New owner with 4+3 problems
Thread Starter
Racer
Joined: Jul 2009
Posts: 454
Likes: 0
From: None None
Thanks a lot skybolt. Your technique worked great. I just took my car for a quick spin and with the O/D turned off the transmission acts fine, without any grinding. The only downside is that I have to shift a lot quicker now because the unit is turned off. But Id much rather shift more often than be grinding gears!
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
The button in 86/87/88 doesn't turn the OD on or off actually, it enables or disables the OD programming itself. As soon as you start the car you can hit the button to turn off the program. Unfortunately chevy new put an indicator light in the car to tell you if the program is running or not which I always found slightly annoying.
You shouldn't have to shift too quickly, the gears in this car and its torque mean you can take it up to something like 80MPH in 2nd and 110MPH in 3rd. I forget exactly, it's been a while.
You shouldn't have to shift too quickly, the gears in this car and its torque mean you can take it up to something like 80MPH in 2nd and 110MPH in 3rd. I forget exactly, it's been a while.
Thread Starter
Racer
Joined: Jul 2009
Posts: 454
Likes: 0
From: None None
The button in 86/87/88 doesn't turn the OD on or off actually, it enables or disables the OD programming itself. As soon as you start the car you can hit the button to turn off the program. Unfortunately chevy new put an indicator light in the car to tell you if the program is running or not which I always found slightly annoying.
You shouldn't have to shift too quickly, the gears in this car and its torque mean you can take it up to something like 80MPH in 2nd and 110MPH in 3rd. I forget exactly, it's been a while.
You shouldn't have to shift too quickly, the gears in this car and its torque mean you can take it up to something like 80MPH in 2nd and 110MPH in 3rd. I forget exactly, it's been a while.
Are you saying that those speeds are possible even with the O/D off? Because when I had mine off it felt like there was no way I could hit 80mph in 2nd haha.
Safety Car
Joined: Oct 2007
Posts: 4,426
Likes: 229
From: Pennsylvania
I have an 85 with the 4+3 also. There is an indicator light telling you only when the O/D is engaged, not disengaged. This light will say "Overdrive Engaged" when you shift the transmission to O/D. It is located in the small black box area in the middle of your dash. It's known as the Driver Information Center. Same as as where your "Security" light and "Door adjar" indicator lights are. The early 85's like mine had a small toggle switch on the console to switch the O/D on or off and later cars had the switch mounted directly on the top of the shifter. This light will go off automatically when you are in first gear and come back on when you shift to 2, 3, or 4 if you leave the O/D switch engaged. Always use your clutch when you shift in or out of O/D. 
Pro
Joined: Mar 2009
Posts: 639
Likes: 1
From: Brookfield CT NCM#522998
there is a button on the console or on the top of the shifter depending on what year your car is. Pushing the button engages or disengages the OD, depending on whether it is engaged or disengaged at the time. If you do nothing, once the car is warmed up and you are out of first gear, the car will engage the OD. So when you then pull up to your first stop light, push the button and take it out of OD mode. Then just shift up through the gears normally as if you had a 4 spd. Then when in 4th, clutch it and hit the button for OD. That is the way that I used to use mine, make it into a 5 speed. The only problem was when I would forget to hit the button when I was stopped and then I would shift to second and it would engage the OD, the jump from 1st to 2nd OD was a big one..................
That is not the way mine works; When I start the car and drive, the OD is off until I turn it on by pushing the button on top of the shifter. I believe that this is the way the unit is supposed to work for an '86 because I got a 'crib sheet' with the car from the original owner in Indiana. He said that he shifts the car up through the gears and only engages the OD in fourth on the highway.
Thread Starter
Racer
Joined: Jul 2009
Posts: 454
Likes: 0
From: None None
My car is an 85 with the button on top of the shifter. I'm pretty sure the o/d unit is on as soon as the car gets to 140 degrees because the unit kicks the rpms down as if its up shifting to another gear, at least that's how it seems on my car. However, after driving the car today and trying every combination of shifting and pushing the button I couldn't get a light on the dash to show up.
Pro
Joined: Mar 2009
Posts: 639
Likes: 1
From: Brookfield CT NCM#522998
My car is an 85 with the button on top of the shifter. I'm pretty sure the o/d unit is on as soon as the car gets to 140 degrees because the unit kicks the rpms down as if its up shifting to another gear, at least that's how it seems on my car. However, after driving the car today and trying every combination of shifting and pushing the button I couldn't get a light on the dash to show up.
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Thread Starter
Racer
Joined: Jul 2009
Posts: 454
Likes: 0
From: None None
I like the sound of the O/D unit being off until you choose it to be on because this is pretty confusing, to me atleast haha.
But anyways, I know that the screen in the dash works because it does display door ajdar, hatch adjar, and security. How would I be able to check and see if the light is good or if its a bad wire or relay? or would I have to take the dash piece off and by that time I might as well change the light anyways since Im already in there?
