I got bad vibes, man- FIXED. Go to page 9

Update.
Picked up the re-retubed rear shaft at lunch and @thebrotherinlaw was gracious enough to swap it in for me. He drove it and came back with a frown.
Vibes worse than before.
We put it in stands and sure as can be, crooked as hell and nowhere near straight
Ordered a new shaft from Tom Woods. I don't have any more time to screw around.
Local shop gonna make it right and refund me some $$$.
 
Jody Treadway said:
Update.
Picked up the re-retubed rear shaft at lunch and @thebrotherinlaw was gracious enough to swap it in for me. He drove it and came back with a frown.
Vibes worse than before.
We put it in stands and sure as can be, crooked as hell and nowhere near straight
Ordered a new shaft from Tom Woods. I don't have any more time to screw around.
Local shop gonna make it right and refund me some $$$.
Click to expand...
How in the heck are they so bad at doing the only thing they do?
 
Why not Carolina Driveline?
He's an hour from you, would build it same day, and he's a wheeler?

Legit curious. Allegedly at one point they were OEM building Tom Woods shafts for them for east coast customers.
I dont know if thats true, but I do know there was a stack of tom woods tubes new in wrapper in his shop...
 
Ron said:
Why not Carolina Driveline?
He's an hour from you, would build it same day, and he's a wheeler?

Legit curious. Allegedly at one point they were OEM building Tom Woods shafts for them for east coast customers.
I dont know if thats true, but I do know there was a stack of tom woods tubes new in wrapper in his shop...
Click to expand...
Legit answer.
I was going to, but heard their quality has gone down over the last short time. Was informed through an industry colleague.
 
Why not just chop and sleeve an XJ/ZJ/TJ front shaft since everything else seems to be shit?
 
Jody Treadway said:
Who's gonna retube it and make sure it's square/straight/balanced? Locally, of course
Click to expand...
Why bother? A round tube on a previously balanced round tube should still be balanced.
 
Jody Treadway said:
No shirt, just a sticker pack.
Stickers are like t shirts in 2022 dollars
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Vintage
20220920_194830.jpg
 
I would think that if the shaft was bad or bad bearings or bent flange or something was binding it would get worse and worse with more speed and load. Sounds to me like shaft whirl which is a spinning shaft resonance. Every spinning shaft has specific rpms that it will resonate at, even perfectly straight and balanced shafts. The solution is to change the length, stiffness and or mass of the shaft so that the resonant frequency is outside of it's operating range.

Many vehicles come with a pressed on donut around the driveshaft to force the shaft rotating inertia and hence it's resonance frequency out of the operating range of the vehicles speed range.

When you changed gears the driveshaft spun faster for the given mph hence with 4.56's gears the driveshaft reached it's resonance frequency at a lower mph range.

I didn't read every post in this thread so hopefully this isn't a repeat, but this is the stuff they said in engineering school that came in handy designing propulsion systems for large yachts with lots of spinning stuff involved.

If woods hasn't started yet, maybe ask them to go up a tube diameter, that would definitely changed mass and stiffness, or ask them to smash one of those donut thing a ma bobs on the tcase end behind the joint. Or use a thick wall tube. For what it's worth, Tom's gets all my driveshaft business.

Clubbs
 
Clubbs said:
I would think that if the shaft was bad or bad bearings or bent flange or something was binding it would get worse and worse with more speed and load. Sounds to me like shaft whirl which is a spinning shaft resonance. Every spinning shaft has specific rpms that it will resonate at, even perfectly straight and balanced shafts. The solution is to change the length, stiffness and or mass of the shaft so that the resonant frequency is outside of it's operating range.

Many vehicles come with a pressed on donut around the driveshaft to force the shaft rotating inertia and hence it's resonance frequency out of the operating range of the vehicles speed range.

When you changed gears the driveshaft spun faster for the given mph hence with 4.56's gears the driveshaft reached it's resonance frequency at a lower mph range.

I didn't read every post in this thread so hopefully this isn't a repeat, but this is the stuff they said in engineering school that came in handy designing propulsion systems for large yachts with lots of spinning stuff involved.

