Who can diagnose this noise?
09-29-2017, 11:02 AM
#1
Who can diagnose this noise?
I got my 1999 F-150 a few weeks ago from the original owner (68 year old man) with only 91,000 miles. The pinion seal was leaking on him so he had a shop put in a new seal. When you drive the truck, it doesn't make any whining noise until about 30-40mph. When you are on the gas pedal, the sound is a little louder. If you coast in that speed range, the whine is still there but not as bad. When you get over 40mph, you don't hear the noise anymore, maybe because of road/wind noise? I changed the differential fluid last week and the fluid was dirty gray, but found no metal in it at all. The noise hasn't got any worse, but I want to address the issue before it does. I was thinking maybe the shop that replaced the seal tightened the pinion nut too much? You can grab the driveshaft at the pinion flange and there is zero play, can't make it move which is good. Could it be the inner pinion bearing? It has the 9.75 rear differential if that helps. Thanks in advance for some helpful advice!
10-01-2017, 02:38 AM
#4
Senior Member
Nothing wrong with it...turn the radio up. 
Ford addressed the problem with a kit you can have installed, -your own dime. It's expensive. They pretty much all do it to some degree. I wouldn't really call it a whine, but I can see how you might. More like a dull hum and only at about that speed you mentioned, perhaps a little slower. Then it goes away.
My 98 has been doing this for as long as I can remember. I've had this one from new. A quarter million miles plus. Hasn't changed pitch.
Ford addressed the problem with a kit you can have installed, -your own dime. It's expensive. They pretty much all do it to some degree. I wouldn't really call it a whine, but I can see how you might. More like a dull hum and only at about that speed you mentioned, perhaps a little slower. Then it goes away.
My 98 has been doing this for as long as I can remember. I've had this one from new. A quarter million miles plus. Hasn't changed pitch.
10-01-2017, 07:46 AM
#5
Thank you Jbrew! Out of curiosity, what is the kit called? I bet it's expensive. I had my dad ride with me and he couldn't even hear it haha. I'll just drive it unless it gets worse then I worry about it. The truck runs and drives like a new one!
10-01-2017, 06:31 PM
#6
Senior Member
There isn't a name, it's a TSB that has the replacement parts listed...part numbers and such. No one out of warranty goes threw with it since it doesn't cause any harm.
Anyway, if your really interested, look through the TSB's, - it's always there lol.
Anyway, if your really interested, look through the TSB's, - it's always there lol.