Yet another problem
Thread Starter
|
Senior User
Joined: Jul 2009
Posts: 163
Likes: 0
Yet another problem
It's me again Margret. LOL well my problem now is that going down the road, my speedometer will just randomly jump all over the place and will just resume where its supposed to be. I am pretty sure its just the instrument cluster, but what do you guys think? Its been doing it a while but wasn't worried about it. But it is getting worse. I hate being poor, I would like to do a lot of things to this truck.
Lead Driver
Joined: Nov 2003
Posts: 6,900
Likes: 3
From: Campbell River, B.C.
What year is this truck? Sounds like the speedometer cable might be snagging on something as it spins in the tube. 1992 and newer have no speedo cable.
Sometimes you can take the speedo cable out and find crud in the end of the tube. Cleaning it out and pouring some ATF in the end might fix the problem. Also apply some grease to each end of the cable before reinstalling it.
Sometimes you can take the speedo cable out and find crud in the end of the tube. Cleaning it out and pouring some ATF in the end might fix the problem. Also apply some grease to each end of the cable before reinstalling it.
Thread Starter
|
Senior User
Joined: Jul 2009
Posts: 163
Likes: 0
Its a 1992 MFD 12/91. When I say jumping I mean I can be running 60mph it will shoot to 15 mph or so and just as fast as it jumped down it pops right back to 60. It does it at many different speeds. I know what you mean by the needle bouncing but mine is definitely not doing that. It jumps almost like there is a short in the cluster.
Lead Driver
Joined: Nov 2003
Posts: 6,900
Likes: 3
From: Campbell River, B.C.
Ok, I assumed you had the speedo popping above normal reading. I agree that this is electrical, but could simply be a weak contact. Do road bumps affect it?
Some folk have reported cures to problems like this simply by removing the cluster and reinstalling it. The theory was that the main connector that plugs the cluster display in can get dirty with light dust or even some corrosion. Automatic transmission problems are usually what they report as being the first symptom.
Is your rear ABS acting up at all?
Some folk have reported cures to problems like this simply by removing the cluster and reinstalling it. The theory was that the main connector that plugs the cluster display in can get dirty with light dust or even some corrosion. Automatic transmission problems are usually what they report as being the first symptom.
Is your rear ABS acting up at all?
Thread Starter
|
Senior User
Joined: Jul 2009
Posts: 163
Likes: 0
No, bumps don't affect it at all. Not sure about ABS acting up. I have the 5-spd manual tranny. When I got the truck the ABS light was on but that was over 5 years ago. Hooked scanner to the truck back then and it wouldn't give any codes for the ABS so I just removed the bulb. Not sure if this has anything to do with it. Never had any problems with brakes at all other than wheel cylinders going bad every 9 months and replaced master cylinder twice.
Lead Driver
Joined: Nov 2003
Posts: 6,900
Likes: 3
From: Campbell River, B.C.
The RABS and speedometer get their signal from the same sensor on the rear differential. Might be time to inspect the wiring near or at the sensor and also pull the sensor to see if any metalic particles are clogging the magnetic sensor probe.
Thread Starter
|
Senior User
Joined: Jul 2009
Posts: 163
Likes: 0
I'll try taking a look at in tomorrow. The wiring shouldn't be a problem because with the exception of the roof having a little bit, the entire truck is rust and corrosion free. It's a canada built truck but has been in South Carolina for a very long time. Is there still a chance the cluster is bad? The reason I ask this is because back in November at 205,000 miles the factory clutch finally gave out and I replaced it. I know the clutch has nothing to do with it but my point is that after getting it back together and firing it up the tach didn't work. I let it sit overnight and fired it up to test drive to make sure things were good and it has been working since. Sometimes I swear my truck just has some ghosts in it just to F**K with me.
Trending Topics
Postmaster
Joined: Apr 2008
Posts: 4,802
Likes: 1
That '92 has no speedometer cable, it uses the VSS in the rear axle for both the ABS and speedometer. If the other gauges on the cluster are reading normal I'd rule out the bad ground for now, as clusters usually have only one ground and when it's bad all the gauges go nuts. Speedometer acting up and ABS light on at the same time tho to me points straight to the VSS, either the sensor itself or its harness. If that truck is anything like my '90 (and it should be) the VSS harness sits very close to either the fuel tank seam (very sharp) or the frame rail edge (again pretty sharp) so it can rub on them and eventually short out - mine wasn't quite there yet, but I did make sure it's nicely covered with plastic loom and then I zip-tied it to the e-brake cable so it stays put for good.
Opening the rear diff and inspecting the internals for debris is also a great idea, and chances are the fluid has never been changes so this would be a perfect opportunity for cleaning all the crap out and filling the axle up with fresh gear oil.
