Noise coming from front axle under drivers seat

Hey guys need some advice. I have had large amount of water in my airlines. The wet tank is spewing large amounts of water and I am draining it 4-8 times a day. I ordered the rebuilt kit for the air dryer. Air is pouring out of the bottom of it. I did push the valve back closed as best I can but still some air comes out. My main concern is while going down the hiway at speed i get a noise and vibration that sounds like I am running over the rumble strip along the curb of the road but I am in the center of the lane. The noise seems to be coming from the front axle under the drivers seat. My question is could the water in the lines be somehow partially engaging the front axle lock in? I have engaged the front axle and left it on while in high range and not heard it since but only made it about 20 miles before I blew a trailer tire on my M322. Today has not been good. Hoping it is something simple. Any thoughts would be a big help. Thanks guys!

Nice alligator.

Start easy on the noise. Remove your drive flange on the front and see if your noise goes away. If it is still there then you know you are dealing with a suspension issue. If it goes away then you know you have a internal movement noise. Put the flanges back on and pull your front driveshaft. After you have inspected the joints. If it is still there then maybe internal axle.

Noises on these trucks radiate alot though. Also check your hood or cab that may be rubbing anywhere

Thanks Simp. When it does make the noise it also slightly slows down the truck. Don't think it is a minor rubbing thing. It is LOUD!

Model of truck would be helpful, I'm going with a M939 series truck. The water issue is a dead dryer, time to service/replace the unit. The noise/vibration under the truck may be the carrier support bearing for the front axle drive line. I say "may" because not all M939 trucks are equiped w/ the carrier support bearing. If equipped with the support bearing, remove the front axle drive caps and take it for a drive. With the caps removed the axle and drive line do not rotate and the noise/vibration will cease. The bearing supports are available. As for partial front axle engagement due to water, that doesn't happen. The engagement occurs in the transfer case with air pressure. As for the blow tire, well that's anything...good luck, let us know what you find.

M925A2



Thanks guys

it is a 923a2. M939a2 trucks did not have the support bearing for the front axle unless it was modified due to a previous issue. a U joint could make a racket especially not under power like when the front axle is not engaged but still has force on it.

Could be the u joint, pull the axle end caps and take it for a spin. That front u joint will not be rotating. The pictures of the u joint look good, failing u joints look like poop, lots of grease and metal spall .

I would look at axle u joints and the axle support bushings also don't rule out wheel bearings.

Worn out spindle bushing. The ID of the bushing has become too big and is letting the axle wobble inside. You'll ruin the axle shaft if that continues. If you have to drive it, then pull the drive flanges and cover the hubs till you get to where you need to be.

So a quick update. Took off the front axle flanges. Simp walked me through it. Thanks Simp!!! 140 miles and no vibration or noise. Bad news is that I blew the spare trailer tire I just put on!!!.....grrrrr

So, it was the axle flanges?

Swamp Donkey said:

Worn out spindle bushing. The ID of the bushing has become too big and is letting the axle wobble inside. You'll ruin the axle shaft if that continues. If you have to drive it, then pull the drive flanges and cover the hubs till you get to where you need to be.

Click to expand...

That is my thinking as well.

Other than the trailer tire blowing AGAIN....the trip home went well. Truck had plenty of power for being stock. No noises or vibrations. What could it be if the flanges are removed and now no noise?

I have to admit I read the title of the thread and the first thing I thought was "well stop and help the person"

Removing the flanges stops the front driveline from spinning.

The front prop shaft slip spline joint was worn out on my M925a2, at only 20,000 miles. I back-dated mine to the earlier front prop shaft with the carrier bearing to support the weight of the shaft, rather than the spline joint supporting the weight. Mine had vibration over 40mph, which would go away if the front axle was switched on (t-case 6x6).

Your issue could be the slip-spline joint, U-joint(s), or what Swamp said, shaft bushing in hub or t-case output area. Make sure the t-case fluid level is adequate as well.