I went for a cruise in my 72 Challenger last night and had some 727 tranny trouble. When I left home it felt like it wanted to stay in 2nd but eventually shifted and did fine. After cruising for for about 30 minutes it started feeling like it was slipping or more like going into neutral. I headed out from the cruise and on the way home it started getting worse it started going into neutral as I was driving when I let off the throttle it would engage again. It finally went into neutral and would not engage at all. I stopped in a parking lot figuring I would need towed home. After about 10 minutes I started the car again and the tranny worked fine for about 3 miles then it did it again. I let it sit for about 10 minutes and it worked again. When I got home it wouldn't make it up the slight incline my driveway has. I let it sit for about 10 minutes added some Mercon 5 fluid in it fired it up and was able to back it up and pull it up the driveway to put the car away. I couldn't see any signs of a leak at all. This tranny has about 1,000 street miles on it since a complete rebuild using billet everything and an ACC Boss HOG 3,500 rpm stall converter. Does anybody have any ideas of what could be wrong before I take it back to the guy that built it and get smoke blown up my *ss ?

Last trans I had do that was cured by a fluid and filter change. The filter was getting plugged while it had fluid going through it and after stopping the drain back through it would clean enough gunk out of it to allow fluid flow again. It sounds like either you are plugged up or you are runing low on fluid somehow.

isnt the stall(3500) a bit high for street use?

If this tranny has a plugged filter after less than 1,000 mile it must have something wrong wouldn't you think? Unless the guy dipped the parts in sawdust before assembly.

I'd drop the pan & good visual/check the 2 band adjustments & as Stump said change the filter & see if that solves it.

Yes it's way too much stall I need to change it but it came with the rest of the parts for the motor when I bought it. Besides I don't drive the car very much like I said it has less than 1,000 miles on it. It might be safer to say less than 500 miles on it and it's been done for 16 months now.

I will replace the filter and fluid to see if it fixes it.

If a fluid/filter doesn't fix it the problem is leakage at the front clutch, as the fluid gets warmer and thinner the leakage results in the clutch releasing and no third tgear.

I checked the tranny fluid and it's full maybe a little over full. I used Mercon 5 tranny fluid and it's black not red not orange just black. the tranny has 887 miles on it as black as it is I don't think it's worth throwing a filter at it and wasting the tranny fluid. What do you guys think.

toast

If the fluid's black it's full of friction material that should still be on the clutches.

That's what I thought from the way it was feeling last night. this is the second tranny this company built for me that took a crap in less than 5,000 miles it's getting old.

Pop the pan off and tell us what is on the bottom ...

I think I'll let the guy that built the tranny do that or the new guy that will build the new tranny that I will charge the guy that built this tranny for. Like I said this is the second tranny this guy / company built that went bad in less than 5,000 miles. The last 1 was in my Vette ( yea I know ) it cost me $1,500 to have the tranny built $500 to have it redone to get it to what I ordered $1,000 to replace the broken shafts after he screwed up when he re-did it causing a 1-2 bang shift and $1,200 for a new glass top that shattered when the shafts broke from the 1-2 bang shift. Yea I know I need a new tranny guy.

Thr trans didn't go into neutral. It was slipping the front clutch. Sounds like the seal rings on the reaction shaft. Yes you smoked the front clutch. Take it back.

I know it didn't go into neutral that was the only way I could explain it. I plan on calling them in the morning I will post his response after I talk to him.

I talked to the guy that built the tranny today he said he would warranty it. I need to pull it and bring it to him. He said he would fix the tranny for free and have the converter freshened But if the converter caused the problem then I would have to pay for the converter rebuild. I imagine I'll have to pay for the fluid again also ( merc 5 spendy stuff) What are the chances that the converter caused the problem? he didn't supply the converter so I can only guess that he's going to say the converter caused the problem. The converter is a 3,500 RPM ACC boss hog converter.

Way too many unknown to pinpoint the cause of the failure. I guess the first obvious question is if using a valve body that requires the throttle linkage, are you using the throttle linkage and is it adjusted correctly? Also, are you using a larger trans cooler, and are the lines clean and flowing good? Sorry I have to ask you since it sounds like the trans builder did not do the install.
If all that checks out, then you might want to question the trans builder? If he is cool, maybe he will let you watch him take it apart and and inspect the trans. That way you will know what went out, and maybe find out why?
I have seen a few "mechanics" that though they were transmission rebuilders, but I watched them just replace the frictions and steels, but not even disasemble the clutch pistons to replace the seals which were likely the cause of the failure in the first place
I don't know about the converter? I guess if it was pretty inefficent it could have generated alot of heat?