120mph-whats up with that?

[Carl D.]

OK, this morning it was 2 degrees out. Started the old X up without a problem, after it warmed up for 10 minutes drove down the street and speedo shot up, past 85 and all the way to "D" I'm guessing 120 mph. Stayed there for about 15 minutes of driving. Who say X's aren't fast. Anyway would zero out when stopped then back up. Now it's reading 20-40 mph faster than normal. When starting from a stop it jumps up to 40mph instantly. Odometer seems to be working alright. Whats up.

 

[Alec]

Maybe you need to lube the speedo cable.

 

[gensic11]

your speed sensor may also be bad, i had similar problems a long time ago with a different car.. get it checked out, a speed sensor is no more than 50$ or so

 

[mhn3773]

lol i swear officer i was not going 120 down the middle of town..the car was lieing =) tee hehe

 

[VairKing]

My 91 does this also, but only when its really cold out. I never found out why, just used the RPMs to guestimate my speed. Lubing the cable could help, but I really dont see how a unlubed cable would make the speed read higher...

 

[Texan01]

Sounds like your mechanical speedo is worn out. try pulling the speedo out and putting a drop or 2 of 3-n-1 oil or some other really light oil in there.

Dad's old '87 Dakota would go from 0-95 when it was cold or taking off from a stop, it would eventually read somewhat right. considering that the truck couldn't do 95 unless it was going down hill with a tail wind. This I know, flat out it'd do 90. loaded like the hillbillies it'd do 55.

 

[Carl D.]

Thanks, I try a little lube and maybe replace the speedo gears, needed to do that anyway to correct for larger tires. Gotta love that cold weather, it always brings out the best in our vehicles.

 

[410Fortune]

carl with a jump like that its either the cable ir the gear

Pull the bolt off th speed sensor in your t case (I think your 98 its still in the t case??) and check the gear's teeth.

I dont know how you are suppossed to lube a speedo cable, its gets its lubrication from the ATF in the T case, I suposse you could put some oil in both ends with a syringe, but I personally just replaced mine when it went bad (actually melted on headers) I am on my 3rd cable now!! hahaha damn headers melt everything...you can get them from Ford, not too bad $30 I think it was