My '49 Cadillac will not shift to fourth until I've driven it about 3-6 miles. After that shift finally happens, the trans performs flawlessly for the rest of the day. Ambient temperature and warming the car up before seems to have no effect whatsoever. I've even tried warming up with it idling in drive against a wheel chock to give the trans some exercise. Anybody have thoughts on anything to check?
How long since the pan was dropped, the screen cleaned, & the fluid changed? Are you using DEX-MERC III(or lV)?
Been a long-long time since I had any hands on dealing with an early hydramatic, but I am thinking they used type "A" fluid, is that compatible with Merc III or IV?
I did a cleaning/change two summers ago, thinking it would help with this exact same problem. It was Dex-Merc that I used, but don't recall if III or IV, I still have an extra bottle on the shelf and can confirm tonight. Sent from my iPhone using The H.A.M.B. mobile app
Did the cleaning do the trick? The manual available here http://chevy.oldcarmanualproject.com/trans/4655hmt/ suggests the typical 20 possible remedies for that symptom. I don't think Hydra-Matics got filters until '56, but it would make sense that some passages are somewhat narrowed and the tranny fluid won't flow enough until it thins out with heat.
I would think that the 3-4 shift valve may be stuck when cold and frees up after heating enough. What I would do is pull the side cover and then pull the valve body. Carefully take the valve body apart and check the valves to see if there is any binding going on. My guess is that you will find a sticky valve.
Is there an easy way to check if the throttle pressure is too high and/or the governor pressure is too low during a cold drive-away condition? And if so, would it possibly only affect high gear?
That manual seems like it will be very handy, thanks Clunker! Thanks also d2_willys and Dan, I'll start with that valve. Sent from my iPhone using The H.A.M.B. mobile app
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