Transmission won't engage

[chevy06burban]

Hello everyone,

I have a 72 Blazer 4x4 with TH350 transmission. Yesterday driving home from work going about 40mph suddenly seemed tranny was in neutral. Pulled over and checked gear shift by shifting into other gears. Didn't take long to get the tranny to engage in drive (3rd gear). Though shifter was in 3rd, tranny wouldn't up shift. Any time I have to stop, have to rev the engine to get tranny to engage. Bottom line only can get tranny to engage by reving engine. Won't engage in any of the 3 gears, even reverse, without reving the engine. And yes I checked the fluid and all is good. Any ideas what the problem could be? Thank you in advance for any advise.

Lauren

[maxwedge]

Internal pressure loss, time to pull it out.

[Blue Bowtie]

But... But... Max - It's not even 50 years old! How can the servo / shaft seals be leaking?

Agreed. Either a pump pulling air or unable to maintain line pressure. You can test this with an external pressure gauge on a TH350 (400 PSI gauge) to confirm, but unless you get really lucky, it probably is not going to be a through-the-pan repair. The tough part is that not as many of that trans series will be set up for 4WD, so a swap is less of an option.

[chevy06burban]

Update. After much research I have found that it could be the governor. Pulled the governor out and inspected it. The gear and weights all were in good shape. The shaft or piston in the governor wasn't moving. Cleaned it with brake cleaner and put it back in. And sure enough tranny is shifting again and engages.

[maxwedge]

Great, bit you said you had no forward or reverse, fhe governor does not control anything like that?