quote:Originally posted by GT4Peter:
The problem is : what happens when it fail?
The zf specialist said that I should change it.
He have build some zf for the m1 and this will fail in about 5000 km .
Does someone know what happens when the pinion break ?
Thanks
I would say, "bada boom, BIG BADA BOOM".
As Boss Wrech said, it will probably destroy the case also, BUT it MIGHT NOT fail. Maybe?
You HAVE TO look at the contact patterns on both the ring and the pinion. That will show you where they make contact. That is the stressed area.
If there is no contact at that "imperfection point" there is no loading on it.
Steel crankshafts get wrecked all the time and a large portion of the time they can be ground down to take the imperfection out.
My concern would be that the hardened surface of the steel could continue to separate itself from the softer layers inside and will act like the grains of wood separating in layers.
Like plywood that gets wet and the layers of the veneers start separating. Super hardened steel can do that also.
The steel won't peel off like wood veneer would but it will flake off probably .015 or .020" deep about the size that you already have with material missing.
The real problem is that at this level you really need to use some kind of an examination system like magnaflux or I think zyglow is similar to look for patterns in the surface of the steel. It will look a lot like glass cracking in a random pattern.
Then those parts become at best paper weights on the work bench. The temper of the metal is just done at that point.
The experts are not wrong. They simply can not tell the nature of the imperfection and presume the worst case scenario.
The cost is relative here. Here you are wagering a $3000 ring and pinion vs. a $12,000 transmission.
I actually discovered a very inexpensive way of checking for cracks purely by accident. You take the real heavy duty wheel cleaner that smells like battery acid and smarts you eyes.
You squirt the stuff on the polished surface of the part you are "cleaning" and let it sit for about 15 minutes.
Then you hose it off with fresh water.
IF there is a crack in the STEEL, (works on iron too) the part will separate right in front of your eyes and create a fisher like we would see in a glacier.
Works every time.