Rumble when braking with hubs locled

[Lordwestbrook]

Hey guys- I have an 86 k15 that has developed a rumble from what seems like the front hubs when braking. Only when the hubs are locked. Happens when both engaged in 4 or not engaged. Only happens while braking. Anybody out there can clue me in on what may be causing that rumble???

Thanks in advance!

 

[1987 GMC Jimmy]

How many miles and how much abuse that you know of? I think you should check your driveshaft for centrifugal play with the front wheels jacked up (safely) and see how the universal joints are doing just for kicks, especially the front joint. Play when applying centrifugal force to the front u-joint that results in less than reasonable or no wheel movement may prove a clue in the diagnosis of bad axle spindle bearings. If that's the case, I'd look at replacing the axle spindle bearings on both sides and seeing if that fixes it. If it doesn't, it may be a good idea to replace both front wheel bearings. I don't feel like this is necessarily a braking issue so that's why I'm thinking to look at things that like to hum, growl, or rumble when they wear out. High mileage and/or high wear and abuse may justify replacing those items in itself.

 

[Lordwestbrook]

Thanks for the heads up- not sure about abuse but I've had the truck for 10 years and it may or may not have roughly 100k on the driveline. And it may or may have not been a plow truck at one time, coming from NH. 4wd really only gets used to get around the snow when we get it. I'll get under it and check for play.

 

[1987 GMC Jimmy]

I gotcha. And don't forget to make sure your hubs are locked when you do your checking.