Two things, and before you flame me, remember I didn't come up with this info firsthand...
1) On Syncromesh- I ran the Pennzoil for a while. Wasn't impressed. I actually swapped for RP after a guy on here (who isn't around much) forwarded me some emails where he was talking with a Pennzoil tech, and the tech said do NOT run that product in our transmissions. IIRC it was apparently designed for a specific application and will not work well with some of the metals used in our tranny and/or synchros. If in doubt, shoot an email to Pennzoil and see if you get confirmation on this. It's easier than a tranny swap.
2) On Redline Shockproof- I'm no expert on tranny oils, but we have a guy on the 323/GTX boards who has spent a big chunk of the last few years researching them in an effort to find out what works best to prolong the life of the rare and expensive GTX trannies and diffs. He concluded (and apparently with confirmation from Redline) that Shockproof is meant as a racing fluid that will be quite frequently changed. It's evidently good stuff, but he warned all of us that the same thing that makes Shockproof good at what it does (tons of calcium particles), is also what limits its long term use. After these calcium particles get crushed absorbing the shock, you're left with, in his words, "pisswater". He said that the Redline guys told him that only specialized analysis can tell you if it's still good or not, so most teams change it very frequently to be safe. I think they recommended the MTL, and that may be what he settled on. Redline makes good s***. Food for thought, though. Again, if in doubt, check with Redline and see what they say. I wouldn't take any single person's opinion on this forum over what the manufacturer of the product says unless there was a solid argument for it.
Hope that helps.
