My friend has a 78 Formula with a 400 sbc, that I'm getting ready to buy. It has a th350 he put in it and was built by someone in his family. The problem is, the car will not shift into 3rd, ever, and will only shift into 2nd if you give it very light gas. If you get on it or give it any kind of gas it will downshift to 1st and not shift out of it. HE thinks it is the vaccum modulator. Anyone else have an opinion? The guy who built the tranny does it for a living, so I dont think it has anything to do with that.

Thanks
Jeremy

 

A bad modulator (or the line to it) will cause late shifts at WOT only. But they are cheap enough so might as well give it a shot. Might also consider it could have 2 different problems, like the modulator and maybe misadjusted linkage.

 

Do you mean the linkage inside the pan connecting the shift rod to the valvebody or to the shifter? I dont think it was the shifter bcuz we didnt have one in to make sure it wasnt that and we even checked the linkage, but we were pretty sure we where in drive when we did the intial drive around after the tranny install.

 

Well, I'm not a trans guy, but I've heard that if the line pressure is too high, that it won't shift into the next higher gear. Also, if someone had the shift governors apart to try to raise the shift point of the transmission and they botched that job, it could also do what you're saying.

 

One more thing that I forgot to mention, it leaks trans fluid and we are not sure where it is comming from. We dont think it si the pan or the stick, and my friend made the comment that it is comming out of the shifter cable. He said that he put a seal in there from a working trans that he had, but didnt fix it.