The rear in my 99 F150 4.6, extra cab is 3.55, 8.8, 10 bolt. Would anybody happen to know the dimension of the axle. I have a mean Vibration(hopping) in the rear durring braking. Changed brakes and all 4 rotors. Had the new rotors dialed to make sure they were not warped. New tires, balanced twice. New shocks. Checked entire front end and the problem still exists. I have leaking axle seals so durring the change I would like to replace the bearing and also make sure the axle is ok before replacing that also. Any help is much appreciated.

 

What dimension on the axle are you wondering about?
Did you have the rotor runout checked with the rotors installed?
That's how it should be done to also check for axle flange runout.

 

Sorry for the late reply.
I did a runout on the rotors when they were installed and also a runout on the hubs.
Id like to check the dimension of the axle where the bearing is to make sure there is no wear. I know sometimes you can see the wear in the axle but Ive heard that the slightest wear sometimes cant be seen. The truck hops the worst a 40mph. under breaking. The hopping in the rear seems like an unbalancing issue. Ive read somewear that the dimension of the axle is 2.093. Could be wrong, I have no clue. I have owned 3 150's but this is the first truck I have had over 36thou. miles. Im a trade-in kind of guy. This truck I would like to keep for a few more years so its time to learn how to repair things myself. Im more then happy to find this website because you guys are extreamly helpful. Most mechanic shops dont want to answer questions, they just want the doe.
Thanks again

 

I think the only way you'd get a spec for the axle would to measure a new one.
If the axle isnt worn enough that you can easily and feel it I doubt you'd have a problem with it.

 

Just to throw a new angle in at you...
What about the ABS modulation? When I lean into my brakes (steady pressure) my rear brakes feel like they are hopping. I'm pretty sure it's the ABS at work, vibrating at their ungodly rate and making a really low thumping noise, like a strange kind of machine gun.

-Kerry

 

Thanks for all the thoughts.
Now for the ABS, I had disconnected the ABS and the problem was still there. The only this is that Im not sure if when you unplug the ABS that it will totally disengage itself. I tried to hammer on the brakes and could not get ABS to kick in. So I beleived it to be off. Today we rip the rear apart, change the bearing and seals a hope for a freakin miracle!!!

Thanks
Gary

 

Took the rear apart, changed seals and bearing and the vibration is still there.
Is there any way to determine if it is the ABS. I have unplugged the ABS under the hood and the sensor on the rear. Im not sure if disconnecting completely turned off the ABS. Is there a way to check this myself? Im guessing this is something Ford is has to do.
Does your truck do this at any certain speed and has this been happening since you purchased the truck?
Im ready to give up.

Thanks
GHayde

 

My truck makes this sound and vibration when I brake with a steady pressure and it feels like it should start locking up the brakes (in my older truck I'd lock them up for sure). It's made the noise and vibration for since I bought it in September... an aquaintance's truck has done it since '97 with the rear drum configuration,vs. disc's... differrent rear size (8.8 vs. 10.25).

As far as the vibration goes, if it happens at any speed and any time you aren't on the brakes, then I'd suspect other things, such as driveline balance, the torque convertor shuddering....

The ABS... I'll leave that to Dave (Racerguy). I know not, how this thing really works other than a magnetic pick up? senses the speed of the wheel and the ABS systems compensates for the possibility of lock up by causing the pulse modulation of the brakes.

-Kerry

 

Anytime you disconnect anything that has to do with the ABS it should turn the light on on the dash. When the light is on the ABS is disabled.

 

Thank you for the info.
Im going to take the truck into Ford to have the Trans. tested, maybe while braking at 40mph the truck is in the middle of a downshift causing the vibration. Im at a loss for ideas!!!

Ghayde

 

I dropped the truck off at Ford today for a diagnosis, What a headache. I received a call 1 hour later claiming that my rear axle seals were leaking. I then mentioned that they were replaced a week ago along with both bearings, and boy were they quiet. Maybe they will actually look at the truck now. I know that some Ford dealers are honest, I guess its Friday and there looking forward to the weekend.
I cant win!!!!!

GHayde