Posted 01 January 2013 - 08:08 PM
Tore Z31 diff carrier down again. Started by measuring all the discs and plates with my new Harbor Freight micrometer.
Savage42 clutch discs: 4 were 0.0623", 2 were 0.0633".
Stock clutch discs: varied between 0.0685 and 0.0691" (I have 4 stock discs, 2 from this diff and 2 from my other one).
Stock clutch plates: varied between 0.0666 and 0.0695" (there are 4 clutch plates in the stock diff)
Stock spring plates: varied from 0.0688 and 0.0690" (there are 4 spring plates in the stock diff)
Stock spacer: 0.1275 and 0.1280" (there are two).
I inspected the clutch discs from Savage42. Three of the 4 had some burs that looked like weld splatter on the "gear teeth." I had previously judged these to be in a position that made the burs inconsequential. That is true, unless the burred discs is placed directly on the "center section." I cleanned all the burs off with a dremel tool.
Put it all together with all 6 new clutches and no shims. Dipped each clutch part in diff oil. Wet test in the vice was 45# with both a breaking-style torque wrench and a wand-style torque wrench. Breakaway was 45 both with and without the ring gear on and torqued. Slapped it into the case, added 2 tubes of Trans-X and a quart of synthetic 75W-140 oil. Put an Energy Suspension insulator on the front awaiting a new RT mount. Diff cover is tapped for an NPT 3/8" fitting for external venting to a puke tank. I think the problem was a combination of using too many stock discs to the point that there was more added total clutch thickness than the thickness removed by removing the spacers, and possibly burs on the clutch discs. Thanks everybody, especially for encouraging me to not give up. Mission Accomplished.
1972 240z, purchased in 1991 for $900. Bone stock LS2/T56/DBW from 2006 GTO, swap completed in 2011. 400rwhp/435 rwtq. 2400# minus driver. JCI swap, Mantic ER2 clutch kit, JTR headers, single exhaust, Borla muffler, MGW shifter, M2 Differentials shortened Z31 CV axles, Z31 CLSD R200, Chequered Flag Racing billet stubs and companion flanges. MSD 2-step, Hurst roll control, both operated from switches on clutch pedal. 9" Hoosier drag slicks on Weld Draglites, 245/45/16 Hoosier A6/R6 on 16X8+10 Rota RBR. 225/250 sectioned coilovers, Koni 8610-1437RACE shocks, DP and EMI camber plates, MM shortened rear control arms, TTT front control arms, poly and aluminum bushings. Top speeds: Ohio Mile 174mph, C/GMS class record holder, best 1/8 mile 6.96 at 100mph, best 1/4-mile 11.0 at 126mph, best 60' 1.43, best 1/2-mile 148mph at GA 1/2-mile. Home Track-Jake's Dragway, Moulton, AL. SCCA autocross club - TVR, Huntsville, AL. Lets race!