I am tired of listening to the diff whine on my 99 4.6 3.73 Supercab. I replaced the axle bearings with saver bearings last summer as the stocks had gone bad. I used the saver bearings to avoid replacing the axles as they had a bit of a groove beginning to wear into them.

I have heard that the pinion bearing is often the cause of the whine, and I'd like to start by replacing that. Will it be necessary to replace the other two bearing sets in the differential too or are those usually not the problem? I'd really hate to just replace the pinion bearing and have to tear the thing apart again to replace more bearings.

Also, I'm due to graduate this spring (maybe summer...) so I'll be buying another truck sometime next winter. Aside from the noise and harm the whine will do to the resale value, I'm fairly certain that there will no other consequences of just leaving it be. Am I correct in this assumption?

I'd also like to know any other known causes of the infamous F series diff whine.

 

is the whine at around 80kmh on accell,if so there is a tsb on crown and pinion replacement (comes complete with bearings and seals)

 

I have seen that TSB. I suppose I ought to get a price from a dealer and send the parts list to a part shop and get quotes.

The whine is at its worse between 45-50 (around 80 kmh). It begins near 40 then worsens and gets better above 49 mph. It is present at all times after that, but not as loud.

 

does it whine under load or even while coasting? if ony under load its gear noise. if it all the time and more of a growl then wine its bearings. or it could be loose pinion bearings in which case you will need both bearings and gears.

 

Get back up to the speed you say it's happening at, go on and off the gas and if the whine comes and goes with that, it's the ring and pinion. 99.9% of the diff noise concerns I worked on at the dealer were ring and pinion. If you were just gonna replace bearings, it's best to do the pinion and sides at the same time but not absolutely neccesary.

 

It occurs under load and while coasting. There is a whine and a growl. The growl especially occurs while coming to a stop.

I have seen ring and pinion bearing kits for about $110, but I shouldn't need a all the shims and bolts. It should just be a matter of pulling and pressing a bearing, right?

Will the ring and pinion show excessive wear if the pinion bearings are loose? In my experience, the components will move back and forth if the bearings are shot. Is this the way to diagnose loose pinion bearings?

Like above, it occurs under load and while coasting. Why would a bad ring and pinion make all that noise? Is it because the teeth are worn to be the point of being misalignment?

 

personally, i would take this time to move to a slightly lower ratio, perhaps 4.10's?

 

Assuming that everything is stock, the truck has 3.73s. I bought it used 5.5 years ago just before I got my license. I could swear that the ratio feels lower than 3.73, so it may have 4.10s on it. That may be possible as the previous owner was an avid mechanic/truck enthusiast.