If woods hasn't started yet, maybe ask them to go up a tube diameter, that would definitely changed mass and stiffness, or ask them to smash one of those donut thing a ma bobs on the tcase end behind the joint. Or use a thick wall tube. For what it's worth, Tom's gets all my driveshaft business.

Clubbs
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This. Working in the driveline industry, this is exactly the things I have to explain to people about why they experience a vibe going 150mph in their mid life crisis 2018+ GT Mustang. NVH and Harmonics are ever present and typically unaccounted for. Forbid, in an offroad vehicle, its never an issue because the critical speed limit is never reached with 35” tires and 35” shaft and some other variables. But that shouldn’t be your issue. Harmonics can be a funky thing to trace. Hollow tubes (like a driveshaft) are a great places for these frequencies to resonate. Do you have a poly motor and trans mounts? OE Rubber can help absorb the harmonics…typically. Thats if that is even your problem. Just a wild ass guess.
 
Clubbs said:
I would think that if the shaft was bad or bad bearings or bent flange or something was binding it would get worse and worse with more speed and load. Sounds to me like shaft whirl which is a spinning shaft resonance. Every spinning shaft has specific rpms that it will resonate at, even perfectly straight and balanced shafts. The solution is to change the length, stiffness and or mass of the shaft so that the resonant frequency is outside of it's operating range.

Many vehicles come with a pressed on donut around the driveshaft to force the shaft rotating inertia and hence it's resonance frequency out of the operating range of the vehicles speed range.

When you changed gears the driveshaft spun faster for the given mph hence with 4.56's gears the driveshaft reached it's resonance frequency at a lower mph range.

I didn't read every post in this thread so hopefully this isn't a repeat, but this is the stuff they said in engineering school that came in handy designing propulsion systems for large yachts with lots of spinning stuff involved.

If woods hasn't started yet, maybe ask them to go up a tube diameter, that would definitely changed mass and stiffness, or ask them to smash one of those donut thing a ma bobs on the tcase end behind the joint. Or use a thick wall tube. For what it's worth, Tom's gets all my driveshaft business.

Clubbs
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Critical speed on that shaft should be in the 6000 rpm range. Cruising at 70 the driveshaft speed is less than 1/3 of that.
 
I dunno, haven't run the math on it. You're probably right though at first critical speed being around 6k. Generally all the shaft line calcs I did had to include all sort of end frequency, engine firing order, number of cylinders, gear ratios, propeller weight and number of blades, pto accessories and all sorts of stuff. There was also most always some noise that lined up perfectly wrong within the normal operating range. Hence the dampeners and stuff we see on today's vehicles.

I would think just about any driveshaft shop with a high speed balancer would have a shaft right enough for the shaft itself to not be the only issue. But drastically changing the shafts mass and stiffness could move the alignment of excitation for the whole system outside of normal operating conditions.

After all we've all run some pretty cobled together driveshafts in our days (got one under my rig right now from pretzeling one on the last trip). It's sort of straight, and not balanced at all with used joints. But it runs smooth at 65 mph with 35's ok 4.56:1 gears. But my old diesel tow rig about shook the paint off because the factory dampener rotated on the shaft. So it's probably not just the shaft, but the shaft is the easiest thing to alter in mass and or stiffness to get the rest of the "system" at play to settle down.
 
kcox506 said:
This. Working in the driveline industry, this is exactly the things I have to explain to people about why they experience a vibe going 150mph in their mid life crisis 2018+ GT Mustang. NVH and Harmonics are ever present and typically unaccounted for. Forbid, in an offroad vehicle, its never an issue because the critical speed limit is never reached with 35” tires and 35” shaft and some other variables. But that shouldn’t be your issue. Harmonics can be a funky thing to trace. Hollow tubes (like a driveshaft) are a great places for these frequencies to resonate. Do you have a poly motor and trans mounts? OE Rubber can help absorb the harmonics…typically. Thats if that is even your problem. Just a wild ass guess.
Click to expand...
OEM mounts throughout. I installed the Tom Woods shaft and the vibes are minimally improved. I have some routine maintenance to do one evening this week and I'm gonna look things over with a fresh set of eyes.
 
Have you tried running in 4low at about 20-22mph in top gear yet?
 
I'll give you $1500 for the rig since it's basically junk at this point. Problem solved.
 
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