Vibration and noise PLEASE

[72chevyLWB]

I am totally confused here. I went on a road trip with my 72. Out on the highway at about 65 it makes a whah whah whah kind of noise (dont laugh) and a vibration comes with the sound. Does it sometimes but not all of the time. If I am really steady with the throttle it won't do it, but if I move the throttle around any it will. I have a 3.73 rear end. I have a 3 series carrier with a ring gear spacer. I checked the pattern on the gears and everything looks good. It has a 1 piece driveshaft that is straight and all u-joints are good. It did that for a while, but all of a sudden one night I have this nasty vibration that shakes everything inside the cab. Anything over 45mph it vibrates no matter what you do, even slowing down. It is also really bad when put in neutral while slowing down (almost gets worse). My wheels are balanced and there are no thrown weights ( I checked). While I had the cover off I re-torqued the ring gear bolts because you have to with the spacer and I got 1/8 to 1/4 turn max out of it so that shouldn't be the problem. I have the original open carrier and might have to throw that in and go from there. Any other help or ideas would be appreciated.

[72chevyLWB]

ring gear pattern

[72chevyLWB]

spacer

[Chevyc10!]

Don't forget to check the motor/ transmission mounts. A broken mount can cause the vibration...
Jake

[Wasted Income]

When I rebuilt my 700r4 in my burban, I noticed a nasty vibration that wasn't there before I rebuilt it. It lasted like that for a couple of thousand miles before one day it puked. Boom no forward, no reverse. Park was all I had. Replaced the torque converter, all was well.

Too bad you have a one piece driveshaft, cuz my '69 was doing the exact same thing a couple of summers ago. The carrier bearing had seized up and it twisted off of the mount. The damn thing was just spinning in the crossmember.

Also........if you've replaced u-joints recently, check to see that they are centered in the yoke. I had one about 1/16 off center and it vibrated so badly that it turned the needle bearings in the bearing cap to dust in about 100 miles.

Keep us posted.

-Jeff

[Stepside]

Is it the pic, or does some of the teeth look fractured? Might be the gear oil. I dunno. The pattern looks real full on the shiny (non-shadowed) teeth. Almost too full. That lends me to think the pinion depth is shallow. If the shadowed teeth look like this normally, your gears are shot. ¿ A carrier bearing or a axle bearing will give these symptoms.
Stepside

[68 Stepside]

I'm glad I'm not the only one that noticed the teeth looking a little nasty. Are they chewed up, or is that the pic? The gear itself also appears to have gotten quite hot. Was the fluid low? Did it have an shavings in it?

TJ

[72chevyLWB]

The gears are good shape. that is persian blue grease on it to check the pattern. The gears are nice and sharp. Possibly the pinion could come ahead. I have a new converter for it too. I put in the new tranny, posi and flip kit at the same time so I don't know what is causing it. The converter is a non lockup so I need to get it out. Should I do that first? Also when I did the flip kit I got angle shims to get the u-joints straighter. They aren't perfectly straight with the tranny but really close.

[72chevyLWB]

here, I wiped it off with a rag quick

[Super Chevy]

really dumb question,but sometimes overlooked,did you get your 1pc driveshaft balenced with the new yoke and all?

SC

[72chevyLWB]

I have to drive 250 miles to get it balanced up here. I put it on jack stands and ran it up to 60 and quickly crawled under and it looks perfectly straight. It vibated before, but I replaced it and it was fine then because the first one was bowed (don't know how). But why would it not vibrate but make a noise and then all of a sudden vibrate like crazy the next day. I might put the rear end back together and put in the converter first. Keep ideas coming.

[Super Chevy]

did it throw a wieght on the driveshaft mabe,if it had wieghts tacked on for balencing

SC

[72chevyLWB]

no weights are or were on the shaft before or after the problem.

[Super Chevy]

last thing i can think of is mabe your drums are unbalenced,mabe a warp in them or something

[Scrub]

I'm with Super CHevy one this one. Check to see if your brake drums are warped, Does pressing the brake have any effect on the vibration? Jack the rear up and spin the tires. Do you hear the brake rub in one spot and not other spot?

Just a thought

[Rabid]

Buddy had a similar problem once. Turned out to be packed mud in his wheel hubs. Didn't make the strange noise like you mentioned though. Only things that made that sound on mine was the rear end.

[colohusker]

My money is on the converter, since you say it gets worse when thrown into neutral. But just in case, when you had it on the stands and running 60, where were the stands at? Under the axle, or under the frame? Just curious whether the suspension was under load at the time, giving the same angles on the u-joints as when it would be on the road.

Keep us posted! And if all else fails, you could always give the truck to me.

[67Fleetsidedream]

It sounds to me that it is your drive shaft. Where did you get it?
This is a common problem when the 2 piece shaft is replaced with a 1 piece shaft. Check the slip yoke for excessive play and wobble. The 1 piece shaft out of a later Chevy extended cab is about 1/4 inch shorter than the 2 piece with a Saginaw 3 speed.
So check this. Sounds to be that you have excessive wobble on the slip yoke.

Ben

[72chevyLWB]

I had the stands under the axle at the time. There is no play in the driveshaft either. Everything is tight.

[67Fleetsidedream]

Checked the wheel bearings? How about the front control arm bushings. Does it do it when you turn?
Ben

[72chevyLWB]

Its coming from the back. The control arm bushings and such are all new and tight.

[COBALT]

I'm going to throw a new one in here.

Check your carrier bearings.

Before I had my differential overhauled I had a similar problem. At 45-50 MPH I would start to get this hum from under the truck that got worse the faster I went. The whole cab vibrated. I could feel it in the steering wheel. If I was easy with the acclerator it would go away. If I let off the gas it would go away, but if I gave it any throttle at all it would come back. It started to get progressively worse until it was starting at 35 MPH.

Turns out my carrier bearings were totally pitted. They had flats worn on them they were so bad. Here's the kicker: the ring/pinion were PERFECT. The wear pattern was good, and they can still be slapped into another carrier with no problem (I had them swapped out for 3.90s).

You've checked the gear set. Now check the carrier bearings, pinion bearings (inner/outer), and work your way to the engine checking everything along the way. Since throttle is involved I wouldn't think it had anything to do with the wheel bearings, or brakes unless you feel changes when breaking or when turning corners.

[bowtie]

First of all I'm leaning towards the drive shaft being out of balance.

2nd I'm had mud/snow stuck inside the rims and this caused a nasty vibration, clean them out and its fine

3rd I built a stepside and there was a nasty noise and vibration coming from the rear of the pickup and it only happened at certian speeds. It turned out to be the bushing in the rear panhard bar, this would only apply of course if your pickup was a coil spring setup in the rear.

[jku72]

This is a classic example of a driveshaft imbalance, but sometimes the causes and symptoms are harder to pinpoint.
The wah wah wah is usually caused by a harmonic imbalance. My truck does it, but not with your severity, and my problem is a worn rubber cushion in the center bearing housing. That wah wah noise has also been traced to flywheels being loose, or even the tranny bolts loose. The engine and trans are too heavy to detect loosness by moving, so try a couple of the bolts. tighten the converter to flywheel bolts, if you can.

[Stepside]

You mentioned using angle shims to get the u-joints straighter. Now I'm thinking your driveline angles are not right. The angle of the pinion should be the same as the angle of the trans output shaft. Not pointing straight to each other.

.............. <trans

...............<pinion

http://www.ring-pinion.com/gear/g1198.shtml