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Diesel This is a forum dedicated to diesel engines and their applicable accessories.


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Old 05-23-2012
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Is it normal for the drive shaft to move in an out by half an inch??

I replaced the pulley on my driveshaft with a larger one so my alternator would spin faster at low RPMs. During the process, I noticed that my driveshaft moves in and out about 1/4 to 1/2 inch. is that OK or should it not do that? I wonder if I caused it to do that when I was trying to pry the old pulley off with a screw driver? I am guessing I put about 50 pounds of pressure on it. I finally gave up, got a wheel puller and removed it.

When I first started the engine with the new pulley. I noticed that it was rubbing on the engine slightly, but i was able to stop that by pulling the drive shaft away from the engine. I am concerned that it might move back again, so I re-set the pulley on the drive shaft 1/4 of an inch further away from the engine.
Should I be concerned about the movement in the drive shaft and if so, what can I do about it?

Thanks for your help.

Larry
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Old 05-23-2012
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Re: Is it normal for the drive shaft to move in an out by half an inch??

What engine? Can you post a picture? Not too sure what you mean by 'Driveshaft'... if you're talking about the crankshaft then no, definitely not normal- if even possible...

Or are you driving an alternator with the propshaft?? unusual but I suppose it's possible but rpms would be rather low.... Even so that shouldn't move in and out either..

Need clarification!!
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Re: Is it normal for the drive shaft to move in an out by half an inch??

Folks are going to ask you what make of engine, year, condition, details like that. It would be a good idea to put them out there now. Oops, see that Faster is already asking--see?
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Old 05-23-2012
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Re: Is it normal for the drive shaft to move in an out by half an inch??

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Originally Posted by justonemoreproject View Post
I noticed that my driveshaft moves in and out about 1/4 to 1/2 inch. is that OK or should it not do that? I wonder if I caused it to do that when I was trying to pry the old pulley off with a screw driver? I am guessing I put about 50 pounds of pressure on it. I finally gave up, got a wheel puller and removed it.
Larry
Larry... I hope that wasn't a classic "uh oh" knowing little about the insides of engines but knowing something about crankshafts in hvac compressors I would say it's not good to be prying on them to get things off.
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Old 05-23-2012
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Re: Is it normal for the drive shaft to move in an out by half an inch??

Fast- I was thinking "1/2" of movement in the propshaft?", didn't even think about the crank! Ouch! Will wait for clarification from the OP.
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Old 05-23-2012
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Re: Is it normal for the drive shaft to move in an out by half an inch??

It is your thrust bearings that have failed.
These bearings go on each side of the shell bearings on each main journal and stop crank walk. There should only be tops 8/1000" end play in your crankshaft.
If you have a lot of end play, pull your oil pan off and look for pieces of bearing material. It will be soft metal, peutor in colour.
Eventually your pistons will start hitting the cylinder walls and this will cause serious fatal damage. It's time for a rebuild before it gets worse and costs you some serious coin.
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Re: Is it normal for the drive shaft to move in an out by half an inch??

Wow. Lots of responses. Sorry for the lack of clarification.
Sorry for the misinformation. The play is in the crankshaft on the forward side of the engine. Not the drive shaft.
I have a 32 year old Petter, AC1W diesel engine with 750 hours on it. (its in a sailboat that has been used mostly as a liveaboard all these years.
ITs a 6 1/2 HP one cylinder, that starts right even after several months of not being started. It is fresh water cooled with a heat exchanger which is the only reason it has survived all these years. I change the oil, pump out the old diesel and clean the filters once a year, although I only run about 5 -8 gallons through it per year.
I have never had a problem with this engine.
Thanks for your help.

Larry
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Old 05-23-2012
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Re: Is it normal for the drive shaft to move in an out by half an inch??

Now I know what engine you have, single cylinders can handle more end play than a multi cylindered engine. You engine's end play should not exceed 5mm.
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Re: Is it normal for the drive shaft to move in an out by half an inch??

Quote:
Camshaft end float ................................ 0.003/0 010in (0.08/0.25mm)
Crankshaft end float (new)........................ 0.005/0 01 Pin (013/0 43mm)
Crankshaft end float (not to exceed)......... 0020m (0 51mm)
From this site: http://www.eygthene24.com/images/cm_...petter_AB1.pdf
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Re: Is it normal for the drive shaft to move in an out by half an inch??

Quote:
Originally Posted by justonemoreproject View Post
I replaced the pulley on my driveshaft with a larger one so my alternator would spin faster at low RPMs. During the process, I noticed that my driveshaft moves in and out about 1/4 to 1/2 inch. is that OK or should it not do that? I wonder if I caused it to do that when I was trying to pry the old pulley off with a screw driver? I am guessing I put about 50 pounds of pressure on it. I finally gave up, got a wheel puller and removed it.

When I first started the engine with the new pulley. I noticed that it was rubbing on the engine slightly, but i was able to stop that by pulling the drive shaft away from the engine. I am concerned that it might move back again, so I re-set the pulley on the drive shaft 1/4 of an inch further away from the engine.
Should I be concerned about the movement in the drive shaft and if so, what can I do about it?

Thanks for your help.

Larry
That seems like a whole lot of end play. It appears that the wrist pin is keeping the crankshaft somewhat in place? Whatever thrust bearing arrangement it had appears to be basically gone. Did it have this much play before you pried on the pully? if not you may have damaged whatever was in place originally. If it had that much play to begin with it appears the engine may tolerate it? Suggest you watch it while under power to see if it is moving back and forth. If it stays put you may be lucky enough to let it be. Possibly, excessive movement could result in sudden piston, wrist pin, or rod failure, not good.

Paul T
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