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Old 23-09-2019, 11:06   #1
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Removing coupling nut on 72 series borg warner or velvet drive

I will need to replace the seal on the reducing gear output and was just wondering how do i prevent transmission from rotating while i try to crack the output nut. Manual does not specify if engine should be in gear or does it matter?
leak is definitely coming from the spline. I say this because i am catching the leak at the PSS shaft collar, which is very close to the prop shaft coupling(not much room in my setup). I dont see any leak from transmission side of the coupling flange which would indicate its the seal. I will replace the seal while i'm at it.

unfortunately I have to haul the boat for this because there's not much room. Prop shaft has to come out.
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Old 23-09-2019, 11:26   #2
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Re: Removing coupling nut on 72 series borg warner or velvet drive

The easy way is an impact wrench and socket. It will usually loosen the nut whether the trans is in gear or not. You can usually rent an electric impact tool at some rent centers.
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Old 23-09-2019, 11:40   #3
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Removing coupling nut on 72 series borg warner or velvet drive

If itís leaking it will probably be hand tight. I use a block of wood braced against one of the bolts and the hull to loosen the nuts. After you pull the coupling and clean it and the splines, replace the coupling and fill the cavity with RTV sealant and put on a NEW nut. It will push the RTV into the splines and seal it. Torque to 200 ft/lbs the best you can. The nut is a one time use.
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Old 23-09-2019, 11:54   #4
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Re: Removing coupling nut on 72 series borg warner or velvet drive

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Originally Posted by meridian28 View Post
If itís leaking it will probably be hand tight. I use a block of wood braced against one of the bolts and the hull to loosen the nuts. After you pull the coupling and clean it and the splines, replace the coupling and fill the cavity with RTV sealant and put on a NEW nut. It will push the RTV into the splines and seal it. Torque to 200 ft/lbs the best you can. The nut is a one time use.
"One of the bolts" which bolt are you talking about?
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Old 23-09-2019, 14:57   #5
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Re: Removing coupling nut on 72 series borg warner or velvet drive

Put a bolt back into the coupling flange
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Old 23-09-2019, 15:04   #6
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Re: Removing coupling nut on 72 series borg warner or velvet drive

By far the easiest and most efficient way to remove the drive flange is to make up a simple tool to hold the flange rock solid while you undo the centre nut. The tool is an 18" long bit of flat bar with two ⅜" holes drilled in it to match 2 of the closest holes on the flange. This flat bar can be 1" wide but needs to be fairly thick, maybe ⅜" and has to have the two holes drilled very close to the edge so as not to block access for the big socket wrench. The nut might be loose to remove but it needs 200 ft lbs at refit as mentioned by another poster and that takes a bit of muscle.
You might find that the bearing preload needs to be reset, especially if the flange is loose and the bearing spacer is a bit flogged. This would mean that when the nut is finally tensioned the preload could be too tight and a wider bearing spacer needs to be fitted , it's a fairly easy procedure but the big nut needs to be removed and refitted several times to get it right and you will really appreciate having that locking tool. use the old nut and keep the new one for the final fit. There is a "crushable" one time only bearing spacer but you need to have a good torque wrench to get the crush right, best to use the solid spacer. Leave the seal out until you are ready to finally tighten down the new nut.
Also check the condition of the splines that you intend to seal, they could be quite worn if oil is passing through them.
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Old 24-09-2019, 06:57   #7
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Re: Removing coupling nut on 72 series borg warner or velvet drive

