Speedometer problems
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Speedometer problems
I'm having some trouble with the speedometer in my '91 F-250. It works OK up to about 30 MPH. Any higher than that and it "jumps". In other words, the needle goes up to a certain point then drops, etc. The speedometer gear had to be replaced to make the speedo work at all. It was worn only at the very ends of the teeth so I guess the gear isn't engaging very well. Does this mean the gear in the transfer case is shot? If so, how hard is it to change? Thanks for your help in advance. 
Laughing Gas
Joined: Jun 1999
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From: Banning CA
Speedometer problems
I dont think the speedo gear is bad, though you probaly have a bad speedo, there is a brass busing in the speedo that goes bad and causes it to jump at higher speeds. You can try removing the speedo and spraying a lube like white lithium, on the moving parts. If not just replace. To remove the speedo gear, pull out the cable at the trans and remove the small bolt holing the cable housing on the tail, after that just pull the housing out and you will see the gear very easy to check and change. Remember to use a drip pan when pulling out your cable, as you may loose some trans fluid out.
Dave
http://a2ztowing.homestead.com/a2ztowing.html
Dave
http://a2ztowing.homestead.com/a2ztowing.html
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Speedometer problems
It seems like the speedo gear is slipping. Like just the ends of the teeth on the gear are engaging. The problem doesn't get really bad until about 30-35mph but sometimes happens as low as 15 mph or so. I guess what I meant to ask was does it sound like the gear inside the transfer case that the speedo gear runs off of is stripped? Sorry, guess I should have made myself more clear.
Laughing Gas
Joined: Jun 1999
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From: Banning CA
Speedometer problems
Pull the gear out and take a look at it, the gear on the cable is plastic and the gear on the trans/transfercase is metal, if any of the gears are bad it would be the plastic one. I still dont think it is the gears though. But it is very easy to pull out and take a look at it.
Dave
http://a2ztowing.homestead.com/a2ztowing.html
Dave
http://a2ztowing.homestead.com/a2ztowing.html
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Speedometer problems
The plastic gear is brand new. The only reason I'm thinking it might be the gear in the transfer case is because the plastic gear that we replaced wasn't worn that badly and the speedo didn't work at all with that one in there.
Laughing Gas
Joined: Jun 1999
Posts: 903
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From: Banning CA
Speedometer problems
Like I said, I really do not believe that the gear inside is the problem. I still believe that the speedo itself is the problem. The gear inside would require you to take the transfer apart just to check. Though you can look at it through the hole if you remove the speedo cable at the transfer. Though with the experience that I have, what you are describing is caused by the speedo going bad. You see inside the speedo is a brass bushing that wears out and allows the spining part of the speedo to either come in contact or come too close to the center part.
Causing a false reading and jumping needle/
Dave
http://a2ztowing.homestead.com/a2ztowing.html
Causing a false reading and jumping needle/
Dave
http://a2ztowing.homestead.com/a2ztowing.html
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Speedometer problems
Thanks a lot for your help Dave. How do I go about checking this brass bushing? What part of the speedo has to be replaced to include it? Also, is it normal for the plastic speedo gear to only engage the very ends of the teeth? Again, thanks for all your help.
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Laughing Gas
Joined: Jun 1999
Posts: 903
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From: Banning CA
Speedometer problems
It is normal for only the tips of the teeth to catch the metal gear in the transfer case. This is why when it is a little worn the speedo does not work. To fix your problem you need to replace the speedo head. The speedo itself. You could probaly find one at a local wrecker or get it from ford. Though ford probaly would want a lot more than a local wrecker.
good luck
Dave
http://a2ztowing.homestead.com/a2ztowing.html
good luck
Dave
http://a2ztowing.homestead.com/a2ztowing.html
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Speedometer problems
Thanks for all of your help Dave. Just one more question. (Bet you're getting tired of that
) Am I correct in assuming that you have to pull the dash apart somewhat to get to the speedo itself?
) Am I correct in assuming that you have to pull the dash apart somewhat to get to the speedo itself?
Laughing Gas
Joined: Jun 1999
Posts: 903
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From: Banning CA
Speedometer problems
You dont need to remove the dash though you will need to remove the instrument cluter. Remove the cover and remove the cluster, the hardest part is removing the speedo cable. There is a lock that you will need to depress to pull the cable out. Almost self explanatory once you see the cable.
To install the new speedo, some times you may need to move the back to get the cable to go in to it.
Good luck and let us know how it goes.
Dave
To install the new speedo, some times you may need to move the back to get the cable to go in to it.
Good luck and let us know how it goes.
Dave
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Speedometer problems
Just remembered that my uncle has basically a complete dash that he bought for parts. If I remember correctly, it is out of a '95 or '96 F-150. He got the parts he needed from it and said if he had anything I needed that I was welcome to it. Do you happen to know if the speedo would be interchangeable? Thanks again.
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Joined: Jun 1999
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From: San Ysidro
Speedometer problems
Hi, i have my speedo gear very damage, so i pick one out of a mustang C6, it is a bit diferent than mine but it still work for about 2 days (20 M) then it start to miss again and the get stock under 0 miles, do you thik is the inside gear bad?
or maybe cause i'm runing 33's need a bigger gear
and that could cause to beat this small gears?
Thank's
1987 Full size bronco 302 carb c6
headers 3'inch exaust with flowmaster
33 tires 3.55 gears no lift.
or maybe cause i'm runing 33's need a bigger gear
and that could cause to beat this small gears?
Thank's
1987 Full size bronco 302 carb c6
headers 3'inch exaust with flowmaster
33 tires 3.55 gears no lift.
