My truck specs: '07 F150, 5.4 engine, "Q" transmission (4 speed auto w. OD), 84 K miles.
Problem: Driving up a gradual incline in OD, 40-45 mph, 1200 rpm, loud/severe "clunk" as tranny tries and eventually downshifts from 4th to 3rd. Rear "jolts" as if I were driving over a bump in the road. Problem doesn't appear when OD is switched to "off". Issue getting progressively worse. All other shift points up/down smooth, no problems.
Lots of suggestions in this forum---is there a typical common denominator to a cause/solution?
Your input is most appreciated!
Great site, great info.!

 

Check the fluid level.

 

I'd bet it's a misfire, not a tranny issue. With 84k your spark plugs are overdue for a change. Those are the classic symptoms of a misfire with these trucks - OD, under 45 mph, increasing load.

 

Just dealt with the same type of issues with my 05 at 76K miles. Same symptoms as you that started to be really noticeable around 70K and progressively got worse, then noticed that when it would finally kick into overdrive on flat surface, driving at just under 2000 rpm, it would surge as if you were feathering the throttle. Since the truck was new I have replaced plugs every 35K miles and flushed the tranny at the same time as well as change all fluids and filters as required in hopes to fend off some of these type of issues. Unfortunately we ended up pulling the transmission and my options were to throw parts at it in a rebuild or replace it, I ended up replacing it with a re-manufactured transmission with a five year warranty. Now the truck drives like brand new and hopefully will last another ten years.

 

Well, if the plugs have 84k on them, they need to be changed anyway. Worth a try before tearing into the tranny.

 

Checked tranny fluid--cold (38 degrees). Looks like level is too high---will need to check again warm.. Fluid is clear, no burnt odor.
TNX for the response.

 

Although the maintenance schedule indicates changing the plugs @ 100K miles, this is probably still a good idea---will do.

 

The 100k recommendation was changed to 60k. Change them.

Tranny fluid is checked WARM with the engine RUNNING in Park.

 

Truck going into the shop tomorrow for spark plug replacement. Possible interesting (?) side note----some time ago when the problem started, a ticking sound developed from the right bank of the engine. Possible exhaust leak, but it occurred randomly whether the engine was hot or cold. Would disappear in a minute or two. Expected an exhaust leak would occur only when the engine was cold. No exhaust leak found. Then, possible vacuum leak(?). None found. No codes or dash messages. Possible bad spark plug or coil? If so, may account for the "clunk" when under load as was suggested. Will have all checked out. TNX for your suggestions.

 

Truck into the shop for new sparkplugs. Shop owner could only remove/replace 3 so far. One plug definitely badly carboned, came apart on the workbench. Problem has suddenly gotten a lot worse even with 3 new plugs installed. Sea Foam used to help remove some of the build up on remaining plugs, in the hope they'll come out without breaking. Even it's a tranny issue, it's till a LOT less expensive than buying a new truck at $60K +. Bummer.

 

Spark plugs replaced. 4 of the 8 original plugs broke on removal. Heavily carboned as expected. Ran the truck for several days on the hilly terrain on our area. No issues. Truck has more power, runs smoother, shifts almost effortlessly. Changing tranny fluid next week. TNX to GLC and others for your help! Enjoy spring!

 

Congratulations! And thanks for the feedback!

 

Hey, somebody listened and got their problem solved!
Awesome and congrats!!!

D

 

Looks like a common misdiagnosis. Engine misfire causes truck to shake, and everyone thinks it's the transmission. Now that there are so many forum post, will people just read the existing posts, or create a new thread?