Volume III, Issue 11, Page 14

Parts guide, identification, sources

Though the notion seems simple enough—take one transmission out and replace it with another of a similar nature, albeit electronically controlled—all is never what it appears to be. Will the bellhousing attachment holes correspond with the ones on the back of the block? Will the driveshaft bolt back in? Will the crossmember accommodate? What about the cooling lines? Will the driveshaft yoke fit? Is the hardware compatible? Before you begin, seriously consider using new fasteners for the project that are available from any GM dealer or aftermarket source.

GM used two types of torque converter-to-flexplate fasteners. Black bolt (left) is metric (10-mm x 14.3 x 1.5-inch) with corresponding nut. Gold bolt (right) is standard GM (3/8 x ½ x 16 coarse)    

Thread size for all cooling lines in all GM transmissions are identical (5/16 x ¼ pipe thread). During 1973-74 model year GM enlarged the head of the fitting to discourage rounding-off corners that render them useless. Large head version (left) was used on TH350, TH400, 700R4, 4L60 through ’96. Thereafter, the fittings were converted to a snap-in type connector.