Vibration issue

[seacolt]

Have a bad vibration on starboard side. Noticed small amount oil on shaft coupler. Unbolted coupler and I can move the flange on the transmission, its pretty sloppy. Can anyone tell me what the fix is? I would assume its a bearing. Does the gear have to be removed or can it be done in place?
Thanks

 

[Genesis]

What gear? Allison?

 

[MikeP]

Long-distance troubleshooting with thing like vibrations can be difficult because we may have different ideas/descriptions/terms for the same symptoms. But here are some questions/thoughts:

Is the vibration more of a rumble/hum or an actual "movement" of the boat that you can feel…like a shuddering or vertical bounce?

Lots of things can cause vibrations/shuddering while underway - some are of no technical importance - like a buildup of barnacles on the prop/shaft. Bad cutlass bearings can also cause vibration as can a bent shaft or a damaged prop blade. Have you or a diver taken a look at the props/shafts recently?

Is the slop in the flange you are referring to the play that exists when turning the flange clockwise/counterclockwise or is it play in the vertical or horizontal plane? There is likely no issue with rotational play which is determined by the internal gear mesh and can seem considerable, especially on large transmissions. Play in the vertical or side-to-side dimension is a different issue and could indicate a worn output shaft bearing. If there is any noise like a heavy click or clunk periodically as you rotate the shaft by hand, it could indicate a damaged gear.

Is the vibration felt at all RPM or just at a specific RPM range? Based on the description, I assume it only occurs with the transmission(s) in gear, not when you run the engines in neutral through the same RPM range where the vibration occurs, right?

 

[seacolt]

The gear is an allison m20r. Yes the vibration is very noticeable at all speeds, the boat shakes and gets worse as speed increases. The flange on the gear does have the clicking sound when moved by hand and it does have some play as I move it for and aft. it feels loose in all directions. If I was to guess maybe an 1/8 inch play. If I pinch the flange I can wiggle it a bit side to side. If its the bearing does that mean the trans has to come out or can bearing be replaced in the boat ?

Thank you

 

[seacolt]

Let me also add the boat is out of the water. The vibration happened on my last run before I hauled out, I would call it shuttering very noticeable on the bridge, you could see railings shake. At the stuffing box I also see movement, The boot and packing gland move in sort of a series of shaking. to best describe it, the shuttering get worse every couple of seconds. the shaking changes its not consistent. The shaft, prop, bearings all look ok some build up but nothing I have seen before. I do have split shaft and that seem ok as well. Mounts are old but don't appear to be sagging, they are old style with shims. I did take a bolt out to see if the rubber was still adhered to the steel, so i'm ruling out mounts. Plus I did have a oil dripping onto the shaft coupling that never had before.

 

[captddis]

Sounds like the coupling is loose on the output shaft and your splines may be damaged. Seperate the shaft from the trans and see if the trans coupling can be wobbled. Rereading your posts, I am certain that the problem is in the gear and the nut has loosened.

 

[mike]

Have a bad vibration on starboard side. Noticed small amount oil on shaft coupler. Unbolted coupler and I can move the flange on the transmission, its pretty sloppy. Can anyone tell me what the fix is? I would assume its a bearing. Does the gear have to be removed or can it be done in place?
Thanks

Assuming you have an Alison trans; there should be no oil on the inside mating face of the coupler. To check if its a trans shaft to flange problem, move the prop shaft/flange back as far as possible, then place a small mirror in such a manner that you can see the end of the trans shaft and the trans coupler. Hold the coupler and roatate it back and forth and see if there is movement / play between the trans shaft and flange, also see if the retainer nut is loose. If the flange to trans-shaft is sloppy or the nut is loose, you may have a potentially serious problem with the main trans shaft and coupler splines. The nut is torqued to 180ft/lbs. so there should be no movement. The gear has to be removed from the engine to replace the shaft and bearings, but can be done in the boat if you have the eng room space. If you remove the the flange and find the splines on both the trans shaft and coupler are still tightly mated you may get away with using Loctite and retorquing the the nut, which does not require removing the trans. Had a similar problem on one of my Alison M20 and had to replace the shaft and coupler. Have many pics if interested.