Opening the rear diff and inspecting the internals for debris is also a great idea, and chances are the fluid has never been changes so this would be a perfect opportunity for cleaning all the crap out and filling the axle up with fresh gear oil.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Postmaster
Joined: Apr 2008
Posts: 4,802
Likes: 1
Tachometer issue is usually associated with a bad sender unit, it's either the sender goes weird and starts reading zero at idle (but reads fine over 1000 rpms) or the insulation for the two wires shrinks from engine heat and the wires get bare where they go in the sender and they sometimes touch and zero out the tach. The sender in question is located on top of the gear housing for the injection pump, if you look at the engine from the front it will be slightly to the right of the oil fill neck, but unfortunately since your '92 uses a serpentine belt setup the sender sits kinda under the vacuum pump and so is a bit hard to see or get to with a wrench.
Slightly offtopic - where are you located? There may be a member in your vicinity that could possibly give you a hand with the truck, and some of us do travel and work for beer/food
Slightly offtopic - where are you located? There may be a member in your vicinity that could possibly give you a hand with the truck, and some of us do travel and work for beer/food
Thread Starter
|
Senior User
Joined: Jul 2009
Posts: 163
Likes: 0
well the tach had only messed up the one time and thats it. Before I bought the truck back in 2005 I thoroughly inspected the truck even underneath it. All the wiring too and the only wiring issues on it with I bought the truck were the GP connecters were all burnt up, So I replaced them. I live in SC. The PO I got the truck from had painted it with an awesome paint job at the time but now all the clearcoat is flaking off and the roof had began rusting so I sanded it and reprimed it. I believe this truck used to be a state D.O.T truck because it has dealer installed A/C and it used to be white in color. When I bought the truck it was in immaculant condition. But is rapidly deteriorated and there is nothing I can do about it because I don't have the money to repair everything. when i check the sensor for metal shavings I'll check the harness along the frame again. I thought the only trucks that had problems with the ABS sensor in the differential were the late 90's dodge trucks. They were infamous on going out.
Postmaster
Joined: Apr 2008
Posts: 4,802
Likes: 1
SC is a bit too far for me unfortunately, I'm currently based in PA and I no longer do vehicle transportation/delivery runs...
The tach wires may have bared right at the sender, if they accidentally touched you got the zero-reading tach, it's entirely possible it was a one time deal - check it whenever you get a chance, shine some light in there (small LED keychain flashlight works great) just to make sure.
The VSS sensor has been a Ford thing from '89 all the way till the late '90s when the 4-wheel ABS came out, it actually works very good and is pretty reliable but like anything electric or mechanical it does wear out with age and mileage.
And I hear ya on the lack of funding for truck projects thing, I'm only able to do upgrades on my truck cause I shop at the junkyard and I do my own work... That ex-DOT truck of yours, is it a crew-cab dually with a service body? Cause that's what most DOT trucks I've seen are...
The tach wires may have bared right at the sender, if they accidentally touched you got the zero-reading tach, it's entirely possible it was a one time deal - check it whenever you get a chance, shine some light in there (small LED keychain flashlight works great) just to make sure.
The VSS sensor has been a Ford thing from '89 all the way till the late '90s when the 4-wheel ABS came out, it actually works very good and is pretty reliable but like anything electric or mechanical it does wear out with age and mileage.
And I hear ya on the lack of funding for truck projects thing, I'm only able to do upgrades on my truck cause I shop at the junkyard and I do my own work... That ex-DOT truck of yours, is it a crew-cab dually with a service body? Cause that's what most DOT trucks I've seen are...
Thread Starter
|
Senior User
Joined: Jul 2009
Posts: 163
Likes: 0
It is an extended cab long bed. When I get some things straight I might post some pics but like i said when I bought the truck the paint was awesome but now its pathetic with the clearcoat flaking and the paint soon after. I'm assuming the guy didn't know what he was doing cause I've seen the truck before he painted it so the paint job only lasted 4 years which is pretty crappy. The only problem around here is NO junkyards keep any of these trucks, and even if they do they only keep them like a week or they are too totalled to salvage anything off of. It sucks.
Thread Starter
|
Senior User
Joined: Jul 2009
Posts: 163
Likes: 0
well i have some good news and some bad news. pulled the vss sensor and it was very clean as it should be. no cracks or anything. before pulling the sensor I checked the connection and harness. the plug was tight and unbroken so the connection is tight with no dirt or corrosion. the harness for the sensor is in its factory wire loom and is burn, corrosion, and pinch free. It remains in the loom completely with no exposure at all even when it joins the main harness along the frame wall. The main harness is clean and intact with its loom all the way to the plug entering the firewall tightly secured with its factory fastners. Its not pinched, burnt, bare or corroded at all. So the bad news is whats wrong? any other suggestions?
