Drive Shaft: '53 Commander Coupe - driveshaft is not the Beach Boys "Good Vibrations"

[irishjr]

I am new to the forum and am resurrecting my '53 Commander Coupe that had not moved since 1989. Everything is working well except for the terrible driveshaft vibrations. I replace all motor mounts, u-joints, center carrier bearing, and center rubber mount bushings. I marked the shaft for phasing as I took it apart. When re-assembled, it was TERRIBLE! Could not drive above 30 mph. Took the car to a friends so we could put it on a lift and solve the problem (HA! HA!). Ultimately found that, even though I had marked it, the shafts were out of phase by 90 degrees. (a service bulletin in 1952 solved a problem with vibration on automatics by raising carrier 1/2" and putting shafts 90 degrees out of phase and continued practice from then on!) Changed the phasing and it improved somewhat. Now I started to check the alignment:

1. Horizontally, engine and pinion are parallel
2. With car on stands at ride height: engine down at rear 7.5 degrees; front shaft (with carrier in #1 holes) horizontal; rear shaft horizontal; pinion down at front 1 degree.

The above alignment does not seem right per normal driveshaft practice (pinion and engine/transmission parallel), but I don't see evidence where it was not that way from the factory.

I am having the driveshaft balance checked tomorrow.

If anyone out there can help me, I would appreciate it. I certainly could use a confirmation of the engine/pinion angles from someone with a stock driveline.

[1954khardtop]

Something to check is the mounting of the center support. There are 4 sets of holes for the center bearing, 2 upper and 2 lower. The upper holes are for coupes and hardtops, the lower holes are for sedans. The left side holes are for right hand control, right side holes are for left hand control. For a left hand control coupe use the upper holes farthest to the right.

[irishjr]

I am aware of all four positions, and have tried the to on the passenger side with no change. On another thread, http://forum.studebakerdriversclub.c...ght=driveshaft, the one solution that seemed to work for two guys, was to use the drivers side top holes, but I want to see if I can solve this with the factory settings. I will have to wait until I get the shaft back from the balancer.

[Dwain G.]

1. Horizontally, engine and pinion are parallel
2. With car on stands at ride height: engine down at rear 7.5 degrees; front shaft (with carrier in #1 holes) horizontal; rear shaft horizontal; pinion down at front 1 degree.

The above alignment does not seem right per normal driveshaft practice (pinion and engine/transmission parallel), but I don't see evidence where it was not that way from the factory.

I am having the driveshaft balance checked tomorrow.

If anyone out there can help me, I would appreciate it. I certainly could use a confirmation of the engine/pinion angles from someone with a stock driveline.

I don't think there is an official 'as-built' specification published for those angles. The V8 engine does sit at a steep angle, and 7 1/2 degrees doesn't appear to be too far off. Still, I'd probably try to raise the rear of the engine to reduce that a bit.
After the first 6,000 or so cars, the rear axle pinion angle was lowered 4 degrees. The memo I have does not say what the old or new angles were, but it probably did end up at or near the -1 degree you read.
I'm not sure I understand what you meant when you said "Horizontally, the engine and pinion are parallel?

[Flashback]

on a two piece driveshaft, the front driveshaft works good with a 1/2 to a one degree change from the transmission.
It would work with 0, except the joints need a change in angle to not wear out fast. With a one degree upward on
pinion and a 3 degree on the rear d/ shaft it works good.

[Pat Dilling]

To me 7.5 degrees down seems like a lot. Can you describe how you are taking your measurements? Here is a very good explanation of how angles need to be configured to work properly together: http://www.airridetalk.com/articles/...-enigma_3.html

[whacker]

If the drive shaft has not moved in 20 years, it very well could be a balance problem. don't change anything until after you try it after it gets rebalanced. That will make a big difference.

[Dan Timberlake]

Fixing a problem is much more efficient with accurate diagnosis.
Diagnosing vibration problems is a lot easier when the "frequency" of the vibration is known.

http://commtest.com/media/filebrowser/velocityspectrum.png

One of these can help identify vibrations over 800 rpm for less than 30 bucks

http://www.manddsmallengine.com/briggs/tools/19200.html

There are applications that turn an iphone into a spectrum analyzer for relatively short money

http://macresearch.org/showcase-vibration-turns-your-iphone-spectrum-analyzer

For rotating machinery frequency is related to rpm
Driveshaft unbalance makes vibration at 1X driveshaft rpm. At highway speed the rpm/frequency is upward of 40 Hz/2400 rpm, and can make an audilble "booming" in the car
Driveshaft phasing with non-CV joints makes 2 kinds of vibration, both at 2X driveshaft rpm. One is torque related, so it tends to be worse in first gear with heavy throttle. The other is from the non constant (changing) velocity of the intermediate shafts, so basically gets worse with increasing rpm.
Wheel/tire unbalance makes vibration at 1X wheel rpm ( roughly 1/3 d/s rpm).
Damaged tires make vibration at 1X wheel rpm. A radial tire with a shifted or broken belt can make a strong vibration starting under 30 mph. A tire with a bad flat spot from sitting can make vibration

Was the car supported by the frame or axles or ?? Did you run the car on the lift? If so, was the vibration recreated? Which components were "shaking"?

Is it strictly MPH related, or does power/throttle position make a difference?
It would take HUGE driveshaft unbalance to be noticeable below 30 mph.

[leyrret]

One thing I found on my car is the shaft at carrier bearing is actually below the pinion with weight on the car. In short the shaft doesn't go down to the pinion. It goes up. The operating angle of the transmission joint should be 1/2 to 1 degree. The two rear joints should ideally be at equal angles or as close as possible Depending on suspension a vibration under very hard acceleration can sometimes be eliminated by adjusting the pinion angle down to allow axle windup. Some times it may require more rigid suspension. I changed the carrier bearing from the more rigid original to a later pillow mount which seems quite a bit smoother..

