Narrowing down vibration - questions

[nb96z]

I’ve been reading lots of threads about this that have been helpful as I’m trying to fix my vibration, but I still have questions as I’ve never worked on drivelines and differentials.

Background: bought truck with a really bad vibration driving at any speed. Took out the two piece driveshaft and had it get balanced. Front shaft towards trans was replaced as it was bent too badly. Rear was re-balanced. New u-joints and carrier bearing replaced. Also replaced the rear yoke as a chunk of metal was missing from it. Smoothed out the vibration and now only get it between 45-50mph and 70-75 mph.

Next, I looked at pinion angle. Found the trans side was pointing down at about 3.5 degrees and rear side pointing up at about 8.5 degrees. Shimmed the rear and now they both are at approximately 3.5 degrees. I’ve heard ideally you want to get between 0-3 so wanted to see if this would help any. Very, very slight improvement with the vibration but still there at the speeds mentioned above.

Got the wheels off the ground and looks like the left axle is bent as the wheel wobbles. The right is ever so slightly, almost unnoticeable but there. Also noticed the yoke is wobbly.

So, my questions are what axles would I need as I see the lengths vary and I’m not sure. It’s a 14 bolt full floater.

Should I do one or both?

How hard is it to change out the axles? I’ve never done this but have done other things like install cam shaft, headers, roller rockers, suspension components, water pumps, etc.

Thanks.

 

[Doppleganger]

You talking (both) as in front left-right, or front-rear? This is whats in your sig - a C20?

Its the end of a holiday weekend so I'm still slightly impaired.

 

[Turbo4whl]

Full floating axles do not support the weight, the two bearings on each side of the hub are supported by the axle spindle.

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Semi floating axles support the load with one bearing.

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So if your full floating axle hub wobbles, it is a bearing problem, not an axle problem. Could be as simple a the bearing adjustment is too loose, or could be worn out parts. Early GM full floating axles used barrel bearings and both the inner and outer load from the inside. This could also be an issue if not assembled correctly.

Please post a picture of the rear wheel, hub cap removed.

 

[nb96z]

Video of left rear wobble.

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Left rear wobbles, right rear barely.

 

[nb96z]

See pic

 

[Redfish]

Might just be my angle but it almost looks like that may be in the wheel or tire. Have you verified that it is in the drivetrain and not just a wheel/tire balance issue?

 

[nb96z]

That’s what I’m trying to figure out.

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I don’t think the yoke is supposed to be do this either.

 

[Turbo4whl]

Looking at the drum spinning looks even. Yes I agree with Andrew, bent wheel or bad tire.

Looks like just the dust shield is mounted crooked on the yoke, non issue.

 

[nb96z]

Thank you guys. I’ll work on the wheel issue.

 

[Turbo4whl]

Answer to your first question, the axle is very easy to change on your full floater. Remove the 8 bolts and it slides out. To re-install, slide it in, rotate and push down to make the inside splines lift up to move into the differential side gear. This is not your issue.

I would remove the wheel and tire and have it spun balanced to see if it is bent rim or bad tire. While the wheel is off look to see if the hub mounting surface is flat or has a rust bump.

 

[nb96z]

Update on this. Yes, it was a bent wheel. No more vibrations at 45 and 70 mph. Thank you guys for the replies.