speedometer going to 120+ and convertor stuck in lockup

LKuilder

LKuilder

New member
Joined
Jul 10, 2008
Messages
158
I was on my way to church this morning and my speedometer started acting up going to like 127 mph for a few seconds at a time. That is all it was doing. I just went to leave church and head to the shop and more problems... As soon as I turned the key on the speedometer instantly pegged out again. The truck started fine and when I went to leave its like the convertor was stuck in lockup. I let the truck sit for a few minutes and tried again and everything seemed to be fine this time.

Any suggestions please?
 
After much reading I'm leaning towards the vehicle speed sensor. I'm assuming probably the one on the rear end? Any help would be greatly appreciated.
 
That's kind of what it sounds like to me, though they usually throw a code.. But yes it is the one in the tailshaft..only 20 bucks at the dealership
 
I replaced the sensor on the rear axle and it is still doing the same thing with the speedometer and when the speedometer pegs out the tranny stays in high gear.
I also am not pulling ANY codes on my Scan Gauge II. Should I have the truck hooked up to a regular scanner and will that tell me what sensor needs to be replaced?
 
I replaced the speed sensor on the back of the transmission yesterday morning and wouldn't you know it... same junk! I traced every bit of wires and could not find a problem there.

So I drove it a few times and it was doing the same thing its been... working fine then all of a sudden pegging out. Got back to the shop and shut the truck off and started messing with unplugging the power to the Superlift TruSpeed box. All that did was remove the speed signal all together. So after plugging the power back in to that box and the speedo pegging out just turning the key on I gave the TruSpeed box a good whack and wouldn't you know it problem went away. So I guess its a call to Superlift today to see what they say.
 
you may look into a superchips or smarty that will change tire size, its all in the pcm, that way if that box screws up it wont hurt anything, my buddies carvan smoked itself inabout 30 miles because of that sensor just trying to get it home.
 
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