Re: Ultramatic gearbox problem slipping direct drive clutch

Posted by HH56 On 2024/7/7 17:00:52

Quote:
This shift between gears is something Packard worked on several times during the life of the original Ultramatic because as transmissions from other mfgs became available they found themselves somewhat at a competitive disadvantage. The shift is possible in theory as Packard described it -- providing all the conditions are exactly the same each time it is done. In practical fact if done carefully and not under a lot of power it can be done safely and reliably.

The issue starts when one driver might have the engine running wide open when he does the shift while another might not. One driver might move between gears as fast as he can while another moves slower. Of course, sometimes improper adjustment of the throttle rod thwarted even the best of intentions in shift actions. The original low high shift valve design and single pin as a restriction to slow down oil flow just didn't seem to work very well under all conditions. Thruout production Packard changed the restriction pin size and then the valve design and then the restriction size again all in efforts to better fine tune the low-high timing. While it was improved it was never completely successful to the point of being a reliable shift under all drivers and conditions.

The 54 GS and later Ultras were designed for this operation but even the GS and early 55 units had some of the same issues. Thru 55 they worked on some of the timing and pressure issues and finally got the throttle rod positioning and some of the valve designs more in sync. By 56 production they had things working fairly well. Most all of the later changes were applied to the earlier gear start and 55 units to improve their operation.