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#1 |
Registered User
Join Date: Nov 2011
Location: 19
Posts: 607
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Rear gear ratio
Pulled my rear cover off and counted the teeth on ring and pinion
16 on the pinion and 41 on the ring gear, which means its got 2:56 gear ratio. Originally it had a 305 with a th350 trans. And I swapped in a 700r4 but I need to figure out which speedo gears to get. Seems odd that it would have a 2:56 ratio. Anybody else have a th350 and know what their rear gear ration is?
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1999 Chevy K2500 RCLB 350 4L80e 2004 Chevy 3500 C&C Dmax Allison |
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#2 |
Registered User
Join Date: Dec 2011
Location: Arlington WA
Posts: 1,728
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Re: Rear gear ratio
i dont recall trucks having 2.56? i thought 2.73 was the highest the trcks went. i have 2.73's useless on anything but the freeway
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GMC C15 355 SM465 3.73 80 C10 cruiser build thread 79 short stepside crew cab. big and ugly. build thread |
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#3 |
Registered User
Join Date: Nov 2011
Location: 19
Posts: 607
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Re: Rear gear ratio
Yea 2:56 seems kinda odd to me
Got all the numbers off the ring gear: GM 1235401 16 41 11 83 Last batch "11 83" I think means built 11/83 which would be right in a 84 truck.
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1999 Chevy K2500 RCLB 350 4L80e 2004 Chevy 3500 C&C Dmax Allison |
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#4 |
Account Suspended
Join Date: Dec 2008
Location: indisclosed
Posts: 1,515
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Re: Rear gear ratio
Yes, i have 2.56 with a TH-350C.
Stiff as hell. This kind of setup of good for if you use the truck for light hauling---lumber, appliances, weekend projects etc. It is not so good for other things such as towing. P.S. my GVWR is only 4900 and i guess yours is too. |
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#5 |
Registered User
Join Date: Nov 2011
Location: 19
Posts: 607
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Re: Rear gear ratio
^^^ Good to hear, so I guess I am identifying it correctly then.
I am fine with the ratio, I am dropping a 6.2 diesel in it and see what I can get for mileage with it. Not gonna be in a big hurry to get anywhere and more of a show truck than a work truck.
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1999 Chevy K2500 RCLB 350 4L80e 2004 Chevy 3500 C&C Dmax Allison |
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#6 |
Registered User
Join Date: Jul 2010
Location: Norman, Oklahoma
Posts: 557
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Re: Rear gear ratio
I was just now taking apart y rear end to clean up and paint and decided to check what ratio I have. It's 16 41 2 81. So I have a 2.56 as well.
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Max Max's bagged 81 81 rcsb bagged, 22s, build in progress 09 ext cab, 24" U2's, DD sub/amp |
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#7 |
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Join Date: Oct 2009
Location: Prescott, Arizona
Posts: 2,396
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Re: Rear gear ratio
2.56 is actually a very common gear found in the 8.5's in both cars and trucks.
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#8 |
C/10 junkie
Join Date: Nov 2010
Location: Stockton Ca
Posts: 9,093
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Re: Rear gear ratio
Are there two dots between the 41 and the 11. On my rear end there was which meant the ratio was 3.73, 41 divided by 11.
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Shawn 70 LWB C10 current driver/project http://67-72chevytrucks.com/vboard/s...d.php?t=663051 68 SWB C10 Work in progress.....SOLD http://67-72chevytrucks.com/vboard/s...d.php?t=559520 72 LWB C10 Sold 71 LWB C10 Sold 68 LWB C10 CST Sold http://youtu.be/kbB0QrBIs9k My mom always had the best advice. It was just a tad late. After a fall that involved blood, she'd say....."Careful!" ![]() |
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#9 |
Registered User
Join Date: Jul 2010
Location: Norman, Oklahoma
Posts: 557
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Re: Rear gear ratio
Is a 2.56 rear end useless? I've never heard of people wanting that high of a ratio...
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Max Max's bagged 81 81 rcsb bagged, 22s, build in progress 09 ext cab, 24" U2's, DD sub/amp |
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#10 |
Senior Member
Join Date: May 2009
Location: Fort Worth, TX
Posts: 6,370
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Re: Rear gear ratio
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#11 |
Registered User
Join Date: Jul 2010
Location: Norman, Oklahoma
Posts: 557
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Re: Rear gear ratio
Is the 2.56 at least good for gas mileage? I don't plan to do any towing or anything? Will keeping it affect my acceleration or anything?
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Max Max's bagged 81 81 rcsb bagged, 22s, build in progress 09 ext cab, 24" U2's, DD sub/amp |
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#12 | ||
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Join Date: Dec 2008
Location: indisclosed
Posts: 1,515
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Re: Rear gear ratio
Quote:
Quote:
As far mileage, probably good with a th-350 or other 3 sp trans. i think i tach around 1800 at 55 mph. P.S. It affects acceleration big time. Switching to say 4.56 will make a world of difference. |
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#13 | |
Senior Member
Join Date: May 2009
Location: Fort Worth, TX
Posts: 6,370
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Re: Rear gear ratio
Quote:
With 28" to 30" diameter tires & 3 spd auto......A 3:08 gear will return the best mileage in my opinion. 3:42's will give better acceleration with a small increase in fuel consumpsion at highway speeds. |
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#14 |
Registered User
Join Date: Nov 2011
Location: 19
Posts: 607
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Re: Rear gear ratio
I am swapping in a 6.2, so these gears with an ole slug 6.2 and a 700r4 it will take a week to get up to speed but I will be able to pass a few gas pumps though
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1999 Chevy K2500 RCLB 350 4L80e 2004 Chevy 3500 C&C Dmax Allison |
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#15 |
Registered User
Join Date: Mar 2012
Location: Woodbury, Ct.
Posts: 1,680
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Re: Rear gear ratio
My truck had the 2:56 rear.. When I went with the 700 tranny, it was practically asleep on the highway with a 30" tire...found a nice posi carrier and 3:73 gears at the boneyard really woke up my TPI..
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