Funny transmission problem
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Mountain Pass
Joined: Nov 2001
Posts: 222
Likes: 5
From: NE PA
Funny transmission problem
This has happened about 4 or 5 times to me. As I apply the brakes going down a hill, I let off the brakes and the truck seems to jerk or spudder like it is between gears. I think the OD light flashes briefly. I can only get it to happen once in a while, but I would like get it fixed before I hit 36K because after that I have to PAY.
Fleet Mechanic
Joined: Jan 2007
Posts: 1,293
Likes: 18
Its the trans deciding whether the high vacuum condition means you have reached speed and OD can be engaged or whether you're coasting down and it can downshift. I don't know if anything can be done about it, but always the first thing is to check fluid level and condition.
Post Fiend
Joined: Jan 1997
Posts: 23,165
Likes: 18
From: Enjoying the real world.
The OD light flashing indicates a transmission fault code has been set. Sometimes it will go away, sometimes it stays. If you have a code reader connected to the truck while driving you'll be able to pull codes immediately when it happens before they are erased (if they are, as I noted sometimes they go away).
Elder User
Joined: Dec 2006
Posts: 662
Likes: 2
From: CO
The whole powertrain is controlled by the PCM (hence the name), so any code should be stored there to be pulled by an appropriate reader. Seems like some folks have reported older readers not working even though they supposedly used the right protocol.
Post Fiend
Joined: Jan 1997
Posts: 23,165
Likes: 18
From: Enjoying the real world.
Any reader which supports the CAN protocol (not all do) should be able to pull the codes. Leave it plugged in while driving, keeping both it and the cable tucked in a safe location so it can't interfere with driving. Some codes can be transient and will go away, often within a mile or so, sometimes by simply turning off the ignition. I had this happen with a trans fault code. It was set going up a huge incline in Virginia and went away before I could find a place to pull over and read it. On the next incline I had the reader plugged in and caught the code while driving before the PCM cleared it.
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