Tranny Tailshaft Vibration?

[swebster]

I'm stumped. My driveline vibration is back in force. I'm begining to suspect the transmission output shaft/bearing/bushing and could use some advice from my good friends on the forum once again.

First some background; the issue centers around a growing vibration in the coach itself between 35 - 45 mph. It feels like a lower volume version of driving your wheel over the rumble strip on the shoulder of the highway, not nearly as bad, but you notice it. The difference is that it's not just in the steering, it's everywhere - the entire coach is vibrating. In fact, recently the mirrors have begun to vibrate so much when this happens that I've considered changing the safety placard to say "objects may appear blurrier than the actual are"

The vibrations goes away above 45. It returns again above 65 but it's more like a high pitched whine. No real vibrations. Since I don't spend too much time between 34 and 45 it's not a big issue but since it's getting more noticable I would like to deal with it.

I have "repaired" this vibration in the past by tightening up the bolt that holds the transmission yoke into the tailshaft. Every 1000 miles or so it would start to vibrate again, I would tighten it and it would stop. After my last trip (2400 miles) it happened again and got noticably worse. Since the trip was so long I figured it was just "more looser" (as my five year old would say) so I grabbed my tools, shimmy'd under the motorhome, dropped the driveshaft but when I tried to tighten the bolt - it was already tight.

So now I'm thinking bearing/bushing/yoke, etc.

Related to the driveline and for the sake of having the "rest of the story" here is a list of what has been replaced on the the chassis to date: replaced all four driveshaft u-joints, replaced both driveshaft carrier bearings, replaced front shocks and steering stabilizer with bilsteins, replaced rear shocks, replaced tag axle shocks, replace front air bags, replaced rear transmission seal. Keep in mind that my 345 has 175,000 miles on it so many of these parts were replaced along the way to ensure safe and reliable operation. The transmission fluid is changed and checked regularly (ever other fuel stop). It always is clear red and smells clean.

Now I can handle a lot of repairs on the 345 myself but transmissions are like black magic to me so I have a few questions:

When I replaced the rear seal (two years ago) no real fluid came out of the tailshaft (it just sort of weeped). Is there supposed to be a lot of fluid back there? If there isn't should I be budgeting for a tranny?. I assume the tailshaft is fed from the transmission itself and not it's own gear oil? I have no leaks as far as I know and I've never needed to add fluid in operation over almost 30,000 miles. Again, the fuild is alway picture perfect.

I've been reading on other forums that many driveline vibrations with descriptions that match mine have been repaired by replacing the rear bushing or bearing on the transmission. Some mention driveshaft runout, but because I have "cured" mine in the past in the trans/yoke area I have not reconsidered a driveshaft balance issue. Any thoughts on this?

NAPA lists the rear bearing on their site. I've seen a few posts about it being a driveway replacement but unforetunately I can't find many details on the procedure. Any thoughts/recommendations on replacing the bearing (or bushing). What about the yoke? Is it wiser to just replace the entire tailshaft assembly? What would be involved?

As always all advice is appreciated.

[Nye Thatcher]

Steve. It sounds as if you may have been repairing problems caused by a misalingned drive shaft.The yokes must be aligned correctly. One spline off will cause a vibration in the drive train you might not feel in the cab.The more splines out of alignment, the heavier the wibration. This is just a thought. Hope it will help.

[axleman]

Steven,

I don't mean to state the obvious - but - have the drive shafts checked, by a professional, for balance and straightness. Most likely this cannot be done at home!

My two cents,
Henry

[driftwood]

Henry is on target for one of the most common problems.

In the manufacturer of 1000's of rear drive limousines, 80% of our vibrations were cured by proper straightness and balance of the drive shaft.

Other problems we encountered were sometimes related to worn or failed transmission/pillow block mounts or failed engine mounts. When the torque increased, the alignment of the drive train would temporarily change.

Another can be related to excessive angle at the union of a two-piece shaft.

Have you listened to the trans for 'chatter' when in a specific gear?

[Chuck]

Originally Posted by axleman

Steven,

I don't mean to state the obvious - but - have the drive shafts checked, by a professional, for balance and straightness. Most likely this cannot be done at home!

My two cents,
Henry

I'll second this. It may be obvious, but its also very commonly overlooked. "KISS", remember? (keep it simple...).

My brother-in-law specializes in this kind of work. I've watched him build/repair/balance driveshafts a hundred times. It is very specialized work, requiring very expensive specialized tools, so it may not be easy to find someone in your area. But its also cheap, fast, and easy, for those that do it. definately start there before ripping apart your tranny. You went right by us last summer...should have stopped in!