But anyways, I know that the screen in the dash works because it does display door ajdar, hatch adjar, and security. How would I be able to check and see if the light is good or if its a bad wire or relay? or would I have to take the dash piece off and by that time I might as well change the light anyways since Im already in there?
Pro
Joined: Mar 2009
Posts: 639
Likes: 1
From: Brookfield CT NCM#522998
right, it's probably the Od light only if others are ok. When the key is on, but the car if off, I think all of the lights will light, just so that you can see that they all work; then they all go out as the car is started. The empty space in the console is where the bulb must be burned out. I am not sure about taking it apart, but I am sure someone here has done it, and recently, and will be on any time now to tell you exactly how to take it apart, and what part number you need for the new bulb.
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
I have an 85 with the 4+3 also. There is an indicator light telling you only when the O/D is engaged, not disengaged. This light will say "Overdrive Engaged" when you shift the transmission to O/D. It is located in the small black box area in the middle of your dash. It's known as the Driver Information Center. Same as as where your "Security" light and "Door adjar" indicator lights are.
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
That is not the way mine works; When I start the car and drive, the OD is off until I turn it on by pushing the button on top of the shifter. I believe that this is the way the unit is supposed to work for an '86 because I got a 'crib sheet' with the car from the original owner in Indiana. He said that he shifts the car up through the gears and only engages the OD in fourth on the highway.
Now... if you met one of the conditions in gears 1/2/3 (certain combos of RPM & TPS voltage) that prevent the OD from engaging until cruising in 4th, that would be normal.
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
A normal L98 might have trouble reaching 6K in those gears, but modified ones ceratinly can. I can attest to 150 in 4th with a broken OD pretty easilly.
3rd Gear
Joined: Jul 2009
Posts: 3
Likes: 0
I have an 84 and was going to change out the Doug Nash od unit because it would not operate properly. When I ordered the factory manual I found the od would not worrk at under 178 degrees. When I checked the thermostat it was a 160 degree unit which is just fine for an automatic. First thing I would do is get a manual. Get the original Chevrolet shop manual not just a Haynes or something like that. They are all helpful though.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Makes no difference what trans is in car
Read
http://forums.corvetteforum.com/c4-t...hermostat.html
http://www.corvetteactioncenter.com/...-vs-180-a.html
Read
http://forums.corvetteforum.com/c4-t...hermostat.html
http://www.corvetteactioncenter.com/...-vs-180-a.html
Pro
Joined: Mar 2009
Posts: 639
Likes: 1
From: Brookfield CT NCM#522998
That doesn't sound right. The OD program has always AFAIK been on be default at startup. There are some bits in the ECM you can alter to change OD to be off by default, but this isn'r normal unless you've reflashed the car.
Now... if you met one of the conditions in gears 1/2/3 (certain combos of RPM & TPS voltage) that prevent the OD from engaging until cruising in 4th, that would be normal.
Now... if you met one of the conditions in gears 1/2/3 (certain combos of RPM & TPS voltage) that prevent the OD from engaging until cruising in 4th, that would be normal.
The original owner may have done something to reflash the ecm then; there are lots of 'improvements' under the hood where some 'work' has been done; so it wouldn't surprise me. However, I like the way it works now, and if it was always on at startup, I would want to turn it off anyway. I dont want the unit constantly downshifting everytime I jump on the gas!! Right now, the only time the unit will automatically downshift is in 4th when I jump on the gas.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Thread Starter
Racer
Joined: Jul 2009
Posts: 454
Likes: 0
From: None None
FYI.. this light was later moved to be with the tachometer. It is a small [D] looking light right above to two large digits under the tachometer curve. There is also a light on the dash that gives suggestions about when to shift into OD, but what only lights up once during the initial startup dashboard test is the light beneath it that says "FOR BEST ECONOMY".
Racer
Joined: Sep 2004
Posts: 258
Likes: 0
From: Coram NY
Bottom line, there are alot of things - temp & vacuum that the ECU senses to drop our of OD, or to go into OD. but the grind in 2nd gear
coupled with what sounds like transmission slipping in reverse (you didnt mention that) more pronounced when hot leads back to the clutches wearing into the OD case and slipping, this can happen in or out of overdrive. The #1 rebuilder of the 4+3 overdrive unit is here on Long Island - S&K speed in Lindenhurst speak to Brian he's been around for along time doing these OD units, even has a cut-away OD to show you whats going bad in yours.
1075 Route 109
Lindenhurst, NY 11757-1003
(631) 957-9525
Tom
coupled with what sounds like transmission slipping in reverse (you didnt mention that) more pronounced when hot leads back to the clutches wearing into the OD case and slipping, this can happen in or out of overdrive. The #1 rebuilder of the 4+3 overdrive unit is here on Long Island - S&K speed in Lindenhurst speak to Brian he's been around for along time doing these OD units, even has a cut-away OD to show you whats going bad in yours.
1075 Route 109
Lindenhurst, NY 11757-1003
(631) 957-9525
Tom