I replaced the speedo gear in the transmissoin because the needle jumps and is way off. Says i'm going 45 when the officer said i's going 75. Cost me a ticket. Anyhow, I'm stumped as far as what else is in the speedometer system. A friend told me the speedometer cable is probably bad and it's slowing down the needle and causing it to jump. Could the gear inside the transmission be bad? I wouldnt think so being it's metal and the gear on the end of the cable is plastic. any help appreciated.

 

What model truck , transmission etc ? 2 or 4WD ?

 

gingerbreadmaniac

Ok i had a simalar problem with my 85 f150 4x4, The speedo would jump like you say. I talked to a few people about it and i was told to spray dry silicon spray directly into the cable. its powder in a can. i was told that would clear it right up. i never did it because i priced out a new cable and it was like $25 canadaian so i figured if im going to go to all the work of removing the cable i should just put a new one in. The cable than stopped acting up and seemes to be just fine. I found if i was out hunting and went through some deep puddles it would make the speedo jump and act stupid. but i cant see anything being wrong with your transmission.

keep us posted on how u make out

gingerbreadmaniac

aka JOSH

 

its a 84 f150 2wd XLT AOD

 

I've had a number of vehicles to have this problem (the speedometer needle jumps). On all, the problem was due to the speedometer cable needing to be lubed. While the problem doesn't appear in warmer temps, when things turn colder the cable binds inside the housing, causing the needle to jump. Many recommend powdered graphite, although I have had good luck by removing the cable and greasing it thoroughly with Outers Gun & Reel grease, and replacing it in the housing. You should be able to remove the speedometer gear at the transmission, and pull the gear and cable from the housing there without needing to take the dash apart. After lubing the cable, slide it back into the housing from the transmission end, rotating it slightly back and forth to be sure that the diamond-shaped square-drive end properly engages the speedometer.

 

So all i need to do is pull the square cable only, out of the housing. What bout where it goes into the back end of the needle? What holds the needle up while the cable's out?

 

The guage and needle will stay together. The backside of the speedometer has a socket to which the speedometer cable-housing (and the cable with the square drive end) snaps into. While you can take the dash apart and disconnect the cable-housing from the back of the speedometer, this isn't really necessary. Instead, when you take the opposite end of the housing loose from the transmission, you can pull the cable itself out of the housing. I'm trying to remember..... you may need to remove a small "C" or "E" clip and remove the speedometer gear (located on the tranny end) first. (Likewise, you may not..... it will be fairly straightforward once you get a look at it). When you pull the cable out, it will resemble a very tightly wound spring, and the end coming from the speedometer will be square, forming into a point to allow it to smoothly engage the back of the speedometer. Grease it up, and carefully slide the cable (with the square/pointed end first) back into the housing. When it's all the way in, just rotate it back and forth to be sure the cable has once again engaged the speedometer. You'll know you're in good shape if the speedometer gear assembly isn't sticking out further than it should be. If it is, pull it toward you by a couple of inches and, while rotating it back and forth, again push the cable into housing. It should not give you any trouble, and should slide into the speedo with no problem. Replace the gear assembly into the tranny (after replacing any clips you may have needed to remove previously), and you should be set.

 

I appreciate it restorit. Maybe now i'll know how fast i'm goin without having to follow other drivers!

 

Hope this solves your problem. I've cured the identical problem on 4 vehicles so far. All had over 100K miles, and all developed the jumpy needle syndrome in cold weather. In the meantime, don't guage your speed by following that blue-haired lady in the left-hand lane..... you can probably go at least 30 MPH faster without breaking the speed limit!

 

I did as you said, and i couldnt get that darn cable out. I even put a pair of vise grips on the cable and pulled and twisted and it wouldnt budge an inch.

 

Wow..... you've got me. Mine (on an '85) slid right out. I guess the other thing to try would be to take the instrument cluster loose, and remove the speedo cable from the back of the speedometer and, after taking the speedometer gear off at the tranny end, trying to remove the cable from the housing from the speedometer end. The speedometer cable housing unsnaps from the back of the speedometer by gripping the white plastic ring on the cable housing end with your thumb and forefinger, pushing it to one side, and at the same time pulling the housing away from the back of the speedometer. If there's a c-clip or flange or otherwise preventing the cable from being removed any other way than by taking it out from the speedometer end, I apologize for the misdirection. I swear I recall taking mine out from the other end (tranny), though......

 

I'll use my off time at work to take a look at it. Oh...I'm gonna change the brake booster out cuz its got a vacuum leak. Any tricks on this one?

 

The last one I did was on a '78. No real tricks on that one, just the mounting bolts to the firewall and the pushrod from the brake pedal (and the master cylinder swap). I don't believe there'll be much difference on yours, but I'm sure someone will post if there is. Good luck!

 

10 - 4 good buddy
:-X11

 

I have the same problem with my 85 F250 4x4 Diesel. The speedometer needle jumps up and down all the time. I will try to get my speedometer cable out of the car next week. I will post my expierences with the speedometer here in this forum then.

Thanx in advance for your good posting here ; )


Ronny

Bremen, Germany