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04-10-2015, 07:58 PM
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#1 |
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Registered User
Join Date: May 2004
Location: Ontario Canada
Posts: 164
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E Rod and a 4L65E
I'm planning on putting a connect and cruise setup (LS3 with a 4L65e) in my 70 shortbox stepside and I'm looking for some suggestions for the right rear gear ratio to use. The truck with 29.6" tires has a 3.08 in it now which will rev at 1704 rpm at 70 mph. 3.73's will rev at 2085 so I'm thinking maybe 3.55's may be better at 1964 rpm. Is anybody using the 4L65 or anything with a .70 (.696) OD and similar rear gear ratio that can tell me how they like it?
Suggestions appreciated. Jim |
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04-10-2015, 08:03 PM
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#2 |
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Registered User
 
Join Date: Oct 2005
Location: Sacramento, CA
Posts: 1,970
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Re: E Rod and a 4L65E
I think the general consensus is 3.73's are the best choice for auto 4 speed overdrives. 700R4 in mine with 3.73's.....works great!
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72 Cheyenne SWB Fleet Nut & bolt frame off in progress...99.9999% - supercharged 383 - 4 wheel discs - relocated fuel tank -  My Build Thread |
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04-10-2015, 08:07 PM
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#3 |
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Its a Truck Thing......
Join Date: Dec 2004
Location: Sierra Vista, Arizona
Posts: 3,158
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Re: E Rod and a 4L65E
3.42 for all my 700R4's.
Good take off and great on the highway. Smitty
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71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 71 C20 Longhorn/Ole Yellor 69 C30 Former Motor Home, Flat Bed time |
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04-10-2015, 08:23 PM
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#4 |
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Registered User
Join Date: May 2004
Location: Ontario Canada
Posts: 164
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Re: E Rod and a 4L65E
Thanks for the replies. 3.42's will get me to 1892 rpm at 70. What size tires are you guys running?
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04-10-2015, 08:25 PM
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#5 |
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Registered User
Join Date: Jun 2012
Location: Lakewood,New York
Posts: 502
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Re: E Rod and a 4L65E
I have that erod /4l65E in my truck...just got it in December.
the documentation with it recommended 3:42 with about a 29 inch tall tire as I recall |
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04-10-2015, 08:32 PM
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#6 |
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Registered User
Join Date: Mar 2013
Location: Marquette michigan
Posts: 828
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Re: E Rod and a 4L65E
I just finished going to 18" wheels and a 28.2 diameter tire from a 26.5 diameter running through the same 3.08 ratio with a 5.3/4l65e and suspected a reduction in low end take off, and was correct. Rear end change/ratio change in the future and will be going to at least 3.50 or higher.
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04-10-2015, 08:45 PM
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#7 |
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Registered User
Join Date: May 2004
Location: Ontario Canada
Posts: 164
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Re: E Rod and a 4L65E
Thanks for the replies! I think I'll check out the GM documentation before I decide. I had a 2010 Corvette with a 26.7 tire and a 3.42 rear gear and in 6th with a .50 OD I was revving about 1509 rpm. A little sluggish but 6th was a fuel economy gear. 30 mpg with the LS3. I wonder if rpm that low would work in my C10?
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04-10-2015, 09:07 PM
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#8 | |
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Registered User
Join Date: Oct 2011
Location: DWG, Texas
Posts: 43
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Re: E Rod and a 4L65E
Quote:
Jim, My LS6 and 4L65E are running 3.73 (w/posi.) It absolutely runs like a champ.  [IMG]  [/IMG][IMG]  [/IMG][IMG]  [/IMG]
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70 GMC Serria Grande Short 70 Chevy C/10 Short LS Powered 72 Jeep J2000 4X4 86 El Camino (22k original miles) |
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04-10-2015, 09:10 PM
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#9 |
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Registered User
Join Date: Feb 2012
Location: Southern Ohio
Posts: 292
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Re: E Rod and a 4L65E
I've got a 3.25 9" with a 4L80E.
Granted, I just got the truck driving yesterday, but the 3.25 seems too tall for anything other than highway driving. I don't think you'd be dissapointed with 3.73's.
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1970 C10 Turbo LM7 5.3/LS6 cam PT7675/4L80E/Holley Dominator EFI/E85 Moser 9" 3.25/4 wheel discs 11.16@121.07 |
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04-10-2015, 09:17 PM
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#10 |
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Registered User
Join Date: Apr 2015
Location: Abilene, TX
Posts: 136
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Re: E Rod and a 4L65E
Depends on the type of driving that you are most likely going to be doing. I chose 3.73s because I drive mostly in town and I'm not going to be doing much highway driving.
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04-10-2015, 09:38 PM
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#11 |
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Registered User
Join Date: May 2004
Location: Ontario Canada
Posts: 164
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Re: E Rod and a 4L65E
I'm planning on both highway and city. Around town and those long road trips to the Goodguy's shows. I have a 2006 Silverado with 3.73's and a 6.0 Vortec Max and a 4L65E and it runs about 2000 rpm at 70 and has a 30" tire. The C10 is a lot lighter so I should be ok with something like 3.55 to 3.73. Thanks everybody for you suggestions! Really helps the decision.
Jim |
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04-12-2015, 10:02 PM
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#12 |
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Registered User
Join Date: Sep 2007
Location: Katy TX
Posts: 1,268
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Re: E Rod and a 4L65E
I have both a 3.73 and a 3.42 ratio rear end with the overdrive trans. I like the 3.73 but the 3.42 is the perfect combination of acceleration and mileage. If building from scratch I would always do the 3.42 ratio.
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 HSRACERSlammed 53 5 window Blown/Bagged 54 Pickup Patinaed 67 LS stepside Supercharged 67 Nova Bagged 69 Suburban Turbo'ed 5.3 LS |
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