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08-23-2011, 04:02 AM | #1 |
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Join Date: Oct 2010
Location: Buckeye Arizona
Posts: 470
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Eaton Rear End Gear Ratios
I have 4.56's right now.
Is lowest I can go 4.11's? Some 3.90's would be awesome. |
08-23-2011, 07:19 AM | #2 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: Eaton Rear End Gear Ratios
the lowest you can go is a 5.13.
the highest you'll find is 4.10 there's some 3.90 gears out there, (aftermarket) but they are very far and few between. Doing the junkyard crawl, look for small block or big block trucks with an automatic, then double check to make sure it is a 4.10 and not optioned otherwise. (4.10 was standard in V8/auto) Don't forget to look at the one ton trucks too. |
08-23-2011, 11:10 AM | #3 |
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Re: Eaton Rear End Gear Ratios
I knew you'd be the one with a definite answer for me!
Who manufactured the 3.90's and do you have any idear of where I might be able to find a set? |
08-23-2011, 12:12 PM | #4 |
Six in a row makes it go...
Join Date: Mar 2009
Location: Vacationland: Maine
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Re: Eaton Rear End Gear Ratios
I think Yukon manufactured them. Maybe if we all keep calling them they'll do another run of 3.90s.
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08-23-2011, 01:28 PM | #5 |
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Re: Eaton Rear End Gear Ratios
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08-23-2011, 11:16 AM | #6 |
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Re: Eaton Rear End Gear Ratios
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08-23-2011, 12:10 PM | #7 |
20' Daredevil (Ret)
Join Date: May 2003
Location: Jefferson State
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Re: Eaton Rear End Gear Ratios
Per the thread title, his diff is an Eaton (GM Corporate). Andy nailed it.
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
08-23-2011, 02:37 PM | #8 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: Eaton Rear End Gear Ratios
You could probably locate a 14 bolt with 3.73 or even better. Shouldn't be too hard to swap in there if you are able to install a cummins
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08-23-2011, 05:59 PM | #9 |
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Re: Eaton Rear End Gear Ratios
i put a dana 70 with 307s in mine and it was perfect,but i didnt haul real heavy loads,, I agree that even 390s with the cummins would be to much.
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67 chevy short step 2wd 427 71 chevy short fleet 4x4 396 72 gmc jimmy 2wd 377 71 chevy blazer 4x4 454 69 chevy longhorn 5.9l cummins 72 chevy 400 2wd custom camper 67 chevy lwb 4x4 454-in pieces 67 chevy panel soon 4x4-400 67 gmc dump 4x4 1 ton-305 WTF!! 72 chevy 3/4 ton 4x4 burb 350 70 chevy panel 2wd 302 5 speed tko "THERE IS NO REPLACMENT FOR DISPLACMENT"!!!!!!! |
08-23-2011, 07:45 PM | #10 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: Eaton Rear End Gear Ratios
I wouldn't put a 67 - 72 chevy C/20 dana in there though. The axleshafts shatter way too easy. (not the dana70 mentioned above)
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08-24-2011, 01:11 AM | #11 |
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Re: Eaton Rear End Gear Ratios
Well, even though I'm an 18 year old kid, I'm not much of one for hauling @$$ everywhere.
My dad and I drag race for a reason, lmao. We don't need radical street cars. If I can cruise 65mph at 2k RPM I'll be more than happy. That's what I'm shootin for. |
08-24-2011, 07:08 PM | #12 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: Eaton Rear End Gear Ratios
you don't need to be hauling ass to shatter an axle shaft. A heavy load, or just romping the throttle. Large tires, steep hills, torquey motors... each can do it, a combination of them is asking for trouble.
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08-24-2011, 10:43 PM | #13 |
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Join Date: May 2009
Location: Eliot, Maine
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Re: Eaton Rear End Gear Ratios
my 72 Burb C20 turns 3,000rpm at 60mph with stock tires. that is with the 4.10 ratio swap which is 90% of the original 4.57. beauty of the Corp axle is the removable 3rd member (like a Ford 9 inch). only using the 3.90 aftermarket gear would require you to take the diff apart rather than just swap for the unit with the gears you want. the 3.90 is only 5% softer than the 4.10 and probably about equal to a 1/2 ton (w/ the stock shorter tires) with 3.73 gears.
i heard a 6.13 ratio was available also (probably only in the HO72 in the 1 ton trucks). and the 4.56 and 4.11 are ratios found in 1/2 ton trucks....different axle |
08-24-2011, 11:06 PM | #14 |
Carpe manana
Join Date: Dec 2010
Location: Eau Claire, WI
Posts: 12,357
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Re: Eaton Rear End Gear Ratios
I didn't know that about the C20 Dana 60's. I just got one from a 70 camper special and new spring perches to be installed in my K20 in place of the Eaton. Bummer.
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