I have a 97 F150 Super Cab 4x4 with the 4.6 auto and a 3.55. I just bought it a couple of weeks ago with 42000 on the clock. When going up hills (mild grade) and keeping the truck at about 40mph (3rd gear approx 1400-1600rpms - requires light throttle), the truck makes a vibration that feels like I'm going over shallow rumble strips - like the ones on the side of the road. If I take my foot off the gas completely the "rumbling" stops. Anybody have any idea what could be causing this or experience this with their truck?

I also posted this in the tranny forum, so if you see it there please don't flame!

 

i don't know, but my 4.2 5-speed 4x4 gives one hell of a rattle going down the highway. It has started doing it recently, and stops once it is good & warm. i notice it only does it at around 100km/h (60mph)... and will eventually stop...

I just wonder how many others have this problem...

 

I had a simular problem and found that changing my PCV valve all but cured it. I did the blow test and the old valve seemed to be working but it obviously was not. Now my tranny down shifts out of torque converter lock-up when on these grades. It probably wasen't able to produce enough vacume with the bad PCV to unlock the torque converter. Costs only $3 to find out. Could be a cheep fix.

 

Just got back from the Ford garage. My torque converter is bad. Because of my warranty, they are replacing the entire transmission.

 

I have a similar type of vibration. Mine occurs between 35-45 mph, and when I go to pass just before it downshifts, I get that same type of "rumblestrip" type vibration. Have read many different post describing this vibration under similar and varied conditions. No one has seemed to come up with a sure fix for it, but many people seem to have it. Since I get this vibration just before downshifting, would that point to a bad torque converter? This vibration feels as though the drive shaft is out of balance.

I would love to think it is the PCV and not something more expensive and elaborate to fix.

Any solutions out there??? Unfortunately, I don't have any.

 

I have posted this in a couple other places as well. In one of the posts a Ford tech said that he sees this all the time and that the fix is to change the fluid in the tranny AND torque converter and replace the filter. I was extremely surprised that they didn't want to try this fix on my vehicle before they decided to go ahead and replace the whole tranny.

If you can be sure that it is a tranny problem, I would say spend the 150 bucks or whatever and have this done and use MERCON V fluid. Others have said that worn U Joints can also have the same "rumble strip" effect, but if your truck is only doing it in a certian gear or something, it is obviously not U joints.

 

that's nice for you automatic tranny guys... but what about us with the manual trans.... mine does the same damm thing, allthough it is going to the shop for numerous other things (all under warranty)...

 

My wife had a 98 Windstar, same problem when the tranny was shifting out/in of OD. Changed the tranny filter, worked fine for a while and then started again. I just bought a 2002 SCREW 4.6 Auto, hope this problem doesn't start with it. If so, all I can say is Ford needs to take another look at there trannies. It's too common and in too many different makes and models....... I've owned nothing but Fords for the last 18 years, but only recently had any tranny problems at all.

 

Had this problem on my old 91 F-150. It did just what you describe. Went through all the u-joints and such with no change. Brought it to an experienced tranny guy and he said it was the torque converter. That fixed it.