Highway Noise... is it the tranny? (1 Viewer)

TexFJ

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Happens at highway speeds, in both 4th and 3rd gears under load as it goes away when foot is taken off the accelerator... There's the engine noise and then the humming.

sounds like the humming coming below me.

 
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Looks like you need a new exhaust. I’d start by greasing the joints in the driveshaft and then check the fluid level in the diffs, transmission, and transfer case.
 

TexFJ

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Ha, I noticed the muffler as well recording this video. No wonder why it sounded like a V8.

I've taken more videos and can say it's not the differential. I've filled up the Transfer oil and it seemed to improve a little (not sure where the hell that oil is going as I added around 3/4 of a quart before it reached the top. I've greased the U joints but may drop the driveshaft and have it balanced, just in case.

It may be a worn bearing in the transfer case, perhaps on the input side...
 

TexFJ

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I had a hum while driving that was difficult to pin point, and would come and go under.
It was the rear driveshaft u-joints.
U-joints are definitely the way to start here. Cheap and easy to replace.
 

HemiAlex

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Get under the truck and see if you can move the driveshaft ends in the x or y direction. If you grab it and try to twist it around, you’ll only feel the gear lash.
 

lcolon

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I was getting a noise from my driveline and it turned out to be the little shield that protects the seal behind the flange on the transfer case. The weld had broken on it and when that sheild was up to speed it was rattling
 

TexFJ

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Good point... It may be a stop on my way to see if I can replace the bearings in the transfer case... I'd like to do it without dropping the transmission but hope I have enough room to for the tools.
 

HemiAlex

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I had a groaning noise from under my truck that droned and hummed under the passengers side the truck. The transfercase Outputshaft bearings were shot.

My t case was 100,000 miles overdue for a refresh.
 
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dogfishlake

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You could drop the rear shaft, lock your front hubs, put it in 4 high and drive it in front wheel drive and see if it goes away. Time consuming, but otherwise free. Also if it is a rear joint, you will find it right away with the shaft out.
 

TexFJ

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You could drop the rear shaft, lock your front hubs, put it in 4 high and drive it in front wheel drive and see if it goes away. Time consuming, but otherwise free. Also if it is a rear joint, you will find it right away with the shaft out.
What you're saying is that if it goes away then you've isolated the noise to rear output bearing, u-joints, or possibly drive shaft splines? If it doesn't go away, it can still be the transfer bearing or the front input bearing.
 

TexFJ

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Update.

I rebuilt my transfer case and discovered the wear on the input gear, it was bad... IMHO.... some say it's normal wear. The video shows the backlash on the good part of the splines. the backlash is much worse if the gear slides onto the work splines.

TC was rebuilt and the hum is gone. Funny the quieter noises you discover once the big noise is not masking them any more :)


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Yup, that’s why I asked if you were using a McNamara gear aka long spline input gear in your other thread.
That trans shaft has some significant notching, in extreme cases the splines can wear through smooth, that’s a no go situation.

I’ve often wondered how much wear is on the shaft splines vs. how much of the wear is inside the input gear.
 

TexFJ

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Yup, that’s why I asked if you were using a McNamara gear aka long spline input gear in your other thread.
That trans shaft has some significant notching, in extreme cases the splines can wear through smooth, that’s a no go situation.

I’ve often wondered how much wear is on the shaft splines vs. how much of the wear is inside the input gear.

Wear seems to be 50/50... Crazy part is that I thought the output shaft splines with the clutch would also be destroyed, but they were clean as a whistle. I'm blaming this on the oil leak between the tranny and TC. It left the highest gear without any gear oil hence the wear only there.
 

TexFJ

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spliced some videos together for those curious on rebuilding the transfer case. Just the disassembly as there are some good vids out there on the assembly.

I usually try to film some of the work so I can go back and see what the heck I did wrong or where those parts were supposed to go.

 

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