are factory auto truck rears geared better or worse for highway

[dragn91]

Wanted to know if I should snag the rear out of an automatic parts truck to get better highway gears in my stick truck or would it be worse? She use to tach up pretty high on the interstate
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[jocko]

that's a good question - to the best of my knowledge, 3.08 and 3.73 were what was available, but I always forget what was standard and what was the option. But I do believe both were available in auto/manual trans trucks - so the bottom line is it really doesn't matter what trans is in the truck/car that you're considering nabbing the rearend from, what matters is strictly the actual rear end ratio in the vehicle you're considering grabbing the rearend from. If your manual tach'ed up, am guessing you had a 3.73, or perhaps a 4.11 (was that an option also or am I mixing it up with the AD trucks!?).

[Captainfab]

My '66 Suburban was an original 283, powerglide burb, and the rear had 3.73 gears.

I agree with jocko. first you need to know what gears you have now, and then pull some covers to find the gears you want.

[oem4me]

I believe the 3.73 was given to all trucks where none was specified.

[jocko]

that rings a bell in my brain housing group oem4me - thanks, I believe that is correct - the "option" was the 3.08.

[Wrenchbender Ret]

Generally the auto trans rear ends were geared higher & are better for the high. Like the guys say you have to find out what you have & what the donor is & go from there.

[DBear]

Does this apply to 3/4 ton or 1/2 ton? I have a '62 3/4 that came with 283/ powerglide. Curious to what it has in the rear also!
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[Captainfab]

I'm thinking the GMC would likely have a Dana 60 rather than the Eaton HO52, so it's hard to say. You might be lucky and have the 3.54 gears. If you do have the Eaton HO52 you will have either 4.11's or 4.57's.

Originally Posted by DBear

Does this apply to 3/4 ton or 1/2 ton? I have a '62 3/4 that came with 283/ powerglide. Curious to what it has in the rear also!
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[DBear]

Originally Posted by Captainfab

I'm thinking the GMC would likely have a Dana 60 rather than the Eaton HO52, so it's hard to say. You might be lucky and have the 3.54 gears. If you do have the Eaton HO52 you will have either 4.11's or 4.57's.

The 62 is a chevy! What's the best way to id rear?
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[Captainfab]

Ooopps, I just looked at your sig and saw the GMC.

I don't have a pic handy, but the Eaton HO52 has a perfectly round rear cover with a fill plug. It also has the drop out 3rd member on the front side.

Originally Posted by DBear

The 62 is a chevy! What's the best way to id rear?
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[DBear]

Originally Posted by Captainfab

Ooopps, I just looked at your sig and saw the GMC.

I don't have a pic handy, but the Eaton HO52 has a perfectly round rear cover with a fill plug. It also has the drop out 3rd member on the front side.

Captain, here a couple pics of my rear end, thought maybe you could help ID it for me...thanks bud

Also, didn't mean to hijack thread....

[chemlab]

my experience with original rear ends is they top out around 55 on the freeway with todays speed limits. back in 66 the limits was much lower so the ratio matched the speed.
this page might be of use to find out what you want based on tire size after you find out what you currently have.

[Surfdaddy]

My 61 3/4 ton with a Hydra-Matic has 410's but that was ordered that way. I really need to get something like 323's or something for better highway driving

[collins10672]

while i am not 100% sure without looking in the spec book i don't think the 3:07 rear end was available with the powerglide.the 3:73 was.the 3:07 was available as an option with the 3 speed.my father had an original 1964 chevy short fleet with the 230 6 cylinder,3 speed and 3:07 rear axle and it ran really well out on the highway.it would cruise at 60-65 mph all day long and was really easy on gas too,but gas was only .80 per gallon then lol.

[likaroc13]

my '66 previously had 3.73's....we swapped in a '72 rear with 3.08's for better highway driving...but the truck originally had a 283/Powerglide combo, and the PO swapped in a 327

[tincan1966]

My 1969 C-30 had the Eaton HO72 with the 4.57 gears top speed- about 50! LOL! Just swapped out for a newer, but not as strong, corporate 14 bolt with 3.73 non locker. Highway driving is much more pleasant and the 427/TH400 doesn't have it's tongue hanging out after a trip down the highway.

[6flee3]

63 C10, was a 6cyl, 3 on the tree ... had 12bolt with 3.73's