CY & CX 400THM: differences & similarities

[copo-2]

<span style="font-weight: bold"> </span> Concerning the CY transmissions that came in the Gibb Nova's, there was a special bulletin sent out to GM dealerships dated July 12, 1968. It reads:

NEW HEAVY DUTY TURBO HYDRA-MATIC TRANSMISSION

A new heavy duty or &quot;high speed&quot; version of the Turbo Hydra-Matic transmission will be available with the 425 HP 427 V-8 for Chevrolet models, the 396 375 HP Chevelle, Camaro, Chevy ll's and the 430 and 435 HP V-8 Corvette's. Previously pnly manual transmissions were available with these engines. The new transmissionincludes modifications to accept the greater engine torque, higher RPM, and generally more rigorous operation anticipated with these high output engines.

To accomodate engine speeds up to 7800 RPM, 1600 RPM higher than normal operationg speeds, a special torque converter assembly is used, with all pump and turbine blades welded rather crimped in place. The converter assembly is bolted to the engine flywheel at six points, double the number of the standard unit.

Because of the higher torque loads experienced during hard acceleration, premimum quality driven plate facings are used in the intermediate clutch, which is applied to accompolish the 1-2 upshift. Firmer upshifts are obtained through modifications to the accumulators in the itermediate 1-2 and direct 2-3 clutch apply circuits to reduce cushioning action. Gover calibrations are also revised to raise the maximum upshift point from 5100 to 6300 RPM.

All other design details, including converter ratio and gear ratios, are common with the Turbo Hydra-Matic use with regular high displacement engines.