Hello all new to the site and in desperate need for help. So 1996 7.3. The last couple weeks while I am driving the truck especially on the freeway my OD will not shift in. Now I know that the OD Light will flash at you. Now mine does not do that it will shift into overdrive and right back out of overdrive maybe two or three times for only a couple seconds and then stays in third gear. But if I need to pass somebody it will shift into overdrive and as soon as I come do a steady speed it's just back out of overdrive. I've been looking around at this site and people are saying it could be the shift still annoyed I have beginning to think that it is the transmission itself 174000 miles on it I think it might be time for a rebuild. But I did change you oil about a month or so ago and it was very dirty I've only had the truck for about eight months and I don't think the guy before me I change the oil ever. While I was changing the oil I did not notice any metal shavings of that sort. So I changed oil change the filter and put it all back together and the truck actually ran much better Until this problem started happening so if I could hear some feedback from you guys it would be much appreciated thanks 👍🏼

 

The first thing to check is the fluid level. Check it with the trans warmed up, in park, and the engine idling.

 

Are you sure it's not shifting into overdrive or just not locking the converter? Does your cruise control work? A bad break pedal switch or burned out 3rd brake light or some led lighting for the brakes can cause the converter to lock and unlock. If it's over drive I'd read about the wiring on the shifter for the od button and a member hear recently changed everything to find it was a a bad pcm causing it

 

well I have tried using cruise control. And I replaced all my exterior lights with aftermarket lights. I put leds in the rear and HIDs in the front

 

I checked the tranny fluid probably 3-4 days ago? And it was fine no loss of fluid.

 

If you have an issue with the 3rd brake light or bake pedal switch cruise control will usually not work

 

If you push the overdrive button down does it rev even higher or does the rpm stay the same?

 

ok I'll give it a try tomorrow on my way to work. Say it does work then what?
Also could it be a possible tranny overheating?

 

it revs higher

 

and by third brake light out you mean the light in the rear above the bed right?

 

Well you need to find out if it's overdrive not engaging or just the converter not locking first. Led lights can affect converter lock. I purchased one with a tow bed because of a "bad converter" that ended up just being a burned brake light and poorly wired led brake light causing voltage interference on the 3rd brake light Circuit. It's how it know to unlock your converter when cruising.

 

If it revs higher than you are already in overdrive and pushing it kicks it out of overdrive and into 3rd gear. It sounds like your converter isn't staying locked. Check your 3rd brake light and pull the bulb. Make sure there is no voltage going through the circuit with the bulk removed.

 

I've had the brake light out since I got the truck. I did not replace that light with an led. So it doesn't work and the problem had just come up about 2 weeks ago

 

so you don't have a 3rd brake light bulb in there at all?

 

correct I do not have a brake light there