I have a ‘18 F-150 XLT with 3.5L with 170,000 miles & started feeling as if I’m running over rumble strips in 10th gear pulling a 12’ tandem axle trailer with lawnmower. After removing 10th gear, 9th pulled just fine. Today, pulling my 22’ boat, I felt it until I got down to 8th gear. It feels just like hitting ruble strips doing 70 mph. I wasn’t sure if the fluid & filter was ever changed, I bought it at 125,000 miles. I was considering changing them to see if it makes a difference but thought I’d get other opinions before wasting the money if it’s pointless. I do have the famous hard shift from 3-4-5. Any ideas?

 

Just a suggestion.....change your transmission to TOW/HAUL when towing and DO NOT tow in 9th or 10th gears and possibly 8th as they are overdrive gears. 7th may work better as it is 1:00 to 1:00, you need to get the RPM up into the torque band at highway speeds. Higher revs also result in more efficient cooling.

 

a fluid and filter change is a good idea and add a bottle of Motorcraft friction modifier

 

I do use the Tow Haul every time I pull a trailer, regardless of the trailer size. If the RPM levels off, it will shift up to 9 & 10. Even so, there's still an issue with the bumping feeling in 9 & 10 which bothers me.

 

Have you changed yours & if so did you do it yourself? I haven't looked into it yet, but evidently it's a sealed transmission but do like doing maintenance myself. I've been reading up and most claim that changing the fluid won't make any changes so I'm not sure which route to take. Have a shop look at changing the oil and see if there's any shavings or anything in there?

 

Check the Flying Wrenches YouTube channel. They have a good explanation of all the potential problems and symptons. My guess is a bad CDF drum. Ford has an improved version of it.

 

If you have 3-4-5 issues and hesitation/slamming in 9/10 you're toast. You can change the fluid but it will not fix the issues, you have physical wear and damage. Either trade the truck while it still drives or start saving your pennies for a replacement.

 

The only shifting issue I have is 3-5. I only have shutter when I’m pulling a trailer after its already shifted into 9-10. Without a trailer & normal driving I can avoid the 3-5 hard shift & the 9-10 doesn’t show up.

 

If true then I would for sure sell it now.... Let the buyer beware!

 

I’ve had the 3-5 issues for 50,000 miles and it hasn’t worsened. It drives fine normally, just started having this shutter in 9 or 10 when I’m pulling a trailer.