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#1 |
Registered User
Join Date: Jan 2009
Location: Denison, Texas
Posts: 245
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gears in the rear
I have a 71 gmc 1/2 ton. i have a 350 with a stock 350 trans and 275-60-15 tires on it, I have no idea what gears i have in the rear but am wanting to put someting new in. does anyone have some advise on a good ratio.
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#2 |
1970 Daily Driver
Join Date: Jun 2007
Location: Glenns Ferry IDAHO
Posts: 1,037
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Re: gears in the rear
We need to know what Ratio you currently have to go from there. It is easy to find out. You can look on the top of your passenger side axle tube and find a stamped code that will have the info needed to see what you have. If you get the code PM me and I will let you know what you have. Or you can put a piece of tape on you tire and on your drive line. Have some one turn the tire on rotation and count how many times the driveline goes around. If it is just over 3 times you have a 3.07, 3-1/2, you have a 3.41, 3-3/4 you have 3.73 and so on. Hope this helps.
We also need to know if you want more top end or more low end. You can't have both unless you get an overdrive.
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#3 |
Never Ending Projects
Join Date: Jul 2006
Location: San Diego, CA
Posts: 3,836
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Re: gears in the rear
It depends on what you are planning to do with it. Are you planning to haul things, just cruise around, mainly freeway driving, city street driving, drag racing, etc? Are you keeping the tranny or will you replace it with an overdrive tranny?
Without knowing what you have and knowing what you want to do, it's really hard to recommend anything.
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#4 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: gears in the rear
you should have a 3.07 gear, and running right about 2500 RPM @ 65 mph.
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#5 |
Registered User
Join Date: Jan 2009
Location: Denison, Texas
Posts: 245
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Re: gears in the rear
I will have to get out and see if i can find the stamp on the axle tube. I plan on the truck being in town some highway use.
I have been thinking about putting an over drive trans in it but dont know yet. should i wait on the rearend till i figure that out? |
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#6 |
The Older Generation
![]() ![]() ![]() Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,518
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Re: gears in the rear
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There are several ways to tell your current ratio. The one I usually use is the letters stamped on the housing. That way if the rearend has ever been replaced it will still give you the correct ratio. I have included a couple of pictures that show the location of the letters. (use the first two or three letters) When you have the code go to the following web site and look it up in the axle section. (you have to select the year of your truck) If you're not sure if it's the original rear end you can just check all of the years. http://www.americanclassic.com/paint.htm Another good way is to take the cover off of the rear housing and look at the numbers stamped on the gears. The good thing about using this method is that you put fresh gear oil in the rear end to replace the 40 year old oil that is in there now. Below are the numbers for the different ratios. The last two numbers in each row are the ones that will be stamped into the gears. Rear Axle Ratios Ratio 2.56:1 - Tooth Combination 41,16 Ratio 2.73:1 - Tooth Combination 41,15 Ratio 3.07:1 - Tooth Combination 43,14 Ratio 3.08:1 - Tooth Combination 40,13 Ratio 3.08:1 - Tooth Combination 37,12 Ratio 3.31:1 - Tooth Combination 43,13 Ratio 3.36:1 - Tooth Combination 37,11 Ratio 3.42:1 - Tooth Combination 41,12 Ratio 3.55:1 - Tooth Combination 39,11 Ratio 3.73:1 - Tooth Combination 41,11 Ratio 4.10:1 - Tooth Combination 41,10 Ratio 4.11:1 - Tooth Combination 37,9 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 - Last edited by LockDoc; 01-15-2009 at 02:36 PM. |
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