Don Elgan

1987 F150, 4 speed manual, 300 6 cyl., 2 wd. When I bought it, when you went down a steep grade and let off of the gas, there was a faint roar that I thought can from rearend. Been that way for 2 years. I thought I was having a universal joint going bad, so I had both sets done last month. Now, when I go down the road above 45 mph, a roar starts in and gets louder the faster you go. At 55 it is unreal. I took it back to the place that replaced the u joints and they couldn't find anything. Took it to a tranny shop and they thought it was right wheel bearing. Had them checked today and they are good. When you drive with your hand on the shifter, there seems to be no vibration, but when I was riding along with the tranny guy, I noticed vibration in floor board. Anyone got any ideas?

89F150

Does it occur at different engine speeds or just the 45mph?
Possibly have something to do with driveshaft

351w

it sounds to me like a pinion bearing or the gears are mis aligned in the rear.
actually the pinion doest have a real bearing it is known as a crush sleeve but they are known to wear and cause a whirring kind of noise.
does the rear leak any fluid where the pinion enters the housing ?.

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Don Elgan

Mainly noise is from 45 upward--thats when it is loadest. When going down the road, take it out of gear, you can hear the noise but not as loud--just enough to hear it. I had it out of gear and reved the engine couple times with no difference. There is no leaking of fluid anywhere. I was wondering: could they have tightening the u joints too tight when they installed them? I took it back as soon as I heard the noise thinking maybe they hadn't grease the joints. They raised it on rack and there was no niose when they put the speed to 45. This is about to drive me nuts. The noise seems to come from the tranny area, but not sure. Thanks for any help.

'92BigBronco

Actually, the crush sleeve provides the preload on the pinion bearings, which is why it must be replaced whenever the pinion seal is replaced. There are tapered roller bearings on the pinion shaft. The pinion nut is tightened down against the crush sleeve (basically a piece of soft "pipe") until the proper bearing preload is obtained. It's similar to giving front wheel bearings a preload with the adjusting nut.....

I will agree that it sounds like either a carrier bearing or pinion bearing. I've also heard of numerous complaints of stress cracks forming in the carrier of the Ford rearends, which can cause a whirring noise as the spyders will be misaligned. Just pull the differential cover and look things over. You'll know it if something is on its way out. Pay special attention to the carrier and look closely for any visible cracks. If that lets go, plan on a costly repair.

If everything looks ok, refill it with the proper lube and, if it's a posi, add 4 oz of the friction modifer from Ford.

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1992 Ford Bronco
351W
E4OD- B&M Stage 2 shift kit
Full 3" stainless Bassani Exhaust
32" BFG's/stock suspension

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