output shaft runout

enjenjo · August 02, 2011, 12:24:27 PM

Quote from: "wvcab"he stated in a earlier post that it vibrated while on jack stands....

how are the mounting bushings on the arms holding the rear axle assy?

new, urethane.

kb426 · August 02, 2011, 07:51:53 PM

The list of possibles has grown with no solution. Is it time to run it on jackstands and start removing parts until you find the cause? Frank, you're good at this so something is hiding. Anyone got any other ideas for isolation?

wayne petty · August 02, 2011, 08:41:01 PM

is there any way to secure a yoke in there without a drive shaft..

or a sawed off yoke. so its smooth on the outside and easy to retain in the back of the transmission with it spinning.. keeping the output shaft centered in the tail housing bushing..

to see if the transmission or flywheel is actually creating the imbalance...

does this drive shaft have in inertia ring??... some are really thick...

has the drive shaft itself .. been checked for balance.. been checked for runout .. perhaps caused by a dropped needle bearing in one of the cups..

are the rear drums or rear rotors new.. and might have missed the balancing machine at the factory production line..

i had one drum on the front that would always turn if you let go of it and the heavy spot would stop at the bottom..

got a bubble balancer sitting in the corner of your shop to drop a drum or rotor on.. see if they are actually in balance.. there is probably not enough mass for a conventional tire spin balancing machine to really get a good reading.. one of the motorcycle shaft and cone type might work if you have a proper size pair of cones.....

a good question... if the vibration the same in 4th gear.. as it is in 5th

as the same engine RPMs??

enjenjo · August 02, 2011, 09:13:37 PM

I have thought of some other things to try, but it will be the weekend before we can get to it. I'll let you know.

chimp koose · August 03, 2011, 08:23:57 PM

I once replaced an axle in a 9" that was forged/machined so far off centre that the axle bearing diameter barely cleaned up to size. This could be a problem but it didnt cause a problem on the 62 'bird it was in.

1800guy · August 03, 2011, 09:04:53 PM

Does this car have a known history you can go back on? It must have been okay at some point in it's life. I've had customer cars where I've spent a week chasing some obscure problem, and then when I find it - they say something like "Oh ya - forgot to mention that". Grrr.

Pete · August 05, 2011, 02:11:54 PM

I had one with the same problem last year.
It turned out to be a bad rear yoke...It was a new Ford part but when
the guy assembled it he didn't check side clearance of the cross bearings.
It had about .015 and was working back and forth under load.
New Ford part cured the problem.
As a side note on T5's we put 2 tailshaft bushings in next to each other.
Helps stabilize the slip yoke under heavy load.

PeterR · August 06, 2011, 09:35:00 AM

Quote from: "enjenjo"We are chasing a vibration on a 90 Mustang 5.0.... I did find a shakey output shaft bushing.....

Many, many years ago I experienced a similar problem. After spending a lot of time poking around under the car the only thing vaguely suspicious was some side play in the slip joint due to wear in the extension housing bushing.

This was so long ago I would be guessing at the amount of play, but I can say it was well within the limits of normal serviceability and seemed a real long shot, but in the absence of any other identifiable problems I replaced it.

To both my relief and amazement the vibration was cured.

unklian · August 08, 2011, 10:19:02 AM

Have you tested it on stands without the rear wheels ?

If it still shakes, how about pulling the axles and repeating the test ?
That would isolate it to the input yoke, or r&P.

Crosley.In.AZ · August 09, 2011, 11:44:18 PM

We had a GM 2500 series service bed work truck come in (our trans in it) .. 4L80e trans.

It had developed a vibration and noise since trans install a couple yrs ago.

see photos.. the yoke had started to rub on the mount metal base... wrong design mount too.

rooster · August 13, 2011, 12:39:20 AM

Quote from: "enjenjo"
Quote from: "unklian"Have you tested it on a chassis dyno ?

That would isolate the front suspension.

We ran it on stands up to 70 MPH without the front wheels turning. It vibrated

does it have rear disc brakes?

Daughters mustang had a hand brake that would hang, but it would heat up if you drove it far enough! At times it vibrated also!

enjenjo · August 22, 2011, 08:31:07 PM

Problem solved!! Unfortunately I'm not sure what fixed it.

We decided that the pinion angle needed to be adjusted, so we made a pair of adjustable upper control arms. But when the pinion was corrected, the vibration was better, but still there. Doing a recheck, we found that the angle change pulled the driveshaft out of the trans more than we liked, so we changed the driveshaft again with one an inch longer. That cured it, no vibration up over 100 mph.

Charlie Chops 1940 · August 22, 2011, 08:55:18 PM

This got to reading like the all-inclusive vibration FAQ. Glad you found it.

Charlie

wayne petty · August 22, 2011, 10:05:07 PM

Quote from: "enjenjo"Doing a recheck, we found that the angle change pulled the driveshaft out of the trans more than we liked, so we changed the driveshaft again with one an inch longer. That cured it, no vibration up over 100 mph.

perhaps the yoke was not far enough into the transmission to let it ride on the bushing.. next time you have it out... i hope its a LONG time till next time.. but can you read the wear pattern the bushing makes on the yoke surface... perhaps its just too short a yoke....

i have had weird disasters like this... on a 78 cad seville Milan.. a what..

as seen on the TV show quincy.. the grey seville 2 door convertible that had 28 inches chopped out of the back seat.. the drive shaft had a double cardin joint at the rear.. the angle was steep... the drive shaft tube was slightly bent.. i could not figure it out. but the car was barely drivable.. it was like a bucking bronco... i got cannon engineering to build a complete new drive shaft.. cost like 350 bucks.. oh man was that smooth. oh... the car owner was so thrilled .. he went down and bought a new set of tires..

when he left the tire shop.. the vibration returned as bad as usual..

i took the shaft back to cannon.. they looked at it.. said it was bent.. did a minor fix and rebalance.. got rid of about 98%... he took it back to the tire shop to complain.. they put it up to look at it.. WHAM.. the massive vibration was back.. he brought it to me.. this time the shaft was really dented. he called me from the tire shop.. i had driven past that shop hundreds of times and been in there a bunch as they supplied the wholesale tires for where i worked.. they had a blue car lift for tire work.. the one with the rubber pads that lift the sides of the frame rails.. problem.. the rear crossbar on this lift. HIT the drive shaft mid point and bent it each time they lifted it.. sometimes just enough to bend it .. the last time it left a big dent.. i pointed this out and let them figure it all out.

the car owner.. Eddie garrett passed away a few years later.. he was terribly dejected.. he had gotten a great photo job.. as an major airline pilot model for print ads.. but wait.. eddy was probably 75 at that time and hair white as santa's beard.. not what the airline heads thought of as a senior pilot.. this is the same guy who almost fell over from laughing after i told him that his carb might just have a few bugs in it.. when i pulled out dead bugs with the pair of tweezers .

glad you got it fixed.. i am still worried that it might not be pushed in deep enough..

Fat Cat · August 22, 2011, 10:25:07 PM

Quote from: "wayne petty"
Quote from: "enjenjo"Doing a recheck, we found that the angle change pulled the driveshaft out of the trans more than we liked, so we changed the driveshaft again with one an inch longer. That cured it, no vibration up over 100 mph.
glad you got it fixed.. i am still worried that it might not be pushed in deep enough..

The first driveshaft was too long. It was so long we had to take the rearend loose from its mounts to get it out of the car. For a time, I though the output shaft of the trans was bent due to the driveshaft being too long.

The driveshaft in the car now is the third one since Josh bought the car.