OK:
S.C. - I have three Muncie 4-speeds in three different vehicles. The speedometer driven gear in two are the same, but neither of them will work in the third. It appears that I need a larger driven gear in this one as the others do not mesh with the drive gear. I bought these transmissions used and do not know what year they are or what they came in. Does anyone know if certain year Muncies took a different gear?
H50 - The Muncie gears interchange with all Chevrolet-built transmissions, and this includes all GM manuals, Powerglides, THM350's, and THM200's found behind Chevrolet engines. The speedometer gear will have 17 to 25 teeth, and the gear on the output shaft will have 7 to 10 teeth. This gear set is common on Chevrolet manual transmissions and THM350's, but the THM350 output shaft gear along with Saginaw 3 and 4 speeds, Powerglides, and THM200's use a plastic gear retained with a clip. My Muncie M20 has a steel gear, which is pressed onto the output shaft, and early Muncies are common for the steel output shaft gear. Later Muncies will have the plastic gear, possibly those manufactured after 1970. The speedometer gear is common with the 7 or 10 tooth output shaft gear, and I have seen these on THM350's. There was a chart that was published in the October 1989 issue of Super Chevy, and they listed the gears and the ratios together.
P.B. - It might be a good idea to remove the tailhousing and inspect the drive gear. If it is attached with a clip, then the clip could be broken. That was the problem in my M21.
.B,.T. - I always thought all the driven gears were the same, even the ones in the automatics could be used in the Muncies.
R.C. - I think that the older Muncies (pre '66 or 67) were different. I had this same problem after switching tailstocks once. Also, there will be different gears for the same transmission depending on the rear axle ratio.
Archivist: Tom Wilson
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