Quote:
Originally Posted by skipperpete View Post
By far the easiest and most efficient way to remove the drive flange is to make up a simple tool to hold the flange rock solid while you undo the centre nut. The tool is an 18" long bit of flat bar with two ⅜" holes drilled in it to match 2 of the closest holes on the flange. This flat bar can be 1" wide but needs to be fairly thick, maybe ⅜" and has to have the two holes drilled very close to the edge so as not to block access for the big socket wrench. The nut might be loose to remove but it needs 200 ft lbs at refit as mentioned by another poster and that takes a bit of muscle.
You might find that the bearing preload needs to be reset, especially if the flange is loose and the bearing spacer is a bit flogged. This would mean that when the nut is finally tensioned the preload could be too tight and a wider bearing spacer needs to be fitted , it's a fairly easy procedure but the big nut needs to be removed and refitted several times to get it right and you will really appreciate having that locking tool. use the old nut and keep the new one for the final fit. There is a "crushable" one time only bearing spacer but you need to have a good torque wrench to get the crush right, best to use the solid spacer. Leave the seal out until you are ready to finally tighten down the new nut.
Also check the condition of the splines that you intend to seal, they could be quite worn if oil is passing through them.
Good stuff, thanks, by the looks of it, there are numerous lengths for spacer available. I am doing a quick haul for this and time might be of essence. So I guess procedure is to take the spacer out inspect for wear. Use old nut and spacer to check the rolling torque. Then if needed order appropriate spacer. Then once I get rolling torque within spec, I install the spacer, seal and new nut hoping rolling torque doesn't change.

Onc question I had is what is the play they mention in the Note. Should coupling flange move back and forth at most 5 mils?
one other question...from pic i posted, is spacer (13) able to come out without pulling the matched bearing set (15 or 10)? Pic seems to indicate matched bearing set (15) needs to come out.
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Old 24-09-2019, 11:15   #8
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Re: Removing coupling nut on 72 series borg warner or velvet drive

Quote:
Originally Posted by phorvati View Post
Good stuff, thanks, by the looks of it, there are numerous lengths for spacer available. I am doing a quick haul for this and time might be of essence. So I guess procedure is to take the spacer out inspect for wear. Use old nut and spacer to check the rolling torque. Then if needed order appropriate spacer. Then once I get rolling torque within spec, I install the spacer, seal and new nut hoping rolling torque doesn't change.

Onc question I had is what is the play they mention in the Note. Should coupling flange move back and forth at most 5 mils?
one other question...from pic i posted, is spacer (13) able to come out without pulling the matched bearing set (15 or 10)? Pic seems to indicate matched bearing set (15) needs to come out.
It's a pretty hard task to accurately guage rotating torque.
You'll need a clear open rotating perimeter.
And some experience.
If you want this to last,it's needs to be correctly done.
Have you really looked at the ability to raise the rear of the gear,enough to possibly clear the shaft and remove it compleatly?
0.005 isn't much end play so for sure you have that much, not much more though.
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Old 24-09-2019, 11:26   #9
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Re: Removing coupling nut on 72 series borg warner or velvet drive

Quote:
Originally Posted by phorvati View Post
Good stuff, thanks, by the looks of it, there are numerous lengths for spacer available. I am doing a quick haul for this and time might be of essence. So I guess procedure is to take the spacer out inspect for wear. Use old nut and spacer to check the rolling torque. Then if needed order appropriate spacer. Then once I get rolling torque within spec, I install the spacer, seal and new nut hoping rolling torque doesn't change.

Onc question I had is what is the play they mention in the Note. Should coupling flange move back and forth at most 5 mils?
one other question...from pic i posted, is spacer (13) able to come out without pulling the matched bearing set (15 or 10)? Pic seems to indicate matched bearing set (15) needs to come out.
It doesn't look from the pictures that the spacer you mention would come out.
The cages with the bearing rollers might be pressed on.
But not certain of that. Question what is your ratio on that gear, that looks to be a reduction gear.
Talk to a rebuilder?
Good luck.
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Old 24-09-2019, 13:51   #10
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Re: Removing coupling nut on 72 series borg warner or velvet drive

Quote:
Originally Posted by phorvati View Post
Good stuff, thanks, by the looks of it, there are numerous lengths for spacer available. I am doing a quick haul for this and time might be of essence. So I guess procedure is to take the spacer out inspect for wear. Use old nut and spacer to check the rolling torque. Then if needed order appropriate spacer. Then once I get rolling torque within spec, I install the spacer, seal and new nut hoping rolling torque doesn't change.

Onc question I had is what is the play they mention in the Note. Should coupling flange move back and forth at most 5 mils?
one other question...from pic i posted, is spacer (13) able to come out without pulling the matched bearing set (15 or 10)? Pic seems to indicate matched bearing set (15) needs to come out.


