I would have to go and relearn the history of how synthetics came into existance, but from what I can remember the Germans under Hitler developed synthetic oils so that the tanks and trucks on the battlefield could extend the oil change interval. They almost accomplished what they set out to do except for those damn Russians!....
Also, Hitler Germany also developed water injection to reduce the octane requirements on their fighter planes when climbing and placing the engine under great loads and stress. That's all I can pull from memory at this moment. I may do a search and post more...

 

The Germans invented lots of cool stuff with hydrocarbons around then, as far as I can tell mostly because they had supply problems.

Back to the original topic, what is the builder recommending that he run in that tranny? Synthetics have the basic advantage that they’re much more durable and tolerant of extremes, and I would say that 250* on one pass is getting up there, it’s in the range that most conventional lubricants start having problems. The only advantage that conventional lubes claim to still have (and I’m not sure I believe it, but there are enough well respected rear axle builders that recommend them for this reason that I’ll listen to the argument) is that they provide better high pressure protection and cling better to the parts, both fairly important in protecting gears and gearboxes…

 

So there is some "trade-offs" using a synthetic tranny fluid? I thought synthetics were superior in every aspect...
First time that I ever heard that synthetics had downfalls...
Interesting fact:
The first commercial synthetic oil produced by Mobil 1 cost appx. $35 a quart retail!....

 

This got me thinking, so I called Carl Rossler (who built my TH400) to get his take on this. Previously, Rossler had recommended synthetic, but I didn't really get into detail. So, today I asked for some more info. Carl said that the cars which really need synthetic are cars with a very high stall, which generates a lot of heat. My own combo, with a 3,200-3,400 stall, should be fine with a non-synthetic. In fact, he prefers it for heavy cars with relatively low stalls for some of the reasons being discussed in this thread. He did say that if you see very high temps, using a synthetic is a good idea. He also said that for a street transmission, synthetics will have a longer life and that they operate better at cold temps.

OTOH, he said that optimal operating temp is 140-180 degrees and that 250 degrees is quite high. He suggested that a more efficient cooler was needed if temps this high are seen.

Rich Krause

 

Never mind, ordered the book anyways... should be a good read.

-Mindgame

 

I know that I brought the other side of this up, but I still find it curious about how those people that seem to know what they’re doing and deal with gears prefer conventional lubes. The thing is that I’m not sure I even believe the explanation that I listed, after all, if you’re only putting stuff in the lube that is there for a reason, why couldn’t you ‘build’ a synthetic gear lube and ATF that has good pressure and ‘climbing’ qualities, even if it would slightly compromise it’s heat tolerance?

I also find it somewhat more surprising that that explanation works with auto trannys since ATF is forced through them under pressure, they don’t rely on parts passing through the bath of lube and clinging to them.