So, what color is the fluid? Does it smell burned? One and a half qts low is a lot for this trans. IF the mod is bad it can pass a lot of fluid through the vacuum hose to the intake. Just because it does not smoke doesn't mean it isn't burning it. A really hot exhaust will act kinda like a cat converter and burn up the smoke before it hits the tailpipe, so no smoke. The fluid is going somewhere and if it is not leaking or ending up in the FD, it's gotta be burning it. These symptoms (accept the low fluid) happened to me 12 yrs ago when I bought our coach. Backed it up into the driveway...chattered like hell. It was the direct clutch. Hope that is not your problem. I was lucky I made it home. The modulator is a cheap test. Crossing my fingers for you....

...OH, of coarse...pull the vacuum line at the carb. IF there is trans fluid there....you got your answer.

ALMOST made it home with the coach.

Here is the situation: Left the Dixielanders rally in Savanna this morning at 7:30 CST and drove hard for about 400 miles, running 65-70 on the interstate. Coach ran great! At about the 400 mile point, 50 miles from home, we were climbing one of two mountains between Atlanta and Huntsville (1250' climb...big hill to most but it's pretty big to us), anyway, I pulled it into second and got into the secondaries and ran up the hill about 3400 rpm. No problem. Topped the hill and eased it back into drive. A few minutes later it the rpms climb up to about 3000 then back down to the 2400. It does this pretty frequently. According to the tranny temp on our Accugauge, the tranny temp is about 140 (it never moves once it warms up.)

This continues to occur so I pull into a gas station and check the trans fluid. Down a quart and a half. No visible leaks, no smoke, nothing appears amiss. No fluid on the toad or dripping from the chassis. I saw no smoke from the tailpipe but might not given my mirror setup. I use a backup camera and have my exhaust side (passenger) mirror sit to show the dead spot.

This is a Manny Tranny with about 4500 miles on it without a prior hitch.

Add the fluid and expect the problem will be gone. Nope, same thing. Of course by now, I'm listening to every sound and bump and trying things. Pull the tranny into second and it will run up to 3000+ fine. First gear MAY be holding in a bit longer, I was driving pretty carefully and didn't pay that much attention to tell the truth.

I'm not sure it is actually downshifting. With the RPM at about 2200 if I accelerated any or hit an incline, the RPM would fairly quickly spool up to near 3000 and then about as quickly spool back down to 2200. Almost like it wanted to shift but about the time it got there changed its mind.

Decided NOT to try and make the 1500' climb of Monte Sano with it's lack of shoulder and left the coach at my Sister-in-Laws and came home in the Saturn.

One final data point, when I was backing up to my Sister-in-laws garage, the coach was shuddering a bit in reverse. Not a lot but a 'what the hell was that moment'.

Automatic transmissions are black magic to me but here is what I THINK. I'm soliciting opinions but will talk to Manny before doing anything.

1- I strongly suspect the vacuum modulator has ruptured the diaphragm. That would account for the loss of fluid but I'd think that ALL gears would be effected. Perhaps they were and the shift points were all off and including the issue with reverse....I don't know.

2- Don't think it's the governor because as I understand it, when they go, you'll never get out of second.

3- I guess it's possible that something has failed internally and the clutches are slipping and just not holding. Don't know.

If Manny thinks it the modulator, I'll change it out and drive it home. Otherwise, I'll get to try out my Allstate towing coverage.

Your thoughts are welcome.