it will not shift

every time you plan to service your transmission you should first add a solvent called TRANS X to your tranny, this will disolve the old varnish stuck to the casing and tothe valve box.New oil contains detergent which will also remove all the varnish but it will not dissolve it causing the valves to get stuck and plugged.If this is the case then you will have to have the valve box removed and cleaned.You can try adding this TRANS X as it is and shift gears several times and see if it loosens up.If it does then replace filter and all the oil including the oil in pan and in the converter.I hope this helps. rgrecio31

First - my opinion differs on the use of "solvents" like "Trans X", because many times loosening things up after 20 odd years is not the best idea... OK. This is an A4LD automatic transmission, which is vacuum operated. Any thing affecting engine vacuum could be causing you troubles with shifting. However, I'm more concerned about it "bogging down" because that sounds like a driveability problem more than a transmission shifting problem. You could even have an exhaust restriction for example that is causing a lack of power. If your engine doesn't develop power, it won't shift...but that's a secondary problem. Try to assess if this is an engine performance problem first -- then address that prior to jumping to any conclusions on the transmission.