Basically my trucks rpm is fluctuating by about 200 only when i tow. It doesnt happen at idle or acceleration only when i get up to 50+ plus mph when i keep the speed steady

i know it isnt a tps i changed that about 4k miles ago
97 5.9 2wd 290k miles

 

Are you in tow/haul mode? How much weight are you towing?

I suspect what you are seeing is torque converter clutch unlocking/locking. Usually, that is a TPS thing. What brand TPS did you install?

 

What are you towing and do you have the overdrive off? Just because you replaced the tps doesn't mean it's working correctly. Why did you replace it same issue?

 

My truck does this with no load at about 55mph with OD on…for me it’s because I’m at 1800rpms and it lugs, shut off OD and it stops. So now I don’t use OD till I’m 60-65mph+ and haven’t had issue again

 

honestly i have no idea what brand it is, i went to advance and they gave me one. What brand would you recommend ?
also i didnt know there was a tow mode is that the little switch beside my od?

and my od has never worked since i bought the truck. When i turn it on it runs at 3k rpm

ive been having evap problems. Dont think this could cause it. But i have changed out the pcv valve. Pcv hose, charcoal canister, solenoid, and the lines from solenoid to charcoal canister but the check engine will not go away

 

O/D off button should be on the right side of the instrument cluster. If the light is ON, O/D is OFF. If you aren't getting O/D at all, regardless of the button, need to find out why. Are there any codes stored??

 

i think you are trying to scare me👀. I had assumed when the light was off that od was off.
i have a BIG problem then. I have always driven with the light off. When i press the button and the light is on is when my truck feels like it loses half its power and moves up to 3 k rpm. Weird that it loses power but rpm goes up

 

It should actually feel MORE powerful with O/D off, it remaps shift points a bit, and delays TCC engagement. And of course, disables O/D......

Yeah, if the light is ON, overdrive is OFF. O/D should engage at right about 42 mph, assuming there isn't anything else untoward going on.

 

Well heyyou. This truck is old its got 290k with the original trans and engine. The previous owner DID NOT take care of her too well. Rust all in the coolant systems. Oil leaks everywhere. Ive changed out almost all the easily accesible gaskets. Rear diff fluid was black when i changed it. I mean she was just in real poor condition

so far ive changed the diff fluid and gasket replaced almost tge whole evap system minus the parts where i need to drop the tank. Put a hughes plenum in. Cleaned the intake and throttle body, steering gearbox, power steering hose, shift sensor, trans governor sensor, water pump, coolant hoses,

ive taken care of almost all the power loss issues i was having. Took care of the stalling i was having. Trana doesnt slip anymore.

but i mean my current problem as well along with the rpm surge. Is im 99% sure i have a blown headgasket or part of the block is cracked.
ive been losing slight amounts of coolant for abt three months. I popped off the radiator cap and let it run. It didnt bubble but theres definitely slight amount of oil in there. Is giving that rainbow look.

i know its almost rebuild time. But ive sunk a pretty penny in my own tine and money in her and i just cant afford to put anymore esp with the age.

sidenote i do beat the hell out of her

i mean two-three times a week i put a 3600 pound pallet of sakrete in the bed which i know is WAY overloaded. And i also haul way more than the gvwr reccomends sometimes by about two tons. But the issue is i have a small concrete business and i have to do what i have to until i can afford a bigger truck.

 

It could be cracked heads.