humming sound and vibration over 50 mph

Jeremy001995

Jeremy001995

diesel mecanic
hi, got a small problem with my new rebuild nv4500 shift smooth and no sound until 50mph in 5th gear, like a small humming and shifter is shaking, all ok in 4th gear even at 50mph or more. made almost the same sound but more like gear rattle downhill in neutral over 50mph, double disc clutch with solid hub( no spring) have made shortened the rear driveshaft, but not made it ballance( never have any problem in the past doing like this) ram 1994 cummins 5.9 tanks!
all ujoint are new, rear diff re gear to 4.10 with all new bearings.

tanks!
 
Jeremy001995 said:
hi, got a small problem with my new rebuild nv4500 shift smooth and no sound until 50mph in 5th gear, like a small humming and shifter is shaking, all ok in 4th gear even at 50mph or more. made almost the same sound but more like gear rattle downhill in neutral over 50mph, double disc clutch with solid hub( no spring) have made shortened the rear driveshaft, but not made it ballance( never have any problem in the past doing like this) ram 1994 cummins 5.9 tanks!

all ujoint are new, rear diff re gear to 4.10 with all new bearings.



tanks!
Click to expand...
First thing I thought was U-joint phase-angle and then you said that the shaft was modified which makes me even more suspicious of it.



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biggy238 said:
First thing I thought was U-joint phase-angle and then you said that the shaft was modified which makes me even more suspicious of it.



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nope all straight one piece driveshaft its a single cab 8ft box
 
Just wondering.

Sounded like the common complaint from someone going from a DM Flywheel to a solid. If you've been running it, that's not the case.
 
Jeremy001995 said:
nope all straight one piece driveshaft its a single cab 8ft box
Click to expand...
That has no relevance on whether the angles are correct or not, and actually makes it more likely to be a cause than an OEM drive line.


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biggy238 said:
That has no relevance on whether the angles are correct or not, and actually makes it more likely to be a cause than an OEM drive line.


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truck is not lifted, all stock rear traction bar so no axle wrap
 
biggy238 said:
That has no relevance on whether the angles are correct or not, and actually makes it more likely to be a cause than an OEM drive line.


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Click to expand...

What he said. Get a digital angle finder and check the angle between pinion and driveshaft. And the angle between the driveshaft and transfer case.

Did that truck have a 2 piece drive shaft and you just converted it to a one piece? Or has it always had a one piece?
 
fatty said:
What he said. Get a digital angle finder and check the angle between pinion and driveshaft. And the angle between the driveshaft and transfer case.

Did that truck have a 2 piece drive shaft and you just converted it to a one piece? Or has it always had a one piece?
Click to expand...

will do! had a nv5600 before with 44 1/2 weld to weld , now nv4500 with 49 1/2 weld to weld, since i got the truck its aleays been 1 piece driveshaft, 4 inch driveshaft, im sure its been like this from factory
 
All standard cab 2nd gens are one peice shafts.

I'd take that driveshaft you referred as "welded" and have them attempt to balance it, I bet the issue will show itself quick.
 
Put the rear wheels on jack stands. Using a dial indicator check for runout of the tube just inside from where you welded the tube at both ends of the shaft while spinning the rear tires
 
originaly on the driveshaft it had one balance weight welded at each end of the driveshaft, one was gone because we shortened the driveshaft, the other one still there, have remove it ans the vibration are almost gone, will made balance rear and front driveshaft at same time!
pinion angle was like 3, stock block under leaf and stock height truck

tanks all of you guys!
 
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