AlbertoA

I have read countless threads on similar issues though they seem to each have their slight differences from mine. So here is my problem:

My truck has a vibration when I accelerate from a stop either going forward or backward with the wheels turned. It does it for the first 5-15 feet. The vibration can vary from somewhat noticeable to feeling like I'm in FWD which I am not.

It does not do it at all when the wheels are straight. If I leave the wheels turned, it will do it for a bit then go as normal. But if I am rolling slowly, once the vibration stops and I reapply the brake, it will start anew. It strangely happened right after a wheel bearing hub replacement. The bearing was screaming when I changed it.

I have read about friction modifier but does it fit my problem?
I also have been told it may be front axle CV. Is there a way to double check?

Thanks in advance.

jprevat

iTrader: (1)

Look at your door jam. There us a sticker with an axle code. If it is a letter and number it needed to have friction modifier added to the rear end after the bearing change.

AlbertoA

Axle type is "h9". What difference could that make?

jprevat

iTrader: (1)

H9 means you have a limited slip rear end. It is a clutch style traction aid and does not function well at all without friction modifier.

It was a rear bearing you replaced right?

AlbertoA

No. Front wheel bearing. That's what's getting me.
300k km (200k miles) but I bought it used over a year ago. I don't recall feeling anything at all before noticing the bearing noise etc

jprevat

iTrader: (1)

Ok then forget everything before now. Lol

How do your cv boots look? Are all 6 bolts still firmly attached?

Did you grease the splines where the cv goes into the hub?

AlbertoA

Boots look good and the bolts as well. I greased the splines and tightened the hub but to spec. I also took apart the other side to check the bearing, regreased everything and tightened as well.

jprevat

iTrader: (1)

The only thing I can think is that maybe the collar isnt fully disengaging or maybe the cv is bound somehow.

drj2171

I have a very similar problem as the OP. I know this is an old thread but did you ever figure out what was wrong? I had my front end rebuilt about 2 years ago and 1 4x4 shaft was replaced and this started happening a few months ago. Any suggestions?

1999 F150 4x4 Lariat 5.4

AlbertoA

My problem was the rear end, was the clutch packs, but was not solved by the addition of friction modifier.
I've learned that the problem is caused by the wear of clutch packs. You can potentially get away with adding friction modifier to your diff fluid without draining it or doing anything else. Some respond to this. But, if that does not work, odds are you need to replace clutch packs, which means the fluid gets dumped, which means you have to ensure whatever you put in fluid wise has to have said modifier already in it, or you add it yourself depending on what you get.
Unfortunately, I can't tell you amounts, or much more detail. It's been 7 years, and I just replaced the whole rear end with a used one, then a few months later sold the truck and bought a 7700.
As far as diagnosis of rear end (diff) vs front end (CV or bearing), dont over think it. If it feels like it's coming from the rear/middle of your truck: Rear end. If it feels like it's coming from the front/through your steering: Front end.