Crazy Speedometer

ok well about a week ago my speedometer started going CRAZY!!! once I get above 30-35 or so it starts jumping around and it seems that the faster I go the more it jumps. ie. i was going aprox. 45-50mph and it was jumping all the way up to 70+ and them back down and immediately up again. so basically it jumps way around. whats the cause??? just gone bad???
Thanks,
Dan

91 won't have a cable...it's electronic. There is a speed sensor that goes into the transmission at the tailshaft....sounds like this is your problem.

hmmmm don't know anything about it. you don't think it could be the actual speedo do you? I'm just trying to rule things out.
Thanks,
Dan

Sounds like the speedsensor to me to, a common problem 38 dollar part.You can check it with a digtalmeter

ok well in that case could you tell me where exactly it is? and how to get to it?
Thanks,
Dan

i have been in a few forums and most agree that a repair manual is the most important tool you can own. if you can't get one ,they might have one at the library. they have pics of where the parts are located.

yeah i've got a haynes manual i'll check it out

do you guys think its the speedometer cable that needs fixing or is that something else aside from the speedo sensor

yea either the connection is bad or the sensor

www.autobooksbishko.com get a factory service manual. It will pay for itself many times over.

There is no cable. It is electronic.

The speedometer gear inside the cluster likes to go bad on these trucks, too. Check the speed sensor on the tail shaft. If it checks out, your speedometer gear would be the next thing to suspect.

There's a place who sells them that's been posted before. I'll try and find a link.

I've had a similiar problem with the plastic gear on the end of the speedo cable not being adjusted right. I swapped a A999 in my `88, outside, laying on ice and snow and didn't the gear lined up just right. (It's hard to get the right 'feel' for a job when you can't feel your hands anymore.) For me, it's meant getting another gear from the scrapyard... but I waited until spring. I've seen similar gear in my 727 out of my 1968 Dodge, but can't say what is in anything newer then `88.

yeah i have to check a few more connections but i don't have a cable. mines a 91 which means its electronic but thanks for the info
Dan

I'm just taking a guess in the dark. Could this electronic setup be nothing more
then a sensor instead of a cable hooked up to the same type plastic gear?



Dodge / Jeep 2WD / 4WD Speedometer Gears

These gears are used with most Jeep and Dodge truck electronic speed sensors for the speedometer. You can increase or decrease the number of teeth depending on tire size to make your speedometer more accurate. The drive gear has 13 teeth and is machined into the output shaft. These are the late model type with a short shaft. Comes in 28 tooth to 43 tooth. Cost $65.00.
Source: http://www.transmissioncenter.net/dodge.htm

If what they're saying here is true, my `88 used a cable, so sometime after that, they hooked up an electronic speed sensor instead. I've also looked and the same 'type' of transmissions were used past `88... so maybe mechanically it isn't so different (used the plastic gear) but the wiring and electronics changed? Anyways, this was the 'mechanical' problem that produced my bouncing speedometer.

I have a similar problem with mine I think it either has to be the speed sensor going out or maybe the teeth are stripped on the sensor

uhhh weird enough I just unplugged the connector at the trans and made sure it was clean and it hasn't bounced since. lol I don't know but maybe just dirty??
Thanks for the help,
Dan

yeah I dont know mine would work and then not, bounce and then quit, now it doesnt work at all

hmmm i'm ust not sure maybe its the cable? if its mechanical or maybe its a gear on the electrical ones

checked it today broke the end off the drive on the sensor wierd huh

yeah that's no good man sounds like you have some replacing to do...