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.
My car leaves pretty decent off the foot brake. Mid to high 1.2X 60ft @3350-3550lbs depending on ballast. It's on it's 4th R&P. The first three all tightened up from the .007"-.008" they were set at to zero. Two of them cracked pinion teeth. One actually broke a tooth off. The cracks always start under the head of the pinion. Ring gears appear undamaged. Three different brand gear sets including one that was a pro gear. I sought out help from Moser, Strange, and a local guy Leo Zynda. All three said the same thing. Loosen it up. Don't run synthetic. First set went 425ish no cracks Motive street gear), 2nd set no brand 160ish broke pinion teeth, 3rd set 150ish (pro gear cracked teeth). The current set (Motive street gear) have 300+ with no noise. They are set at .012" wit h Lucas 85/140. Could always tell when there was a problem coming. Coast with the engine off into staging. Click, click, click.
Doug [/quote]
A long time ago (70s) Chrysler engineers found out the Dana under harsh load (clutch dropped @ rpm) the gears would actually suck (bend) into the pinion, so they recommended 12-15 thousands backlash. I think they set pattern a little different too
