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General Specifications and Cost

The Spec 25 transmission is based on our replacement line of Muncie "M22" style 4 speed transmissions. It comes only with a GM style 1.125" diameter by 26 spline input shaft. The output shaft is 32 spline. The main uses the standard General Motors bolt pattern found in all Muncie, Super T10, Saganaw, and GM T5 transmissions. The sealed front bearing retainer has an outside diameter of 4.680". This is the standard GM retainer dimension. All transmissions come with a alloy vent and rollerized 1st speed gear, thrust button case and modular counter gear. Ratios are also available and sanctioned for SCCA A-SEDAN class. Call for A-SEDAN applications. You can order a Spec-25 with a 27 spline output shaft.

Lead time and Cost:
Average lead time is 3 weeks and cost is $2995.00 Price is direct to you. The Spec-25 is not sold through dealers.

Ordering Information:
Call us at 561-743-5600 or email us at support@5speeds.comVisit our direct Muncie portal at

Synchro Assemblies:
The synchronizer hubs are nitride hardened. Synchro blocking rings are forged bronze rings and fitted to each gear. Sliders and hubs are fitted for anti rocking. Light weight sliders are used with investment cast steel shift forks.

All gears use the standard M22 style semi helical configuration. They are deburred, shot peened and then processed using the Mikronite system. They are of 8620 alloy which is optimized for strength and wear. 1st gear is rollerized and uses a 20 degree pitch angle, which is much larger then the standard M22 pitch.  The countergear section is modular and the stub section that drives first and second gear is made of 9310 alloy.

Mainshaft is rifle drilled to reduce rotating mass. Both 27 spline or 32 spline outputs have this procedure done.


Filtered vent shown.

Shifter Shafts:
Linkage arms fasten to the shifter shafts with grade 8 5/16-24 bolts and unit comes with adpater clips for later style Muncie Arms. The 5/16 bolt allows for direct compatibility and replacement of Super T10 Transmissions. Shifter shafts are tig welded.

All hardware is Grade 8. Fill and drain plugs are drilled for safety wire. Transmission comes with a new speedometer fitting or can be blocked off.

Gear Ratios:
The Spec-25 is offered in 2 different ratio sets
Model Type Ratios
S25 2.20 1.64 1.28 1.00
S25X 2.20 1.51 1.17 1.00

SPEC-25 in a Corvette Grand Sport