I had to replace my broken front differential assembly with a used one from the boneyard. mechanic cleaned it up and reinstalled. The gears makes a very noticable variable pitch noise when it approaches 40 mph and gets loud by 55 mph and starts to quiet down after 65 mph.

It will only make this noise if under power. if it is coasting, no noise at all. I also notice that coasting below 30 mph, I can hear lower pitch gear winding noise.

Is there any fix to this. I assume my mechanic may not have moved my original gears to the used differential housing.

Thanks,

 

Sounds like possibly a bad pinion bearing.

So long as it has the correct gear ratio, just fix the noise problem, don't worry about the gears.

 

I will have to assume it should be the correct ratio (3:92), otherwise, the front end drive train may be going up in smoke otherwise.

I am not knowledgeable when it comes to the drive train aspect of my truck. Just the engine side.

Where is the pinion bearing located on the front drive train?

 

The pinion gear is the part the driveshaft bolts to. Which means..... the axle has to be removed, and pretty much disassembled to change those bearings. Not an inexpensive repair, rather labor intensive.

 

yup as long as the replacement diff was the same ratio as the old ones then no need to swap gears into this housing. I can find front diffs pretty cheap, probably quickest/ easiest way to get back underway... swap the whole unit.

 

Yeah, I gotta agree with this sentiment. How hard is it to find the correct gear ratio though? I know some were FAR more common than others.... at least, on the trucks.

 

Most likely pinion bearing like others have said. Currently having my mechanic rebuild my rear end for the same noise complaint.