66 shutters and shakes pretty hard

[BiffWilley]

Hey all! I've been driving my 66 pretty much everyday with no issues! The ol girl turns over and runs like a champ every morning!
Recently I've noticed that she shutters and shakes pretty aggressively when i hit around 35-40 mph. She has new tires that are balanced so I don't believe thats it. If I accelerate through or let off she immediately stops the shutter.

I'm thinking its my drive shaft/ujoint area. wondering if anyone has had this issue or could aim me in a good direction of troubleshooting.

I know my front cab mounts need replaced, but the shutter sounds and feels like its in the area where the two drive shafts meet right under the seat.

Thanks so much in advance for the help and advice!
Cheers,
Biff

[slick4x4]

Carrier bearing ?

[Limestone66]

Check the front end for any loose parts, kingpins, pivot point bushings, drag link, broken or worn front shocks, radius arm bushings or anything that would contribute to its mysterious condition. Check for play on vital steering parts as this could also cause that kind of problem.

[BiffWilley]

Thanks guys! I will definitely check into those. Who knows where those are as far as condition.

Cheers,
Biff

[jwh f-100]

Here do you feel it most? At the steering wheel or at the seat?? Many times (but I wont say all times) if it is a front end issue you feel it in the steering wheel and If you feel it in the seat or even the cab it is a driveline issue....

[Gritsngumbo]

I had a similar issue. After replacing the U-joints and various tweaks without success, I took it to my mechanic friend. Turns out I had apparently failed to properly tighten the lug nuts on the left front, and they had wallowed out and that was causing the vibration and noise that I thought was coming from underneath the truck. Didn't really notice anything in the steering.

[BiffWilley]

after talking to some more people here at work, I'm leaning more towards the carrier bearing. I don't feel it much in the steering and in my wind imaginative head it seems like its a drive shaft deal.

Thanks for all the input guys. I'll check tonight and let you know what I find!
Cheers,
Biff

[R Pope]

I'd bet its the center bearing rubber mount. The good news is, the bearing and mount is the same piece up into the late '70's or even later, so they are easily available.

[SomeNewGuy]

Any solution found? I have been driving my 66 for the last three weeks and it started the same issue. Mine feels more like a very strong vibration almost like driving over rumble strips on both sides at both times. I found my differential fluid was a little low, and topped that off. Thinking now it might be carrier bearing even though it looks good.
Let me know if you found out what your issue was.
Before it started doing that i was hearing a sound that sounded like something rolling around in the bed of the truck, but there was nothing back there to roll around.

[BiffWilley]

I'm thinking its the center bearing. I haven't had a chance to get out and check it, but it is VERY VERY similar to what you are describing aswell.

I hope to at the very least get a peak at it this weekend. I'll be sure to let you know what I come up with
Cheers,
Biff

[totten]

X2 on the lug nuts backing off, ck carrier bearing housing rubber is bad.