So I did a big fluid day (coolant, engine, rear diff, tranny) yesterday, and used castrol hypoy C 80w90 (MT5, synthetic blend) for the tranny and my diffs. The diff is happy again, but my transmission now feels like it came off of a tractor. Very notchy, when it's cold I am almost catching the synchro in second off guard (never had transmission issues before the fluid change)
Did I use too heavy a weight for Seattle driving? The shop ran out of Hypoy C in 80w90, so I had to mix in a quart of valvoline synthetic blend 80w90. Could this be the culprit? Could it be that I used MT5 instead of MT4? Should I really drop the coin on synthetic, and does it make that large of a difference in tranny feel? This is just my truck, not a race car, so I've always used mid grade products with it and just kept on top of maintenance.
The truck has a capacity of 7 quarts, but using the drainplug only evacuates 4. If I need to get rid of what I put in or change the weight (previous weight/make that I mixed the new stuff in with is unknown) should I just drop the pan and do the filter/gasket while I'm at it? or just do a couple more flushes over this month to get things mostly right?
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Also have run it in quite a few of the hot rods that we built. Borg-warner t-56's haven't had any problems either.
We ran it in our old rodeo (same vintage as my pathfinder) for over 200k miles, never had a problem. That's why I've never even known it was such a big deal. From what I read, it's only synchros made from soft brass that really care.
that said, I might as well just switch to GL-4 anyways. It's no more expensive, and even if 200k is fine, who knows what 300k might look like (and I expect transmissions to last that long)
