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Cleaning out my shed found a tranny. looks to be a 4 speed. Came across the following #'s
tailshaft 3857584
housing 3925660
shifting plate 3884685
Anyone know what this is ?

I'm pretty sure that's a Saginaw 4 speed, but check the shift arm locations to be sure. Saginaws have the reverse shifter in the side cover, and muncies have it in the tail housing.
T-10's have T-10 cast in the main housing somewhere.

Thanks. The reverse shifter is in the tail so i will assume it is a muncie.

Does it have a groove or two in the input shaft? That will tell you your ratios.

BW T-10's also have the reverse shifter shaft on the tail housing. I believe the Muncie has 7 bolts on the side cover,the T-10 about 9 or 10. Muncies are all aluminum,all have the traditional GM manual bolt pattern and are 21 inches long from the front of the case to the tip of the tailhousing.Maybe some Vette Muncies had the speedo gear on the right side? Some T-10's are all aluminum, some are cast iron.There is only 2 basic ratios for the Muncie, a 2.20 and 2.50 something first gear.T-10's came in a variety of ratios and bolt patterns.

Transmission Ratios

Muncie 4 Speed

1st 2nd 3rd 4th
No Lines 2.56 1.91 1.48 1
1 Line 2.2 1.64 1.28 1
2 Lines 2.52 1.88 1.46 1

Second Design T-10 (Super T-10)

1st 2nd 3rd 4th
2 Lines 2.43 1.61 1.23 1
3 Lines 2.64 1.75 1.33 1
5 Lines 3.42 2.28 1.46 1
6 Lines 2.88 1.91 1.33 1

AFAIK, Muncie and Saggie boxes have speedo gear on the driver's side. T-10 is on Pass. side, IIRC.
M-20 and M-21 Muncies use the same driveshaft yoke as Saggie box and TH-350.
M-22 uses a yoke from a TH-400 (one that is the same size, it's larger than the others).

At one time, I have owned one each of ALL of these tranny's........the T-10 I had I bought with a broken "ear" (common problem). I welded it back on and sold it..........I just had to have an M-22............ :rolleyes:

Saggy boxes die easily if not driven judiciously.........at that time I did NOT drive with prudence and many $40 transmissions died....

Couldn't kill the M-22 and I sold it for 3 times what I paid for it .

I thought only the M-22 rockcrusher Muncie was aluminum, and the M21 and M20 were cast iron?

248, good info,I believe the first first T-10 design were 2.20 and 2.54 ratios in GM cars and 2.36 in Fomocos. My experience with Saginaws behind 300 hp or less and not drag raced with slicks was they hold up ok.The front bearing wear is a mantenance problem when driven hard.As a young man I had no problem tearing the cluster teeth off a Muncie in my 327-300 Impala,and later twisted a main shaft in a reasonably stock 396-375 Chevelle with tires.I was really brutal,blew 7 trannys in as many months in my first car,a 56 Fomoco.One time busted the tranny, tore off the clutch disc facing and the rear end spider gears all at the same time.
So maybe I'm not the best guy to get tranny info from
Four, all the Muncie's I ever saw were aluminum.M-21 etc is an option code, Saginaws 4spds also carried those numbers.

Hey can anyone take a look at the one I have on my page?
it is on the my new truck set of pics and the second page there is a pic called trans.

What could it be?
Thanks,
Sean

Deep, that's a Muncie 3 spd, used by Chevy from 55-64 on their cars and trucks.It's very similar in design to the earlier 3 spds used on torque tube models.Your's has a rear mount so it's most likely from a 58 and up car.They all have the same 2.94 first ratio, except for the rare close ratio version with a 2.50 ish first gear.

Thanks for all the help. Transmission is aluminum and has seven bolts on the side cover. I didn't see any groves on the shaft. I'll check again tonite.