I have been dissapointed about my chances of getting my +3 part of the 4+3 to work without going to the tranny shop and paying a ton of money that I don't have so finally I decided to just get under the car and do the basic electrical and switch connection checks and cleanings. I was delighted when I found what I thought might be the problem. There is a connection that goes into the side of the overdrive unit. The male terminal is actualy attached to the OD and the female part plugs in(just so you know which connection it is). On the female end there are 2 slender slits that are supposed to recieve the male connection from the overdrive. On the overdrive I only have 1 terminal, not the 2 like the female plug would suggest. Is this normal? It doesn't seem to be. So just to test things out I switched the holes that the single male terminal went into, and then I drove it. With the plug the way it was originaly I was able to downshift and the tranny would run just like an old school 4 speed, with the exception of the OD light coming on, and the upshift light coming on at the normal RPM's. After I made the change with the connection, while driving the overdrive light and upshift light would still come on like normal but the OD still wouldn't engage. I know this because at 62mph in 4th, the car was still running at 2400 rpm's. The thing that changed though was when I let off the gas the car would seem to kind of come out of gear and just roll freely, then when I would press the gas (not WOT, just ease onto the gas) the tranny would go back into gear. Whenever I went to slow down I couldn't engine brake because whenever I would downshift the car wouldn't go into gear until I tapped the gas again. It would stay out of gear and the OD light would stay on all the way till 1st gear (normaly it was off in first gear). I know this has got to be the OD trying to do something. What should be my next move? Where can I get the male connector if it is at all broken? I'm excited at the fact of having a working OD so please give me some help. Thanks.


[Modified by tarheelracer, 2:37 AM 6/19/2002]

 

My '86 has only one OD switch on the trans versus your '87 having three (at least I've read the '87 has three), but I can tell you that when I got my '86 the OD light worked with the button but no OD engaged...We found a blue wire at the switch crushed underneath a sidecover bolt; it came off when we poked at it, so I don't know if it was grounded out or just broken...

...But reconnecting it fixed the OD! Works real good now! I never use it, but occasionally I poke it just to confirm that it still works!

 

I don't know how much you've checked this problem, but if the fluid is low in the OD unit it will not engage. You also could change the fluid if it's old.

 

Ok, what fluid type would y'all sugest(haynes manual doesn't say). I think I might have figured it out, but I will deffinately change the fluid tomorrow. I'll let you guys know about the results.


[Modified by tarheelracer, 3:36 AM 6/19/2002]

 

Ok, i found it in the manual, Dexron 2 ATF, sound good?


[Modified by tarheelracer, 3:42 AM 6/19/2002]

 

That's it...There's a filter that needs to be changed also, most of the Corvette parts companies have it (Ecklers, Mad, etc.), make sure you change it too.

 

If you search past threads you'll see that the best fluid for the overdrive is Mobil 1 ATF (buy 2 quarts), you can get it at autozone. Make sure you change the filter also.

 

I'm too anxious to find out if it will work, I'm ordering the filter, but I'm gonna change the fluid and try to clean the filter because it looks just like a screen until a new one comes in.


[Modified by tarheelracer, 4:40 AM 6/19/2002]

 

Nevermind, that's a bad idea, I'll just be patient and save my OD.


[Modified by tarheelracer, 5:02 AM 6/19/2002]

 

That's exactly what mine does!
With the od off, it's just a four spd.
With it on, it does the exact thing your describing. My fluid was just changed with no differance!
I was told that the disc's were shot and it would need to be gone through! Not that the guy who told me that knows what he's talking about, but niether do I, not yet! Out with the 4+3, in with the 700r4!

 

No.....fight that temptation, if anything go 6-speed


[Modified by tarheelracer, 5:16 AM 6/19/2002]

 

Ewwww..... one of the weakest autos ever. :)

 

New fluid and filter are in. There is still no change. Does this sound like an OD rebuild?

 

Hmm.... first thing to do. Go back under the car, disconnect, clean, and reconnect all plugs. On '87 you should have.

1. 1st Gear Switch (on 4-speed)
2. OD Solenoid (side of OD)
3. Speed Sensor (tailshaft of OD)
4. Reverse Light Switch (on 4-speed near reverse rod)

Can't hurt. Can you try to explain a little clearer what the symptoms are again? I don't think I'm quite following.

 

Right....If what you are saying is that when the overdrive is engaged and you are at speed, the engine responds to throttle but the driveline does not (tranny freewheeling), and you believe it is the o/d, then your direct clutch plates are probably burnt. It's considered a "soft parts" rebuild. IF that is what it is then you should take care of it as soon as possible.
Over time it will get worse, you may kill your sprag clutch and/or loose the ability to shift into reverse. Then it's likely you will need a complete overhaul.

If that description above fits your situation then your problem is almost certainly NOT electrical, but mechanical in nature.

 

I agree with dublinvette. When I re-read your first message, this stuck out:

when I let off the gas the car would seem to kind of come out of gear and just roll freely, then when I would press the gas (not WOT, just ease onto the gas) the tranny would go back into gear

At no time should the od freewheel - either the inner clutch or outer clutch should be engaged at all times with the sprag clutch taking over during the shift. This is regardless of the electrical signal.

My recommendation - shoot David Fulcher an email. He is over in GA, I believe.

 

Scorp- All electrical connections have been cleaned with contact cleaner and electrical grease and reattached. This is about the best I can do on explaining-With OD hooked up, Transmission runs fine until you let off of the gas then it disengages. Whenever you hit the gas again it rengages. There is no overdrive shift ever. When you try to slow down and down shift, the car stays out of gear until you hit the gas again.

Dublinvette-The engine and tranny both respond to throttle, it is only when I let off the gas that the tranny disengages. When you say direct clutch plates do you refer to the clutches in the OD or the main clutch assembly in the 4 speed half of the transmission? I have a new clutch so I know the 4 speed half is working fine. The OD is disconnected until I get this prob. figured out so there shouldn't be any damage done to it.

Hendej- What's David Flulcher's email?

I don't have the means to deal with this myself, and I've only found 1 transmission shop that has ever worked on one. He said he couldn't give me a price until he got it out of the car, and by then, it's too late to back out of the deal. Does anybody have an idea of a price on the rebuild? If it is going to be $1000+ I can just tolerate not having an OD, but if it is reasonably priced I'll get the work done. The only reason I'm concerned is that I'm going off to college and I'll be doing alot of Hwy. driving and I don't like my car running 2,900 rpm's for an hour and a half. I appreciate all the help y'all have given. Thanks

Oh, almost forgot. Another fact: When the OD is connected and you stall the car and recrank it the car runs just like the OD is disconnected. I don't know what this means but maybe it will help. That was the main reason I had thought that it was electrical.


[Modified by tarheelracer, 4:03 PM 6/20/2002]

 

The clutch's referred to are in the OD unit.

Dave in on the forum. He also does one of the cheapest rebuilds around.

If the clutch has failed, you definatly don't wanna be using the OD. I don't remember if running around in non-OD will cause you any problems. I believe teh non-OD has the sprag as a backup device.

 

David-F
dfulcher5@juno.com

 

Ok, thanks, I'm gonna tell the guy that rebuilt my last transmission, y'all's theories and see what kind of price he can give me and then I'll give Dave an email.