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02-15-2023, 01:41 AM
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#26 |
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Registered User
Join Date: Mar 2015
Location: washington
Posts: 2,151
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Re: What's rear gear ratio are you running?
I just looked up the gearing for the 8L90 transmission.
1- 4.56 2- 2.97 3- 2.08 4- 1.69 5- 1.27 6- 1 7- .85 8- .65 |
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02-15-2023, 03:03 AM
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#27 |
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Senior Member
 Join Date: Dec 1999
Location: Southern California
Posts: 2,691
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Re: What's rear gear ratio are you running?
Putting 5.13's in my 72 with 37" tires. 6L90 installed. The low first gear should be fine and allow for good acceleration from a stop. IIRC final gear is .67. Expecting around 2100-2200 rpm at 65. Which is right where my 94 is with 3.73 and 32's. High gear ratio is not always good for mpg. My brother had told me that people were installing lower gears in the newer Toyota's and milage increased. Low RPM at cruise is not good if motor is struggling.
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Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746 |
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02-15-2023, 06:27 PM
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#28 |
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Senior Member
Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,016
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Re: What's rear gear ratio are you running?
I have 2 trucks running.
'68 C/10 Stepside -- 292/SM465/12-Bolt 3.73 '71 GMC Jimmy K/1500 -- 350/SM465/NP205/12-Bolt 3.73 posi [Auburn] And 2 rigs in ordinary: '67 K/10 Suburban -- 454/TH350/NP205/12-Bolt 3.73 posi [Eaton] '72 K/5 [tub on frame] 000/ooo/xxx/12-Bolt 3.07 [open] All K trucks have D44 front diff w/ matching gear ratios as rear.
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Every 25 years I like to rebuild that 292, whether it needs it or not. |
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02-26-2023, 01:41 PM
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#29 |
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Registered User
Join Date: Jan 2013
Location: Calgary Alberta
Posts: 1,164
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Re: What's rear gear ratio are you running?
Mine I am pretty sure is 3.07. It comes from a 71 truck and the guy I bought it from said it was 3.07 and I think I confirmed that. 3.08 must have different tooth counts but overall pretty well the same. I like the 3.07 with straight through transmission. The 3.73 was way too slow on the highway.
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66 fleetside 350 4sp |
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03-13-2023, 05:57 PM
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#30 |
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Registered User
Join Date: Sep 2012
Location: Idaho
Posts: 623
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Re: What's rear gear ratio are you running?
81 k20 350, turbo400, 4:10, 35" tires
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'81 K20 Silverado , '99 Dodge Cummins 4x4, '05 Dodge Cummins 4x4, Pinstriping-Lettering-Specialty Painting |
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03-23-2023, 03:43 AM
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#31 |
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Senior Member
Join Date: Feb 2010
Location: Falls City, Nebraska "100 Miles From Nowhere"
Posts: 2,219
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Re: What's rear gear ratio are you running?
72 C/10 350/350THM 3:73 12-bolt posi, 30" all four corners.
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Michael of the clan Hill, "Two Seventy Two's" 71 1-ton Dually 350 4-Speed 71 C/50 Grain Truck, 350 Split-Axle 4-Speed 02 3/4 ton Express 14 Indian Chief Vintage 1952 Ford 8N, "Only Ford Allowed On The Property"  "Be American, Buy American" 
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03-23-2023, 09:24 AM
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#32 |
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Senior Member
Join Date: Mar 2003
Location: Colfax-California
Posts: 8,382
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Re: What's rear gear ratio are you running?
91 suburban, 4.56 gearing, 4l80e auto with 32.8'' tall tires (285/75r-16)
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04-19-2023, 04:51 PM
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#33 |
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Registered User
Join Date: May 2011
Location: mich
Posts: 654
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Re: What's rear gear ratio are you running?
5:13 gears with a 33inch tall tire , no I do not drive it on the street much.
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05-23-2023, 05:54 PM
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#34 | |
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Registered User
Join Date: Jul 2022
Location: Rockford, Mi
Posts: 62
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Re: What's rear gear ratio are you running?
Quote:
And it's a 3.07 gear not a 3.08 according to the rear diff stampings. |
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