Muncie 4 Speed Decoding

sftibbs · September 30, 2009, 04:21:42 PM

My 4 speed Muncie is stamped with my VIN # so I know it matches my 69 Camaro. However the tranny code is P9S27A. Decoded, it tells me it was a M20 built on November, 27 1969. The problem is my car was built in January 1969. Can anyone help with the disparity? Thanks.

1968RSZ28 · September 30, 2009, 05:18:17 PM

Quote from: sftibbs on September 30, 2009, 04:21:42 PM
My 4 speed Muncie is stamped with my VIN # so I know it matches my 69 Camaro. However the tranny code is P9S27A. Decoded, it tells me it was a M20 built on November, 27 1969. The problem is my car was built in January 1969. Can anyone help with the disparity? Thanks.

The 9 in your transmission assembly code refers to the model year, not the calendar year, so your transmission was assembled on November 27, 1968.

Paul

sftibbs · September 30, 2009, 07:42:39 PM

That makes sense. Thanks for the clarification.

Steve

Gramps69Z · September 30, 2009, 10:29:39 PM

Check out this link. http://www.camaros.org/drivetrain.shtml#trans

sftibbs · October 01, 2009, 05:14:02 PM

Perfect. I was able to decode the Muncie. Thanks for the link.

KurtS · October 01, 2009, 08:00:21 PM

So, what your car? SS, Z, or LM1?

sftibbs · October 01, 2009, 09:22:48 PM

It's an SS 350...very original and straight, which is good for my first restoration. Also has the fold down rear seat which was a rare option. I was hoping it was outfitted with the M21 but it came with the M20.

KurtS · October 02, 2009, 09:16:27 PM

The M21 was never available with a SS350, the M20 was the only 4 speed available.
http://www.camaros.org/diffs69.shtml

sftibbs · October 05, 2009, 05:19:16 AM

Okay, thanks. What's the difference in the two as far as what they were built to do?

Stingr69 · October 05, 2009, 06:22:55 AM

The M20 and M21 refer to the internal gear ratios, more specificaly the ratio spread. The M20 is a wide ratio and the M21 is the narrow ratio. Both transmissions have the same 1:1 4th gear but the M21 has the ratios set up so the RPMs do not drop as much when you shift gears as compared to the wide ratio M20. If you have a torquey engine with power over a wide range the M20 is preferred. If you have a more high strung, high RPM powered car, the M21 was preferred. Speaking in general.

-Mark.

william · October 05, 2009, 12:47:03 PM

For crusin' the wide is preferred due to the 2.52:1 1st gear. A Z/28 with a wide ratio and 3.73s has a total 1st gear of 9.40; with a close ratio it is 8.20. A friend built his '68 Z/28 with the one year only 2.56 1st Muncie.

The shift into 4th with a wide seems like a 40 mph headwind though...

sftibbs · October 05, 2009, 04:27:34 PM

Good information...thanks.

RAfbody · October 05, 2009, 07:01:15 PM

Quote from: KurtS on October 01, 2009, 08:00:21 PM
So, what your car? SS, Z, or LM1?

I may be wrong but I didn't think the LM1 could get a Muncie 4 speed.

1968RSZ28 · October 05, 2009, 07:38:10 PM

Quote from: RAfbody on October 05, 2009, 07:01:15 PM
I may be wrong but I didn't think the LM1 could get a Muncie 4 speed.

Russ -

You're right about being wrong!

You could get a Muncie 4-speed with the LM1; read this...

http://www.camaros.org/lm1.shtml#drivetrain

Paul

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Muncie 4 Speed Decoding