I recently purchased a 1979 300d with auto tranny problems for $250. Here are the symptoms. First day, the car flares 1-2 and 3-4. I drove about an hour before it go hot and would not go forward. I decided to jack it up and look under it. I read many post of possible b2 failure. This is the tranny with four bolts on the pan. I noticed atf all around the pan. I cleaned the b2 pistion cover off to check for leaks. The fluid level is full. I decided to take a test drive. I only made it 2 miles before the tranny got hot and would not move. While waiting for tranny to cool off, I checked the fluid again. Full. When the tranny cools off it is off to the races again for another 2 miles. Is this tranny toast or can it be saved? What should I check or replace next?

I know that a tranny won't go forward if it does not have enough fluid in it. And you said yours has a substantial leak. It could be as simple as the drain pan gasket. But that would not explain why it still goes forward when it is cold. Have you checked the fluid level?

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"There are a lot of pebbles on the beach, but there's a Little Rock in Arkansas."

Logan

1983 300D Turbodiesel
1976 300D Rustdiesel

I did check the fluid. It is full.

I alos have not been able to locate vacum to the transmission. Are there some that do not use vaccum?

Try changing the filter also.

Did the car sit for a long time before you bought it?

An old Pontiac with the TH400 tranny did that to me as well. Turned out the car sat for 2 years, and the seals dried out. Cold fluid would let it build pressure to move, once hot, the fluid was pumped around and through the seals, resulting in a no go when hot. A tranny rebuild solved that.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Early cars do not use vacuum...I believe '79 is around the transition year.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

instead of a vac modulator, look for hard linkage that goes from the throttle linkage behind the ip to the passenger's side of the transmission. easy to recognize because the arm that goes across the top of the trans has a spring-loaded adjustment bit on it.

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1973 280 - Current Project Car
1979 240d - 100% Stock
1982 380sl - 100% Stock
1985 190e 2.3 - Heavily Modified

Being that it does not have vaccum. How would you adjust for flare?

You're overheating the transmission. Eventually it will not come back. If it's low on fluid, and gets over heated there'll surely be trouble..

Your senario unfortunatly is not very good in my opinion. You can pull the transmission filter and try first it but your best probable solution is to get a good used transmission.
An automatic dropping out after reaching operating temperature is not that uncommon. You might want to speak to a good practising auto transmission rebuilder for an opinion on the probable exact internal common cause. Operating fluid pressure probably is getting too low to function after the transmission fluid warms up and thins out. It is not unusual to let the car sit for 10-15 minutes and the function restores for a short while.

The fluid is full. I presume that is thinning and leaking internally.

Is there any fluid or treatment that will not allow the fluid to thin. Basically, Is there a thick solution?