I'm no HM expert, but .....

This guy (can't remember his name) supplies HM parts and his web site says he rents out the adjustment tools. Scroll most of the way towards the bottom of THIS PAGE.

That 2-3 upshift can be wicked because it requires a band-to-clutch change in one planetary set and a clutch-to-band change in the other at the same time. Improper adjustments lead to 2-4-3 shifts when the front set shifts faster than the rear set and 2-1-3 shifts when the rear set shifts faster than the front set.

I think the best book for us amateurs to use while tweaking adjustments on HM transmissions is THIS ONE

From experience (daily drove a '57 GMC with Hydra-Matic for 21 years) I think doing the band adjustments using the internal tools (requires dropping the pan) gives much better results than using the external tools.

Last edited by Bill Hanlon; 07/29/2022 4:07 PM.
'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.