Some expressed their doubts about me not using a hardened 300m shaft on my trans repairs. Here is Alan Brown of DirtyDog Performance explaining why the 300m hardened stub shaft is not the way to go vs. his hardened direct drum and oem shaft:
"The problem is caused by bind up not power, The 300m stub shaft will just cause the drum to twist on a stock drum. That does way more damage. If you notice the drum twisted with the shaft. By hardening the drum the shaft becomes stronger as the drum prevents it from twisting as easy. At that point the shaft becomes a fuse because if you use the 300m unit you will strip the back of the forward drum out, or the forward hub or the direct hub. Whichever has the most wear at that point A broken shaft is a cheap easy fix, the rest of the problems are not. The only real answer is to prevent the problem that causes it. Clutch slippage on shift is better than parts breakage.
Low line pressure can delay the shift timing and increase these failures. This can be caused by a worn pressure regulator valve and/or a worn pressure control solenoid. The general rule to prevent the problem in a good transmission is never play in overdrive. If you are going to be hard on it always turn off overdrive and wait for the downshift before doing so.
We can go all out use a 300m shaft and a 300m drum, but you’ll still break one of the other components when the problem occurs and in most cases those will not only make the car not move at all, cost way more to fix and contaminate the entire transmission, torque converter and cooler. When the stub shaft breaks you still have first second and reverse, the problem stays contained well and can be fixed for under $50 in parts."
"The problem is caused by bind up not power, The 300m stub shaft will just cause the drum to twist on a stock drum. That does way more damage. If you notice the drum twisted with the shaft. By hardening the drum the shaft becomes stronger as the drum prevents it from twisting as easy. At that point the shaft becomes a fuse because if you use the 300m unit you will strip the back of the forward drum out, or the forward hub or the direct hub. Whichever has the most wear at that point A broken shaft is a cheap easy fix, the rest of the problems are not. The only real answer is to prevent the problem that causes it. Clutch slippage on shift is better than parts breakage.
Low line pressure can delay the shift timing and increase these failures. This can be caused by a worn pressure regulator valve and/or a worn pressure control solenoid. The general rule to prevent the problem in a good transmission is never play in overdrive. If you are going to be hard on it always turn off overdrive and wait for the downshift before doing so.
We can go all out use a 300m shaft and a 300m drum, but you’ll still break one of the other components when the problem occurs and in most cases those will not only make the car not move at all, cost way more to fix and contaminate the entire transmission, torque converter and cooler. When the stub shaft breaks you still have first second and reverse, the problem stays contained well and can be fixed for under $50 in parts."
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