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Old 02-13-2017, 07:46 PM   #1
Jcfcamaro
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Gear ratio

Hey guys, what's the best gear ratios for a 72 k10 with either 33/12.50/15 or 35/12.50/15 tires with a turbo 350 trans and a stock 350ci motor. I will be doing only highway driving and occasionally pulling a car trailer. I don't want to high of Rpms but don't want a real dog either. Any help would be grateful. Would a overdrive trans be better for me. I'm pretty sure my trans is going to need rebuilt. There quoting me 850.00 starting out and up depending on the condition of it. So I could drop a grand real easy.
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Old 02-13-2017, 09:12 PM   #2
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Re: Gear ratio

With a tire that size I'd say 4.10
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Old 02-13-2017, 09:22 PM   #3
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Re: Gear ratio

On a stock 350 and t350 trans I have ran both 33/12.5's and 35/12.5 with a 4.10 gear ratio, and have zero issues with lack of power and cruise at 65 pulling around 2100 rpm
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Old 02-13-2017, 10:26 PM   #4
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Re: Gear ratio

Quote:
Originally Posted by codejitsu View Post
On a stock 350 and t350 trans I have ran both 33/12.5's and 35/12.5 with a 4.10 gear ratio, and have zero issues with lack of power and cruise at 65 pulling around 2100 rpm
Wonder what 3.73 would tach out at 65 to 70 mph
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Old 02-13-2017, 10:47 PM   #5
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Re: Gear ratio

If you are gonna stick with 33s, the 3.73s would be a better route for you imo
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Old 02-14-2017, 12:12 AM   #6
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Re: Gear ratio

Quote:
Originally Posted by Jcfcamaro View Post
Wonder what 3.73 would tach out at 65 to 70 mph
http://www.grimmjeeper.com/gears.html take a look
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Old 02-14-2017, 12:14 PM   #7
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Re: Gear ratio

TH350

1st gear ratio:
2.52

2nd gear ratio:
1.52

3rd gear ratio:
1.00


Rear axle ratio:
3.73

Speed (mph):
70

1st gear RPM is:
6252

2nd gear RPM is:
3771

3rd gear RPM is:
2481
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Old 02-14-2017, 06:18 PM   #8
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Re: Gear ratio

That might be a little high rpm on the highway. Maybe I should really think about a overdrive trans. What overdrive trans would you guys go with
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Old 02-14-2017, 07:36 PM   #9
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Re: Gear ratio

700R4 Transmission( that is what I put in Hulk Jr.)

1st gear ratio:
3.06

2nd gear ratio:
1.63

3rd gear ratio:
1.00

4th gear ratio:
0.70

Rear axle ratio:
3.73

Speed (mph):
70

1st gear RPM is:
8135

2nd gear RPM is:
4333

3rd gear RPM is:
2658

4th gear RPM is:
1861
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HULK BUILD
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Old 02-14-2017, 11:49 PM   #10
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Re: Gear ratio

2500 rpm on 70mph is not that bad .

better than my 4.10 / 235/85/16 ( 31.73" ) tires does at 70 rpm 3211
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Old 02-15-2017, 12:40 AM   #11
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Re: Gear ratio

I agree with a trans swap to 700r4 but i don't think it will work without a gear swap for what you are doing. I'm willing to bet that at cruise speed the trans wont go into OD negating it's purpose. The steeper 3.06 vs 2.52 gear will help a lot especially with a new converter which someone else with more knowledge will have to help you with. If you start adding performance goodies or towing etc, you'll need to regear regardless. That trans wont be happy with the load of tall gears with big tires and additional load. You wont like the performance either without gears. I guess it all depends on what your expectations and use of the vehicle are as well as how long you intend to keep it. It's money.
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Last edited by snj8198; 02-15-2017 at 12:50 AM. Reason: thpelling
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Old 02-15-2017, 01:29 AM   #12
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Re: Gear ratio

Id be looking at an OD trans for sure. I put the NV into mine for towing and haven't regretted it yet. Towing or not. Im sure that the 700s can be built to tow well although I personally would be after a 4L80, the 3.70 gears and 33" tires. If running the 35s, I like the 4.10s.
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Old 02-15-2017, 01:30 AM   #13
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Re: Gear ratio

And Steve's right... "Its money"
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Old 02-15-2017, 01:44 AM   #14
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Re: Gear ratio

Agreed Chris, although with a manual we can force the motor to lug in OD vs the automatic not willingly shifting in and/or hunting between gears.
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Old 02-15-2017, 02:47 AM   #15
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Re: Gear ratio

For sure od with 4.10s. I have 3.73 and regret it.
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Old 02-15-2017, 12:10 PM   #16
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Re: Gear ratio

Quote:
Originally Posted by bilfman View Post
For sure od with 4.10s. I have 3.73 and regret it.
Bifman, What tire size and transmission are you running?
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1956 Chevy Bel Air 2 door
1956 Chevy 210 4 Door
1968 K10 LWB Dark green my son calls it "THE HULK Jr"
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1970 K20 LWB project the Hulk build
HULK BUILD
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Old 02-16-2017, 12:39 AM   #17
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Re: Gear ratio

They come out at about 32 inches , running a 4L80e.
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Old 02-20-2017, 12:27 PM   #18
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Re: Gear ratio

I have 265/75-16 tires that are about the same 32" with 3.73 and a 700r4. Works great as a daily driver all around truck. If I was going to a >33" tire 4.11 would be good. Rock crawlers mud trucks etc. than of course it won't work as good. But for a daily all around truck it's great. At least where I live. My .02!
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1956 Chevy 210 4 Door
1968 K10 LWB Dark green my son calls it "THE HULK Jr"
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1970 K20 LWB project the Hulk build
HULK BUILD
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GO GO!!!
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Old 02-20-2017, 02:07 PM   #19
Jcfcamaro
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Re: Gear ratio

Has anyone on here ever seen any new/good used 411 gears on the classifieds for sale? If so what did they bring in price.
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Old 02-20-2017, 02:26 PM   #20
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Re: Gear ratio

Can someone confirm this rearend is factory. Looks like a car rearend to me but I have no clue.
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Old 02-20-2017, 02:33 PM   #21
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Re: Gear ratio

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Can someone confirm this rearend is factory. Looks like a car rearend to me but I have no clue.
Here's the front. What's thee ring gear and pinion sizes I need to be looking for.
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Old 02-20-2017, 03:46 PM   #22
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Re: Gear ratio

Looks like a rear GM 12 bolt truck rear axle and a Dana 44 front axle.
As far as used gears.....my time is worth a lot so I would just get new gears and installation kit and be done.
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1956 Chevy Bel Air 2 door
1956 Chevy 210 4 Door
1968 K10 LWB Dark green my son calls it "THE HULK Jr"
Hulk Jr
1970 K20 LWB project the Hulk build
HULK BUILD
1970 C10 Yellow/White Deluxe LWB w/ 5.3L-LC9/6L80E
GO GO!!!
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Old 02-21-2017, 12:17 AM   #23
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Re: Gear ratio

Ditto, new gears are not that costly, Yukon make good gear sets. 259 brand new.

https://m.summitracing.com/parts/yga-24034
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Old 02-21-2017, 07:25 PM   #24
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Re: Gear ratio

I have a 72 K10, TH350, stock-type 396 build with 3.73's and 32" tires. The 3.73's are just about perfect for all-around use, I can go 75 on the interstate and be happy and still have plenty of power around town.
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