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Old 05-06-2010, 03:57 PM   #1
Big Cliff
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Factory gear ratio's

I have done a search and could not find anything. I have a 1985 swb 2wd 10 bolt that came factory with a 5.0l 305. What did the factory offer for gear ratios? 2.73 or 3.08???????

Last edited by Big Cliff; 05-06-2010 at 03:58 PM.
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Old 05-06-2010, 04:07 PM   #2
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Re: Factory gear ratio's

You should be able to use the RPO codes (in the glove box) and figure out what you have, as long as it has not been changed over the years. I believe most common is 3.42. RPO code is probably a G** one for your year model.

http://www.73-87.com/chevy_ids/rpo-eg.htm#rpo-g , easier way is to just link you. Has been a wonderful link for me decoding some stuff.

Last edited by RandyP; 05-06-2010 at 04:15 PM.
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Old 05-06-2010, 04:45 PM   #3
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Re: Factory gear ratio's

My guess on which ones was the most common would center around 3.08 gearing. There seems to a lot of those rear ends in the salvage yards.
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Old 05-06-2010, 04:57 PM   #4
baclay9
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Re: Factory gear ratio's

Should the codes on your truck tell you what you have? Only thing is I know the glove box in mine isn't original. Any other way to tell your gearing? Mine has a 12 bolt rear in it.
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Old 05-06-2010, 05:39 PM   #5
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Re: Factory gear ratio's

I have an 86 SWB with originally a 305 in it and it has 3.08's in the rear.
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Old 05-06-2010, 07:42 PM   #6
foamypirate
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Re: Factory gear ratio's

87 LWB, 305 and 3.08s.

It's slow.
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Old 05-06-2010, 10:24 PM   #7
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Re: Factory gear ratio's

79 gmc factory 350.... 3.08's :[
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Old 05-07-2010, 09:46 AM   #8
Big Cliff
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Re: Factory gear ratio's

Thanks guys, it has the 3.08's. I ordered a set of 3.42's should help it.
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Old 05-07-2010, 11:25 AM   #9
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Re: Factory gear ratio's

What transmission? tire size? That's a pretty expensive swap to not nail it exactly...
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Old 05-07-2010, 11:28 AM   #10
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Re: Factory gear ratio's

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Originally Posted by LONGHAIR View Post
What transmission? tire size? That's a pretty expensive swap to not nail it exactly...
29.5 inch tall tire/th 350. I put a pretty high reving sbc in and a 2000 rpm converter. I think it will go 1/8 mile in first gear......lol
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Old 05-07-2010, 12:23 PM   #11
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Re: Factory gear ratio's

a 700R4 will be spot on after that. The low 1st gear is better, too.
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Old 05-07-2010, 12:35 PM   #12
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Re: Factory gear ratio's

What would a C30 6.2 4 speed have 4.10?
dont have RPO cods or the tag on the rear end
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