I've got a 1966, coupe, automatic, 302. All is well with it except it clunks and hits pretty hard when I shift into reverse, not that bad whenthe engine iscold but noticeable when it's warmed up. I've taken it to a few tranny shops and have heard everything from "it's the nature of the beast,"to "that's the way C4'sare" to "it could cost $2,000 to fix it.

It doesn't seem to be the U joint because I had it replaced recently, the idle seems about right, and none of the technicians have said anything about the vacuum modulator needing to be replaced.

So, I'm wondering if any one has any ideas on what could be going on withmy drive train.

 

Go to http://www.fordmuscle.com/forums/, great forum on C4's. I'm not a tranny guy, but sounds like the planetary gears are shot. If you're willing to pull the tranny yourself, a basic build is about $500. I just had mine done, I pulled it, bought all the hi-po parts: servo, converter, valve body, deep pan, clutches, etc, total $400, got it custombuilt for cost of labor, in this case $600. I can confidently put 400hp to this tranny, and not sweat it... Too many guys overlook their tranny. It's money well invested if you want it to be. Stock trans don't last, a well built tranny will last forever.

 

I appreciate this. I'll check out the link you provided.

If I could know for sure that the planetary gears were shot, then I'd consider doing a rebuild. Would there be any other symptoms of worn out planetary gears?

It's unlikely that I could pull the tranny myself -- I don't have a good way to get under the carfor doing major work like that, but would look for a shop to do it.

 

The one guy was right by saying "Its the nature of the beast".I too have a 66 with a 302 and c4 same thing.Ive worked on or driven probably a dozen 1st gen mustangs and they all do it.