Speedo going haywire!
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Post Fiend
Joined: Feb 2009
Posts: 8,005
Likes: 7
From: Ottawa, Ontario
Speedo going haywire!
So the speedo in my '91 E250 Club Wagon has been going haywire last 2 days.
Just after a 20 hour straight road trip.
Parked, it sits on 20km/h (15mph), and soon as you start moving, it starts flying all over the place, twitches, goes all the way around, almost back to 0, and stays stuck there sometimes, and cruising on the highway around 55-60mph, it'll read way over 100mph!
What the hell is going on?
It is a speedo cable, not an electronic speedo. E4OD tranny.
Just after a 20 hour straight road trip.
Parked, it sits on 20km/h (15mph), and soon as you start moving, it starts flying all over the place, twitches, goes all the way around, almost back to 0, and stays stuck there sometimes, and cruising on the highway around 55-60mph, it'll read way over 100mph!
What the hell is going on?
It is a speedo cable, not an electronic speedo. E4OD tranny.
Posting Guru
Joined: Dec 2012
Posts: 1,065
Likes: 2
From: western washington
it is an electric speedo, the cable is for the odo, look at the cable where it leaves the trans, there is a sensor that the cable plugs into, it has two wires, its $16 dollars it is the vss, if your tranny is not acting funny it could be a bad connection, some ware else, the sensor in the rear-end is for antilock brakes, in 1994 they integrated the systems. look at the OD light, is it blinking?
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Post Fiend
Joined: Feb 2009
Posts: 8,005
Likes: 7
From: Ottawa, Ontario
This is the old body style van, and as far as I know, it's a cable driven speedo/odo. There is a cable for sure, I see it coming up through the floor beside the steering column.
Everything works fine with it, no flashing OD light, only thing that doesn't work, and it never really did work, is the TC lock up, it will lock up everynow and then, but very rarely. Otherwise works perfect, the tranny is fully rebuilt and upgraded with 50k miles on it.
The Odo is working correctly, just the speedo that's all over the place.
If it was a bad cable, wouldn't it just quit working? And what's the speedo head? Is that in the trans. or behind the cluster?
Everything works fine with it, no flashing OD light, only thing that doesn't work, and it never really did work, is the TC lock up, it will lock up everynow and then, but very rarely. Otherwise works perfect, the tranny is fully rebuilt and upgraded with 50k miles on it.
The Odo is working correctly, just the speedo that's all over the place.
If it was a bad cable, wouldn't it just quit working? And what's the speedo head? Is that in the trans. or behind the cluster?
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Logistics Pro
Joined: Sep 2007
Posts: 3,737
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From: Western Mass
Speedo head is behind the cluster.
I would think a bad cable would stop working. A bad cable can cause speedo's to jump around. Not sure it would make it stick.
I would think a bad cable would stop working. A bad cable can cause speedo's to jump around. Not sure it would make it stick.
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Lead Driver
Joined: Oct 2003
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From: Madison, WI
Just speculating, but I could imagine a binding cable slowing down at the speedo head end, then when the bind releases (enough "twist" from the tranny end), it catches up, and this would manifest itself in the speedo dropping and then swinging high. Total cable revolutions would be the same as if it's working normally, so no odo error. Again, just a guess. I would start by disconnecting the cable at both ends, then find a way to turn the core and just see/feel/hear how it turns. You may even be able to disconnect it at the tranny end and turn it with a drill, and see what the speedo does. Then do the same with the drill turning the speedo head directly (not using the cable) Might narrow down the problem.
i ain't rite
Joined: Mar 2005
Posts: 65,481
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From: Marlboro Mental Hospital.
Just speculating, but I could imagine a binding cable slowing down at the speedo head end, then when the bind releases (enough "twist" from the tranny end), it catches up, and this would manifest itself in the speedo dropping and then swinging high. Total cable revolutions would be the same as if it's working normally, so no odo error.
Again, just a guess. I would start by disconnecting the cable at both ends, then find a way to turn the core and just see/feel/hear how it turns. You may even be able to disconnect it at the tranny end and turn it with a drill, and see what the speedo does. Then do the same with the drill turning the speedo head directly (not using the cable) Might narrow down the problem.
Postmaster
Joined: Aug 2010
Posts: 2,554
Likes: 7
From: Northern Arizona
What you describe is exactly how my speedometer behaved when my mechanical cable died. Eventually it bound completely and twisted in half. As it was binding and dying the pulse generator on my GVOD pigtail also went whacko and the truck started slamming violently in and out of overdrive... felt like I was getting rear ended over and over. Like Ill never forget it and stuff. I wish there was a way to use the differential tone ring as the GVOD sensor, but I am way off track. I am betting your cable is dying.
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Post Fiend
Joined: Feb 2009
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From: Ottawa, Ontario
So took the cluster out, the problem is indeed the head. Theres a very small copper looking bring between the head and the back of the speedo face, it's not giving enough resistance anymore to hold the speedo back, so it kind of turns with the drum of the head, I tryed lubbing it with electric motor oil, it helped, but still isn't working to well.
So next summer I'll replace the speedo, and play with the mileage to keep the original mileage of the van.
So next summer I'll replace the speedo, and play with the mileage to keep the original mileage of the van.
Fleet Owner
Joined: Jul 2006
Posts: 20,357
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From: Mi'kma'ki
So took the cluster out, the problem is indeed the head. Theres a very small copper looking bring between the head and the back of the speedo face, it's not giving enough resistance anymore to hold the speedo back, so it kind of turns with the drum of the head, I tryed lubbing it with electric motor oil, it helped, but still isn't working to well.
So next summer I'll replace the speedo, and play with the mileage to keep the original mileage of the van.
So next summer I'll replace the speedo, and play with the mileage to keep the original mileage of the van.
Postmaster
Joined: Dec 2011
Posts: 3,860
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What you describe is exactly how my speedometer behaved when my mechanical cable died. Eventually it bound completely and twisted in half. As it was binding and dying the pulse generator on my GVOD pigtail also went whacko and the truck started slamming violently in and out of overdrive... felt like I was getting rear ended over and over. Like Ill never forget it and stuff. I wish there was a way to use the differential tone ring as the GVOD sensor, but I am way off track. I am betting your cable is dying.
I realized long ago that all it is is a solenoid which, when on, engages the GVOD. Hook it directly to +12V with a switch in between(hint: My GVOD came with a gearshift mounted switch).
The GVOD will then stay locked in as long as you want; I've braked to a stop and started again with it still locked in. If it's not locked in(and you attempt to engage it), it takes longer to engage at lower speeds though.
You *may* want to hook a NC relay to the reverse light circuit(i.e. light comes on, contacts open, GVOD disables), because it will /stay engaged/ in reverse if you don't remember to take it out, and it /hates/ that. Or just remember to flip the switch off before going into reverse.
The only thing to be aware of is torque; it's apparently not as beefy in OD gear than direct drive, so flooring your truck in 1st over with a heavy trailer on isn't good for it. I've certainly used it in 2nd-over hill climbing, though, and it's never slipped or anything(it uses a conical clutch for engagement), so I'm pretty happy with mine.