speedo problems
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Senior User
Joined: Mar 2010
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From: South Bend, IN
speedo problems
My truck has a speedometer with a mind of its own some days it works perfect, others it dosent work at all, and then there are the days that it will work till about 45mph and then it just starts to bounce arround. The truck is a 91 F250 5 speed 4x4. The end of the cable seems to be in good shape not worn or broken. There is a spot for what looks like an electronic speedo hookup next to the cable. So to the question whare should i start to look to fix the mechanical speedo and if that dosent work can i get an electronic speedo from somewhare eg. Autometer or Golwshift.
Lead Driver
Joined: Mar 2006
Posts: 5,107
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From: western SD
91 trucks should be mechanical driven speedometer. If the gear on the cable that plugs into the transfer case is good, look at the gear inside the transfer case. It is plastic and can wear. It should be flat across the teeth of the gear.
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Senior User
Joined: Mar 2010
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From: South Bend, IN
I havent checked to see if the gear is worn. But if it is what is the procedure to replace it? Do i have to take appart the transfer case? This is my daily driver as its the only one legal on the road. And what kind of price would i be looking at to replace it?
Lead Driver
Joined: Mar 2006
Posts: 5,107
Likes: 1,534
From: western SD
The only one I teplaced was on a 205 case. The 91 should have a 1356 case. I believe the tail housing has to come off, The gear probably is held on by a snap ring. I have no idea on the cost. If I remember right you have to get the same color gear (green blue ect.) to get the speedo to read right. Some one that is maor versed on the 1356 will probably chime in to give you the low down.
Fleet Mechanic
Joined: Jan 2011
Posts: 1,709
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From: 8600 ft in Colo
I haven't changed one on that t-case, but if it's like every other one I've seen, you don't have to dis-assemble the t-case. There should be a forked hold-down bracket holding the speedo cable in the t-case. Take that bracket off and the cable pulls out, with the plastic gear on the end. The gear is held on the end of the cable by a c-clip. Pull the clip and the gear comes off. The different color gears have different tooth counts. That's how you adjust for different differential gear ratios and different tire sizes.
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Senior User
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From: South Bend, IN
Thanks for the help guys im gonna see what i can do this weekend. I will probly have more questions as i get into it.
PHY: I took the cable out of the tcase as you described and there was no plastic gear on the end. If im seeing this right the gear is on the drive shaft and it spins the cable directly not thru another gear?
And when i get this thing out dose anybody know what the part is actually called when i got to the parts store. Most of the things that ive had to buy for this truck they claim to have never seen. Like the glow plugs the guy brought out spark plugs the first time, i dont know whare he got the part number for diesel spark plugs. He assured me they were the right part and that the old one i brought in dosent work in trucks.
PHY: I took the cable out of the tcase as you described and there was no plastic gear on the end. If im seeing this right the gear is on the drive shaft and it spins the cable directly not thru another gear?
And when i get this thing out dose anybody know what the part is actually called when i got to the parts store. Most of the things that ive had to buy for this truck they claim to have never seen. Like the glow plugs the guy brought out spark plugs the first time, i dont know whare he got the part number for diesel spark plugs. He assured me they were the right part and that the old one i brought in dosent work in trucks.
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Lead Driver
Joined: Mar 2006
Posts: 5,107
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From: western SD
76ranger I thought that when you said that the end of the cable looked good in your first post, you were talking about the gear on the end of the speedo cable. There should be a plastic gear on the end of the cable, held on by a c-clip, that comes out of the transfer case, as PHY said. If you don't have that gear on the cable, the c-clip may have come off alowing the gear to slip on the cable. Check in the hole in the transfercase to see if that little gear is setting there.
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Fleet Mechanic
Joined: Jan 2011
Posts: 1,709
Likes: 4
From: 8600 ft in Colo
This is what I'm used to seeing...
(from a Bronco II...)
Go half-way down the page.
https://www.ford-trucks.com/forums/9...rive-gear.html
(from a Bronco II...)
Go half-way down the page.
https://www.ford-trucks.com/forums/9...rive-gear.html
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Senior User
Joined: Mar 2010
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From: South Bend, IN
Well i got a chance to dig into the problem today. I found a few things some good some bad. To start with the good the plastic gear inside the tcase is in good shape.
But that leads to the bad two things that i noticed while i had it apart. 1. The cable slides into a metal collar inside the housing holding the plastic gear and it looks as if it may be some what rounded didn't get a pic of that. 2. The cable its self actually slides back and forth in its outer casing about 3/4 of an inch is it supposed to do this?
Im gonna make a trip to the junk yard tomorrow and see if i can find a new cable and housing for cheep.
But that leads to the bad two things that i noticed while i had it apart. 1. The cable slides into a metal collar inside the housing holding the plastic gear and it looks as if it may be some what rounded didn't get a pic of that. 2. The cable its self actually slides back and forth in its outer casing about 3/4 of an inch is it supposed to do this?
Im gonna make a trip to the junk yard tomorrow and see if i can find a new cable and housing for cheep.
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