are factory auto truck rears geared better or worse for highway - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dragn91 · 10-09-2011, 10:04 PM

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** · 10-09-2011, 11:57 PM

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** · 10-10-2011, 12:57 AM

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 · 10-10-2011, 01:04 AM

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

**jocko** · 10-10-2011, 01:56 AM

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

Wrenchbender Ret · 10-10-2011, 10:05 AM

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 · 10-10-2011, 02:16 PM

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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chemlab · 10-10-2011, 07:28 PM

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.

**Captainfab** · 10-11-2011, 12:33 AM

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.

Quote:

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 · 10-11-2011, 12:43 AM

Quote:

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** · 10-11-2011, 12:46 AM

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.

Quote:

Originally Posted by DBear

The 62 is a chevy! What's the best way to id rear?
Posted via Mobile Device

DBear · 10-20-2011, 08:34 PM

Quote:

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....

**Captainfab** · 10-21-2011, 12:53 AM

Yep, that is a Eaton HO52. If you're lucky it will have the 4.11 gears. If not it will have 4.57 gears.

Quote:

Originally Posted by DBear

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....

Surfdaddy · 10-21-2011, 06:06 PM

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 · 10-21-2011, 11:38 PM

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 · 10-22-2011, 01:22 AM

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 · 10-22-2011, 06:17 AM

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 · 10-22-2011, 08:21 AM

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

10-09-2011, 10:04 PM	#1
dragn91 Registered User Join Date: Aug 2007 Location: charlestown maryland Posts: 272	are factory auto truck rears geared better or worse for highway 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 Posted via Mobile Device

10-09-2011, 11:57 PM	#2
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,960	Re: are factory auto truck rears geared better or worse for highway 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!?). Last edited by jocko; 10-10-2011 at 01:56 AM.

10-10-2011, 12:57 AM	#3
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,246	Re: are factory auto truck rears geared better or worse for highway 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. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

10-10-2011, 01:04 AM	#4
oem4me Registered User Join Date: Aug 2010 Location: Burbank CA Posts: 3,055	Re: are factory auto truck rears geared better or worse for highway I believe the 3.73 was given to all trucks where none was specified. Last edited by oem4me; 10-10-2011 at 02:43 PM.

10-10-2011, 01:56 AM	#5
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,960	Re: are factory auto truck rears geared better or worse for highway that rings a bell in my brain housing group oem4me - thanks, I believe that is correct - the "option" was the 3.08.

10-10-2011, 10:05 AM	#6
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,208	Re: are factory auto truck rears geared better or worse for highway 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.

10-10-2011, 02:16 PM	#7
DBear Registered User Join Date: Nov 2008 Location: Rowlett, TX Posts: 863	Re: are factory auto truck rears geared better or worse for highway 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! Posted via Mobile Device

10-10-2011, 07:28 PM	#8
chemlab Registered User Join Date: Feb 2010 Location: Phoenix, AZ Posts: 114	Re: are factory auto truck rears geared better or worse for highway 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.

10-21-2011, 06:06 PM	#14
Surfdaddy Registered User Join Date: Jan 2011 Location: Newhall Ca. Posts: 463	Re: are factory auto truck rears geared better or worse for highway 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 __________________ 1961 GMC. Start date 1/20/2011 Past projects: 1958 Fleetliner 14ft Runabout 1966 Caprice 2dr 1970 VW Squareback

10-21-2011, 11:38 PM	#15
collins10672 Registered User Join Date: Jan 2009 Location: bean station tennessee Posts: 398	Re: are factory auto truck rears geared better or worse for highway 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.

10-22-2011, 01:22 AM	#16
likaroc13 Rollin' Old Skool Join Date: Jun 2007 Location: Hattiesburg, MS Posts: 5,371	Re: are factory auto truck rears geared better or worse for highway 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 __________________ _____________________________________________ Phillip My Build threads: 1966 Chevy C-10 "Black Betty" shortbed, fleetside, BBW, 327 V8/ Powerglide (under construction) http://67-72chevytrucks.com/vboard/s...ighlight=betty 1997 Chevy Tahoe, 2dr/2wd, mild custom (Daily driver) http://67-72chevytrucks.com/vboard/s...d.php?t=601142 Pics: '66 C-10 https://flic.kr/s/aHsjHWD4h9 '97 Tahoe https://flic.kr/s/aHsjGZ7wKP '93 C-1500 https://flic.kr/s/aHskxdpdnQ '88 S-10 Blazer https://flic.kr/s/aHsjYGx4Md Previous Rides: 1993 Chevy S-10 ext. cab, 4.3L, 4/5 drop (Sold) 1993 Chevy C-1500 short/step Retro-Rod (Sold) 1988 S-10 Blazer 2dr/2wd mild custom (Sold)

10-22-2011, 06:17 AM	#17
tincan1966 Registered User Join Date: Oct 2010 Location: Independence,KS Posts: 1,477	Re: are factory auto truck rears geared better or worse for highway 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.

10-22-2011, 08:21 AM	#18
6flee3 Registered User Join Date: Mar 2011 Location: Sacramento, CA Posts: 28	Re: are factory auto truck rears geared better or worse for highway 63 C10, was a 6cyl, 3 on the tree ... had 12bolt with 3.73's



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