So this ones a doozy.. I just put in a rebuilt 5.0 motor in my '96 F150 XLT less than a year ago now something else is going. I have had a whirring noise happening for a while now and it only happens when my foot is on the gas. The second i take it off the whirring stops. Today, i took my foot off the gas and there was a loud clunk from the front end and then grinding noises. I stopped, put my truck in park then back in gear and tried to drive slow again. The clunk only happens when i take my foot off the gas and then the grinding starts. I was able to drive home by keeping my foot ever so slightly on the accelerator all the time to try and avoid this clunk and grind phenomenon. When I got home, I tried to put my truck in 4wd, i heard my auto lock hubs click when i backed a few feet then when i tried to go forward, it sounded like all hell was breaking loose under me. I quickly stopped that... I am a college student with both limited funds and limited time to play around. Please let me know what you guys think and what the heck I should do about this...

 

What you describe sounds very much like you had an auto-locking hub that failed to disengage when the other one did so you have been driving with your front differential being spun on one side and mostly stationary on the other side; thus spinning the spider gears and wearing them to the point where they have now grenaded inside the diff housing. I would suggest you raise both front wheel off the ground and spin them individually. Also turn your front driveshaft by hand. Listen and feel for what I regret to inform is probably lots of little metal pieces (mostly teeth from your spider gears) rubbing against one another. You could also remove the fill plug on the front of the differential housing & inspect it for metal shavings & the condition of the teeth on the ring gear. When (about how many miles ago) was the last known time you had your hubs locked in & the transfer case (4WD mode) engaged? Hopefully it is something much less costly & time-consuming. Please keep us posted on what you discover.

dn.

 

Donner,
I just lifted the truck on stands and dropped it into drive. What i heard was horrifying. With my foot on the brake the whole time, only the rear passenger wheel spun and the driver side rear tire spun ever so slightly. All the while grinding to all hell. Post experiment, I noticed that the rear drive shaft had about half an inch of play fore and aft into the rear diff. I was able to turn the shaft in neutral and this also didn't make pleasurable noises inside of the transfer case. Im going to assume the rear diff now needs a full rebuild, my front diff exploded, and my transfer case was stuck in the middle of all of this and had one hell of a time. Tomorrow I'm going to drop the shaft at the Tcase and see what that sounds like in drive and open up the rear diff. Any suggestions as to where to start or what went wrong would be greatly appreciated..

 

Start by pulling the diff cover and talking a peek. But, what you described about it sounding worse in four wheel drive makes me think the tranfercase is bad. This is a thing that has been known to happen the pump has problems and stops lubing and not long after the bearings die.