I just installed a rebuilt 700r4 in my 66 and went around the block a few times before developing this problem. I initially suspected burned clutches from possible incorrect tv cable adjustment, but upon further inspection the fluid on the stick smells normal and shows no sign of metal particles. I'm now thinking the torque converter may be shot. It is making a loud rattling sound when I put it in gear. It will only go forward real slow when revved way up. The tranny still has reverse, but when backing up slowly I'm hearing a noise while backing up that's almost a grind and is consistent with the speed I'm backing up. If my car wasn't having tranny problems I'd almost relate this to the rearend. On my first few drives it felt like the tranny was shifting and pulling well, but today's run was a complete bummer. What are your thoughts on this?

I just checked it out again and now when I put it in drive initially there is no response, but after several seconds it slips into gear and will pull. Another odd point is that when I stomp the gas and then let off with it in drive or reverse it will pull hard and die when I let off the gas. It doesn't do this when in park. Almost like something is lugging it down. The engine runs strong. Initial timing is set at 17 deg BTD and the vacuum advance is pulling another 12-13 degrees at idle. What's up with all of this?

Okay, one more piece of the puzzle for those of you who want to take a stab at this. I checked the shift linkage and the adjustment is dead on. I put the rear of the car on jackstands and with the car in drive I manually spun the rear wheels to see if I'd hear any clunking. Sounded fine. Secondly I started the car and put it in drive. There was no reaction from the rear wheels at all until I gave it a little gas. Once it engaged, the wheels spun and seemed normal. After spinning for a few seconds I hit the brakes and stopped the spinning completely. When I let off the brake it began spinning again on its own without giving it any gas. What would cause a 700 to be hard to get into gear like this? I'm clueless because it seemed fine a couple of days ago.

I think you have an internal problem with the input drum. Leaking fluid pressure causing it to slip.

Hard to say but in any case with the noises you have, it needs to come out and be torn down for inspection.

I think you have an internal problem with the input drum. Leaking fluid pressure causing it to slip.

Hard to say but in any case with the noises you have, it needs to come out and be torn down for inspection.

I've read many posts regarding sticking lockup switches. Could this be part of my problem?