Since I've had my 04 Cobra, the T56 has been rather notchy - more than I would like and would have thought. To see if a fluid change would make any noticeable difference, I've tried 4 different tranny fluids. From this experience, I have developed some perceptions/conclusions based on driving the car with those fluids.
Stock fluid: As noted above, rather notchy.
Royal Purple Synthetic Syncromesh: I had high hopes for this fluid, but unfortunately, it did not perform for me. Even when warm, I rate the shifting performance as worse than stock (notchy and a bit harder to get in and out of gear overall). That really disappoints me, as Royal Purple supports racers (NMRA contingency), and I like to support the vendors that support me (I still use their oil). It was ~$5.50 per quart.
Proline Dexron III/Mercon: This is the cheap ATF from Pep boys. It actually wasn't that bad, and I perfer it to Royal Purple Synthetic Syncromesh. Basically, it shifted like it did with the stock fluid (and in reality, it was probably virtually identical). I purchased a gallon jug for ~$5.50 (easily the best deal of the bunch).
GM Syncromesh. Though not much better than stock or the Proline, the tranny is a bit smoother, and this is what I'll keep. The main downside is the price of this stuff - $10 a qt. Ouch.
Hope this helps somebody.
Stock fluid: As noted above, rather notchy.
Royal Purple Synthetic Syncromesh: I had high hopes for this fluid, but unfortunately, it did not perform for me. Even when warm, I rate the shifting performance as worse than stock (notchy and a bit harder to get in and out of gear overall). That really disappoints me, as Royal Purple supports racers (NMRA contingency), and I like to support the vendors that support me (I still use their oil). It was ~$5.50 per quart.
Proline Dexron III/Mercon: This is the cheap ATF from Pep boys. It actually wasn't that bad, and I perfer it to Royal Purple Synthetic Syncromesh. Basically, it shifted like it did with the stock fluid (and in reality, it was probably virtually identical). I purchased a gallon jug for ~$5.50 (easily the best deal of the bunch).
GM Syncromesh. Though not much better than stock or the Proline, the tranny is a bit smoother, and this is what I'll keep. The main downside is the price of this stuff - $10 a qt. Ouch.
Hope this helps somebody.
