Speedometer is wrong
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Freshman User
Joined: Jul 2005
Posts: 47
Likes: 0
From: SoCal
Speedometer is wrong
On my 1991 F350 the speedometer jumps to 80 and back again when it wants to. Bounces around any place between the real speed and pegged.
Odometer reads right. Cruz control does not surge.
Spedometer head is dead?
Odometer reads right. Cruz control does not surge.
Spedometer head is dead?
Senior User
Joined: Jan 2007
Posts: 175
Likes: 0
I have delt with this many times.#1-check the head on the pole senser its the peice that gose in to the tailhouseing on the tranny or t-case if it 4x4.if that is bad change it.these parts are plastic.if that dosen't work then step #2.all 5 ot these thing Ive done this has been the problem.remove the tailhouseing of your tranny(2wd)or t-case(4wd).there is a plastic gear on the shaft that engages the gear on the pole sensor.this iner gear on the shaft is usualy stripped.it takes longer to pull the tailhouseing apert and drop the driveline than it dose to change the part.you have to get it from a dealership.dont worry its only 12 bucks or so.for best results chang both gears.
Senior User
Joined: Jan 2007
Posts: 175
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if this isn't the problem then move on to other parts.9 times out of 10 its one of the gears.either the sensor gear or the shaft gear.they are plastic and onlt last about 50 to 60.000 miles.Ive put 2 sets in my 91.
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Elder User
Joined: Oct 2006
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Just curious, the speedo in my 91 reads about 10-15 mph high, but only when it's cold (less than about 75 degrees in the cab). After driving a while and the heater kicks in, the speed registers good. Is this also likely the sensor/gear, or is there another possibility for temperature-related strangeness? This doesn't happen in the (Texas) summer heat.
Should I start another thread or just chime in like this?
Should I start another thread or just chime in like this?
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Senior User
Joined: Jan 2007
Posts: 175
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you sound relivent afterall we are talking about speed-O problems.dose it bounce around or dose it hold a steady higher reading?I have never heard of a cable driven speed-O runing that fare off.that may be a problem in the gauge it self.not positive.my buddys 90 has a giant lift and rolls on 47in swamper LTBs and the tire size don't throw it that fare off.I know a guy that works on gauge clusters only I'll try to give him a call and get back to you on that one.
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 16
From: Nutter Fort, WV
My truck with 33" tires will run 91 MPH at 3300 RPM with 3.55 gears.
If I installed 47" tires it would run 130 MPH at 3300 RPM with 3.55 gears.
That would take 5.13 gears to have the speedometer anywhere close to right.
If I installed 47" tires it would run 130 MPH at 3300 RPM with 3.55 gears.
That would take 5.13 gears to have the speedometer anywhere close to right.
Elder User
Joined: Oct 2006
Posts: 597
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Originally Posted by whitefordaward
dose it bounce around or dose it hold a steady higher reading?I have never heard of a cable driven speed-O runing that fare off.that may be a problem in the gauge it self.not positive.my buddys 90 has a giant lift and rolls on 47in swamper LTBs and the tire size don't throw it that fare off.I know a guy that works on gauge clusters only I'll try to give him a call and get back to you on that one.
It doesn't bounce around at all...rock solid always. When I first got the truck, I checked out the spedo with a stopwatch and mile markers. It was pretty close. About a year later, I started to ask myself "why is everyone passing me today?". That's when I started to notice that on a cold morning, the speedo reads real high for the first 15 minutes or so.
I tend to think it's the spedometer itself, but was wondering if anyone thought it could be something else. Does the 91 have a cable or is it electric? Is there some kind of "module" between the sensor and the speedo? Has anyone ever seen a sensor read high when cold?
Sorry, I guess I could answer most of these questions myself, but its raining.
Junior User
Joined: Dec 2006
Posts: 63
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From: Chicagoland
My '91 F350 7.3 IDI 4 x 4 started with the needle bouncing on very slow speeds and the jumped right up to being pegged over the odometer while riding down the road. Then sometimes it will settle down within the 40 - 50 MPH range when actually running 20 - 25 MPH. I haven't had much drive time with it being like this. It came out of the trans shop this way. Only the trans was dropped. The cable spins freely and the same bouncing and pegging action occurs with a drill applied to the cable down by the transfer case. I tried a new speed sensor, which attaches to the transfer case side of the cable, and I got the same results. The gear on the cable is in perfect condition. I don't think the gear in the T-case is bad. However, the speedometer will get stuck around 15 MPH when I'm standing still. As soon as I roll in reverse, the needle goes back to zero. The odometer seems to be accurate. I'm leaning towards the speedo is shot.
I made a quick call to an old timer who does speedo repairs and he said parts aren't available. He said I was better off to get a new one instead of a used one. With a used one, I could end up with the same problem sooner then I think. I guess time killed it and not the 69K miles.
Anyone else, have luck with getting theirs fixed recently?
I made a quick call to an old timer who does speedo repairs and he said parts aren't available. He said I was better off to get a new one instead of a used one. With a used one, I could end up with the same problem sooner then I think. I guess time killed it and not the 69K miles.
Anyone else, have luck with getting theirs fixed recently?
Senior User
Joined: Jan 2007
Posts: 175
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I know a new speed-o is not cheap.I looked for one and the only one I found was in a dealership in texas.at 350 bucks + shipping.besides just keep up with trafic and if you get pulled over.sorry officer my speed-o is brock at the moment.got out of a couple tickets that way.
Junior User
Joined: Dec 2006
Posts: 63
Likes: 0
From: Chicagoland
That's good for when there is traffic on the road. Unfortunately, this truck isn't always rolling with traffic, which makes it hard to judge how fast you truly are going.
At least I'll get a break on the speedo...wholesale pricing helps a bit.
At least I'll get a break on the speedo...wholesale pricing helps a bit.
Laughing Gas
Joined: Aug 2003
Posts: 919
Likes: 4
From: Newberg Oregon
I have a few low mile gasser used speedos if someone wants for shipping costs, I fixed mine by cleaning the grease out of it and using teflon on the moving parts. Also the Tcase gear was bad, 300k will do that.