[irishjr]

Thanks for all inputs. I think I have described the angles correctly, which is just what is driving me nuts as a mechanical engineer. The front u-joint turns 7.5 degrees because that's what the designers needed to clear the front of the engine with the steering pivot and keep the tunnel low at the back of the engine. Then they had to fight a ridiculaously large operating angle (7.5 degrees) by putting the front and back shafts out of phase 90 degrees and pointing the pinion down at 1 degree. I have had the shaft straightened and balanced (at 90 degrees out of phase and will try it in the car when I get back from Ohio to Maryland later this week. I will post the results (hopefully a smooth running automobile)

[irishjr]

Fixing a problem is much more efficient with accurate diagnosis.
Diagnosing vibration problems is a lot easier when the "frequency" of the vibration is known.

http://commtest.com/media/filebrowser/velocityspectrum.png

One of these can help identify vibrations over 800 rpm for less than 30 bucks

http://www.manddsmallengine.com/briggs/tools/19200.html

There are applications that turn an iphone into a spectrum analyzer for relatively short money

http://macresearch.org/showcase-vibration-turns-your-iphone-spectrum-analyzer

For rotating machinery frequency is related to rpm
Driveshaft unbalance makes vibration at 1X driveshaft rpm. At highway speed the rpm/frequency is upward of 40 Hz/2400 rpm, and can make an audilble "booming" in the car
Driveshaft phasing with non-CV joints makes 2 kinds of vibration, both at 2X driveshaft rpm. One is torque related, so it tends to be worse in first gear with heavy throttle. The other is from the non constant (changing) velocity of the intermediate shafts, so basically gets worse with increasing rpm.
Wheel/tire unbalance makes vibration at 1X wheel rpm ( roughly 1/3 d/s rpm).
Damaged tires make vibration at 1X wheel rpm. A radial tire with a shifted or broken belt can make a strong vibration starting under 30 mph. A tire with a bad flat spot from sitting can make vibration

Was the car supported by the frame or axles or ?? Did you run the car on the lift? If so, was the vibration recreated? Which components were "shaking"?

Is it strictly MPH related, or does power/throttle position make a difference?
It would take HUGE driveshaft unbalance to be noticeable below 30 mph.

I measured the angles with the car on wheel stands so it was at ride height. If the vibration still persists after I have tried the newly balanced shaft, I will run it with the rear supported on axles stands and see what I can find. Thanks for your input. I have a Harbor Freight tachmmeter, so I will be able to measure the frequency.

[leyrret]

Seems 7 1/2 degrees into a bearing with nothing to cancel would cause noticeable vibration. Don't see how going 90 out on the other would remove it. Depending on operating angle would seems it would make it worse, but I've learned to never say never. Let us know how it works out.

[irishjr]

Seems 7 1/2 degrees into a bearing with nothing to cancel would cause noticeable vibration. Don't see how going 90 out on the other would remove it. Depending on operating angle would seems it would make it worse, but I've learned to never say never. Let us know how it works out.

Got the newly balanced driveshaft in place (90 deg. out of phase as per original) and things were improved but still vibrating.

Put car on lift and tried adding shims under rear engine mount (3/8") to reduce the 7.5 deg....no change.

Removed shims and lowered carrier to lower set of holes on pass. side......no change.

Put stand under rear end and ran in drive in high gear......WHOA, rear wheels are noticeably bent. (Forgot that tire mounter in Tenn. told me that they were bent and to put them on rear.

Put bent rims on front and drove home. Car still vibrating (as expected) but cannot determine if driveshaft is any of the cause.

Ordered new wheels from Summit (15x6 w/ 4" backspace - #WVI-20-561204). Not going to do anything concerning driveshaft until I have the new wheels on the car!

Going back to working on channeling my '40 Ford!

[PlainBrownR2]

Put stand under rear end and ran in drive in high gear......WHOA, rear wheels are noticeably bent. (Forgot that tire mounter in Tenn. told me that they were bent and to put them on rear.

Put bent rims on front and drove home. Car still vibrating (as expected) but cannot determine if driveshaft is any of the cause.

I think that might be more than part of the problem. If a wheel is not true, or it's out of balance, it may produce a vibration at road speed. With something as severe as a bent rim, the bad wheel may become my next hose reel, since it's not usable anymore, but that's just me. A wheel that's out of balance will also produce a noticeable "thump thump thump" noise at road speed. Usually to pinpoint the noise just takes a trained ear to find which wheel is out of balance.

[irishjr]

I think that might be more than part of the problem. If a wheel is not true, or it's out of balance, it may produce a vibration at road speed. With something as severe as a bent rim, the bad wheel may become my next hose reel, since it's not usable anymore, but that's just me. A wheel that's out of balance will also produce a noticeable "thump thump thump" noise at road speed. Usually to pinpoint the noise just takes a trained ear to find which wheel is out of balance.

I had them balanced on a Hunter 9700, which measures road force (I swear by them!) but it cannot fix a bent rim. The vibration feels more like a shudder in the driveline, but I won't know for real until the new wheels are on the car. - Another story: I was heading out to Bonneville in my 33 Plymouth and had racing tires waiting for me in Denver (Coker Excelsior) When mounted, one absolutely shook the car. It registered a downforce of 64 lbs on the Hunter machine! Had another tire air-freighted in to Salt lake City and went just under 130 (in 2006...went over 130 in 2009)