Cracked bearing carrier on main input shaft
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Texasmark
Elite Member
- Joined
- Apr 24, 2012
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- Tractor
- Ford: '88 3910 Series II, '80 3600, '65 3000; '07 6530C Branson with FEL, 2020 LS MT225S. Case-IH 395 and 895 with cab. All Diesels
I can't locate the crack in the second photo. Is it in the same place? I'm guessing it would be as that appears to be where the material is the thinnest even though they put a bulge in the casting to help overcome the slot.
The left side doesn't look all that thick. Without 360 degrees of support one wonders how long it will be before the left side cracks also and the whole shebang fails. I know cast metals will fail under repeated impacts but this is smooth-fairly constant radial stress which isn't the same critter.
Questions that would be nice to know would be how many hours are on both housings and when did each crack. Knowing that might provide your answer.
I did a www search on "yield pressures for cast iron" and came upon at least one interesting article: http://fulltorque.com/pdf/GMRC white paper.pdf
Might want to read it. One thing it did point out that I suspected was stresses on the casting were relieved in the crack. On your application, with stresses relieved and the radial stresses on what's left not exceeding the yield point of the remaining bracket you may be good to go.
Tough call.
Edit: Surely you have heard of "green castings" and stresses associated. The mentality here is that a "seasoned" casting usually has the stresses stabilized whereas the green casting has to go through the "sweat". I think your answer is in finding the yield point of cast iron and once you have that number, try to find out what the lateral stresses are on the bracket caused by the gears interfacing and pushing away from each other. Being on the input shaft to the tranny, you have no reduction so if your tractor is putting out 123 ft lbs of torque at the flywheel at WOT then surely not more than 10% of that would be in lateral stress and removing the feet you have lbs of force pushing against the casting.
I don't have the number in front of me but suppose your tractor engine is rated 100 ft-lbs of torque on a dyno. at rated rpms. With no feet and pushing on one square inch of casting, taking 10% would be 10 psi of force. Sounds like a no brainer. Even if it were the whole 100 on 1 square inch you are still at 100 psi. On the same Google site I found another entry and it talked about Grey Iron, Class 20 as an example at 20,000 psi yield strength. So one can assume that a Class 1 will be at least 1000 psi.
The more I mull over this the more comfortable "I" would be with moving right along with your repair and to not worry about it. Besides if you were to tear one up you have the other as a backup to decide what you want to do.
Best I can do,
Mark
The left side doesn't look all that thick. Without 360 degrees of support one wonders how long it will be before the left side cracks also and the whole shebang fails. I know cast metals will fail under repeated impacts but this is smooth-fairly constant radial stress which isn't the same critter.
Questions that would be nice to know would be how many hours are on both housings and when did each crack. Knowing that might provide your answer.
I did a www search on "yield pressures for cast iron" and came upon at least one interesting article: http://fulltorque.com/pdf/GMRC white paper.pdf
Might want to read it. One thing it did point out that I suspected was stresses on the casting were relieved in the crack. On your application, with stresses relieved and the radial stresses on what's left not exceeding the yield point of the remaining bracket you may be good to go.
Tough call.
Edit: Surely you have heard of "green castings" and stresses associated. The mentality here is that a "seasoned" casting usually has the stresses stabilized whereas the green casting has to go through the "sweat". I think your answer is in finding the yield point of cast iron and once you have that number, try to find out what the lateral stresses are on the bracket caused by the gears interfacing and pushing away from each other. Being on the input shaft to the tranny, you have no reduction so if your tractor is putting out 123 ft lbs of torque at the flywheel at WOT then surely not more than 10% of that would be in lateral stress and removing the feet you have lbs of force pushing against the casting.
I don't have the number in front of me but suppose your tractor engine is rated 100 ft-lbs of torque on a dyno. at rated rpms. With no feet and pushing on one square inch of casting, taking 10% would be 10 psi of force. Sounds like a no brainer. Even if it were the whole 100 on 1 square inch you are still at 100 psi. On the same Google site I found another entry and it talked about Grey Iron, Class 20 as an example at 20,000 psi yield strength. So one can assume that a Class 1 will be at least 1000 psi.
The more I mull over this the more comfortable "I" would be with moving right along with your repair and to not worry about it. Besides if you were to tear one up you have the other as a backup to decide what you want to do.
Best I can do,
Mark
Last edited:
Both housings have the same crack in exactly the same location, the service shop doing the repairs tell me they do mot want to install. I said its a stress crack use the better of the two housings and put it back together. The first housing the multi-power exploded and took out a few other gears, therefore another was picked up to do a complete swap. Im just trying to get a common reply as to use and chance it or waste more $$ and find another housing not cracked at all.
I would not replace a damaged part with another damaged part. I would look for a new or pristine used housing. Think about this, the shop puts it back together and the first time you try to use it breaks and does extensive damage, who are you going to blame, yourself or the shop? Who will have to pay labor twice, you or the shop?
I think the shop is trying to prevent your making a bad decision. Repair shops I frequent would not reassemble without someone signing they have been told a serious problem existed and damage was going to occur when reassembled and used. Most repair facilities have been burned before by doing such and have gotten wise.
Texasmark
Elite Member
- Joined
- Apr 24, 2012
- Messages
- 3,703
- Location
- N. Texas
- Tractor
- Ford: '88 3910 Series II, '80 3600, '65 3000; '07 6530C Branson with FEL, 2020 LS MT225S. Case-IH 395 and 895 with cab. All Diesels
Based upon what I see and the analysis I have attempted, I wouldn't have a problem signing off on fixing what they have there. Like I said, who knows how long it has been cracked? Who knows how long the second has been cracked? Who knows how many thousands of them are out in the field working daily with cracks? How has a crack in another unit contributed to a verifiable failure?
I ran the numbers and I would chance it. Odds are in his favor. But forget it. Just go out and buy a new tractor!!!!!!!!!!!!! You can chance a new tractor. At least it's in warranty with it's "green" castings. And while you are paying the monthly installment you can lavish in the comfort of the warranty and how you did the right thing.
Just like when I go to the doctor. He says bla bla bla. I say, it's my body and my money. You are the hired help. Thanks for your opinion but the choice is mine and I will sign off on that if it bothers you!
Two main subjects are Cholesterol and Prostate cancer. I tell them I couldn't care less about either. We move on. My body, my decision. His tractor his decision.
Mark