Re: Twin Ultramatic Problem

Posted by Peter Packard On 2012/9/9 3:14:19

When you are in D, it starts out on the low range band. Does your slippage occur after the trans shifts to the high range clutch. The difference between H and D is that H starts off with the high range clutch. Worn bushes on the front pump or wear on the high range clutch input shaft will directly affect the pressure available to the high range clutch piston and direct drive clutch piston (The direct drive clutch and high range clutch pistons, upon Governor operation, are fed from the rear pump but use the same front pump bushings to enter the shaft to pressurise the High range and Direct drive clutches). It doesn't take much wear either, around 10 thou is very noticeable.
Using a higher viscosity trans fluid should improve the high range and direct drive clutch pressure, but will almost certainly alter the operation and characteristics of various shuttle and differential pressure valves in the valve bodies. In other words ......It may not be all good news, but probably worth a try. PT.