I have a 12 bolt from a 68-72 Chevelle (not sure what year of those). It's got a 364 gear in it and I need a 411 or at least a 390 for my new setup. Will the carrier work for those ratios? Don't want to buy a gear that will not fit. Thanks
Your current three series carrier should handle ratios up to 3.73:1. To run the 3.90:1 and up you'd need a spacer plate w/longer bolts or an aftermarket ring & pinion set with the extra thick ring gear if available. Devon
3.64??. 12 bolt chevy? Something is wrong there. What is the exact ring tooth count and the pinion tooth count? IF it is a 12 bolt chevy rear you have choices of gears as follows for the 3 series gear that will bolt onto your carrier WITH OUT A spacer or longer spacer bolts. 3.08 3.31 3.42 3.55 3.73 (3.90 4.10 4.56 aftermarket) 3.90 GM gears fit the 4 series carrier Most 3.90 aftermarket gears for the 12 bolt chevy are 3 series gears. I think Motive gears are 3.90 for 4 series carrier. Jim
As usual you all are quick. Don't know much history on this rear. It came in an Olds project we had. It's all new. Never counted the teeth but the owner told me it was a 364 gear. When i mention that to people they say it's wrong. So I did the quick check today and counted the turns on the yoke. It is quite a bit over 3.5 turns but not as much as 3.75 so I assume he was telling the truth. The rear is very clean with all new hardware and drums on it. I have a 342 in the car now. It's a big 10 posi. Time to get more gear.
Oldsmobile had a rear with 12 cover bolts, only 10 bolt internals. It is not the same as a 12 bolt Chevy. from www.jdrace.com 12 Bolt 'O' Type 'O' type posi 'O' type posi U-bolts on yoke U-bolts on yoke Ssymmetrical 12 bolt cover Symmetrical 12 bolt cover 1/4 cut slugs bolt in axles 1/4 cut slugs bolt in axles Ring Gear Diameter 8.4 Olds Cover Bolt Count 12 Ring Gear Bolt Count 10 Ring Gear Bolt Size 7/16 right hand thread / aftermarket gears 7/16 left hand thread Axle Spline 28 bolt in axle 60 degree spline 31 bolt in axle (SPECIAL 67-68 SUPER DUTY OPTION) Pinion Spline 27 Yoke Style U Bolt & Nut Universal Joint retention (reference picture) Pinion Diameter 1.625 <<<< AFTERMARKET GEARS ARE AVAILABLE FOR 12 BOLT OLDS (For 3 series carrier only) Axle Shaft Diameter 1.382 press on bearing Supported Cars: Car Year 442 67-68 Cutlas 442 (USA ONLY) 69-70
Thanks for the info. Larry. I will investigate this rear better soon. Pull the cover and count teeth. It appears to be a regular Chevy rear. At least the cover matches all the 12 bolt Chevies I have ever had. The previous owner was a Chevelle/Camaro builder and that is who put it in the Olds. He came back twice and tried to buy it back but I didn't want to sale. Last time he practically begged for it to go in a Chevelle he was finishing. The economy finally took him out of the car building and trucking company business. Don't really know what he is up to now.
