alexsbuddy

I have a 2005 F150 Supercab XLT, 5.4L Triton, with a 4 speed automatic transmission with overdrive and a 3.55 rear end. It has approx. 78500 miles on it. I am experiencing a shutter/clunk at approx. 1200-1300 rpms and at 43-46 mph, more so when traveling under load or uphill. I believe it is related somehow to the transmission. It does not occur when I turn off the overdrive. I did an OBD scan and had no trouble codes. Any ideas or thoughts would be greatly appreciated.

lewissa81

I'll be the first to tell you, you are not alone. There's a 90% probability that it's your spark plugs. If you do a search on the forum, and wade through the 1000's of posts, you'll find it's very common. You can relax for a minute and stop thinking about an expensive tranny rebuild. Here's the bad news though, these plugs are a pain in the rear! Search through the forum and gather all the tips on changing them out, then decide if you want do this yourself, or pay someone else. Seriously though, with your trucks age and mileage, if you haven't had your plugs changed, then that's the real issue.

alexsbuddy

I saw several of those posts, but can't figure out why turning off the OD would make a difference it its the plugs. However, you are correct....the plugs are original, so they most probably are overdue for replacement. Thanks for input. I really appreciate it. I will postpone getting stressed-out for the time being.

jamie930

I would be willing to bet its not a shutter is a miss. Had the same thing before I changed my plugs, and before I changed the COP boots and springs

tareed94

What I was told by the transmission shop when I feared the same thing is that with overdrive turned on you feel the engine more directly. So the "shudder" it causes is actually an intermittent misfire that you can feel through the truck.

alexsbuddy

Thanks for the input....both explanations make perfect sense. I'm going to start with the sparkplugs and see what happens.