The procedure is simple but given your limited time frame it's best to get the workflow established so ......
Buy the seal and new nut
Get the flat bar tool ready
Get the right size socket wrench for the big nut and the flange bolts
After you release the coupling and the flange is free to rotate, check to see what the rolling torque and endfloat is like and then check again after checking the tightness of the big nut. The rolling torque and endfloat are no big deal so basically if you can get the endfloat down to the 0-.005" the rolling torque should be ok .... but if the nut has been loose and you tighten it , it's likely that the spacer is reduced in thickness and you'll get zero endfloat but a high/ stiff rolling torque.
The drive flange should slide off easily and then you'll be able to remove the seal and then the bearing cone for inspection of the rollers, no pressing or pulling required. The spacer will also come out after the bearing.
If the initial inspection and endfloat check passed ( nut very tight and endfloat only tiny you can put it all back together with a new seal and either sealant or an oring to seal the spline.
If she failed the tests then you need to reset the spacer thickness a bit to get that zero to 5 thou of an inch, do that job with no seal in the housing.
Apologies for being so long winded with the details
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Old 25-09-2019, 21:03   #11
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Re: Removing coupling nut on 72 series borg warner or velvet drive

+1 for skipperpeats posts. had to do this task 15 years ago on a '78 C72 unit while in Mexico. was able to order the seal from a local bearing store, had the socket and breaker bar, but had to make the spanner from local flat iron. does require moving the prop shaft aft to make room for removal of the coupling and seal. end play was not an issue..
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Old 27-09-2019, 06:08   #12
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Re: Removing coupling nut on 72 series borg warner or velvet drive

Quote:
Originally Posted by skipperpete View Post
The rolling torque and endfloat are no big deal so basically if you can get the endfloat down to the 0-.005" the rolling torque should be ok .... but if the nut has been loose and you tighten it , it's likely that the spacer is reduced in thickness and you'll get zero endfloat but a high/ stiff rolling torque.
Reducing gear is 1.91:1
Boat is out and i got the prop coupling off. then i found that 1-1/2" socket is too small. I am getting 1-11/16" socket today and will take the nut off tonight. Yard gave me two weeks before storage fees kick in. With prop out, what i'm noticing is that flange has way more than 5 thou of play. more like 20. the nut is not loose. Would that indicate that spacer is worn or perhaps roller bearings are damaged?
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Old 27-09-2019, 16:48   #13
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Re: Removing coupling nut on 72 series borg warner or velvet drive

So it's exactly what you said. Nut was loose. Bearing is in great shape. But torquing the nut to 200ft-lbs made rolling torque around 120 in-lbs. Way more than 30 in-lbs. 120 in-lbs is more a breaking torque. It took that much to get tranny rotating .I imagine that rotating torque is a lot less. Hard to measure, I would need a strain gauge or something and a lot more room. So better question is what do they call rolling torque?
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Old 27-09-2019, 16:52   #14
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Re: Removing coupling nut on 72 series borg warner or velvet drive

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Reducing gear is 1.91:1
Boat is out and i got the prop coupling off. then i found that 1-1/2" socket is too small. I am getting 1-11/16" socket today and will take the nut off tonight. Yard gave me two weeks before storage fees kick in. With prop out, what i'm noticing is that flange has way more than 5 thou of play. more like 20. the nut is not loose. Would that indicate that spacer is worn or perhaps roller bearings are damaged?


.020" is a good thing if the big nut is rock solid tight because to reset it to .005 you simply need to grind or sand down the spacer a little at a time with numerous test fits. Try for the .005" not the zero. Yes you will need to take a very close look at the outer cone and the cup it runs in but I would be very surprised if the bearing was damaged , the reduction and its bearings is way overbuilt for the small amount of thrust it absorbs from a yacht engine.
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Old 27-09-2019, 17:31   #15
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Re: Removing coupling nut on 72 series borg warner or velvet drive

well, in terms of grinding that spacer...it was the old style and it was collapsible because when i took a look it had a bulge along the middle as though it collapsed. The bummer is I have already installed a seal. and pulling the old seal made me bend it enough that I dont think the old seal is usable. So unless I find a crafty way to remove the new seal without bending it, i will have wasted it. Luckily I have bought two.

So being able to grind it is great news. Ill order longest one and go from there.
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