Drivetrain slop

[68FORDJBM]

I started hearing a clunking that I suspected was coming from the drivetrain because I could hear it at low speeds while speeding up or slowing down. Got underneath and sure enough when a my wife gave a little push while in park to get the truck rocking forward and back I could see and hear the clunk coming from where the driveshaft joins the tranny and differential. I'm assuming a bushing or joint is going out but what end? What parts should I order to get it fixed?

Its a 1968 F100 Ranger with a 360 and auto transmission. I think its a C6 tranny?

Thanks in advance.

[HIO Silver]

Firmly grab and and wiggle the driveshaft... Slop?

Prolly the U-joints... they are always replaced as a set so all have the same amount of installed time. If one goes bad, then the others may not be too far behind.

[68FORDJBM]

Thanks, I'll start with a new set of U-joints. They haven't been changed as long as I've had the truck so they are due for replacin'

[HIO Silver]

Don't just go willy-nilly replacing parts... Ya gotta do more investigation. I said "probably u-joints"... Heck, it could be a bad carrier bearing but that's not the norm.... Crawl under there......

[FoolsOnlyReadDirections]

Consider that your splined connection for your two-piece driveshaft may be binding as you slow or accelerate from a stop. It's a common issue for our trucks. My '68 is bad for this. I have to remove my shaft occasionally and gob into the female splined connection, large amounts of heavy equipment grease that "resists squeeze-out," it says. Try that.

[sargentrs]

I suddenly developed a clunk and vibration in mine a while back. Crawled under there and found that both carrier bearing bolts had loosened up and it was swinging back and forth under there. New bolts, nuts, washers and lock washer and all was good afterwards. I have no idea how that happened!

[Jacksdad]

U-joints fail more often than anything else under there, and should be pretty obvious if you try to turn/move the driveshaft with your hands.
I just changed all of mine out, and one was so bad that it had no needle bearings left

[radioactivelarry]

I started hearing a clunking that I suspected was coming from the drivetrain because I could hear it at low speeds while speeding up or slowing down. Got underneath and sure enough when a my wife gave a little push while in park to get the truck rocking forward and back I could see and hear the clunk coming from where the driveshaft joins the tranny and differential. I'm assuming a bushing or joint is going out but what end? What parts should I order to get it fixed?

Its a 1968 F100 Ranger with a 360 and auto transmission. I think its a C6 tranny?

Thanks in advance.

If you replace your U-Joints take the drive shaft to a drive line service place and have it balanced. My total cost was about $125.00 including the U-Joints. All runs super smooth now.

[68FORDJBM]

Thanks for the suggestion! I might have to do that. That would go nicely with the balanced motor:)