Driveshaft vibrations?

[mibars]

I think I have driveshaft vibrations from both front and rear driveshaft.

Around 55 mph on a clock I start to feel vibration which becomes unpleasant at higher speeds so I drive up to 55 mph.
When I drive 55 mph with front hubs engaged, case in 2WD I can feel even more vibrations now coming from below my feet.

Both driveshafts use universal joints so I don't know if that's a normal thing or not. In my opinion something is not right.

When I was inspecting driveshafts I've noticed that there is some play in them, in particular:

Rear driveshaft rotational play (in rear axle) - transfer case in neutral: (I can't feel any up and down/side to side play on a differential)

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Front driveshaft rotational play in hubs: Transfer case in 2WD, hubs engaged (I can see zero play in the slip yoke in the middle)

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Tiny bit of play up and down on a slip yoke coming out of transfer case:

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Is any of these excessive and something that should be addressed? i see that driveshafts have been marked with a sharpie and especially the rear one has multiple weights attached, so I guess they were checked no so long time ago.

I'm especially worried about the transfer case slip yoke. If the driveshaft has an ability to move tiny bit away from center I can imagine that it can cause some vibrations. But I don't know if the amount of movement I see may be the cause of vibration or it is way too little.

 

[SquareRoot]

I just went thru this. For starters, rotational play or slop in the shafts generally don't cause a vibration, just clunking when its being loaded/unloaded. If the vibration is speed related (as in your case) it's not an issue with the drivetrain angles. That leaves one possibility: worn out or unbalanced parts (including U-joint phasing). I had brand new components including a new rebuilt transmission, transfer case, rear axle (yes it's spelled AXLE...lol) and 100% new driveshafts....and still had a bad vibration that started at 55mph.

Mine turned out to be a rear output shaft bearing not being fully seated in the T-case. A worn bearing on the output shaft or the pinion shaft will cause vibration as it slowly self destructs. The amount of movement it takes to cause vibrations is almost not detectable by hand. When I took my yoke and CV to the shop to have them rebuilt he laughed and said they're junk without even picking them up. I would remove the front shaft and focus only on the rear until it is fixed. It's not hard, just a bit time consuming.

 

[SquareRoot]

Seriously bummed with this drivetrain setup right now :(

Many of you know that I recently made some serious progress on my truck. A complete rebuild of the NV4500 and 205 T-case. Only the best parts available, meticulous attention to detail following the manual and everything visually inspected and measured with a micrometer. Brand new driveshafts...

www.gmsquarebody.com

@mibars Read thru this post. It may help you.

 

[mibars]

Thanks guys!

For the front driveshaft checking pinion angle is a great suggestion in that other thread. If I can't see any obvious signs of play (other than rotational play which should not result in vibration) in a front driveshaft then maybe that's the issue.

Also with front driveshaft I can try driving with and without it with hubs engaged or disengaged to rule out that vibration does not come from the axle.


Regarding rear and in particular yoke: I can see that tiny bit of movement, when I watch the video it is barely visible with whole transfer case moving insead, less than 1 mm, but if you say that it may be something worn causing it. I can't say if the vbrations are for sure not present at lower speeds, maybe they are just not noticeable and increase with force with speed.

 

[mibars]

I think I found tiny bit of play in U-joint between transfer case and rear driveshaft.

Guys, how to tell which one is needed? Looks like there are couple different sizes that show up in catalogues on Rock Auto and Summit:

1990 CHEVROLET V1500 SUBURBAN 5.7L 350cid V8 Universal Joint | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

1990 CHEVROLET V1500 SUBURBAN SILVERADO 5.7L/350 Chevy small block Gen I U-Joints Transmission & Drivetrain Parts & Accessories | Summit Racing

Find 1990 CHEVROLET V1500 SUBURBAN SILVERADO 5.7L/350 Chevy small block Gen I U-Joints and get Free Shipping on Orders Over $109 at Summit Racing!

www.summitracing.com