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 An exploded view like this,...  An exploded view like this, found in the 1971 Pontiac Service Manual (as well as other years), can be a great asset when rebuilding a manual transmission. Not only does it contain proper orientation of all the parts within the unit, but it also provides correct terminology for each component. |
 Brian Carson found this M20...  Brian Carson found this M20 Muncie transmission and, after determining that its input and output shafts turned freely, and after removing the side case cover to inspect for major internal damage, he handed over $200 and walked away with the perfect manual transmission for his Pontiac project. Having the required tools on-hand and a hydraulic press available, he was able to perform a complete rebuild in one day. |
As reliable and consistent as automatic transmissions are, the novelty of selecting gears on your own is one of the reasons manual transmissions remain in vogue with hobbyists. Units from Muncie and Borg Warner were commonly found in Pontiac applications during the '60s and '70s, and, though modern Overdrive manual transmissions are quite popular today, there remain a large number of owners who prefer an original four-speed to an aftermarket unit. This is especially true of restoration projects, where the coding and VINs found on many transmissions are important to the value of a numbers-matching Pontiac.
Richmond Gear currently produces new Super T-10s, and enough Muncie components are presently available from the aftermarket to essentially build a new unit. There are also a fair amount of manual transmissions in usable condition that are completely adequate for most combinations and, with a proper rebuild, can provide many miles of trouble-free performance.
Hobbyist Brian Carson had considered the different transmission options for his Pontiac. Though matching numbers was not a concern for his project, he still wanted a rebuildable, original-style unit. He was lucky enough to locate an M20 Muncie four-speed from a '69 A-body at a reasonable price. It seemed the perfect candidate for his project, so he purchased it with the intent of complete disassembly and a proper rebuild using a $110 kit. Follow along in our two-part story as he completes the process in one day. Part I will cover teardown and Part II the assembly of the transmission with new parts.
Required Tools
A wide array of hand tools is necessary when rebuilding a manual transmission. While many hobbyists already own a majority of these tools, most don't have the required equipment readily available to pull or press components on or off. That portion of the rebuild can be outsourced to a suitable shop, but by simply asking around you might find a local hobbyist or club member with the professional-type equipment required to complete the task. So before spending your hard-earned cash on tools or equipment that you'll use only once, a little prior coordination can not only reduce rebuild time, but can leave more cash in your pocket for the next project, too!
SAE wrench or socket set Various flat-blade screwdrivers or prybars Soft-face mallet Standard hammer Gasket scraper 3/16-inch diameter punch Hydraulic press A length of 1 3/4-inch diameter steel pipe A length of 1 5/8-inch diameter steel pipe 3/4-inch diameter steel dowel Bearing driver set Bearing separator tool Snap-ring pliers, external, notched-tip Clutch gear bearing retainer tool