The Stovebolt Site Forums The Shop Area Engine Shop 59 rear for 57

Will the third member from a 59 fit into my 57 axle. I belive 59 was the first year Chevy came out with a 3.38:1 for the 3100 series. My 57 has 3.9:1 made at Detroit G&A, from what I read G&A was the only company in 59 to make the 3.38:1 gears for the 3100 series. I'm trying to find a used set of gears that will fit my third member and not have to pay $400 for a new set. Any info on the 59 or any other gears would be healpful.

any gears from any TF year will fit, but good luck finding a one year item like the 'Maximum Economy Gearing option' - I'd expect about 90% of the 1/2T's came w/ the 3.90's - don't know of any other years that'll fit the carrier, but you could always consider the various overdrive possibilities or change to a newer axle w/ better gears

Bill

Thanks for the info. One more question. How will 3.9 gears work at 65 mph?

depends on 6 or 8 - my 235 will do it on flat roads, but is pretty flat out and screaming, the 283 is wound up pretty good too, but doesn't mind it so much and can do 70-75 if it's pushed

yer best bet is the OD trans, either a stock 3spd OD, which can be found if yer patient, or one of the later OD 4spd's like the NP A833, which can be a direct bolt in if ya find the right configuration - search around here and you'll find info about various OD trannies like the T5

Bill

Tell me more about this max economy gear option. Was 59 the only year available & how could I identify one. Good luck finding a new set even if you have the $400 in your pocket.

I was looking in the "Catalog of Chevy truck ID numbers 46-72" for rear ends that would match mine (57 1/2 ton.) In 59 the ratios & stamped codes on the 3100/3200 series were as follows; 3.9:1 AF or AR, 3.7:1 AJ, 4.11:1 AV, 3.38:1 AY, & 3.92:1 (no code listed). Numbers after the letters indicate date made. Example: AY 212 is 3.38:1 built Feb 12. The codes are stanped on the right front of differential carrier flange.
As for the $400 for a new ring & pinion (3.38:1) there are some places that sell them, plus another $210 for install kit and another $65 for speed adaptor plus shipping and handling. Golden State Parts is one company that sells the set. I hope this helps.

I,ve tried to order a set from several suppliers & they all say they are on back order. At that price it seems like they would have plenty of them. Maybe China could build some.

I have about gave up on the 3.38:1 gears. I've talked to a lot of folks and no one has seen them. I've even been told they might only existed on paper. Also, that the 3.9:1 were hihgway gears. Being hihgway gears you can go 60-65 on the highway without over straining the engine. Plus going down hills or mountains the engine will hold you back and you don't have to use as much brakes. When going up hills with the 3.38:1 you would also have to shift to second way before you would with the 3.9:1 gear set. I'm keeping the truck as orginal as possiable, with the 235 & 3 on the tree. I was worried about only being able to do 50-55 on the highway and getting rear ended. Also, the rearend I have has bad gears, so I wanted info (which I got a lot of Thanks) on what the cost differance would be to swap out gears. I still got to find a set of gears and buy the install kit but, there is a large swap meet tomorrow so, you know where I will be. I belive I'm going to stick with the 3:9 gears. One more thing that might help you can use the rear out of a newer truck as long as the distance between the back plates is the same distance; I belive Blazer up to 87 and GM trucks. Cut the leaf spring mounting brackets off your axle or buy new ones and weld them on the newer axel. Well thats all I got on the subject I hoped it helped.

Rick - the 3.38's existed, it was a buddy who's been in the wrenchin and wreckin field all his life who first told me about them, and who pointed out they're very rare - remember they were put about as a fuel economy option, and farmers need low speed power - go with the OD 3spd, which from the factory actually came w/ the 4.11 rear - callin the 3,90 "highway gears" simply reminds you that the highways were 50mph everywhere back then!! don't try to go 60-65 regulatly for prolonged periods w/ the 3.90's, especially w/ a 235, as you'll shorten it's life a lot

Bill

Thanks for the info. I have a little while before I'll be ready for the rearend. Now I pelnty to think about before I make a decide which way to go.