OldBlue:
I think the best HydraMatic manual to start with is the "On The Car Adjustment Service Manual for 1946-55". It has about 10 pages of theory and then describes adjustments you can make without removing the tranny.
I have that book, a 1954 GMC Hydra-Matic Operation and Maintenance Manual and two other HM leaflets in .pdf and .jpg form that I can send you via email. Drop your email address into a PM to me and I'll get the manuals to you.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
| 
