Little Trucks, Big World

Hi guys, thanks for having me aboard. I have a bone-stock '84 regular cab that runs very well. However, there is a terrible low-frequency drone sound in the cab when driving or idling. It is worse at midrange and lower rpm's. I have tried to pinpoint the sound by manipulating the exhaust with a piece of pipe while idling. I have also looked at the motor mounts, and they look good. The engine is not shaking or doing anything crazy. Any ideas?

Thanks in advance!

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If you have 2 part driveshaft rubber donut is toast. Option 2 is universal joints worn out or combo of both

Thanks, Channing. Drive shaft is a 2-pc unit, hanger bearing is new, u-joints are fine. The drone sound happens even when in "park". That's what is so strange to me.

Thanks for ideas!

Does it go away when pushing in clutch?

It's an automatic. You think it may be torque converter vibration?

Unlikely the driveshaft if it does it at idle.

Hole in muffler. Not likely forward of it or would be loud tic sound.

Look for anything near the exhaust pipe or where the pipe would move and come into contact with the body.

Transmission mount?

Cab or hood loose?

Thanks datzenmike for the ideas. I will check those this week when I can put it on the lift!

Cab noise update:

Noise was coming from multiple areas. The problem while driving was happening at 45 mph+. We put the truck on the rack this week, and found a problem at the rear diff yoke. The u-joint cup was a loose fit on one side, causing the joint to work side-to-side in the yoke while driving. We tack-welded the yoke to hold the u-joint in place until proper repairs can be made. This solved most of the driving noise, although I still have the horrible drone at low rpm's whether driving or in park.

The tranny was replaced about 3k ago by the PO, and work was performed by a shop that doesn't have a really adept mechanic. The bellhousing has been welded on the bottom, and I suspect someone torqued the bolts while mis-aligned with the dowel pins and cracked the bellhousing. I am starting to suspect a warped/cracked flexplate or TC problem. However, she still shifts and runs 100%, so I'm gonna run it!

Thanks, Guys.





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