TH350 issue

[Judge]

Hello, I have a th350 trans in my '72 C10 that has me perplexed. Admittedly, transmissions are not very familiar to me. Anyways, a few weeks ago I was leaving work and went put the truck into drive, it didn't engage. I tried reverse, low, drive again but nothing. I waited for my wife to come pick me up and when she did, she hopped in to stear while I pushed to get back in a parking spot but when I told her to shift into neutral with the engine running she shifted into drive and it engaged no problem. Fast forward a few weeks to today, after driving the truck daily with no problem, the issue happens again. First it wouldn't engage then after letting it sit and try again it worked. So now it's parked in my driveway indefinitely, until I can figure it out. Thought I'd reach on here for some ideas before I have it towed to a trans shop in a town I just recently moved to. Thanks in advance for any tips or advice.

[Green Hornet]

I would check all linkages first then replace the filter. Two things could be going on. The seal/O ring around the filter could be leaking causing the fluid to leak back into the pan or the filter could be clogged. If the filter is clogged chances are the trany isn't long for the world anyway.

[Judge]

Thanks for the reply, I'll definitely look at linkages and the filter. I planned on rebuilding it or swapping it for a 200r4, just not right now due to funds.