Devin3429

Hey guys,
When my truck is in overdrive the RPM's shoot way up to 3500 to 4000 RPM's and it is very jumpy. So I have to drive with my overdrive off and it runs at 3000 RPM's which means I don't get as good as a gas mileage. Doesn't matter what speed I am going, the overdrive just does not want to work. Is it the timing chain or what?
I checked the timing with a timing light and it was ranging on how off it is and I know that timing chains are a problem in f150's so could that be what is causing my problem?
Also, my reverse lights are not working???? Everything else works but they are not. I think it has something to do with the Transmission Range Sensor is what I read on another forum but I'm not sure about that.

I drive a 2004 F150 4.6L New Body

Mechanik

Sorry, but I'm not quite grasping the issue. Are you saying that overdrive off=3000 RPM while OD ON=3500? At what speed? 3000 RPM is better gas mileage than 3500 at a given speed. Please clarify and we'll see what we can come up with.

Devin3429

Yeah when the overdrive is on, the RPM's shoot up a lot. It starts going crazy and jerking when I go anywhere faster than 30 mph with the overdrive on. I used to be able to go on the highway with the overdrive on and be going around 1800 RPMs but not the truck won't even drive 30 mph with the overdrive on so I am forced to drive with it off. Which means I am driving at around 300 RPMs on the highway instead of just cruising at 1800 or so. So my gas mileage has been terrible since this started happening.So yes the OD on= is around 3500+ RPMs anywhere above 30mph while OD off is around 2000 RPM until around 50mph then it goes up to 3000 RPMs gradually but its steady with the OD off. When it is on, it shoots up in RPMs and is extremely jumpy, jumping from 3500 RPM to around 4500 RPM and back down to 3500

Mechanik

I've heard of folks complaining about gear-hunting at around 55 MPH in OD, but I haven't seen it myself except when towing.

The whole shifting process is driven by the PCM, though. It's supposed to be measuring crankshaft speed and trans input speed to figure out slippage in the torque converter, combine that with probably a lot of other stuff, like speed, to decide when to shift or not. So that points to something wrong with those sensors (not likely, but possible), or the PCM (not likely at all) or something wrong with the OD components in the trans (could be likely depending on mileage and use).

I'm hoping someone more knowledgeable than me can chime in here.

tazzini64

I want to thank the people who commented in this thread because you saved me the cost of replacing my transmission. Also I would like to add that I completed the entire process of pulling valve body, finding piece jammed in roller valve, and replacing snap ring but my problem was a bit deeper than your description. After reassembly overdrive was still out so when I described processes to Aamco Technician he told me that since the servo piston had completely fallen out I had to realign the servo pinshaft with the overdrive band then replace snapping. So I took it apart again dropped valve body, dropped servo, stuck long shaft screw driver into servo shaft boar pulled overdrive band over and up, used a piece of rubber fuel line to wedge into fluid return port just below Odrive band and to right of port to hold band while replacing servo.