speedometer problems
 

just recently my speedo was spiking and then it stopped working...

my trip meter and mileage had also stopped working also....

what could be problem???

Re: speedometer problems
 

yes i was kind of leaning toward that....

i heard it was behind the tranny where the drive shaft connects..

but what does it look like????

It threads in AND has a locknut, and a plug with the wires, you can change it out in 15 minutes.

Just ask the parts guy how many turns to back it out after it bottoms out, I can't remember, BUT I think its one turn.

Last time I changed mine it was around $30.

quote="Maniac"]It threads in AND has a locknut,

it has a jam nut, as i stated above.

locknuts have distorted threads or nylon rings that stop a fastener from backing off completely after becoming loose

and a plug with the wires, you can change it out in 15 minutes.

Just ask the parts guy how many turns to back it out after it bottoms out, I can't remember, BUT I think its one turn.

Last time I changed mine it was around $30.[/quote]

bottom it out, then back off a 1/2 turn

cool thanks guys, i just found where the sensor is...

will be digging it out tomorrow....

yeah peterbilt quoted me $43 for the sensor...

are there usually 2 (or more) speed sensors?
is this speed sensor the same as the one used for other sub systems?

quote="possum squat"]are there usually 2 (or more) speed sensors?

no... ...depending

is this speed sensor the same as the one used for other sub systems?[/quote]

it's a magnetic pulse generator..., if that's what you mean.

abs sensors as well as some engine speed sensors are the same type of sensor

well finally pulled it out...

the tip had some fresh oil on it...

i only drove it for like a half mile than i parked....

speedo works...

couldn't really go far because of the weather....

hope that oil on tip isn't an issue?????

yeah it would be possible if it weren't so cold to see the sensor tip again...

so it's normal to be soaked in oil...

what could've had caused that to fail?????

like you said, it's pretty much a maganet...nothing electrical...

quote="KAIMIKAZEE"]yeah it would be possible if it weren't so cold to see the sensor tip again...

so it's normal to be soaked in oil...

what could've had caused that to fail?????

like you said, it's pretty much a maganet...nothing electrical...[/quote]

some sensors are internal and some are external to the transmission... the sensors that are internal are threaded into the trans tailshaft housing and are exposed to the oil in the trans... it is normal for these to have oil on the tip

externally mounted sensors are mounted in about the same location but they thread into an ear or bracket and when you thread them in, you can watch the tip come in to contact with the tone ring (notched tooth wheel on trans output shaft), and these are not exposed to the trans fluid, and therefore it is not normal for them to be wet

the pulse generator is a magnet wrapped in a wound coil... yes, they're electric

owner operator
 

I have a 1998 peterbilt with a cat and a 10 speed eaton transmission and I have problems with the speedometer, the problem is that the speedometer is going down and not giving the right speed unless I coast. Lets see if I can splain this... if I am on the freeway and I got the crouise control on everything is good until I encounter a hill and the truck has t accelerate to keep up with the speed and then is when the needle o my speedometer starts going the wrog way until goes back to 0... if I decelerate it goes back to normal. I already change both speed sensors on the transmission and no result. Please let me know if anybody has an idea what is wrong... could it be the speedometer board?
Any input would be appreciate....

The nut on the rear flange/yoke is loose, the speedometer ring is sandwiched between the yoke and rear bearing, when the nut loosens the ring spins and gives an eratic reading, however the nut is NOT loose enough to fall off, I have tightend them 1/2 a turn and fixed this problem, shop labor should be 1 hour or so, easy fix

Thanks for the help Maniac. I had the same problem as raymundo1 which started after the transmission was replaced. I also replaced both sensors, cleaned the plugs, made sure wires weren't crimped. I even tried another speedometer head. Just this weekend, we pulled the driveshaft down and found the yoke nut was loose. I went ahead and got a new nut and u joint straps and bolts. Speedometer works like new. Cruise control works up and down hills like it is supposed to. Thanks again.