One Piece Driveshaft Vibrations

I purchased a used 2019 2WD 4D with a 6" lift and the vibrations in the drive train at about 70mph are crazy.. Feels like I am driving on orbital sander..

After crawling under the truck I think the original owner swapped out the stock drive shaft system with a one piece unit. I can see where he cut out what appears to be the carrier bearing mounts to make room for the new one piece..

Anybody have an idea as what the source of the vibrations could be? Part of me feels like the drive shaft could be out of balance but wouldn't that cause vibes all the time?

Also, what are the chances I could lower the truck back down to a reasonable 3" or so with that one piece drive shaft? My truck looks like it missed leg day currently and I am not a fan of "spacer" lift kits..

Thanks in advance.. I have little to no experience with the 2wd Tacos but owned a 2014 4wd TForce for 6 years so I am not a complete noob..lol

 

Most likely an unbalanced drive shaft. You can take it to a driveshaft shop and have them balance check it. Could also be a tire.

 

Thank you for the quick response.. Originally the truck had some useless mall crawler 22's on it and I just installed 4 runner wheels and new tires hoping that the vibration was the cheap 22's he had on it.. so point of that is I am positive it isn't the tire wheel combo.
Can I lower the truck 3" with the one piece shaft?

 

What kind of lift is on the truck?

 

Rough Country 6"

 

That lift cut the front frame.

You might be able to fit one of their 4" kits, but going back to stock and starting over is not a simple process.

 

Not if it was for a 2wd like OP's truck right?

 

Bad U joint angles, the original drive shaft was probably fine and the previous owner bought the Tom Woods one piece to try and fix his vibes, when it didn't he got fed up with driving a paint shaker and passed the problem on to you, also a 2WD with a 1 piece has too long of a driveshaft with gearing the RPM will be too high and you can develop a wobble even nore pronounced and harder onset by having bad pinion angle.

The transmission flange should be 90° to the road and the rear diff should be 1° nose down from 90° just out of parallel to the trans flange. This is so it becomes in parallel while under load as the pinion tries to climb the ring gear the diff nose goes up.

I know this because this is my current issue trying to get my drive angles sorted so I can stop driving on invisible wash board.

I also need to get new leafs so I quit pogoing off my rear bump stops.

You probably need axle/leaf angle shims.

You may also have axle wrap bad I see it all the time with cheap block lifts.

 

A couple of key items to look for with a one piece drive shaft, they are super simple to set up properly :

1. It should have been built with a double cardon u-joint at the front / t-case
2. If it is a double cardon one piece drive shaft the correct pinion angle is to have the rear diff aiming right up the same line as drive shaft

A lot of people skip setting up the pinion angle properly for some reason, all it requires are shims at the rear axle housing so it is quite easy to do.

 

I will get some pics today. The rear end is angled upward to match the angle of the drive shaft and I do believe there is only a single u joint at the transmission.
Yesterday I made a call to Rough Country and confirmed that the original owner did in fact have to cut the cross member to fit the lift kit. He also informed me that all the bracketry and other parts associated with the lift kit were the same between the 6" and the 4" kit with the only difference being the front strut tower spacers and the rear blocks.. Dropping it a couple of inches will only cost me about a hundred bucks, so that will probably happen.
As for the driveshaft another buddy mentioned that it may be out of balance. Considering the way it vibrates (high frequency) this seems likely so I will probably remove drive shaft and take it to the race car shop to check the balance and cross my fingers.. Give me a couple of hours to get out of this boring office and ill go take some pics..
THANK YOU to everyone who is trying to help me!! Much appreciated!

 

And pls ffthru with the fix if there is. Would help someone in the future

 

I just went through this... I have a 6" BDS, with rear Deaver 6" springs. I added a 1 piece Tom Woods driveshaft last week. I was getting bad vibes from the original 2 piece. Had the new shaft installed, and it was much worse. Took it back to the shop, they adjusted the angle at the rear diff, smaller degreed shim, and now its perfect....inexpensive and quick fix...

 

Keep us updated I'm curious to see the final outcome and solution.