Packard Forum Index » Post-War (1946-54)

I currently own a 1951 300. The transmission will no go faster than 10 mph in High. I should be able to purchase an Ultramatic from a previously running 1953. Is the 1953 the same transmission as the 1951? Your help will be invaluable.

53 transmission will fit and will have some of the later improvements. Depending on the rear end that was in the car it came out of vs yours, you may have to swap the speedometer gear and governor. Both can be done via a few bolts without tearing into the unit. Since you have a 51 300, there is also a slight chance the universal joint flange is a different size and may need to swap.

Once you do change it, read up and follow the throttle linkage and pressure adjustment procedure to the letter. Other than normal high mileage wear and use, a bad adjustment on throttle linkage can be a killer of the original Ultras. A dimension is available on site here since you won't have the tool to set the cross shaft angle.