300TE Transmission Question

I have a 88 300TE with about 148,000 miles on it. It had a rebuilt engine at about 110 and I bought it shortly thereafter. The trans was maintained
from what I can see in the records. When it gets cold, however, here in Southern California <60 degrees it seems that the transmission has a harder time shifting as I can hear the engine reving more than normal and then it kicks down or it takes slightly longer for it to go from first to second or into reverse. When it is hot outside or when the car is warmed up this does not seem to be a problem. Sometimes it is a matter of stopping the car and restarting it and this seems to solve the problem. I do have a slow leak somewhere in the traanny and keep adding a quart or so every couple of months so maybe it is low on fluid. Any experience with this or thoughts about how to properly test it. Thanks.
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Normal. The transmission is designed to keep the engine's revs higher than normal during warm-up. That's done so the exhaust catalysts heat up quickly so they can scrub the then hydrocarbon rich exhaust.
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