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Old 12-25-2005, 10:05 PM   #15
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drive shaft alinment

less see if I can 'splain lucy

If you would have the drive shaft laying on a flat floor, and looking down it front to back:
Say you turned it so the first cross or U Joint, is at 3 and 9 o clock (this would be the caps that go into the yoke that is bolted to the trans) --that would make the SHAFT yoke at 6 and 12 o clock.
Moving along that shaft,the next yoke on he shaft must also be at 6 and 12
o clock. this is where the yoke can be slid on wrong and be at 6 and 9 o clock. or be any number of degrees turned improperly, in other words on each shaft, the yokes on the ends have to be the same orentation not opposite, Most splines where the shafts slide together have one tooth on the spline that is blunt so to speak, so as to only allow the sliding yoke to go on a mating internal spline or missing spline as it is sometimes called, but not always.
If they are not correct it will cause a vibration or "boom" sound as it is sometimes called.
actually the shaft turns, but it "flops" as it is rotated.
I know, clear as mud.
George
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Old 12-25-2005, 10:27 PM   #16
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George,
Gotcha, at the slip joint. OK...that's between the second and third shafts. I know what to look for. Thanks.

S
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Old 12-26-2005, 07:20 AM   #17
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Vi BURR rations

I have been thinking about your ELVIS problem,
(whole lotta shakin' going on) and some thoughts come to mind,
You have been tightening the yoke bolt over the past while,and replaced the leaking seal. it could be caused by the tail shaft bushing being worn as you and others have mentioned. this could definately cause vibration.
But just thinking about it, seems like a whole lot of movement in that bushing would have to be present to cause the vibrations you describe, and seems like they would be present all the time (above say 35-40) and get worse as speed increases as that drive shaft is turning engine RPM's in high gear. Lets call it a FAST vibration.
I don't want to steer you away fron THE problem but other things could cause this too.
A bent wheel on the rear duals or tag axle? seems like they are Aluiminum. have you spun each wheel and observed trueness? New tires can be out of around, much less ones that have been around awhile and subject to curbs potholes and who knows what.
And boy oh boy, that rig ain't light weight. I have seen broken belts on tires that caused them to waddle, so to speak.
Corrosion between the wheel and the axle it is mounted, can cause a perfectly good wheel/tire assembly to wobble/vibrate.
As a thought, does your rig have the frame extension plates in the rear where the frame it added on to or "extended"?
They should be a few feet from the frame end. they are usually a couple of plates on either side of the frame rail with cutout oval holes in them, this allows the frame to flex but not break.
I Have heard of them breaking on newer FRP airstreams causing tail wagging and vibrations mimmicking a bad tire.
But one thing at a time, check the Drive shaft assembly first.
If you deceide to replace the tail shaft bushing, usually I put a little permatex or other type sealant under the transmission yoke bolt WASHER
(the one you have been tightening) so no fluid finds it's way along the splines and out around the washer or bolt head.( last step before you put the drive shaft back on)
You can unbolt the tail shaft housing to replace the bushing with no problems.
The output shaft in the trans will stay there as it in held internally.
I have not worked on the parking brake drum assembly, but I think it would be easier to remove it before removing the tail shaft housing from the trans.
The bushing is pressed in the tail shaft so It would be nice to have access to a light duty arbor press.
You don't have to drain the trans, but a pie plate or coffee catch can keeps things neat.
You will probably notice the output shaft in the trans, seems to have a lot of radial play, as if something inside is worn when you remove the tail housing,
don't worry, it's normal, the yoke bushing you are replacing helps to support the shaft, when all is assembled.
ol'George
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Old 12-26-2005, 07:21 AM   #18
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Steve, this is a little out there but I remember, like it was a previous life, having to "educate" the U joints before final assembly. The mechanic who supervised my DIY replacement showed me that once the new parts where installed on the shaft you had to wack the U joint a couple of times to assure they would be free moving. I remember the difference in the feel after giving them a couple of heavy taps with a ballpeen hammer.
So the question is does this "education" matter, (and did you do this?) or am I just dreaming this issue up... it was the late 70's and lots of things are "fuzzy" from back then.
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Old 12-26-2005, 07:43 AM   #19
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Hammer eddication

Good point:
What the hammer eddy kation is doing,
is seating the cups firmly against the snap rings.
What it does, is put a little play in the joints or "bed them in"
some joints when assembled, are not 'tight" and they move normally. then you don't need to whack em'
but others are somewhat "tight" or "stiff" so a gentle blow from a hammer at a point to seat the "cup"(s) against the snap ring is done.
a gentle "love" tap won't do it, but a hefty whack with a #5 hammer would be an "overkill"
kinda like a pinch of salt,--- hard to describe--
Not whacking them when "tight" would probably work itself out over time and not cause a problem unless the joint is worked at an extream angle like a moster truck application, then it could cause heat generation in the joint
which could cause loss of lubricant that possibly could cause failature if the joint.--
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Old 12-26-2005, 08:08 AM   #20
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Don't get all hung up on the slip joint alignment, the drive shaft has a double spline at the slip joint and can only go together one way.

