other title didn't post right,sorry -
What are the guidelines for the OD to engage?
mph
temp
rpm
Also what does the cable do? I asume it kicks it out of OD when you go WOT or does it vary pump pressure or both? I ask cause mine is not working. Last owner said it worked fine till the dash went out. I fixed the dash and now the OD light comes on when you hit the switch but nothing happens. Did the fluid change, the old fluid was like mud didn't look changed in 83k mi. I cleaned and refilled with mobil 1 but still nothing. Could a valve or something be stuck? The cable had full range of motion and everything cleaned up, should I drop the valve body and clean it? Any other things I should try?

 

Check out http://www.5speeds.com
They have all the specs and specialize on 4+3's. I had some problems with mine and they recomended what to buy as in parts. In fact the part I needed was not sold by them.

Good luck.

 

Here's another site -
http://www.corvetteobsession.homeste..._dougnash.html

Won't print out for poopie, but some good info there...

 

thanks for the links guys

 

For an 85
min coolant temp for apply would be 140degs. F
first gear only on down shift when O/D was engaged will come out with just about any acceleration
second gear, after warm up and with out hard acceleration in first will come on when shifting from first, no throttle down shift
third gear only when on when shifting into third will not down shift out of O/D with throttle
forth gear O/D will down shift with over 80% throttle will up shift again below 80% will also auto up shift into O/D over 110mph

Throttle cable is only used to adjust apply pressure of the O/D clutches for shift feel.

David Fulcher

 

thanks that helps alot!

 

Let me add a few other things to look at for a possible reason for O/D inop.. First while you are driving and you turn the O/D on do you still feel engine braking if you let your foot off the gas? This is important because with the sound of the fluid you had in the unit there is a real good chance the unit is burned up. If when you turn the O/D on you loose engine braking this is an indacation that the O/D clutches are burned, what happens is the car is able to keep moving forward because of the sprag clutch in the trans which is a one way clutch so the engine can drive the car forward but the engine is unable to slow the car down. If the car was slipping in reverse but could go forward then you would have burned direct clutches also. Now if the car does not loose engine braking when the O/D light comes on then you might need to check the connection at the side of the O/D unit were the power comes into the unit, there can be a poor connection there. Also jumping the ALDL connector A to B terminal and turning the ignition key on and the O/D switch the light should also come on so you can go underneath and check for power down at the unit. But do some of these checks and let us know what you fined out.

David Fulcher

 

OK I have normal engine braking and no slipage in reverse. The fluid wasn't burnt just old and there was a lot of sludge. I'll check the connections as soon as it stops raining,hopefully tomarrow. The OD light stays on in 2,3&4 when switched on should it only light up when the unit engages or when switched on? It also stays on in first when downshifting into first but goes out when the rpm drops. Does any of this sound right?

 

Shoot - I missed what year you have... :confused:

With the coolant temp 122+ F, my '86 OD light is off while the car is not moving. I roll off in 1st gear and it comes on as I shift into second. I have to take the RPMs a little higher in 1st than if OD were not engaged, otherwise I let the clutch out doing 700 RPM. chug-chug-chug....

The OD light stays on while I shift through the gears, even as I slow to a near stop with the *clutch in* and the gear shifter in 1st. When I slow to about 2 or 3 MPH, the OD light goes out. This is kind of a pain because I might want to take off from 4 MPH and it's in OD in 1st gear! It starts to go in '1st OD' and then it bucks once into regular 1st gear. 2nd gear OD would have been too low an RPM, so I've learned to click out of OD an duse straight 2nd in this situation.

This may not be normal, but it's how mine operates. YMMV

 

84,5 and 6 O/D lights are all powered by the O/D relay so if the light is on there should be power to the unit. This also means that using an 85 shifter switch in an 86 shifter and then bypassing the ECM you can turn the O/D control to manual control. It is true that if the O/D is engaged while you down shift into first in an 86 to 88 it will stay in O/D for a short time unless you give it gas or come to a stop believe it or not this was done to get away from a down shift clunk feel when coming to a stop they keep it in O/D untill the speed hits 0, so when in turns off you will not feel the clunk, they also know 1st O/D is also not good so they have the programing in there to kick it out if you go to give it gas. Not the best way to do things but it does work. Also if there was a lot of sluge in the pan when you removed it there sould be a chance that the is so much build up in the O/D shift solenoid that it can not move far enough to alow a shift into O/D. There is also a chance that the wire in the oil pan of the unit may have fallen off, you just can't hook up a meter from the out side to check this out unless you are able to get the rear tires off the ground also, there is a 75psi oressure switch in there that will remain open untill the trans is able build up at least 75psi( again this is to protect the unit from being able to try to engage at to low of pressure). So if you were to hook up an ohm meter from the side terminal to the O/D case it should be open but when you put the car in gear and bring the rear wheels up over 10mph it should show low resistence, this would show two things 1- the trand O/D unit pump is working and able to produce pressure and also the wire in the unit is connected. If you were to remove the pan it is real easy to test the solenoid just jump 12 volts from the one lead at the pressure switch and the groung to the case and you should see the solenoid move, you should be able to clean it out with brake clean, I have not found problems with the valve bodies sticking but anything is possible but my guess the problem would lie somewere else.

David Fulcher