Well, I had the car checked out and the mechanics found a leak in the throttle body, a hole in the EGR valve tube as well as dirty fuel injectors. They resealed the throttle body, replaced the EGR valve tube and cleaned the injectors ($300). Now the car runs quite well...no check engine light anymore. So everything was fixed...except for the transmission problem. I had a code pulled...code 740 ( "tcc circuit malfunction"). The car does fine when "cold"...the tcc locks up and stays locked up. There IS a hint of vibration/shudder though even when cold. The rpms drop at lockup like they should. BUT when the car heats up, the tcc just won't engage at all WHILE MY FOOT IS ON THE GAS. Overdrive does engage. The higher rpms cased by this tcc lockup failure make it just seem like its not in "od". (I understand the tcc lockup causes the rpm drop in "OD" in this transmission.) When I manually shift into regular "d"out of "od" WITH MY FOOT OFF THE GAS, the rpms noticably jump up and stay up. It seems that the tcc, once it gets hot, is unable to lock-up unless I take my foot off the gas. Is this what the SONNAX parts manual calls "low converter apply pressure"? All in all, the manual says that this 740 code and these symptoms point to a bad TCC REGULATOR VALVE system( isolator valve, regulator valve and regulator sleeve) . The shop quoted me $485 total, 450 labor and 38 for the replacement kit. The old transmission has a warranty. I only paid 300 for the transmission, so it looks like this will cost me about 150 if MIDWESTAUTORECYCLING honors the warranty. I just wanted to get some opinions about my conclusion. They have ordered the kit #84754-01k from SONNAX. I want to make sure I'm spending money on the right solution. Am I right about my conclusion?

You might want to look at that warranty from Midwest. Most likely its a "bring it back and we'll give you another one free" type warranty and not one where they would just give you your money back and still let you keep the part for free.

Fixed it with a simple radiator flush. Can't believe this. I discovered the guy I used to have work on my car put 100% antifreeze in it about a month ago, just before I got the tranny put in. Guess what...100% antifreeze messes up the thermostats ability to read temp accurately. The thermostat wasn't opening soon enough, causing a constant heat issue. The heat prevented overdrive from engaging....some sort of tranny safety feature. Now overdrive works, but I think theres a bit more to do. I need to find out the acceptable temp range for the car. What is an acceptable range before the thermostat actuates...mine seems to be at about 210.

Well, i'm back to square one AGAIN!! Drove home after delivering pizzas for a few hours and overdrive would not lock up again. It worked fine for two full days...day one with the heater running the whole time to exhaust the heat and a second after flushing the radiator. But now i'm back to the drawing board. I'm noticing that overdrive has no problem engaging when the car runs at a proper temperature, but when it gets too hot..no overdrive. It seems to peak at 210-215 and it seems to stay at that temp for a bit longer than it should. I put my hand on the heat vent in the car and I swear it seems hotter than normal...feels like it could burn you if it was only a few more degrees. Wonder what the cars temp should be on a flat highway going about 65...under 200?..i swear i remember it always hanging just under 200 when i first bought it...who knows.I had the thermostat replaced over a year ago. I'll try a new one and i'll flush out the system again. I don't know what else I could do. Suggestions would be a big help. The fact the tcc locks up and stays solidly locked up when temps are good really makes me wonder if the torque converter/transmission is the issue. I thought the car had a safety feature that prevented overdrive from working if temps were too high....am I wrong about that? All in all, where should I go from here?

Try the new thermostat and flush first. It does sound as if your car is running a bit too hot. I believe Bill Buttermore solved his lockup problem with an external cooler.

Flushed it again, put some radiator "SUPER" cleaner in it...supposed to run the car 3-6 hour, then drain. After this, i'm gonna try a back flush with a kit I bought. Will also try a 180 thermostat. I won't mess with the tranny cause its new...well new to me...41k on it. It was cleaned up really well. And the fluid/filter are new too. But the tranny cooler, who knows. I am no mechanic, so unless I can get to that in my backyard with a few tools, i'll have to fork out some more dough. I really hope its the radiator/thermostat. I'll know soon enough. What is this "external cooler". Is that the tranny cooler or something else...like an add-on?

Yes, it is an add-on cooler. It'* been sugested to me when I do my trans to run a bigger cooler than what I have, and completely bypass the radiator cooling for it. Though the fluid was new, I bet it aint so new now, esp. since you could cook catfish with those temps. It won't hurt the warranty one bit to change the fluid out...won't hurt the trans either.