[swebster]

Thanks for the replies.

Henry, yes driveshaft balancing is not for the driveway. I had been thinking about the rear tailshaft bearing replacement as a shade tree repair.

No chatter as far as I can tell. Also, this vibration occurs even when I place the transmisison in neutral and coast with the engine at idle. So, I haven't been thinking about a torque, flexplate, mount, etc. related issue.

Sounds like you are all thinking my yoke issue is really a symptom of a driveshaft issue.

Chuck - We'll be in Connecticut next week and back through MA/NH again this summer.

[driftwood]

Well, everything 'keeps-on-turning' ... even when the trans is in neutral !

[swebster]

Norm,
Right, I understand that. My point was that there was no positive loading or torque against the driveshaft when in neutral from the engine/tranny combination, just the opposite in that the diff is now turning the driveshaft.

Anyone else have experience with the tailshaft housing and rear bearing? I can have the shafts checked locally but since I've had "issues" in this area of the drivtrain I would like to ensure that even if it is a symptom of an inbalance that I'm checking/repairing any possible failures in the driveway instead of on the highway.

[markdoane]

Have you tried the trick with the hose clamps to change the weight balance on the driveshaft? I wouldn't recommend it as a fix, but as a diagnostic tool.

[overlander63]

Steven, a quick couple of things to check. Someone has already mentioned this, but maybe it weasn't clear. Check the driveshaft to make sure all the U-joints are aligned with each other, all the way from front to back. If U-joint #1 is in a position that looks like "+", all the U-joints have to be oriented the same way, all caps pointing straight up and down, and side-to-side.
If that is all good, you can try pushing up on the u-joint and yoke coming out of the transmission. If it lifts up more than a smidgen, you probably have a worn output bushing. the tailshaft housing usually needs to be removed in order to replace the bushing, if it is bad.

[Tinsel Loaf]

Problem solved. Just sign over your MH to me and it will be my problem. If and when I figure it out I promise to let you know what it was.

[George]

Hi Steve,
Have you checked the differential yoke?
I've seen them spread so to speak, so that although the U joint is good, and it is tight in the straps, the yoke is too wide, allowing the U joint to have play in it, in other words it slides in the "cups"
this will cause vibrations as the shaft is off to one side or the other.
Also a tire with a bad/ broken belt, altho looking good visually, will also cause a vibration that will literally shake the whole coach.
It seems like you have never really stopped this problem in the past.
does this trans have the parking brake on the rear of the it? could be a problem with the drum out of balance or loose.
is there noticable play in the slip yoke(s) on the drive shaft.

If it were mine, and I have done this, I would jack it up and put sturdy jack stands, VERY STURDY!! under the rear axle and have a TRUSTED helper slowely increase the speed to the trouble range and then the culpret will show itself .
Oh, on the trans yoke, usually very little trans oil will leak out when you remove it, unless you have the coach jacked up REALLY high in the front.
The pan on the trans is full to the top normally,but not up into the case and the output shaft is above that, so little leaks out.
You are correct in dismissing flywheel/torque converter problem as they are turning only at idle rpm's when you have it in netural while coasting, or not at all if you were to turn the engine off (not recomended as you loose power assist brake/steering)

Later, ol'George

[Nye Thatcher]

Steve. Rather than try to explain the line-up of yokes, just slide under any truck with a two piece drive shaft that has no problems and make a diagram of the alignment. It doesn't have to be a P30 chassis but it might be easier. Make sure the U joints are pressed in exactly where they should be. Sometimes a roller will fall into the cup and won't let it be pressed all the way in. Good luck.

[swebster]

Thanks for the continued advice and items to check out. I now have a solid checklist and will go through each item.

Terry - when I replaced the U-Joints I made sure to mark all of the shaft orientations so maybe I'm confused on the "line up" thing. Am I looking for a twist in the shaft with this check?

Tinsel - nice try!

George - yes my P30 chassis has the driveshaft mounted parking brake (manual). It's definately on my suspect list since it's so close to the yoke. I'll check the diff joint and thanks for the info on the tranny.

Again - thanks for the conitued toubleshooting advice. Everyone's collective input is very helpful. I'm still very suspicious of the output bushing so I might drop the first shaft (the 345 has THREE!) and check for lateral play in the yole first. I won't dismiss the other possibilities but something has been talking to me in this area of the drivetrain for a while.

[George]

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

[swebster]

George,
Gotcha, at the slip joint. OK...that's between the second and third shafts. I know what to look for. Thanks.

S

[George]

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

[GlenCoombe]

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.

[George]

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.--

[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