Harmonic Vibration

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Frankenchevy

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He’s not paying retail for the parts, but I would. So $500 extra to have peace of mind of a reputable shop setting it all up is worth it. I just hope that solves my issue.

Only parts left that aren’t new after this will be the np208 and th400. I’d feel confident rebuilding the 208, but I doubt that’s it. I’d think if it’s bearings were bad it’d be rattling some oil out the output seal...maybe not.

If it’s the th400...well we’ll see.
 
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Frankenchevy said:
He’s not paying retail for the parts, but I would. So $500 extra to have peace of mind of a reputable shop setting it all up is worth it. I just hope that solves my issue.

Only parts left that aren’t new after this will be the np208 and th400. I’d feel confident rebuilding the 208, but I doubt that’s it. I’d think if it’s bearings were bad it’d be rattling some oil out the output seal...maybe not.

If it’s the th400...well we’ll see.
Click to expand...

Yeah there is still the TC left to check. Even if it is new...

Back to your shop taking your $$... make absolutely certain they will stand behind their work if there is a problem down the road. Even the most experienced mechanics make mistakes...
 
Frankenchevy

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shiftpro said:
Yeah there is still the TC left to check. Even if it is new...

Back to your shop taking your $$... make absolutely certain they will stand behind their work if there is a problem down the road. Even the most experienced mechanics make mistakes...
Click to expand...
How would I go about checking the TC?
 
Frankenchevy

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Also, my 14ff hubs don’t have two spindle nuts with a lock ring between. They have a single nut with a woodruff key.

anyone know the appropriate pre-load for those?
 
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Frankenchevy said:
How would I go about checking the TC?
Click to expand...

Good question Jeremy... let's take a step back for a moment. Are there any known transmission or TC issues that can cause vibrations?
I'm certainly not sure if there is, but I have heard of a TC going south and causing vibration. I don't know if this is a true story or not.
I can't imagine something inside a transmission going out of round or anything that would cause vibration without an actual fail of parts..
But the TC... I can imagine a fin losing it's 'constitution' and causing an uneven flow of oil... potentially causing vibrations.
 
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Did you have the truck up on jacks or a lift and fire it up... run it up to whatever mph to hopefully watch it shake it's self off the lift?

Also motor mounts and transmission tail shaft mount?
 
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Frankenchevy

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shiftpro said:
Did you have the truck up on jacks or a lift and fire it up... run it up to whatever mph to hopefully watch it shake it's self off the lift?

Also motor mounts and transmission tail shaft mount?
Click to expand...
Both are new and I rechecked torque—all was well.

I’m not brave enough to run it up to 55+ on jack stands.
 
Frankenchevy

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shiftpro said:
Good question Jeremy... let's take a step back for a moment. Are there any known transmission or TC issues that can cause vibrations?
I'm certainly not sure if there is, but I have heard of a TC going south and causing vibration. I don't know if this is a true story or not.
I can't imagine something inside a transmission going out of round or anything that would cause vibration without an actual fail of parts..
But the TC... I can imagine a fin losing it's 'constitution' and causing an uneven flow of oil... potentially causing vibrations.
Click to expand...
The vibration only happens above 55. That’s at about 2200rpm. If it is TC related, I should be able to replicate it in 2nd gear at 2200rpm, right? I’ll give that a go tomorrow.
 
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Frankenchevy said:
Both are new and I rechecked torque—all was well.

I’m not brave enough to run it up to 55+ on jack stands.
Click to expand...

Maybe you would feel better if you used cinder blocks or HELL YA blocks of firewood!
 
Frankenchevy

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The plot thickens...

I took the truck for a test drive and did three things:

1. drove the truck at 55-60 mph (~2300rpm) in ‘D’(3)—pulsing vibration present.

2. drove the truck in ‘2’ at ~2300 rpm—little or no discernible pulsing vibration present.

3. drove the truck in ‘2’ at 55-60mph (~3100rpm)—little or no discernible pulsing vibration present.

The pulsing vibration seems the most apparent in Drive (3rd gear) at speeds above 55mph, but not as apparent in 2nd gear at or above the same speed. Does this make sense to any of the transmission gurus out there?
@Matt69olds @HotRodPC
 
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Frankenchevy said:
I made an appointment for Friday at the diff shop. He’s going to install new wheel bearings and seals that I already have. Additionally, he’s going to put in an Eaton truetrac, new carrier bearings and new pinion bearing. Total for parts and labor is $1400. Does that sound reasonable?

The true trac alone is $750 +tax. I’d say with bearings, shims etc there’s probably $900 in parts...
Click to expand...

About 10 years ago I paid a shop $1,800 to regear my jeep axles. I went from 3.55 to 3.73 so it required new carriers, or was it it just one for the front...I can't remember exactly but I supplied the parts. I'd say $1,400 is a decent price.
 
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Frankenchevy said:
The plot thickens...

I took the truck for a test drive and did three things:

1. drove the truck at 55-60 mph (~2300rpm) in ‘D’(3)—pulsing vibration present.

2. drove the truck in ‘2’ at ~2300 rpm—little or no discernible pulsing vibration present.

3. drove the truck in ‘2’ at 55-60mph (~3100rpm)—little or no discernible pulsing vibration present.

The pulsing vibration seems the most apparent in Drive (3rd gear) at speeds above 55mph, but not as apparent in 2nd gear at or above the same speed. Does this make sense to any of the transmission gurus out there?
@Matt69olds @HotRodPC
Click to expand...
How about driveshaft balance and u joint condition? It can also be tires too.
 
DoubleDingo

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HotRodPC said:
How about driveshaft balance and u joint condition? It can also be tires too.
Click to expand...

I believe he has already had the driveshaft computer balanced
 
HotRodPC

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Yeah, I just answered his tag, didn't read the whole thread.
 
Frankenchevy

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HotRodPC said:
Yeah, I just answered his tag, didn't read the whole thread.
Click to expand...
Yes, drive shaft balanced, new u joints, fairly new tires just rebalanced.
 
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