Got a 740 wagon recently that had it's tranny replaced after it had been donated to a charitable organization with a bad tranny.

after a bit of driving the tranny began to exhibit a delayed response

I had already noticed a brown thick consistency fluid in the coolant reservoir and was planning a coolant flush (simultaneously with a water pump replacement) prior to this taking place.

I checked the fluid level in the tranny and there was nothing on the dipstick

got under there and noticed a leak from (I believe) the tranny pan drain bolt... and interestingly the fluid was the SAME COLOR as that in my coolant reservoir!

I drained the pan and sure enough it's the same stuff. It would seem that somehow the tranny fluid and the coolant are mixing? I have never heard of such a thing (though I am still a relatively inexperienced mechanic), I knew your coolant and engine oil could mix when you have a leak between those two systems (i.e. bad head gasket) but I never knew your tranny fluid and coolant could mix!

Is this a bad radiator? somehow allowing the transmission cooler and the radiator access to each other???

before I flush BOTH systems I wonder if I should replace the radiator?

any thoughts?

thanks

jack
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Bad Blue - '86 245 with 295,000 mi., Good Grey - '89 740 sedan with 188,000, Mean Green - '94 850 with 222,000