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#1 |
Registered User
![]() Join Date: Nov 2018
Location: austin Texas
Posts: 37
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rear end ratio opinions
I've got '68 C10
new 350 V8 -Nothing special 250HP approx Turbo 400 Stock 15" wheels currently 4.10 rear end Not looking to do burnouts or win any races off the line. Just want to be able to easily cruise at 65-70 without winding out the engine. I'm thinking 3.23 What do you think? thanks, steve |
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#2 |
Registered User
Join Date: May 2011
Location: Northern Calif.
Posts: 3,684
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Re: rear end ratio opinions
The 3.08's in my 70 putts along just fine in town and on the highway. I don't use it to tow anything.
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#3 | |
The Older Generation
![]() ![]() ![]() Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,483
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Re: rear end ratio opinions
Quote:
Not sure if you were actually thinking 3.73 or not, I don't think there is a 3.23 for these trucks. There was a 3.36 but I'm not sure what it was used in. If you were thinking 3.73 I don't think it will help you that much. The 3.07 would definitely give you a higher top end but I don't know how it would do on the bottom end with the lower HP 350. LockDoc
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Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - |
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#4 |
Registered User
Join Date: Jul 2009
Location: Space Coast, Fl.
Posts: 1,050
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Re: rear end ratio opinions
Always heard about OPINIONS being like "REAR ENDS"....... and truly, most everybody's got one of each.
![]() I have 3.07's in both of my trucks. The GMC has a mild 350/700r and it'll cruise 60-70mph comfortably in 3rd gear (1-1 ratio). Not lazy off the line either. 700r does have a lower 1st, gear ratio than your 400 trans. You might find a complete rear end on CL or Marketplace.. most I see are around here are 3.07's. It'd be cheaper than buying a gears & having them fitted, unless you can set one up.
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Dad always said, "Son, WISH IN ONE HAND, and ......." -------------------------------------- -------------------------------------- Current toy trucks: '71 GMC 1500 SUPER CUSTOM short/step, orig. dk. blue, 350/700r, ps,pb, A/C '72 Blazer 2wd, ochre & white, 454, tremecTKO 500 5spd. ps, pb, A/C, tilt Last 10yrs of hobby vehicles, had a FEW more in the 50yrs. before these: '66 Plymouth Belvedere City of Miami cop car clone. '70 Nova 406"sb, 13.5-1, solid roller, Brodix, p.glide/t.brake, back halved, 9" Ford, spool 4.88, cage,ladder bar/coilover, 10.5 tire....... SOLD!! '67 C10 short/step side mount spare -- SOLD!! '72 Jimmy 2wd, 350/350, ps, pb, fun driver, lots of bondo & a shiny red paint job..... SOLD!! '69 Nova 350, 4spd, A/C, ps, p.b, ...SOLD!! |
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#5 |
Registered User
Join Date: Jul 2012
Location: Whitehorse yukon
Posts: 1,218
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Re: rear end ratio opinions
you can go for your carrier is 3.73 any gearing smaller needs a new center section
Many of our trucks are 3.08 or 3.73 in 1/2 tons Here is a quick rpm calculator https://www.differentials.com/techni...io-calculator/ |
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#6 |
Registered User
Join Date: Jul 2012
Location: Whitehorse yukon
Posts: 1,218
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Re: rear end ratio opinions
I would look at 700r4 or a built 200r4 and add overdrive with out the need for computer control
https://www.hotrod.com/articles/ccrp...mission-build/ |
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#7 |
Try spinnin 4 rear tars
Join Date: Sep 2003
Location: Salt Lake City, Utah
Posts: 757
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Re: rear end ratio opinions
3.08 gear set. Turns 2500rpm at 65-70. I have a 307ci with a 2-barrel. High altitude and steep hills will slow it down, but I've managed to stay above 60 on the climbs on the interstates.
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SWEET7T 1970 C10, 2wd, LB, 307/TH350/3.08. PS, PB |
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#8 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
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Re: rear end ratio opinions
I'd retain the rear as is because while 3.73 will be nicer on the highway - it's not as nice as a 4.10 with 700R4 O/D, which makes your 4.10s a 2.87 at highway speeds - and retains the exact same current acceleration performance in 1st-3rd that you have today. I'd get built 700R4 though, not a junkyard swap, because 4.10s can be kinda rough on it if you do the occasional burnout...
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#9 |
Registered User
Join Date: Jun 2016
Location: West Palm Beach, Florida
Posts: 295
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Re: rear end ratio opinions
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#10 |
Registered User
Join Date: Mar 2016
Location: hickory, ky
Posts: 1,278
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Re: rear end ratio opinions
I had almost exactly the same set up in my last 72. 3.07 or 3.08, whatever you want to call them, are all you will need with that combo. I ran 2.35/75/15s on mine and got 15 mpg if I behaved. Even driving it hard, it wasn't all that bad.
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:My build thread http://67-72chevytrucks.com/vboard/s...d.php?t=807535 1972 K10 swb/1968 Camaro 350/4spd 1955 210 2 dr sedan/1998 RCSB Z71 |
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#11 |
Registered User
Join Date: Mar 2005
Location: 10-Uh-See
Posts: 5,609
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Re: rear end ratio opinions
3.08 will be a good gear if you just plan to cruise around and be able to run at highway speeds. If you want a tad more punch off the line and still be able to run highway speeds, 3.42 is a great gear.
The only aftermarket gear options for the stock 12 bolt truck rearend are 3.08, 3.42, 3.73, 4.11, 4.56, 4.88, and some offer a 5.13. Keep in mind, to change to a 3.42 or 3.08 from the current 4.11 will require a new carrier. 3.73 and lower gears are a 4-series carrier. 3.42 and 3.08 use a 3-series carrier. The difference is ring gear thickness. This may not help your case, but gearsets are available to put a 4-series gear on a 3-series carrier, but not the other way around.
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#12 |
Registered User
Join Date: Nov 2008
Location: Gwinnett GA
Posts: 1,803
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Re: rear end ratio opinions
If 70mph cruise is your priority, the 3.07 or an OD trans. Even with 3.42s, you would be at 2800 at 70. Not exactly a mellow cruise. With a 3.07 gear swap, you won't be towing anything - which probably isn't happening anyway.
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1982 K10 SWB 1987 V20 - Sold - Doh! |
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#13 |
Post Whore
![]() Join Date: Feb 2016
Location: Portland Oregon
Posts: 11,111
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Re: rear end ratio opinions
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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