C4 Transmission Performance Rebuild - Automatic Authority
| Quick Reference Guide to C4 V-8 Bellhousings | | Model Year | Casting Number/Ford Part Number | Specifics | | ’64 | C4AP-7976-A and C4AZ-7976-A | Five-bolt bellhousing, 160-tooth flexplate, two-bolt starter, 221, 260, 289 V-8 | | ’65-’69 | C5OP-7976-A and C5OZ-7976-A | Six-bolt bellhousing, 157-tooth flexplate, two-bolt starter, 289 and 302 V-8 | | ’72-and-later | D2OP-7976-AA and D2OZ-7976-B | Six-bolt bellhousing, 157-tooth flexplate, case-fill dipstick, two-bolt starter, 302 V-8, cable kickdown | | ’73-and-later | D3BP-7976-AA and D3BZ-7976-A | Six-bolt bellhousing, 164-tooth flexplate, pan-fill dipstick, two-bolt starter, 302, and 351 V-8 | | ’75-’78 | D5ZP-7976-A and D5ZZ-7976-A | Six-bolt bellhousing, 157-tooth flexplate, small torque converter for Mustang II only, case-fill dipstick, two-bolt starter, 302 V-8 | | ’76-’79 | D6TP-7976-AA | Six-bolt bellhousing, 164-tooth flexplate, truck only, pan-fill dipstick, two-bolt starter, 302 and 351 V-8 | | ’77-and-later | D9AP-7976-AA | Six-bolt bellhousing, 157-tooth flexplate, case-fill dipstick, cable kickdown, two-bolt starter, 255, 302, 350 V-8 | | ’77-and-later | D7BP-7976-AA and D7BZ-7976-A | Six-bolt bellhousing, 157-tooth flexplate, case-fill dipstick, two-bolt starter, 255, 302, and 351 V-8 | | ’78-and-later | D7DP-7976-AA and D8OZ-7976-B | Six-bolt bellhousing, 157-tooth flexplate, case-fill dipstick, two-bolt starter, cable kickdown, 255, 302, and 351 V-8 | | ’79-and-later | D9AP-7976-BA | Six-bolt bellhousing, 157-tooth flexplate, pan-fill dipstick, cable kickdown, two-bolt starter, 255, 302, and 351 V-8 | | ’79-up | D9AP-7976-AA | Six-bolt bellhousing, 157-tooth flexplate, case-fill dipstick, cable kickdown, two-bolt starter, 255, 302, and 351 V-8 | | ’82-up | E2TP-7976-AA and E2TZ-7976-A | Six-bolt bellhousing, 164-tooth flexplate, trucks only, pan-fill dipstick, two-bolt starter, cable kickdown, 255, 302, and 351 V-8 | | ’75-up | D5OP-7976-BA and D5OZ-7976-A | For 351M and 400M with big-block bellhousing bolt pattern | 
There are so many types, C4 bellhousing identification will drive you nuts. Always check casting numbers and the number of bellhousing-to-engine bolt holes just for starters. Check depth, which determines whether you have a 157-tooth or 164-tooth flexplate bellhousing. Ascertain whether the bellhousing is a pump mount or transmission main-casting mount. They will not interchange. | 
Shift improvement kits from B&M Racing & Performance make a difference in how your C4 shifts. Count on a firmer shift, which is important to both performance and reliability. Soft shifts mean excessive clutch and band wear. | 
Firm shifts come from solid clutch and band engagement. The type of fluid you use also determines shift quality. B&M's Trick Shift automatic transmission fluid has a friction modifier designed to improve clutch and band engagement. | 
This is the sprag clutch, also known as a one-way clutch. Throw your Ford sprag away, and opt for one from either Mike's Transmission or B&M. Shown here is one from Mike's Transmission, a spring/roller design engineered not to fail. | 
Deep sump pans are nothing but good for automatic transmissions. A deep cast-aluminum sump, shown here with a filter-extension feature (mandatory for fluid pick-up), cools fluid better and gives the C4 greater capacity. If racing, a deep pan and a cooler are vital, and for heavy-duty street use, you can't lose because cooler fluid temperatures enhance transmission service life. Average temperature is around 250-300 degrees. When temperatures become higher than this, transmission life shortens quickly. | 
Another item that stumps enthusiasts is the governor on the tailshaft. The governor reads the transmission-shaft speed, which determines upshift and downshift points. Always check the governor piston for freedom of movement and the spring for integrity. These items must work. |
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