Crack in Trans Case

[lynnmor 7,356]

I have a 1997 520H that developed a crack in the left side transmission case.  My theory is that the weight box, with about 100lb inside, puts a lot of torque on the square ends of the axle housing.  If the top case bolt holds well and the bottom bolt allows a small amount of movement, the case will be pulled torn apart.  Look at the photo showing the entire case and imagine a large wrench torquing the square.  That's my theory till someone can come up with a better idea.  Anyway, I won't be using much weight in the box from now on.

 

 

Edited December 15, 2016 by lynnmor

[daveoman1966 3,762]

I have that same case side for sale from a 1996 520-H if you want it.  I am about 40 miles south of Erie PA at zip 16433.

For details, send an email to me at:

daveoman@windstream.net

 

or call 814-763-5700 after 11am any day.

 

 

[ACman 7,621]

 is the bomb...15 minutes and already have parts located and offered up .

[lynnmor 7,356]

Thanks for the offer, but I got one from a member thru the Wanted Classifieds.  The full photo shows the new case being installed.

[doc724 925]

It is hard to tell from your picture exactly where the crack is located.  Cast iron rarely fails in compression.  It does fail in tension.  A bending or torsional load can cause failure and having 100 pounds does place a torsional load on the axle square axle ends.  Your theory seems sound but I am hard pressed to accept that the weight alone caused the crack.  To me, the root cause was the loose bottom bolt.  This allowed the case to flex (bend) upward under the combined weight of the operator, tractor itself, and the weight box.  A little hard to explain in words, but maybe a simpler explanation is that the left side is like half a clam shell, fixed at the top by the bolt.  The load of operator, tractor and weight box pushes down on the on case and the reaction force from the ground pushes up on the the left axle and wants to pry the clam open.  Since the top of the "clam" is fixed, something has to give.  It has probably been going on for a long time and  every little bump you hit caused flex and eventually a crack started. 

 

Thanks for sharing.  It is a good lesson to us all, check to make sure all bolts are tight!

[lynnmor 7,356]

It is hard to see the crack on the outside, rear view.  It is between the half-moon in the LH casting and the top of the paint scuff on the RH casting.

 

The bolts were not loose, but maybe they could have been tighter.  The weight box hanging well behind the axle would put quite a twist on the axle housing.  Add the fact that going over rough terrain will add even more stress.