ClassicCar

Hudson308

Okay guys, here's a puzzle for ya. I've got three friends that have all regularly experienced a "THUMP THUMP THUMP" when first starting out in a heavily-loaded stepdown. '49 Commodore sedan, '50 Pacemaker brougham and a '51 Pacemaker brougham. Doesn't happen with an empty back seat, but as soon as they load a few buddies in back the noise returns. My '49 Super 6 has never had this noise, even with six adults and a trunk full of picnic gear. We first thought maybe the pinion snubber was gone, but all looks well under the Commodore. Anyone solved this mystery in the past? :confused:

53jetman

Sounds to me like you should check/replace the center drive shaft bearing cushions (2) - available thru K-Gap. This is a simple maintainence job, and more or less a common problem with step-down Hudsons, especially if you tend to step on the old girl's tail more than occasionly.

Hudson308

53jetman wrote:

Sounds to me like you should check/replace the center drive shaft bearing cushions (2) - available thru K-Gap. This is a simple maintainence job, and more or less a common problem with step-down Hudsons, especially if you tend to step on the old girl's tail more than occasionly.

Yeah, Frank tried that... still had the problem.

Ken U-Tx

Check the Panhard rod (rear lateral stabilizer) rubber bushings, one on the axle and other at the body end of the Panhard rod. With dry rotted, cracked and crumbling bushings the Panhard rod can make contact with axle housing and the body mounting bracket as the axle winds up due to the extra torque needed to get a heavy load moving. Also when the car is loaded heavily, the Panhard rod with worn bushings can hang low enough to hit the axle housing/ pumpkin. Seen this on several Stepdowns. K-Gap has, or had the bushings.

Once you get the old bushings out and the new ones pressed into the "eyes" on the ends of the Panhard rod, there is a good chance you will be back in here asking how to get the thing back on the car. Theres a trick to it, but we'll see if you need the advice.

Hudson308

Ken U-Tx wrote:

Check the Panhard rod (rear lateral stabilizer) rubber bushings, one on the axle and other at the body end of the Panhard rod. With dry rotted, cracked and crumbling bushings the Panhard rod can make contact with axle housing and the body mounting bracket as the axle winds up due to the extra torque needed to get a heavy load moving. Also when the car is loaded heavily, the Panhard rod with worn bushings can hang low enough to hit the axle housing/ pumpkin. Seen this on several Stepdowns. K-Gap has, or had the bushings.

Once you get the old bushings out and the new ones pressed into the "eyes" on the ends of the Panhard rod, there is a good chance you will be back in here asking how to get the thing back on the car. Theres a trick to it, but we'll see if you need the advice.

Okay, Ken... we'll look that over, anyway. I'll let you know what we find.

SuperDave

Also look closely to the tail pipe/muffler for marks that might indicate it touching the axle or panhard bar when the springs are loaded. My 49 does it and I know it's the tail pipe touching the axle. It's not serious, so will just have to wait .

hudsonguy

I've experienced similar noises when fully loaded with people, but for me it only happens when I'd turn a sharp corner into a driveway 'ramp', and attributed it to my rear leaf spring bushings (at the front).

hudsontech

You might try something really simple - check the rear shocks.

Hudsonly,

Alex Burr

Memphis, TN

Clutch guy

Several things to check. As Hudsonguy suggests,the front rubbers in the leaf springs are going to be rotten and it lets the spring shift forward causing the driveshaft to be in a bind[too long] and then it allows the driveshaft to growl on the floors?. You also need to try and reposition the center"H"frame the driveshaft is supported by. Other things to check are the engine and trans mounts. If these are bad,they allow the engine to shift and also makes the driveshaft do as you have described. I don't find it very often,but verify the slip yoke at the rear tube does slide easy. Other possiblities are the exhaust hitting only under heavy loads. Can you see any obvious marks on the exhaust system and/or body where it is rubbing?,especially over the axle. Good luck,my 2 cents

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