Pos Doug Nash!!!
Thread Starter
4th Gear
Joined: Jul 2004
Posts: 4
Likes: 0
Pos Doug Nash!!!
Grrrrrrrr.... i got this brand new remanufactured Doug Nash 4+3 transmission. I've had it just long enough for the warranty to run out. And now it's giving me hell. I was hoping you guys could tell me you've had this problem before and it's a simple fix...
Without pressing the button to go into overdrive, it constantly does go into overdrive. If i press on the gas enough it comes out of overdrive but it goes right back in again. IT EVEN TRIES TO GO INTO OVERDRIVE IN FIRST GEAR
When it goes from drive to overdrive or viceversa it makes a big banging sound probably 3-5 times before it actually finds a medium. My sister was driving behind me on the way home when this happened, and she let me know when we got home that the car was giving off a terrible smell.
Please, PLEASE tell me you guys have some ideas on this???
Without pressing the button to go into overdrive, it constantly does go into overdrive. If i press on the gas enough it comes out of overdrive but it goes right back in again. IT EVEN TRIES TO GO INTO OVERDRIVE IN FIRST GEAR
When it goes from drive to overdrive or viceversa it makes a big banging sound probably 3-5 times before it actually finds a medium. My sister was driving behind me on the way home when this happened, and she let me know when we got home that the car was giving off a terrible smell.Please, PLEASE tell me you guys have some ideas on this???
Team Owner
Joined: Mar 2000
Posts: 83,381
Likes: 87
From: Boston, MA
Well something doesn't sound right. If it is trying to go into O/D in 1st gear then it is sensor/switch related. If you don't fix that then O/D will be toast soon if not already. Did the unit come with brand new switches/sensors or did you have to transplant your own?
Team Owner
Joined: Mar 2000
Posts: 83,381
Likes: 87
From: Boston, MA
Originally Posted by jfb
The very same thing happened to my 87's OD. I sent it to S&S and it was rebuilt, no simple fix.
Safety Car
Joined: Jun 2003
Posts: 4,509
Likes: 239
From: Coconut Creek FL
Originally Posted by dave_85
Check the wires on the connector for the OD relay. The insulation
pulls back and the wires can short together and turn the OD on/off
not under control of the ECM.
pulls back and the wires can short together and turn the OD on/off
not under control of the ECM.
Did this to my 84 and got a few more miles out of it...then said the hell with it, put in a ZF6! no more POS! :-)
you would be surprised how the wires are bare on those relays!
Thread Starter
4th Gear
Joined: Jul 2004
Posts: 4
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WOW guys, i REALLY appreciate the help. Every time i come here you guys are FULL of information. Eventually i'll know enough about these things to return the favors and offer some advice of my own.
I'm gonna tell the mechanic to check those wires for a short like you posted Dave. If that doesn't turn out to be the problem, then THIS time i'll spend the extra money for the ZF6!
I'm gonna tell the mechanic to check those wires for a short like you posted Dave. If that doesn't turn out to be the problem, then THIS time i'll spend the extra money for the ZF6!
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Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
I agree with Scorp.. sounds like an electrical problem. The shuttering may be mechanical, but can be caused by the relay also.
For now, I'd hardwire a 12 V switch to the solenoid terminal on the side of the OD, or disconnect it completely to avoid making anythiing worse.
For now, I'd hardwire a 12 V switch to the solenoid terminal on the side of the OD, or disconnect it completely to avoid making anythiing worse.
Team Owner
Joined: Jan 2003
Posts: 20,292
Likes: 239
From: Summerland B.C. Canada
Originally Posted by dave_85
Check the wires on the connector for the OD relay. The insulation
pulls back and the wires can short together and turn the OD on/off
not under control of the ECM.
pulls back and the wires can short together and turn the OD on/off
not under control of the ECM.
Start There
Thread Starter
4th Gear
Joined: Jul 2004
Posts: 4
Likes: 0
Originally Posted by dave_85
Check the wires on the connector for the OD relay. The insulation
pulls back and the wires can short together and turn the OD on/off
not under control of the ECM.
pulls back and the wires can short together and turn the OD on/off
not under control of the ECM.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
The overdrive relay is located on the firewall between the brake booster and distributor. Actually, theres two identical relays there. The one in back is your fuel pump relay. The wires going to both of them shrink overtime and can short out.. ALL older vettes are like this. You might as well fix up the wires to both relays while you're in there.
The way the overdrive relay works... when a certain set of conditions is met (overdrive switch on, RPM below ~3200ish, not in 1st gear, engine temp > 120) and the ECM sends a ground signal to the relay, which closes it and then the relay powers the overdrive indicator light on the dashboard. The relay then also applies 12V to a wire running down the firewall to a blade terminal on the drivers side of the overdrive unit itself. If the internal pressure switch is closed (meaning at least ~150 psi ATF pressure), the 12V signal makes it to the overdrive solenoid, energizing it and thus changing the fluid paths in the overdrive unit.
The way the overdrive relay works... when a certain set of conditions is met (overdrive switch on, RPM below ~3200ish, not in 1st gear, engine temp > 120) and the ECM sends a ground signal to the relay, which closes it and then the relay powers the overdrive indicator light on the dashboard. The relay then also applies 12V to a wire running down the firewall to a blade terminal on the drivers side of the overdrive unit itself. If the internal pressure switch is closed (meaning at least ~150 psi ATF pressure), the 12V signal makes it to the overdrive solenoid, energizing it and thus changing the fluid paths in the overdrive unit.
Team Owner
Joined: May 2002
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Originally Posted by lead foot 85 vet
the overdrive relay is closest to te firewall
I usually use the trial and error method.
Also, for future reference:
If you're ever stranded due to a suspected failed overdrive relay, just swap the plugs on those relays. I know you can drive with no fuel pump relay, (because an oil pressure switch also powers the pump).. but you might need it hooked up at least to start the car.
Team Owner
Joined: Mar 2000
Posts: 83,381
Likes: 87
From: Boston, MA
Originally Posted by CentralCoaster
I know you can drive with no fuel pump relay, (because an oil pressure switch also powers the pump).. but you might need it hooked up at least to start the car.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Originally Posted by scorp508
I've driven with O/D unplugged before and the car it still good for 150mph in 4th gear.
You'd get about 120 miles down the road, and coast for another 20.
