95 tranmission problem

I have a 95 grand am w/ quad four engine. The transmission is the 16 bolt pan type. (I don't know part #) I was driving down the road at about 45 mph. The transmission just acted like it slipped to neutral. I now have no gears at all. You shift the transmission, and the linkage works, but the tranmission will not go into gear. Changed filter and fluid. No bad smell to fluid and no metal or anything in pan.
Just changed the heater core last week. Is there a loose vacuum hose that could be causing this problem? Is it possible that I knocked something loose fighting with the heater hoses? I'm at a loss, and would rather not buy a new car right now. Help!

Thanks!

Welcome to AF !

The trans lines run by the heatercore hose area..... unless you smashed/crimped one and fluid is not flowing. Might check those and the fluid level.

But as far as inside the trans :shakehead to many things to name off that "might" be the problem.

Did it make any noises when it stoped working ?

Have you had problems with the engine killing when coming to a stop?

No, no noises at all. I haven't had a problem with it running at a stop, but sometimes it would surge a bit now that you mention it. I'd had some issues with losing power sometimes. Just push on the pedal and not having any motor, but the engine never accelerated. That had been going on for years. A shop said he'd look at it, but figured it was a 99% chance it would need a new transmission.