C4 Trans advise

I have a C4 in the '67. Previous owner gave me the invoice from the rebuild he had done just before it was parked, 4 years later I bought it from a barn.

I've probably put less than 1k miles on it, car has started slipping out of 2nd gear, mostly when hitting humps at intersections and only after it's warmed up. It has an aftermarket oil cooler only, does not go to the radiator. It acts like it's starving for fluid, but it's full. When I replaced the filter, I found plastic pieces from the speedo gear in the pan (speedo had locked up twisting the cable and shredding the gear).

I'm thinking of adding some brake fluid or over the counter additive to flush it out then replacing filter/fluid again, hoping that I've just got debris plugging stuff up.

Any advise on what else to try before pulling it out and rebuilding?

Do band adjustments require the pan be removed?



Thanks.

Thanks, good advise. I found an old Chilton guide to auto transmisiions I'd forgotten about, so I got the intermediate band adjusted to specs. Torque to 10lbs, back off 1-3/4 turns, torque locknut to 30 lb. Also lists several options for troubleshooting 2nd gear slipping: vacuum modulator or intermediate servo are my next steps if this didn't help.