How do I know if I have Muncie M20 or M21?

If you examine the 1966-’70 wide-ratio M20 input shaft, there are two grooves cut amid the 10 splines. From left to right are the three basic Muncie input shaft/countershaft combinations. On the left is the M20 countershaft and 10-spline input shaft. In the middle is the M21 countershaft and input shaft.

How do I identify my Muncie 4 speed?

Another way to confirm that the transmission is original to your car is most Muncie four-speed transmissions will have a Vehicle Identification Number (VIN) number stamped on the main case. The engine and transmission were stamped at the same time by the final assembly plant.

How do I identify my Muncie M22?

Look for the “GM” sign imprinted on the transmission box to identify the manufacturer of the transmission. Check whether there are any rings around the shaft splines. An M-22 “Rock Crusher” has no rings, so if you see rings in your transmission, it means it is not an M-22 “Rock Crusher.”

What is the difference between M20 and M21 gearbox?

An M21 has a taller first and third gear than the M20. M21 was predominantly behind a 308 and M20 behindA 253.

How do I identify my old GM transmission?

The easiest method of GM automatic transmission identification is to examine the transmission pan. New transmission designs came with new, unique pan shapes, and the general shape of the pan often paints a fairly clear picture of which automatic transmission you are dealing with.

How much horsepower can a M22 Rock Crusher handle?

With the proper rear end gear a new M22 can handle close to 700HP!

How can you tell the difference between M20 and M21 gearbox?

The only differences between an M20 gearset and the M21 gearset are the input gear and the cluster, as previously stated. The input and cluster have to be matched. So you can tell the difference by counting the teeth on the input or the cluster gear that engages the input. M21 input = 26 teeth.

How much torque can a Muncie M20 handle?

The muncies have better cases & handle up to 500-600 lbs-ft of torque. I know my muncie m20 & my friend’s m20 handle our cars at over 500 lbs-ft of torque.