Im new to this forum and i need some help guys.. i have a 97 2500 12 valve and the overdrive seems to be not working correctly. Im getting 2200 rpm at 55mph and i know that cant be normal.. the previous owner has said that the tranny was built to haul and he never told me what was done to it.. the only time you can feel a noticable shift is at 50mph and it seems like passing gear because you can feel the truck move faster. Its hard to explain how it feels but any help would be appriciated.. dont know if it means anything but i have a break light on and the Abs light is on. And when you got your foot in the pedal the tach drops to zero then goes back up to the correct rpm. And if your doing 70mph im at 3000rpm

 

It sounds like you have a number of electrical issues to chase down, and I'm far from the one to give any guidance in that area. I will say the tach issue could be a ground problem, and much of the electrical gremlins with these trucks are. The ABS light could be a sensor or sensor wire, I believe on yours there's a sensor on top of the rear diff, and one in each front hub. The hub sensor wires are notorious for rubbing on the rotor and breaking. Does it stop like it should? Smooth and straight, no pulling or pulsing?

If you don't feel it shifting then it wasn't built to haul. Built means line pressure, and line pressure means it isn't going to shift like a Cadillac anymore. Enough line pressure to do serious hauling means it's going to kick into gear like a mule unless you have it set up perfectly and know just when to feather the throttle. OR, something is simply very wrong. Regardless, it sounds like you either have no OD, no lockup, or low line pressure. Your TV cable could be out of adjustment, and could cause any of those issues if it isn't set properly. It controls the throttle valve in the transmission, essentially telling it when and how to shift based on load. 3K at 70 is ridiculous, unless it has extra low aftermarket gears, but that isn't common on these trucks unless they're purpose built for pulling trees out of the ground.

 

Thank you very much. And yeah i have no clue on the electrical part as well. And no it doesnt pulse or anything. stops like how its supposed to.. And I just noticed that the sensor right above the harmonic balancer is covered in grease and oil from when my valve covers was leaking so that could be the tach issue..

 

It could very well be. I recommend WAB engine and chassis cleaner/degreaser. Juuuuust... don't breath in while spraying it. Or get it in your eyes.

 

Is it safe to spray the electricals with it?

 

Like the sensors and whatnot since there coverd in oil and grease still.. i just changed the valve covers a few days ago

 

I do, I've never had an issue.

 

if my tv cable is out of wack would that cause no overdrive? And what does lock up feel like?

 

Yes it could, if it was out far enough. Your TPS sensor could also be bad. Lock up is exactly what it sounds like: it's when the torque converter stops slipping and locks, making the engine to transmission ratio 1:1. It feels like that point with a standard transmission when the clutch is fully engaged. It should feel stronger in lockup, because once it locks because it's the only time that all of the engine's power is going to the wheels.

 

I appriciate it, and where is the tps located? and how can you tell if its bad?