 

[seacolt]

I removed the flange and cover plate and found the thrust washer was worn, (that was causing flange to wiggle) the inside part of the washer was chewed up pretty bad. found a few metal flakes in the cover plate. Not sure how to check the bearing ? and if I do need to replace it what does that involve, it looks like its pressed in. at visual inspection of the bearing it does not appear to be missing any parts or discolored. Does anyone know what I can do to further inspect the bearing ?

thanks again

 

[captddis]

I doubt it is the bearing. How are the splines? They al;most always are worn when the coupling is loose. Also remove the screen and see how much metal you get up out of the bottom using a magnet.

 

[seacolt]

Could you tell me what to look for on the spline and if its worn is it easily replaceable. Also how do I access the screen, not sure where it is. Sorry for the ignorance, Just not to familiar with the parts on trans.

Thank you.

 

[captddis]

The splines should fit snugly and fill most of the coupling. Sliding the coupling on the out put shaft there should be almost no movement of the splines. If the coupling can be wiggled from side to side the splines and or coupling are worn.
The screen is in the suction hose where it mounts to the case. there are three 5/16 bolts.

 

[mike]

I removed the flange and cover plate and found the thrust washer was worn, (that was causing flange to wiggle) the inside part of the washer was chewed up pretty bad. found a few metal flakes in the cover plate. Not sure how to check the bearing ? and if I do need to replace it what does that involve, it looks like its pressed in. at visual inspection of the bearing it does not appear to be missing any parts or discolored. Does anyone know what I can do to further inspect the bearing ?

thanks again

Agree with captddis (I doubt it is the bearing. How are the splines? They almost always are worn when the coupling is loose. Also remove the screen and see how much metal you get up out of the bottom using a magnet) based on my 2 M20's. The bearing though may be in bad shape. If you can move the shaft fwd and aft direction, as in and out of the case, you may have a bigger problem. The front bearing is held on the shaft with a retainer nut and retainer clip. It is held in the case by a lip on fwd end that prevents the bearing from sliding forward. The lip can be pounded out if there was too much end play from the loose shaft and flange. You may find some of the cast iron lip chips in the bottom of the case.(happened on my stb trans) The bearing is a tight slip fit into the housing; if you can find a way to grasp the bearing and its loose on the shaft you may be able to remove it. The bearing is a double row ball bearing about 2 ½ “ thick. (both of mine bad bearings). On replacement had to warm the case to insert the bearing and shaft assembly.

 

[seacolt]

Great info ! I am thinking the bearings are ok as well, visually they appear ok. I will check the splines and screen. New seal will be here in a few days, Hoping it will all go back together tightly.
Thanks again

 

[seacolt]

Found metal shavings in the screen. Looks like trans is coming out.

 

[seacolt]

Anyone know aprox. weight of m20 gear. Just wondering if it can be lifted out by hand or do I need a rig setup.

 

[saltshaker]

They are heavy but can be handled providing you have room to move. When I had mine pulled from my 46C the yard was supposed to use thier lift to pick it off the boat. Mechanic didn't want to wait for the lift. Two guys lifted it off the boat and onto the dock by hand.

 

[captddis]

Anyone know aprox. weight of m20 gear. Just wondering if it can be lifted out by hand or do I need a rig setup.

Close to 500 lbs.

 

[saltshaker]

Close to 500 lbs.

Is that for an M or MH gear? My mechanics helper picked up the gear by himself! It was on the gunnels waiting for the yard to help and he decided he didn't want to wait anymore. He bear hugged the thing and lifted it off the boat. I remember thinking I wouldn't want to piss him off. Irecall checking the manual and weight was about 340lbs, but that was 15 years ago and my memory could be off.