Bouncing speedo
Posting Guru
Joined: Dec 2002
Posts: 1,297
Likes: 3
From: Billings MT
Bouncing speedo
Click HERE.
Look up your truck and go to the electrical section. I think it might be your speedometer gear in the transfercase. Like it might be worn. I don't know if that happens, but it is a simple cable driven unit.
The above site will show you how to take it out and stuff.
Good luck.
Someone else might have another idea.
Look up your truck and go to the electrical section. I think it might be your speedometer gear in the transfercase. Like it might be worn. I don't know if that happens, but it is a simple cable driven unit.
The above site will show you how to take it out and stuff.
Good luck.
Someone else might have another idea.
Post Fiend
Joined: Nov 2001
Posts: 14,947
Likes: 6
From: Topsfield, MA
Bouncing speedo
There isn't a speedometer gear in the transfer case. There is a sensor on the top of the rear differential that provides the speedometer readings. Try a search with the search engine for this problem, there are TONs of threads on this. Thanks.
Posting Guru
Joined: Dec 2002
Posts: 1,297
Likes: 3
From: Billings MT
Bouncing speedo
Justin, based on this, there is. I thought it was on top of the rearend right above the pinion yoke, too, until I saw this one day.
We all know that manuals can be incorrect.
It says all 1989-1993 or all 1988-1993.
Anyway, Justin is way more likely correct then me.
Last edited by jbalestri; Jun 20, 2003 at 02:04 PM.
Postmaster
Joined: Mar 2001
Posts: 4,968
Likes: 3
From: So Cal
Bouncing speedo
Interesting. Before ABS the speedo usually did run off the tranny and was usually a cable connection. With ABS, I assumed that all the trucks with ABS run off a sensor on the differential.
I would guess for 94 and up(my truck is 94) the speedo is based on the ABS sensor. For 93 and down it is a "classic" speedo cable off the tranny. I could be wrong since I am no where near a Ford expert and I only really pay attention to what I got.
In either case, Speedo jumping is a classic symptom of a problem with the speedo cable on the tranny or the ABS sensor on the diff. There can be other causes, but these are easy and cheap to check and fix, and I like easy and cheap fixes first.
Good Luck,
Jim Henderson
I would guess for 94 and up(my truck is 94) the speedo is based on the ABS sensor. For 93 and down it is a "classic" speedo cable off the tranny. I could be wrong since I am no where near a Ford expert and I only really pay attention to what I got.
In either case, Speedo jumping is a classic symptom of a problem with the speedo cable on the tranny or the ABS sensor on the diff. There can be other causes, but these are easy and cheap to check and fix, and I like easy and cheap fixes first.
Good Luck,
Jim Henderson
Post Fiend
Joined: Nov 2001
Posts: 14,947
Likes: 6
From: Topsfield, MA
Bouncing speedo
Ok lets clarrify. The 91 and below, used a cable system with a small plastic gear in the transmission for the speedometer. In 92+ they moved the sensor to the rear axle because of the problems with that plastic gear constantly being chewed up. Now, 87ish+ had an ABS sensor on the rear axle for the ABS brakes. It wasn't until 92 that they used both the ABS sensor and the speed sensor together for the PSOM. Programable Speedometer/odometer module used on the 92-96 trucks.
Postmaster
Joined: Jun 1999
Posts: 2,719
Likes: 1
From: Lee's Summit MO
Bouncing speedo
Justin is correct, my 93's is on the rear differential, our 96 F350's is on the rear diff, my '89s is on the TC.
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Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
Bouncing speedo
The ABS sensor appeared on the rear axle in '87, but was ONLY used for the RABS. The cruise & E4OD shared the VSS on the base of the speedo cable. It's in the lower L frame of jbalestri's diagram.
In '92, the speedo cable was deleted and the PSOM used the ABS sensor, but the cruise was still the old style, so it used the VSS which had no cable hooked to it. I think that's why that diagram is used for the '92 trucks - not for the cable, but only for the VSS.
In '93, everything went to the ABS sensor.
In '92, the speedo cable was deleted and the PSOM used the ABS sensor, but the cruise was still the old style, so it used the VSS which had no cable hooked to it. I think that's why that diagram is used for the '92 trucks - not for the cable, but only for the VSS.
In '93, everything went to the ABS sensor.
Last edited by steve83; Jun 20, 2003 at 06:34 PM.
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Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
Bouncing speedo
You can test it with a "True RMS" digital multimeter, but those are expensive (like $50-100). I think I've seen people post the price of the ABS sensor at ~$20. Have you even pulled it yet? They often foul with metal filings, and are easily cleaned.
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