Muncie Four Speed Transmission Makeover Part 2 - Pontiac Tech

He follows with the First-gear synchronizer-block ring and First gear. Lightweight engine oil is used for lubrication.

Here's an exploded view from the 1971 Pontiac Service Manual of the Muncie four-speed trans to show you where all the parts go.

Carson installs the rear bearing retainer, but not before he taps a new rear bearing in place using a 1 5/8-inch diameter pipe. He spreads the front snap ring, sliding it over the rear of the mainshaft and fully seating it against First gear. Carson then chooses from the assortment of available rear-bearing retainer snap rings, the one that reduces clearance between the snap ring and rear bearing face to a maximum of 0.005 inch. This limits mainshaft endplay when under load, much like an engine's thrust bearing.

Third gear and the Third-and-Fourth gear synchronizer clutch assembly and snap ring follow. He sets the completed mainshaft assembly aside while the main case is attended to.

A liberal amount of heavy bearing grease is used by Carson to retain the countershaft gear's roller bearings and bearing washers. This procedure includes loading a 0.050-inch washer in one end, followed by a row of 28 roller bearings, another washer, 28 more roller bearings, and the last washer.

He performs the same steps on the countershaft's opposite end until a total of 112 roller bearings are installed.

Carson sets the countershaft gear and thrust washers into the main case. Here, he gently presses the countershaft pin into the case from the rear.

The pin should be flush with the front of the case, and its stepped portion should face downward to clear the rear bearing support. countershaft gear endplay should be checked with a dial indicator if old thrust washers are reused, and it shouldn't exceed 0.025 inch.

As shown here in this diagram from the Service Manual, heavy bearing grease is used to retain 17 new roller bearings and a retaining cage into the main Drive gear cavity before installing the unit onto the nose of the mainshaft.

Carson installs a new gasket onto the front of the rear bearing support, places the Fourth gear synchronizing ring on the main Drive gear, slides the 3-4 synchronizing clutch sleeve forward into the fourth speed detent position, and inserts the entire mainshaft assembly into the main case positions the main bearing retainer so that the guide pin in it aligns with the hole in the case, and taps it into place.

With the unit loosely assembled, he installs the front Reverse idler gear, its tanged thrust-washer into the main case, and inserts the rear Reverse idler gear through the rear bearing support.