If you have been having trouble with the tail shaft bolt loosening and leaks there is a good possibility the bushing has wallowed out. You have a lot of rotating weight with the emergency brake drum, that is a good place to start.

John
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Old 12-26-2005, 08:13 AM   #21
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Quote:
Originally Posted by 74Argosy24MH
Don't get all hung up on the slip joint alignment, the drive shaft has a double spline at the slip joint and can only go together one way.

If you have been having trouble with the tail shaft bolt loosening and leaks there is a good possibility the bushing has wallowed out. You have a lot of rotating weight with the emergency brake drum, that is a good place to start.

John
John, I've been thinking about Steven's problem (a dangerous thing, me thinking) and it could also be from the center support bearing, as well as the bushing in the tailshaft. I am wondering if while he has the shaft out getting the bushing issue taken care of, if he shouldn't replace the support bearing as well. What do you think about it?
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Old 12-26-2005, 08:41 AM   #22
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Terry - I replaced both the forward and rear carrier bearings summer before last. The forward bearing at the time was whining and noticibly sloppy when I hand checked it out of the vehicle. I replaced the rear carrier at the time for good measure and did all of the joints at the same time. This is also when I replaced the output shaft seal, etc.

I have not tried the hammer blow but again....all good things to check. I'm going to check the trans yoke play first. I'll post what I find.

Thanks again for all of the continued "noodle-ing" about this problem.
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Old 12-26-2005, 08:53 AM   #23
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I thought he had replaced them. If not they definitely need to be checked, 3 piece drive shafts need quite a bit of attention to detail to run smoothly. The rubber will probably be the cause of the problem, push up, hang on it, push sideways to see how much movement. There is going to be some because it is rubber, but it shouldn't be excessive (like the pinch of salt).

Steve, if you have replaced them (and as long as we are discussing them) check their alignment. The mounting holes are slotted (and pretty oversized), there is a tendency for them to turn slightly from the twisting of the nut (especially if the lockwasher really bites into the thin metal) as it is tightnened; this puts a slight angle in the solid mounted sections of the drive shaft, 2 of them compound the problem. If they are out of alignment loosen, align, tighten one side until it is just starting to touch, do the other, back and forth a couple of times until it is clamped tight enough so their is no more movement as you tighten.

John
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Old 12-29-2005, 07:01 PM   #24
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Steven,

I stumbled across THIS thread. Maybe Brett has some experience with this problem. You might ask him if he corrected it.

http://www.airforums.com/forums/f159/u-joints-drive-shaft-1087.html

Sorry, I can't make the hyperlink HOT. Copy & past the above.
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Old 12-29-2005, 09:21 PM   #25
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Norm,
Thanks for the link. Actually, I followed Brett's lead on this and replaced all four u joints and both carrier bearings a while back chasing this same vibration. I also figured it was good maintenance since my moho has sooooo many miles on it Only when I tightened the tranny yoke bolt did it stop.
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Old 02-11-2006, 09:13 PM   #26
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Tranny Tailshaft Vibration?

swebster
I had this problem with my GMC van(two piece drive shaft/carrier bearing). After several trips to the commercial driveshaft shop in Chesapeake VA, I got the shop guy to go for a ride with me. He felt the vibration, then looked up under the van when we returned to the shop. He told me that segmented drive shaftsmust be properly phased (ujoints aligned properly) which he marked when I had it in his shop having it balanced and the center bearing replaced. But the vibration continued at initial take off and around 45 mph.
After laying there staring at the transmisson tail shaft for a long time, he said that if you don't give universals something to do they will find something to do and you will not like it. He was trying to remember a previous situation like mine and what eventually solved the problem.
He remembered that if a drive shaft is less that 2 1/2 degrees out of aligment, you will get vibration at that point. Cure, shim the carrier bearing down. After adding a plate to the top of the carrier bearing assembly (1/2 inch thick aluminum 1 inch wide flat bar) to keep the bearing and rubber mount in its place and and another 5/8 inch of shims(fender washers) the vibration went away.
So, study the alignment of the tailshaft of the transmission with the segment of the drive shaft that connects to the Yoke on the transmission and if it looks too straight, it may well be. Shim the carier bearing down, Dont forget to make a flat plate to keep the bearing/rubber shock mount down in the horse shue looking thing that holds the bearing assy.
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Old 02-17-2006, 08:16 AM   #27
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Last weekend I got under there and pulled the drivewshaft off. I was able to push the parking brake/tailshaft assembly up and down maybe a 1/4" with the yoke bolt removed....it did not move at all with the bolt installed.
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Old 02-17-2006, 06:56 PM   #28
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vibration

Steve I noticed vibration in the drive shaft after the rear air suspension went flat because the compressor failed. I recieved help from Fred Hinds about filling the air tank at a truck stop. After the coach was in normal attitude the vibration stopped. When the rebuilt compressor arrives and has been installed I will be checking the ride hight/shaft angle for vibration issues. I'll post my findings. Cheers Tom
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