to hit the brakes for a turn. There is a shorter straight where I see about 110-114 and no OD at that point either. I could see this if there was a slight error in the speedo sensor but if that chart on the link I posted is correct for a 103MPH automatic OD engagement, then there must be something wrong

I hit the button at startup to turn OD off and that works to keep the unit off, but if there is a supposed forced "OD on" at a certain speed, it doesn't seem to work in my tranny. Other than that, the OD works correctly as shown in the chart. The tranny and ECM are originals.