Re: 1950 327 with Ultramatic - Idle Speed

Posted by HH56 On 2023/2/4 14:42:13
Definitely get the linkage oriented properly and check how freely the bellcrank pivots on its shaft. There is nothing more critical in the Ultra operation than throttle linkage and its adjustment. Throttle pressure controls shifts and also modulates a valve that determins how much pressure is applied to lock the high range clutches together. Too low a pressure not squeezing the clutches together when a lot is needed and they can burn quite easily.

I don't think I've ever felt anything resembling a shift when driving. It just sort of feels like one gear, and that's it.

This is correct. The Ultramatic is essentially a one gear transmission and that gear is selected by the operator when he puts the lever in high or low. The transmission starts and stays in the selected gear with the torque converter providing the extra assist a lower gear would provide in starting from a stop. It does this by multiplying torque there instead of the usual extra aid provided by a lower actual gear. Once the car has reached a constant speed of a few miles per hour, the components in the torque converter are essentially all rotating at the same rate so any farther torque multiplication is minimal. At that point the converter essentially becomes a fluid coupling. After all is steady and car is at a good driving speed the direct drive clutch is engaged and instead of the hard shift you would feel with a gear change, in a properly working Ultramatic about all that happens is maybe a slight sensation as the clutch is applied. The larger sensation is a sense of things being more calm and quiet as the engine RPM drops when power flow thru the torque converter (or fluid coupling) is no longer happening.

If the direct drive clutch cork facing has become hard or worn there can be a shudder or even what is sometimes referred to as a "mooing" sound as the clutch engages. No harm will come from either but to minimize the sound and aid the shift into direct drive, letting off on the gas as the shift occurs is recommended. On the Ultramatics made thru 51 the clutch disc is approximately 11 inches in diameter and the piston is a large splined plate behind the clutch. The plates have been known to cock slightly and splines on the plate can catch in their mating groove and cause some issues. If the trans still has the original clutch it could be one that is hard and worn. With your description it does sound like the DD clutch is working though so unless there are other issues maybe just keep it in mind as there does not seem to be anything to be concerned about now.

One thing that is very hard on the original Ultramatics is manually shifting from low to high under power. Because the trans was designed for a leisurely and smooth start many want a fast takeoff more like a stick shift or a modern car. They place the lever in low, start off at a light and then under power shift into high. This is to be avoided at all costs because there is no synchronization between gears in the original Ultras. As soon as the lever is moved, low will start to disengage, high will start to come in and there can be a period where both gears or neither gear is engaged. If both are engaged the engine and trans are essentially locked up and something mechanical can suffer and if neither are engaged the engine will race and then getting things under control again will all fall on the high range clutches. The extra friction trying to slow the engine puts a large strain on them and they facings can be burned in the process. If you must make the manual shift get it to speed then let off on the gas while you shift the lever and wait for the shift to complete before applying the gas again. Packard tried improving this issue with a timing kit but was not entirely successful. The redesigned 54 Gear start and later 55-6 TU's were the first Ultras that could more or less properly make an actual gear shift.

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