Frictions:
Doug Nash Overdrives were produced with two types of clutches or frictions. Corvettes with overdrives built in 1983 to late 1985 had solid frictions. Units manufactured for 1986 to 1988 had "waffled" frictions. Early overdrives had 5 direct and 4 overdrive solid frictions. Late overdrives had 6 direct and 5 overdrive waffled frictions. Apparently the engineers felt that by adding the oil grooves it would improve clutch life. The added oil grooves or waffles may have improved lube to the clutches but it reduced surface area or holding power by 14 percent. They added an extra clutch for direct and overdrive to compensate for the loss or surface area.

We found that the older units never burned up unless a mechanical problem caused excessive clearance and allowed the clutches to loose their stack height. We recommend building the units with the later amount of clutches but with the older style. This yields maximum holding power and high reliability. We stock older style solid frictions which are no longer available from GM.

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