at what point do you need to step up to 1350 u-joints & yokes, or how much can stock yokes and u-joints handle ? figuring a dead hook is it et,mph,60ft,torque,high stall ? thanks for your input. dave
When the need for 1350 r/e flange & u-joints depends on a combination of factors. Basically weight of car & how the rear is torque loaded. Typically, the combo of heavy car running, say 1.55 60 foots or better with loose convertor/ transbrake is very hard on smaller rear u-joint/flanges & weak driveshafts. On the other hand, most often just behind footbraked automatics & slicks, HD spicer 3R u-joints will hold up extremely well. Several 3700-3800 lb A-bodys I've built strengthened 12 bolts & 8.5 A-body rears for, have held up for years & years & hundreds of passes down the track with oem 3R pinion flanges. How quick... well into the low 1.40 60 foot range in 3800 lb cars. Problems with the 3R 12 bolt flange... The oem 3R (BOP) 12 bolt pinion flange has less material around the U-bolt holes, so its smart to to be careful when assembling 12 bolts with this flange. Very easy to chip the corners out of this flange if trying to compress crush sleeves, esp if one's pinion flange holding tool is slightly loose. Best to go ahead & use a common 1310 (chevy) 12 bolt flange, then come back in after confirming pattern with the oem 12 bolt 3R flange upon final assembly. Other problem, in core rears, I get in an easy ten Chevelle 12 bolts to one 3R equipped McKinnon built 12 bolt, so just don't run across that many factory 3R 12 bolt flanges anymore. An aftermarket Spicer 1330 12 bolt flange is avail (if one is set on running a 3R u-joint driveshaft). Still on a fresh HD 12 bolt build, truly needing a larger rear u-joint, I'll just go ahead & order a Spicer 1350 flange. Hope this helps. Got Posi? :3gears: Roger
