sleddude

My 2002 F150 4x4 FX4 Extended cab truck has a vibration (similar to driving over the rumble strip on a highway) when pulling away from a stop. From what I can tell, it happens about 3-8 mph, or about 10 feet after I pull away from a stop, and seems to happen when turning from a dead stop. No signs of it when pulling away straight. Here are some of the details

• Truck has 293,000 miles!! (that's not a misprint). It was my company truck assigned to me with 180K in 2010, and I put the last 110k on it. Prior to 2010 it was in Missouri and is clean/straight and rust free. It has been a phenominal truck and runs excellent. I purchased it in 7 months ago, and my daughter has been driving it to school and back since then.
• About a year ago, ( around 270k miles) the transmission went and was replaced with a remanufactured tranny. Note: I noticed the shudder occasionally/intermittantly before the tranny went, and was surprised it was still there intermittently after the new tranny was put in.
• The mechanic who changes my oil noticed that the transfer case was overfilled on the first few oil changes after the new tranny was put in.
• The truck has been used only about 10 miles a day, back and forth to school for the last 7 months. I had not driven it myself for a few months and last night when I took it out, I noticed the Shudder/vibration had gotten noticeably more prominent.
• Last night, I drove around a parking lot stopping and starting, turning, straight, hard start, easy start, etc. It seemed to be most noticeable on a normal acceleration, during any kind of turn, even a slight turn. It did not seem to do it going straight.
• Out of curiosity, I put it in 4wd (electric) and turned and the problem was extreme when I turned and didn't seem to go away. I put it back in 2wd and it felt like it stayed in 4wd, so I backed up about 50 feet and it went back to normal. The parking lot was dry pavement.

Checking various posts, I believe it is the CV joints, or the differential. Sitting in the drivers seat, it feels like it is in the rear of the truck, but I can't tell for sure.

I know most people would say to walk away from the truck with that kind of mileage, but we love this truck, and it is in such good condition, I feel it is worth fixing.......to a point. Any help would be appreciated.

4x4dave

Sounds like something in the driveline. U joint? I would also look into getting the wheels balanced and rotated if you haven't done so in a while. The differentials are usually pretty solid, but there could be a small chance something is going on inside it.

You may be already aware of this, but If you used 4x4 on dry pavement it will bind up the driveline since the 4 wheels are not slipping and they are traveling at different speeds. This will cause all sorts of nasty noises and vibrations. We recommend not running 4x4 on dry pavement.

RicheysFX4

Mine was doing the same thing. It was the rear differential , I changed it to amsoil with 2 bottles of friction modifier and 50 miles later the chatter was gone.

sleddude

Thanks for the replies. Before I read these replies, I brought my truck to my mechanic today and he thought it was the rear diff, and put a bottle of friction modifier from Motorcraft (I think it was Motorcraft). The pint cost about 7 bucks. He drove it around in circles in a parking lot, and it seems much better.

I am going to let it be for a week or so and see if the symptoms are truly going away, or if it was the typical "didn't do it when I brought it to my mechanic" deal. If it truly is better, I am going to have him pull the cover off the diff, clean it out, and put in new fluid and friction mod. Thanks again for the input.

FordJunky05

iTrader: (1)

I've felt this a couple times in my truck too. Same symptoms. When pulling away slowly from a stop, but not every time. Let me/us know if the fluid change helps. Gonna be doing it soon anyway, but if it helps your truck out then I might do it this weekend. Also thinking about getting my alignment checked and making sure the wheels are balanced.

Tys 4x4

Mine does this every once in a while also. Only under light to moderate acceleration from a stop though and not every time. Heavy accel it doesn't do it. Probably wouldn't hurt to change fluids in the axles.

FordJunky05

iTrader: (1)

Exactly, same here.

sleddude

I originally thought mine was only doing this on normal acceleration, but not when accelerating hard, but what I found was I normally accelerated hard in a straight line, and accelerate easier if I am turning, even if it is a slight turn. So it is not necessarily a hard/easy acceleration, but a straight line vs. turning from a stop situation.

This was a critical fact, because the symptoms only appear if the wheels are turning at a different speed, like in a turn.

sleddude

A few weeks have passed. My daughter takes the truck to school and back @10 miles a day. I got in the truck for the first time since a few weeks ago and the issue is significantly better, barely noticeable.

Looks like adding the "Friction Modifier" worked. Hopefully good for another 293,000 miles!!!

Its nice having a mechanic who you can trust. If you live near Laconia, NH, try Sanborns garage. Not the best looking shop, but they are reasonably priced, and honest about fixing only what needs to be fixed.

Pumpkinhed

My vibration was due to a faulty u-joint on the front driveshaft for the 4x4 Because it free wheels most of the time, depending on where it was resting the vibration would be better sometimes and worse others, difficult to troubleshoot. Lift both front wheels off the ground then start spinning the wheels back and forth by hand and watch underneath.