Hello.

2002 F350 7.3l ZF6 manual transmission.

I was towing about 11,000 pounds the other day and I noticed a grinding rubbing scraping chafing noise along with harsh vibration coming from between the front seats in the floor area.

After finishing the job I got home and got under the truck to find freshly scuffed metal on the underside of the cab.

With the truck parked, there is about a 1-1/4" of distance between the rear driveshaft where it bolts to the transfer case and the underside of the cab.

It appears that while I was towing, something must have flexed enough to cause the driveshaft to shift up and grind on the underside of the cab.

Am I the only person to have this happen? Thanks.

 

That sounds like two possibilities (or both at the same time). Toasted carrier bearing and/or spent rear springs. I had to install ladder bars to prevent the rear axle from trying to pass the front axle when I powered up.

The shifts got crazy smooth (auto) after the bars were installed.

 

Thanks tugly.

I noticed the same grinding rubbing noise today when I was backing the truck up a hill in 4wd.

Something is worn out or loose under the truck, which is causing the excessive movement of the transfer case and allowing it to torque to a large enough degree to cause the rear driveshaft to rub on the bottom of the cab.

My rear leaf springs look to be fine, and I just changed the front leaf springs. I also changed the carrier bearing within the last few hundred miles -- along with a whooooooole lot of stuff under the hood after realizing that I had cracked injector cups and diesel fuel in the coolant. I'm sick of throwing money at this truck.

Yet on the other hand, a rear driveshaft rubbing on the underside of the cab doesn't seem normal unless something is broken elsewhere.

I also replaced upper/lower (4) balljoints in the front when I did the leaf springs. Took the truck for an alignment and was told that I have to replace 6 more components -- tie rod ends both bad, tie rod to pitman arm etc...

Hopefully replacing the rest of the broken ball joints in the front of the truck fixes this rubbing issue.

If not, any other ideas?

Thanks.

 

Side note. This only seems to be happening in reverse.

 

Reverse 4X4 only, or reverse in RWD as well? It makes a difference for troubleshooting.

 

I would suspect broken motor and/or transmission mounts. I would think movement of a component forward of the carrier bearing would be the problem.

 

Today I put the truck in Low gear, (L) and held the brake. I let up on the clutch until the engine almost stalled. Didn't hear any noise. I had a friend operate the truck and I looked underneath. Certainly was a lot of transfer case movement when he abruptly put the clutch back down and let off the throttle.

Didn't hear the noise and was in a hurry so it slipped my mind to try the same thing in reverse.

Thinking back a ways... I have heard the noise several times while backing a 2 ton trailer up a hill. I have only heard it once while driving forward, while engine braking in Low (L) gear down a very steep hill with a 6 ton trailer behind me.

Tomorrow I will repeat the clutch/brake test in reverse and see if I can verify that the noise is indeed the driveshaft rubbing on the underside of the cab. It would make perfect sense that the driveshaft rubbing cab is indeed the source of the noise/vibration. There is a scuffed shiny and smooth spot on the underside of cab. It was not there when I bought the truck, and it is new since I have heard the noise.

Does anyone know where the motor and trans and transfer case mounts are? It'd be nice to know where to inspect for signs of failure. I'm not too keen on laying under the truck while someone holds the brake and lets the clutch up. If the brakes slip, the rear differential would crush my chest cavity as the truck rolled over me. Not much ground clearance.

 

Lay a camera under there and put it on video. Make sure you have plenty of light.

 

How do the rear cab mounts look?

If the upper rubbers are gone the rear of the cab would be sagging about 2 inches or more.

 

Just use a floor jack under the transmission/transfer case and check for movement. The transmission mount is bolted from the crossmember under the transmission to the bottom of the transmission.