The stars aligned for what is probably the last drive of the season. Stopped to vote and then we hit scenic route 20 for a nice ride. Too bad most of the leaves have already fallen... Bu I digress...
With Mrs. Big John in the car, the noise was noticeable 55 MPH ish... and then seemed to quiet down as the car warmed up. From there, I could get it to make a rumble type sound as I let off the gas at anything over 50 MPH. It wasn't constant though. This section of road is quite hilly so on and off the gas happened a lot.
We turned around and Mrs. Big John had a brilliant idea of letting her drive! (She likes driving this car anyway) . While it was quiet with me driving, her driving style, which tends to be a little more "on and off" than mine, got the noise going a lot!
So... It's a rumble, kind of like a bearing noise, but it's mostly under deceleration, but she also got it to do it on acceleration which was something it didn't do when I was driving.
To summarize:
There is no vibration now. We did solve that with the driveshaft rebuild.
The noise does come from the rear, but it kind of reverberates under the floor.
The noise does quiet a little as it warms up, but doesn't go away.
There is no noise at cruise, that is constant speed at any speed (I think I hit just under 70 MPH a few times on the drive)
The noise occurs under mild deceleration from above 45 MPH and under mild acceleration from about 45 to 60+ MPH.
The work done so far:
Replaced all 3 u-joints, 2 of them being in the double cardan front joint. The centering yoke assembly was also replaced. Driveshaft balance was checked.
The rear end was completely taken apart last year as there was some bearing noise. All the bearings in the rear were changed, including the pinion and carrier bearings along with the axle bearings. A sure-grip center section was added at this time.
All leaf spring bushings were also changed at that time.
I drove it minimally after that last year and had issues with chatter on turning, so I changed rear end lube and added Ford LSD additive this spring and no chatter after that.
I also drove it minimally this spring after the rear lube change.
Driveshaft angle was checked and while it could be optimized, I don't think it's the problem. About 5 1/2° down for the pinion.
The pinion nut was checked for tightness and is OK.
The trans mount is hard to really see, but it looks OK.
Conclusion:
I'm thinking it's the gears. According to the notes from the previous owner and my observations, the rear gears were used and swapped into this center section. I then swapped out the center carrier for a new sure-grip unit. I checked the mesh at the time and it looked OK, but not perfect. I did change a spacer under the pinion gear.
I'm going to also address the pinion angle. I can shim the rear up 3° and that should leave me with 2 1/2° down, which I think would be good.
Any thoughts?
