The Stovebolt Site Forums The Parking Lot Big Bolts Can't figure out where the gowl is comming from?

Hey Guys,
I have a 1950 Mack A20 model 2 ton flatbed truck. (I know it does belong here, but you guys have a lot of knowledge and could sure use your insight). Somebody installed a 400Chevy SB and 350 auto trans. The front and rear axles and wheels are stock. The PROBLEM: the truck has a growl when your on the throttle after about 20mph. When you let off the throttle it stops. So my thought was the differential was the problem. I tore it apart and brought the 3rd member into the local truck repair to get their opinion. They thought the gears look worn and possibly could be the issue but overall not to bad. Can't find the ring and pinion. So I found a 1969 C60 with a 2 speed rear end that I ended up swapping in. Still the same growl. I just had the trans rebuilt (growl was their before trans replacement), the drive shafts were brought in and balanced. What could this be? Its only under throttle. When you free rev the motor their is no crazy vibration. Any ideas would be greatly appreciated.

Hy Bodyguy, check the engine mounts, that's about all that you haven't checked/replaced already, good luck.

Hey Bodyguy, Did they check the hanger bearing on the driveshaft when it was balanced ?They will growl under load. Also check the end play on the engine crankshaft without the belts on. The thrust bearing or crank cheek could be worn.

Do you have a one piece or two piece drive shaft set-up? Did the pinion angle get checked when the new engine and trans were swapped in if it's a one piece?

Mike B

Hey guys,

It has a 2 piece driveshaft so it has a nice angle to the pinion. I brought both pieces of the drive shaft to the truck shop and the fellow that runs the place said that the bearing was good- But all he did was spin it by hand. (It is newer and was assembled by a driveshaft shop.) The rear solid shaft was balanced. Gtow -Your making me think that I should bring the shaft with the carrier bearing on it to the shop and have him run it on the balancer. Also, if the end play was off on the motor, wouldn't it have a bad vibration when you free rev the motor?
Thanks for the input guys.

Are your U joints in phase? How is your center bearing. When the bearing is bad, they tend to be noisy when you give it gas.

Well I brought the front drive shaft with the carrier to be balanced today. And it was out of balance - he said the front weight must have fallen off but he said the bering was good. I have had a chance to install yet. Crenwelge - what is in phase? Do you mean clocked where the joints are all facing the same direction?

Yes, if you put the slip joint together wrong, it will cause vibration. I would be very surprised if the weight falling off of the tube would cause a noticeable difference at 20 mph.

this is the same experience that I'm having with my '95 Ranger right now. I took it to the shop,and my mechanic put it on a hoist,and got it up to 60 M.P.H.-No Noise!! when I get up to between 15-20 M.P.h.,it sounds like the rear end is out of lube.It makes a 2-tone whirring/howling noise,like something's being run on a turret lathe. Here's the THING>>>about 2 months ago,I installed a tool box,that is mounted behind the cab,and "runs" transverse. About the same time,the "noise" started. I didn't put 2 and 2 together,until about a month ago. I have an extended-cab,and I had a passenger sitting in back. He opened the sliding window,and said that the gap between the tool box and the bed liner was causing the racket. I don't know,but it could be the same scenario for your noise. Just a thought. Hope that's all it is.

I still haven't had a chance to put the drive shaft in yet. Their is nothing in the bed nor is the bed close enough to make a noise. But I think I will jack it up and run it to see if I can pin point it a little better. Thanks for the input guys.

Maybe it's just me, but I would be looking at the tires. Especially since they remained the same when the axle was swapped out. I've seen tires do some crazy things!

Mark - You may be right. It got to be that or the Motor has a vibration only under load. I put it together tonight and put it up on jack stands and the vibration wasn't as bad as it is on the ground. Nor was it as consistent. FYI - it has Dayton wheels too - which can be a bear to get straight as it is.

Like Dayton spoked wheels?

Yeah. On "Dayton"-style wheels,the spokes are an integral part of the hub. Tire mounts on an open "ring" rim.This makes swapping from bias-ply to radial tires much easier.

Did you get the driveshaft shop show you how to put the U-joints together in phase?

Doesn't sound like you've checked the U-joint angles, they could be way off of ideal and cause the trouble. Also might be out of phase as already mentioned.
All those answers and more about driveshafts and U-joints can be found here http://www.stovebolt.com/techtips/driveline/setup/index.html

Grigg

THis is how they shall be installed. See the 90 degree differance everytime you install the next shaft.
Look from the front and towards the rear:

http://i185.photobucket.com/albums/x264/uffeg/viking%20in%20Eskilstuna/ScanImage001.jpg

It really depends on the u-joint angles if the yokes on a shaft are to be in the same plane or 90° off.
Again, look at the tech tip and manuals I already posted.

Grigg

I had my truck up on a hoist a couple of weeks ago as well. I posted earlier that the sound was wind howling between the tool box,and the bed-liner. I just had to replace the clutch,at another shop. When they test-drove it,they said that my carrier bearing was screaming! It would only make a racket while under-load. It didn't even whisper,on the hoist!! They can be deceiving!

Grigg, I think you hit it spot on. The rear pinion angle was at 4 1/2 degrees up, the rear drive shaft at 5 degrees and the front shaft at 2 1/2 degrees. A fellow that I was talking to that does a lot of hot rod work pick up on that. He asked due to the fact that the stock drivetrain was pulled. He said the vibration sounded like a pinion angle issue. Soooo...I shimmed the rear axle, to a 1/2 degree up. Took it on a test drive and the low speed vibration was gone, felt slight vibration at certain speed. However, still has a vibration at higher speeds(40mph and up). My friend seems to think that if I dropped the carrier bearing to add another 1 to 2 degrees to the front drive shaft that it may take care of the vibration. What do you guys think? Thanks for all the insight, guys.

Sorry for stealing the thread, but I checked mine.
From the rear axle and towards front the rear tube is in a straight line on same angle as the rear end points.
Same with middle axle. The straight line continues towards the first tube that drops a little bit downwards.

If I should move the rear axle a bit up or down might do the trick, will have to measure more exact.

I guess I have to adjust also the carrier bearing up or down to accomodate the best angles too right ?

http://i185.photobucket.com/albums/x264/uffeg/Viking%20PTO/20130930_124729_zps13fa8d3b.jpg

http://i185.photobucket.com/albums/x264/uffeg/Viking%20PTO/20130930_124748_zps3bd720c8.jpg