I don't think there is enough varience in performance to worry. Make sure there is enough to keep some preload after it gets beat on. Otherwise it can beat tthe shims out. The most important thing I've learned is to loosen the backlash up to .010"-.012". If running tighter as the teeth flex they stay bent slightly and loose backlash. Then threre isn't roo for lube causing the pinion teeth to crack. Most drg race gear guys I've talked to don't like synthtic fluid either.
Doug
I was thinking exactly what you said...make sure it doesn't get loose after a good beating, but not so tight it makes heat and kills the bearings. This doesn't see a ton of street cruising, but it's not out of the question that it'll see a 20 mile trip occasionally.
Hadn't thought about increasing backlash. Any theories on why you wouldn't run synthetic? It is a cushion/shock thing? I would think coming off the T-brake hits the ring and pinion pretty hard. I suppose in an 1/8mi not a lot of heat builds up in the rear, so temp isn't a concern so synthetic isn't a huge benefit.
