Reverse in my mom's 68 coupe is slow to engage sometimes. If you step on it hard it will go but if not it will rev freely for a while then move. It's a 289 with a C4. Thanks! and here's a pic in case you wanted to see what it looks like.

 

It's been my experience that is the first sign of a transmission on it's way out. If that is the case it will probably start to slip between shifts.

 

Would a fluid and filter change help any. Would a clogged filter cause this?

 

I have a 1967 289 coupe with a c4 as well and mine had started that about a year ago. But i have a question does it do it often because mine would only do it in cold weather any other time it was fine. But just to make sure its doing the same its like your in drive and put it in reverse and it acts like its neutral and after like 10 seconds it will shift.

 

Yeah it does it every now and then, but with no relation to the weather.

 

My old C6 used to do things like that, even after I got it flushed. But only when the trans and engine weren't warmed up yet. When it was warm it was fine. It still did not take 10 seconds like you mentioned blue, only a second or two.

 

same thing happens in my sisters hyndai, but when you go into drive also.. transmissions on its way out

 

try using about 1or2 oz of brake fluid will help soften the old seals and swell them.unless clutches are allready gone.had c6 that i used this trick on and it lasted another 1 1/2 years.

 

It could be a few things or a combination of other things. It sound to me as if the pump might be going out. There are check ***** and springs and little pistons in the valve body. The valve body looks like a nightmare maze when you open it up with passageways and holes drilled in certain spots. Any one of those could be clogged or fouled. You would be amazed how dirty they get and still operate. I must warn you though, if you drain the fluid and change the filter, it may go out altogether. Some people have been know to drain the new fluid and pour the old fluid back in to see it work again until they could get it rebuilt. Sounds strange but it's true.

 

You may want to do a filter and fluid change if the fluid has been in there for 40 years,Regardless of how many miles/hours it has on it.
I'm not real familiar with your set-up But isn't there a vaccum line that runs from the transmission to the manifold,Check that for clogs or kinks?