bert150

Hello,
Just purchased a 2007 F150 Lariat 4x4. Ive been driving it in all types of ground. Yesterday i noticed a bump while driving 45-50 MPH. I hit 50 MPH let go of the gas and before it reaches 45 i tap for some gas and the bump kicks in hard. Im will be taking it back to Galpin Ford to get looked at. Did I just purchase a problem? Or is this something that can be taken care of?

stump8268

Maybe the U joints have slack and that's the bump. Does it sound like it's in the rear?

bert150

no, its def coming from the from. I honestly believe it has to do with the tranny. But its only when im at those speeds, other than that, the truck runs well.

BUZZFX4

Can you recreate the so called bump at W.O.T.?

bert150

I can recreate the "bump" anytime from 45 mph to 50 mph. What a bummer. And now my 4x4 low light wont turn on when i swithc to it. Can it be from the same problem?

driver444

I doubt the 2 problems are related.
As for the first one, a few things can make a "bump" as you describe it.
1. Slop in u- joints as previously mentioned.
2. an improperly set up rear end or worn bearings (less likely) If this were the problem, your rear end would likely be making a few different noises along with the "bump" like a whining noise.
3. (and this is common) a loose tranmission mount. This is my guess.

A loose transmission mount will cause a single banging noise every time you get on and off the gas pedal. Most of the time you can "feel" it under your feet.

If the truck's not under warranty, it may be worth your time to crawl under it and make sure everything's tight first.

Can it be fixed??? Of course! and usually this kind of stuff is, as I said, something that just needs to be tightened up.

bert150

The way you describe a loose transmission moount sound about right. But would it do it all the time. or between those speeds? Its under warranty. Ive had it for Seven days today.

driver444

A loose tranny mount would eventually do it at all speeds, because they only get more loose, but it'll be more noticeable in higher gears first (earlier) due less gear reduction, and more torque from the engine and transmission. (much like a clutch in a manual transmission will slip in higher gears first).

Is there any chance it could be something messed up with your torque converter locking and unlocking? That could also give you a "bump". If that's the case, usually that can be fixed electronically at the dealer.

Turkey Hunter

Check the u joints. My truck does the same thing and its the u joints

Squirtbottle09

I dunno about the tranny problem, but for the 4x4 low. You have to have the truck stopped, in neutral, and your foot on the break to put it in 4x4 low. The same procedure is required to get it out of 4x4 low.