4+3 Transmission Temp Question
Thread Starter
Heel & Toe
Joined: Mar 2011
Posts: 24
Likes: 0
4+3 Transmission Temp Question
I have the 87 vette with D. Nash 4+3. What temperture sending activates the transmission o-drive? Is it coolant or manifold temp sensor? If so where is it physically located on the car and how do I determine if it needs to be replaced, where can I purchase?
Team Owner
Joined: Jan 2003
Posts: 20,306
Likes: 242
From: Summerland B.C. Canada
The coolant sensor at front of intake. If it's out of whack, the ECM should store a code 14 or 15.
http://members.shaw.ca/corvette86/Code%2014.pdf
http://members.shaw.ca/corvette86/Code%2015.pdf
What problem are you having with your OD ?
http://members.shaw.ca/corvette86/Code%2014.pdf
http://members.shaw.ca/corvette86/Code%2015.pdf
What problem are you having with your OD ?
Thread Starter
Heel & Toe
Joined: Mar 2011
Posts: 24
Likes: 0
Trying to explain what is happening with 4+3 so it is understandable.
When I start the car, oil and coolant temp readings are Lo on indicator (LED).
* Accelerate in first gear the transmission is not in overdrive.
* When I shift from 1st to 2nd it automatically drops into overdrive
(in 2nd gear) without touching the button.
* I have tried running it faster in 1st and it still drops into o-drive when shifting into 2nd (still Lo temp).
* It seems to stop or intermittently continue to do this after the car is up to temp.
When I start the car, oil and coolant temp readings are Lo on indicator (LED).
* Accelerate in first gear the transmission is not in overdrive.
* When I shift from 1st to 2nd it automatically drops into overdrive
(in 2nd gear) without touching the button.
* I have tried running it faster in 1st and it still drops into o-drive when shifting into 2nd (still Lo temp).
* It seems to stop or intermittently continue to do this after the car is up to temp.
Team Owner
Joined: Jan 2003
Posts: 20,306
Likes: 242
From: Summerland B.C. Canada
When I start the car, oil and coolant temp readings are Lo on indicator (LED).
* Accelerate in first gear the transmission is not in overdrive.
* When I shift from 1st to 2nd it automatically drops into overdrive
(in 2nd gear) without touching the button.
* I have tried running it faster in 1st and it still drops into o-drive when shifting into 2nd (still Lo temp).
* Accelerate in first gear the transmission is not in overdrive.
* When I shift from 1st to 2nd it automatically drops into overdrive
(in 2nd gear) without touching the button.
* I have tried running it faster in 1st and it still drops into o-drive when shifting into 2nd (still Lo temp).
The ECM uses coolant temp, RPM, vehicle speed, throttle position, and Mass Air info, to determine if OD will be allowed.
Team Owner
Joined: Jan 2003
Posts: 20,306
Likes: 242
From: Summerland B.C. Canada
If you have a scanner, you could see what the ECM is seeing.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
On this page, look at the 87-88 column for 1st gear. That will show the operating parameters for the OD unit.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
but if the O/d relay is jammed in the On position
( either mechanically or by the control wire being grounded )
then you will get O/d engagement (except in 1st ) regardless of engine temp.
Last edited by vetteoz; Apr 18, 2011 at 10:33 AM.
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Melting Slicks
Joined: Aug 2003
Posts: 3,395
Likes: 393
From: Lakeville MI
Some $32B bins have 50 C for the upshift enable temperature, others as low as 23.75 C (such as ABTR).
Doesn't take very long for coolant temp to exceed 23.75 C.
Note: The throttle position is evaluated in first gear to set the 1st gear look ahead ok flag. Z51 cars have a 25% threshold, others a 40% threshold (despite what the chart says).
Assuming non Z51, If you exceed 40% tps while in first gear, the first gear look ahead ok flag will be set. This will prevent O/D from upshifting until 4th gear has been detected.
