1984 4+3 trans question
Thread Starter
Heel & Toe
Joined: Dec 2010
Posts: 20
Likes: 0
1984 4+3 trans question
i checked the the search i found some info which was useful but when im driving down the hwy with the od engaged after a while about 5mins the car will disengage the od and drop down to 4th would this be caused because i had to slow down a little? the od light comes off when it happens, so do i just need down shift and thats how it works or do i have a problem
Instructor
Joined: Mar 2010
Posts: 216
Likes: 4
From: Shrub Oak NY
Does the downshifting happen when you give it gas and the RPM is down 2000 or less? That might be a programmed downshift. Also if the coolant temp is below something like 175 overdrive is locked out - is the coolant temp getting that low?
I just got mine (1984 too) working so have only driven like 200 miles with an OD that works & I'm still trying to figure out what it wants me to do. I find that on the highway when I give it less gas than an automatic would downshift at the 4+3 downshifts and surprises me.
Also there is a pressure switch in the OD that kills high range if the fluid is low but the light would stay on because the switch is after the light (and not shown on the wiring troubleshooting manual, only in the shop manual-ask me how I know) but that's not your problem.
I just got mine (1984 too) working so have only driven like 200 miles with an OD that works & I'm still trying to figure out what it wants me to do. I find that on the highway when I give it less gas than an automatic would downshift at the 4+3 downshifts and surprises me.
Also there is a pressure switch in the OD that kills high range if the fluid is low but the light would stay on because the switch is after the light (and not shown on the wiring troubleshooting manual, only in the shop manual-ask me how I know) but that's not your problem.
Intermediate
Joined: Aug 2010
Posts: 35
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From: Indianapolis IN
I'm in Indiana, and once it got cold outside my '84 would drop out of overdrive just because the coolant temp would drop below 178ish. Chevy lowered this operating temp for 1985, and then I think again in 1986.
Le Mans Master
Joined: Aug 2000
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From: Australia
Drifting
Joined: May 2006
Posts: 1,428
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From: Chewelah Wa
I would check fluid level and go from there. If the light is shutting on and off, ECM and relay most likely working properly. EDIT: If the light is going on and off with the overdrive, fluid level (pressure switch) is OK, most likely culprit is the OD switch, wiring from OD switch to ECM, ECM to relay wiring, or a bad ground on this circuit (ECM,OD switch) I would check fluid level anyways.
Last edited by powerpigz-51; Feb 7, 2011 at 07:16 PM.
Thread Starter
Heel & Toe
Joined: Dec 2010
Posts: 20
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well ill check the rpms and the temp on the way to work tomorrow. i did the trouble shooting codes and the only thing coming up is 24 which is the vss which i know of and im in the process of getting it fix.
is there a dip stick for the overdrive fluid? and last thing is running 24-2600 rpms too hard on the engine to get to work i need to jump on the hwy and when it drops out it run about 24-2600 rpms what you think
is there a dip stick for the overdrive fluid? and last thing is running 24-2600 rpms too hard on the engine to get to work i need to jump on the hwy and when it drops out it run about 24-2600 rpms what you think
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
The OD unit will not activate until your engine temp gets to at least 123 degrees. after that it will automatically engage in 2nd, 3rd and 4th gears unless you turn it off. When you are in OD mode, in any gear, and you apply a little too much throttle, the tranny will automatically kick out of OD and downshift into the normal manual gear. The transmission should never kick out of OD while you are cruising along.
If you are dropping out of OD without adding throttle, I suggest that you check the OD unit fluid level. While you are at it, change the OD unit filter and clean out the pan magnet. See attached write-up.
If you are dropping out of OD without adding throttle, I suggest that you check the OD unit fluid level. While you are at it, change the OD unit filter and clean out the pan magnet. See attached write-up.
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
There is a fill plug on the drivers side of the OD, fluid should be to the bottom of the hole.....the temp thing has a lot of merit, also. I drove my car for 3 years without a functioning OD, your motor will be fine. OD with no fluid, not so fine. I have my switch wired directly to the relay, bypassing the ECM. (great mod) My OD used to do the same as yours is doing.
Last edited by powerpigz-51; Feb 7, 2011 at 07:41 PM.
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Le Mans Master
Joined: Aug 2000
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From: Australia
Drifting
Joined: Jun 2009
Posts: 1,287
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From: Upstate NY
176F on a '84
http://www.5speeds.com/43table.htm
http://www.5speeds.com/43table.htm
When I first bought my 84, I had this problem. I checked the fluid level and every other possible reason -ended up having a thermostat that was stuck open, so it would work great, until the engine temp would drop to about 176F and it would shut off the OD.
Installed a new stock thermostat and never have the problem once up to operating temperature.
Instructor
Joined: Mar 2010
Posts: 216
Likes: 4
From: Shrub Oak NY
When I first got mine last year the OD did not work at all, no light or anything. So I used to do 55- 60 MPH in the right lane as I don't drive it much & I had way bigger fish to fry then the OD. The car seemed to use a lot of motor oil like that.
I finally looked at the OD problem & the console switch was bad. I was able to open the switch up, clean it & polish the contacts with 400 or 600 sandpaper, lubed it & it works fine now, the switch & the OD. It was really dirty & sticky inside - being in the console where it is the switch is subject to beverage spills - I should have thought of that earlier.
The the OD stopped working - to have loved and lost is WORSE than never having loved at all - but it was just low fluid.
I finally looked at the OD problem & the console switch was bad. I was able to open the switch up, clean it & polish the contacts with 400 or 600 sandpaper, lubed it & it works fine now, the switch & the OD. It was really dirty & sticky inside - being in the console where it is the switch is subject to beverage spills - I should have thought of that earlier.
The the OD stopped working - to have loved and lost is WORSE than never having loved at all - but it was just low fluid.
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Thread Starter
Heel & Toe
Joined: Dec 2010
Posts: 20
Likes: 0
Well on the way to work this morning everything ran fine i noticed that the switch when i first turn it on the od light did not even come on than i wiggled it a little than it came on and engaged. on the way home it ran fine till about a mile from my exit than it just came out again the temp was about 185 and the rpms were at 1800 so im wanting to think maybe the switch is bad or maybe dirty contacts like projectc4 said or low fluid. what do ya'll think?
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Well on the way to work this morning everything ran fine i noticed that the switch when i first turn it on the od light did not even come on than i wiggled it a little than it came on and engaged. on the way home it ran fine till about a mile from my exit than it just came out again the temp was about 185 and the rpms were at 1800 so im wanting to think maybe the switch is bad or maybe dirty contacts like projectc4 said or low fluid. what do ya'll think?
