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Old 04-16-2017, 12:22 PM   #1
rwdmayhem
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gearing

So I've been trying to figure out what kind of rear end ratio to get my 65 c10. I know some members has stated they're running 3.08 however I have a rather steep incline on the way to work. Even my 2000 monte carlo ss has to stay in 3rd to make it up the hill and it makes about 200hp stock versus my c10's 230 which supposedly make 140hp. I would like to go out and find a T5 but I doubt I could even use 4th or 5th on the hill climb to work. what do you guys think I should do for gearing?
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Old 04-16-2017, 01:01 PM   #2
Clyde65
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Re: gearing

Easy to find out. Should be a tag on rear end. Another option is to jack the truck up and turn one wheel and count the revolutions of the pinion. If it does about 3, then you have a 3.07 more than likely. If it goes almost 4, then you have a 3.73.

I would suspect if you have a 3speed trans you probably have the 3.07 gear ratio.

If you want to run a 5 speed, it would serve you best with a 3.73:1 rear gear.
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Old 04-16-2017, 03:18 PM   #3
nail pounder
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Re: gearing

I bet with the t5 you won't need to swap the rear end. I have a 5 speed in my C20 stock 4:56 rear, 1st is super low and 5th spins about 2600 @80mph. In my Apache I have stock 3:90 rear and 700r4 and it also does great in town or on the freeway. See what rear you have, a 3:73 is going to be a great all around gear. Keep in mind your tire size will affect everything as well. You can Google, tire, rear end, rpm, mph calculator and see the difference.
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Old 04-16-2017, 03:50 PM   #4
rwdmayhem
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Re: gearing

well I'm planning on the stock height for the tires so I won't need to mess with the speedometer gear.
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Old 04-16-2017, 10:56 PM   #5
vince1
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Re: gearing

I think 3.73 is OK on the farm or in the city. On the highway an overdrive would be a necessity.

3.07 or 3.08 is a good all round ratio if you don't have overdrive. You've still got 1st and 2cd for groaning up the hill.
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Old 04-17-2017, 11:22 AM   #6
TJ's Chevy
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Re: gearing

With a 230 and stock 4 speed or 3 speed 3.07 or 3.42.

T5, 3.73 or even a 4.11.
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Old 04-17-2017, 12:26 PM   #7
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Re: gearing

Quote:
Originally Posted by rwdmayhem View Post
well I'm planning on the stock height for the tires so I won't need to mess with the speedometer gear.
Since the speedo is being driven by the transmission output, anything which changes between there and the road -- including rear end gears -- will require a change in the speedo gear to compensate.

B
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Old 04-17-2017, 12:47 PM   #8
Lugnutz65
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Re: gearing

I have a T5 with the 0.72 overdrive gear, a 230ci engine, and a 3.73 rear diff. in my 1965 short bed. It drives just fine and the highway RPMs are in the 2100 range. I have 235/75R15 tires which are 28.8" tall.

If you swap to a 3.08 rear I think you will be pretty happy. Then I f you decide later to install a T5, the best option would be to find one with a 0.86 overdrive to match the 3.08. . If you go straight for the T5 swap, then get one with the 0.72 overdrive gear to match up well with a 3.73 or 3.90 rear. The 3.42 rear will tend to bog the 230ci if you have a 0.72.
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Old 04-21-2017, 11:51 AM   #9
scuderia
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Re: gearing

292 with 308's and sm465 gearbox.. still take off in 2nd and cruises nicely at 65 though it now indicates 55.. had 4.11's stock. Not terrible on long grades, not great. But then my motor is well, old.
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Old 04-21-2017, 01:03 PM   #10
vince1
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Re: gearing

In the metric system going from a 3.73 to 3.07 makes it easy. A reading of 50 MPH gives you about 100KMH so just double the numbers instead of doing all that calculating.
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