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Help with #'s stamped in rear


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Trying to help a guy out with a gear swap. I first thought the rad 5291 stamped into the axle housing meant it had a 529-1 ratio. Then I found all the other numbers stamped into the carrier section of the rear. Please mack gods help me out with the ratio. Thanks.

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Thanks for posting, I'm the guy working on the swap into my 1963 B42. right now I still have the gas job rear end with what I believe are 7.85's. The truck has a 673P with either a TRDL 720 or TRDL 7220 I know its one or the other but for the life of me I cant remember right now and its a bit wet right now to go crawl under the truck to verify. Shes on 22" rubber, I'm going to put on some new 24.5's in the spring so tire size will stay the same. With my currant set up I top out around 40 or so, I'd like to get to 55-60 but I would settle for 50-55 as the truck wont be seeing the interstate.

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Rad5291 is the housing series. it usually meant the difference between 6'' or 7'' brake lining, aluminum backing plates and some had the cheaper axle without the centering cones behind the axle nuts. the rear ratio is stamped on the driver side of the hogs head below the round side cover. usually has an R in front of it. id say with an overdrive trans on 22'' rubber you need a high 4.xx to low 5.xx ratio. most single axle b models I have seen with directtrans and 22'' rubber had 4.66 or 4.62 ratio. you gotta watch changing out the hogs head because if you have the cheaper housing, it wont have the webbing inside to support the ring gear.the better rear housings were the Rad508 or Rad512

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Ok so the botom number on the hogs head is the ratio, learned something new today. thats good news as 4.60 would be perfect for what I'm doing. I'll have to check my housing to see if the series is the same otherwise I might have to swap the housing and all. Thanks for the info you guys are a wealth of knowledge.

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yup, 4.60 is the ratio. usually has an R in front of it or some actually say 'ratio'. looks like that ones been reworked with different gears and someone made it a 4.60 as the numbers looks scratched out and restamped. id probably just change the whole housing. if you have the original rear in your B42, it most likely has the smaller brake lining anyways. if the other rear came from a diesel it usually has the 7'' lining.

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I just checked and I have the centering cones under my axle and I have 7" brakes (that are new too) so I would say I have the heavy housing in my truck so if I understand everything I've read correctly the hogshead above will work in my housing. I sent you an email Hobert thanks again for everything.

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