# driveshaft bolt comes loose



## TTr (Feb 8, 2014)

Craftsman 18.5HP twin kohler magnum, 46" deck, PN 917.251492 (Unknown year, 
bought it used in 2005, I am guessing late 90's or early 2000's)

The engine driveshaft is vertical and has the drive pulley and the electric clutch on it. The bolt that holds then on has come loose three times so far. (Bolt #43 in the picture)

The first time, it was last summer while mowing. The clutch fell off the shaft and got destroyed, the bolt was bent and stripped. I got a used clutch, new bolt and cleaned the shaft threads with a round file tip on the electric drill.

The second and third times, it was this winter while snow blowing. With the snow blower attachment the clutch does not have enough clearance to fall off the shaft completely. The second time I cleaned the threads with a tap (same size) a little bit and put everything back. The third time, no damage done, everything went back without any repairs.

I ensure that the bolt is tight on the shaft when I repair it. The washer and locknut are on of course. I use a screwdriver and twist the drive belt around to keep the drive pulley from spinning so I can tighten the bolt. I am sure I get about 40 footpounds of torque on it. (no torque wrench, just my arm and my one-foot ratchet)

It held through the last snowstorm of about an hour of plowing so far and when I was done plowing I checked it and it was on tight.

Any ideas as to what causes this and what else to do to prevent it from happening? Last summer I took all the drive belt pulleys out and checked them, they were all good. I oiled them all before putting them back. 
I cleaned and oiled all the cutting deck and snow thrower pulleys too.

My evaluation is that it is a bad design. I would have loved a threaded shaft with either a large lock-nut or a nut with a cotter-pin on it to keep it from coming loose.

Thanks of any insights and suggestions.


----------



## Fluid (Nov 28, 2013)

Pull bolt #43, clean with degreaser,(brake clean, carb cleaner, or what have you) get some LOCTITE at any auto parts store. There is some for bolts that you will never want to take off again and there is some for bolts that you may want to take off someday. You decide which one you want. Read instructions, apply to bolt, torque bolt tight, let LOCTITE setup, (give it time to dry), done. P.S. Make sure threads in shaft are clean also (the part that bolt #43 threads into)


----------



## TTr (Feb 8, 2014)

I was thinking about the locktite too and I will do that but was asking in case someone knew of a specific reason.


----------



## jhngardner367 (Apr 5, 2011)

This was common on some engines. 
I would recommend using the blue Loctite ,hi-temp formula,and toque it to 70ft/lbs.


----------



## jhngardner367 (Apr 5, 2011)

I've seen this happen on a few machines.
Heat,vibration,and not being torqued when assembled (new),all contribute to the problem.
Clean it,as Fluid said,and apply the blue loctite,but TORQUE it to 70 ft/lbs.
If it still does it,use the red loctite,even though you may need to heat the bolt to remove it,later.


----------



## Fluid (Nov 28, 2013)

The engine manufactures usually put some type of thread dope on those bolts, but I guess not always. If you have a strap wrench you can rap it around the #12 pulley and get a good hold of it, that way you can tighten the #43 bolt good.


----------



## TTr (Feb 8, 2014)

I will definitely use the locktite. But I am concerned about the 70lbs of torque. The bolt in question is 7/16" diameter and 4" long. Might it snap under that much force?

I plan to do this tomorrow in preparation of Thursday's big snow storm in the East.


----------



## Fluid (Nov 28, 2013)

No worries, that bolt can take much more then that. 70lbs is OK


----------



## TTr (Feb 8, 2014)

I used the blue locktite and gave it a good torque, I would say at least 60 pounds. So far so good, I went through over an hour of snow blowing and no problems. Thanks everybody for replying.


----------



## Fluid (Nov 28, 2013)

TTr I was just wondering if the bolt on you Craftsman was still good and tight? Have you work your tractor any more since your last post?


----------



## TTr (Feb 8, 2014)

I have not used it since my previous post. The last two times that it snowed, I did not use the tractor. The snow was only an inch or two and the weather was warm and the snow melted during the day. I will give another update if I use it again or in the spring. I have a feeling that we will go from plowing to mowing very soon and very quickly.


----------



## Fluid (Nov 28, 2013)

OK I was just wondering. Yea lets hope your feelings are right about spring. I've had enough of winter myself. Thanks for the update and think spring.


----------

