Rattling/whirring sound when decelerating?

[david71]

Been in the process of refurbing a 93 C3500. Lowered it and haven't driven it due to prepping for paint. Took it to get the windows installed today and noticed a whirring or rattling sound when I let off the accelerator. Sounds perfectly fine otherwise. No vibrations that I can tell. Wasn't there before lowering it. Absolutely sounds perfect during acceleration. Kicked it in to neutral on the way home and still had the sound. I'm assuming the angle on the drive shaft may be causing the bearing on the drive shaft to have problems? Any one else run in to this issue? I used Belltech's 722SP which is a axle flip for 8 and 6 in the front. Put the shims in like suggested so I'd think that'd be OK. It isn't the first lowering kit they've built for a 93. I'm going to put it on jack stands when I get home and look around but any ideas of what to look for would be great.

Thanks in advance.

 

[618 Syndicate]

Get an angle finder on the driveshaft and see what it tells you.

 

[someotherguy]

Been in the process of refurbing a 93 C3500. Lowered it and haven't driven it due to prepping for paint. Took it to get the windows installed today and noticed a whirring or rattling sound when I let off the accelerator. Sounds perfectly fine otherwise. No vibrations that I can tell. Wasn't there before lowering it. Absolutely sounds perfect during acceleration. Kicked it in to neutral on the way home and still had the sound. I'm assuming the angle on the drive shaft may be causing the bearing on the drive shaft to have problems? Any one else run in to this issue? I used Belltech's 722SP which is a axle flip for 8 and 6 in the front. Put the shims in like suggested so I'd think that'd be OK. It isn't the first lowering kit they've built for a 93. I'm going to put it on jack stands when I get home and look around but any ideas of what to look for would be great.

Thanks in advance.

Did you install the carrier bearing spacer provided with the kit?

I just lowered my '93 C3500 dually with that same kit but my carrier bearing setup won't allow me to use that spacer; the mount is completely different. I'm guessing because my truck has an NV4500 manual transmission instead of a 4L80E..

Richard

 

[david71]

Did you install the carrier bearing spacer provided with the kit?

I just lowered my '93 C3500 dually with that same kit but my carrier bearing setup won't allow me to use that spacer; the mount is completely different. I'm guessing because my truck has an NV4500 manual transmission instead of a 4L80E..

Richard

Yep, installed the bearing spacer and wedge under the leaf springs.

Get an angle finder on the driveshaft and see what it tells you.

Will do that this evening when I get home. Just strange that it only does it under deceleration. Figured if the driveshaft was wonky it'd be doing it constantly.

 

[618 Syndicate]

Yep, installed the bearing spacer and wedge under the leaf springs.

Will do that this evening when I get home. Just strange that it only does it under deceleration. Figured if the driveshaft was wonky it'd be doing it constantly.

Not necessarily, it moves slightly during acceleration and deceleration, and it might be moving enough to cause your issue with no load.