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Anyone know what might be causing this grinding sound? There's a slight whirring while on throttle, but when you lift there's this really loud grinding noise. The noise doesn't seem dependent on wheel speed, if I mess around with different gears the sound will get louder or quieter. Engine is a 350 sbc, th350 trans, 12 bolt rear.
Throwout bearing?
In reply to jharry3 :
Th350 trans, automatic.
Loose pinion nut?
Slip yoke or bolt on? If it's a slip, bad output shaft bushing. Bad U-joints can cause this as well. It behaves under accel (but makes a whirring) and then all hell breaks loose when you decel.
Also, look hard at trans/engine mounts. Could just be the transmission rocking under decel allowing the case to touch the floor pan which instantly transmits all the noises.
In reply to Streetwiseguy :
The pinion seal is weeping, so I'll check that out.
I put the rear end on axle stands and ran it. Could hear the sound coming from the pinion and it was moving in and out, gonna rebuild the diff.
In reply to Curtis73 (Forum Supporter) :
Mounts are good thankfully, the u-joints look new as well.
It's a slip yoke so I'll pop the tail shaft housing off and take a peek at that bushing. Thanks!
In reply to iammclovin804 :
Makes sense. Under acceleration the ring gear is trying to push the pinion forward. Decel it sucks it back.
In reply to Curtis73 (Forum Supporter) :
Yeah it makes sense now that I think about it. It's very odd though, in the cab it sounds like the grind is coming straight from the transmission.
Those vibe-y noises trick you. It's probably louder at the axle but since you're right on top of the transmission, the sound that is transferred through the driveshaft is what you hear the most of.
Replaced the bearings in the diff and all is well now. I appreciate the ideas guys!
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