Re: Twin Ultramatic Shifting

Posted by Peter Packard On 2008/5/27 6:11:39

G'day all, especially Hotrod. Sorry to have come in so late in this thread. I would suggest that Randy's advice about a possible sticking valve is very probable. I would also suggest that you check your throttle linkage adjustment. This is particularly important because your accelerator position has a huge effect on when the gear changes take place. The change may also take over 5 seconds after you lift your foot.
In H you are starting off in converter drive using the high range clutch and the change point into Direct Drive clutch at light - medium throttle is normally at about 25 - 30 mph. This is a combination of throttle pressure and Governor pressure, probably more Governer pressure on light throttle. Once into Direct Drive, the high range clutch and the Direct drive clutch operate from the rear pump and the larger front pump ceases to drive the system and goes into coasting mode.
In D you are starting off using the low range band and converter. The low range band releases depending on throttle position and governor pressure and the high range clutch takes over, operating after this just as if you were in H. The high range clutch continues to operate when the direct drive clutch operates to take the slip out of the converter In theory, the change speed depends on throttle pressure from your accelerator position and governor pressure from the speed of your tailshaft shift. I would check the throttle lever first. Best regards Peter Toet