I have my old ford ranger w the a4ld transmission and it intermittently will slip in first to second and second to third. This only seems to happen during the first couple shifts of the drive time and then goes away. I currently have a shift kit and new valve body gaskets for it that I plan on installing but should that not work are there any other alternatives to try rather than a full rebuild?

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1994 ford ranger 4.0 v6 140k miles stock

How long has it been since a filter change, is the oil still red, or brown, does it smell burnt?