4+3 o.d. problem
Thread Starter
Heel & Toe
Joined: Oct 2005
Posts: 16
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4+3 o.d. problem
I recently purchased an 86 4+3 trans. Everything was shifting o.k for 4 or 500 miles. For about 30 miles the o.d. wouldn't engage. No light or anything. The next day it started working all of a sudden. Now it comes and goes. I also noticed when it doesn't work the fuel average light says zero and doesn't work either. When the o.d. does come on the light comes on also. Any suggestions. Thanks.
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
If the light doesn't come on, that's good news. It means your overdrive relay probably isn't getting the signal to turn it on. I don't know how that'd relate to the mpg display.
The computer looks for coolant temp, overdrive switch position, and what gear you're in, before turning on the overdrive. First check your relay wire insulation where it goes into the relay plug, see if there's any shorts. Then try swapping the plugs with your fuel pump relay to see if the problem goes away. The fp and od relay are the same part number, and right next to eachother on the firewall between the brake booster and wiper motor & distributor. I forget which is which. They have 140something printed on them.
If that doesn't solve it, it could be the console switch.
The computer looks for coolant temp, overdrive switch position, and what gear you're in, before turning on the overdrive. First check your relay wire insulation where it goes into the relay plug, see if there's any shorts. Then try swapping the plugs with your fuel pump relay to see if the problem goes away. The fp and od relay are the same part number, and right next to eachother on the firewall between the brake booster and wiper motor & distributor. I forget which is which. They have 140something printed on them.
If that doesn't solve it, it could be the console switch.
Advanced
Joined: May 2005
Posts: 66
Likes: 2
Originally Posted by rvrrat
Thanks for the advice. wiring looks o.k. Bought a new relay to try. Busy weekend, might be a few days. The switch on the console has never worked. I guessed it switches the o.d. off?
