2003 v8 4x4 started pulsing or bucking tonight.

[shipwreck17]

Hey guys, I was driving home from work today and my Ex started sort of pulsing or bucking around 20-30 mph. It did it a little bit when accelerating and also when braking. Before I got home it quit but I just tested it again and its back. The engine doesn't do anything its just like something is dragging. I've been reading all about the wheel bearing problems on these but I'm not convinced that's it. Any ideas? The truck has 90k miles.

 

[shipwreck17]

Well I just stumped the CarX mechanic. He had no clue.

It only happens after 10-15 minutes of driving. Then once it starts 3 things happen at once.

There's a mechanical "hit" like your driving over a rough road.
There's a noise that sounds like a belt or bearing squeal. Its not crazy loud but audible.
The car pulls hard to the left.

Its very intermittent. Either the truck feels 100% normal or all 3 of those things happen. Once it starts it has symptoms about half the time in intervals.

The mechanic thought maybe a front diff problem? The pulling really confused him, I'm not sure if a diff issue could cause a pull.

He put it on the lift and said he couldn't find any play in the bearings and said everything looked ok.

It doesn't drive ok? Anyone?

 

[kworonowski]

if you can get it back on the lift grab the coil spring and manually turn the tire if you feel a grind its prolly a bad bearing i would expect the front left to feel the worst if you are pulling to the left. Under acceleration the load on the bearing could cause it to lock up a lil and give you the shudder and noise. Did they see ne thing wrong with the brakes maybe a bad abs sensor.

i had mine looked at from brakes plus they showed me the bearing check on the coil springs.

Best of luck

 

[shipwreck17]

It looks like my problem is in the trans...

 

[shipwreck17]

Does this make sense?

Ford says my 4wd is kicking on and off all the time because my truck thinks its slipping.

The truck did just get new tires on the front. The rears were Ok and I was planning on replacing them in the spring. So now when I drive it just goes in and out of 4WD and kicks.

That checks out I suppose, I think I've seen a mod around here to turn off the auto 4wd feature. Could I do this to avoid throwing away tires with plenty of life left in them and spending a lot on new tires right before Christmas.

 

[matt0248]

Ford says my 4wd is kicking on and off all the time because my truck thinks its slipping.

The truck did just get new tires on the front. The rears were Ok and I was planning on replacing them in the spring. So now when I drive it just goes in and out of 4WD and kicks.

That checks out I suppose, I think I've seen a mod around here to turn off the auto 4wd feature. Could I do this to avoid throwing away tires with plenty of life left in them and spending a lot on new tires right before Christmas.

It is a possibility that the different diameter of tires is doing this. I cannot remembler the exact spec. but for AWD and AUTO 4WD all tires should be within 2/32" tread depth or something like that. I think it may be in the owners manual. But with different diameter tires they turn at different speeds. The 4wd system can see this as wheel slip and engage the 4wd.

The mod you are talking about has been refered as the BWM or Brown Wire Mod. There is a sticky thread about it. With this mode you cut the wire to the T-case from the 4WD module that tells the T-case to engage the front wheels. Cut the wire and install a switch so you can turn the auto 4wd on and off manually.

 

[shipwreck17]

Everyone agree this will solve my problem? Are there any other side effects to having new/ old tires. Any issues with the abs sensors. Basically my computer is going to be constantly trying to engage 4wd which even if I cut it off and it cant that doesn't sound good.

 

[kworonowski]

If the tires you got are different in size (circumference) then that would be IMO the problem. I did the same thing got 2 tires that were close in size 2-3/32 difference and had the same issue although they were the same brand and size the difference in years the overall circumfrence was almost 1/4" off and hence the same issue. I have heard of some places that can "shave" the new tire to match within 1/32 but most will only work on brand new tires. If you can take a tape or piece of string wrap around the tire in the center and check length see how much the new to the old tires are off.

Best of luck.