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Old 01-28-2010, 06:55 PM   #1
Winston301
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Question RPO code GQ1

GQ1 - Axle, Std Ratio

I am looking at a 14 bolt sf rear end out of a 82 3/4 ton. It has the 6.2 diesel w/ 400 trans. Does anyone know what the STANDARD RATIO would be?
Thank you!
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Old 01-28-2010, 11:41 PM   #2
C-10 simplex
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Re: RPO code GQ1

GQ1 is 2.56.

The other thing you could do is go to any gm dealer(preferably chevy) and they can type the vin# in the computer and look it up for you.

Last edited by C-10 simplex; 01-28-2010 at 11:42 PM.
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Old 01-29-2010, 10:01 AM   #3
Winston301
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Re: RPO code GQ1

That is a good idea C-10. I will probably do that. Thank you.
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Old 01-29-2010, 12:31 PM   #4
D13
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Re: RPO code GQ1

If it's truely a 14b SF 9.5" then the 'standard' ratio would be 3.42. The lowest numeric ratio would be a 3.23 (unusual) and the highest 4.56.

The standard ratio on my 81 3/4 with a L6 250 and 3OTT is a 3.42.

The term 'standard' means that the customer didn't order anything special. What was 'standard' varied with engine and trans. For example, a 454 in a half ton would get a different ratio than the same in a 3/4 ton, because it was assumed that the half ton was for occasional towing and the 3/4 ton was for heavy loads. Plus the differnece in the tire sizes and the torque capability in the axles which might restrict the gear ratios available.
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Last edited by D13; 01-29-2010 at 12:34 PM.
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Old 01-29-2010, 02:57 PM   #5
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Re: RPO code GQ1

oh yeah....scratch that. i thought we were dealing with 1/2 ton---i forgot about the 3/4 ton part.


This is interesting and useful info.

Last edited by C-10 simplex; 01-29-2010 at 03:06 PM.
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Old 01-29-2010, 03:23 PM   #6
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Re: RPO code GQ1

Well, to complicate matters further(i always do this,

EDIT comments withdrawn----the matter is too complicated for me.

b) Additionally, apparently std ratio varied from yr to yr. For instance my 83 1/2 ton is 2.56 as std ratio(which i thought applied across the board from 81-87 in all weight ratings but apparently not so)

c) i now think, due to more info/intervention by D13+more research(brouchures) you got a 3.08 because of the diesel engine, but i think it's best at this point i withdraw from the thread due to the increasing complexity of the situation and merely observe and learn.

Last edited by C-10 simplex; 01-29-2010 at 03:33 PM.
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Old 01-29-2010, 04:05 PM   #7
Winston301
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Re: RPO code GQ1

Well, I emailed my local GM dealer & he said he couldn't look anything up because of how old it is. He went out in the shop & asked a few mechanics & they said 3.08 (2.75 if it was 2wd).

I am planning to grab a shovel & dig the truck out of the snow & get it figured out. It is supposed to be a balmy 17 degrees here tomorrow so why not do a little work outside.

Stay tuned!
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Old 01-30-2010, 09:34 AM   #8
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Re: RPO code GQ1

3.08's are the most common half ton ratio, all thruout the 70'sm 80's, and even 90's. My 87 6.2 700R4 has them, as well as my 84 250 TH350 and my 83 305 TH350.

BUT the original post said that it was a 14b SF, which would be the 9.5" ring gear, which would be a light 3/4 ton. The only gearsets available for that rear are the 3.23, 3.42, 3.73, 4.11, and 4.56. The 3.42 is by far the most common original gear, followed by the 4.11 (usually a towing package) and 3.73 (usualy a camper package or HD GVW) I've never seen a 4.56 factory in person, usually by time that much torque is needed they would step up to the 10.5" or the Dana. The 3.23 would seem to be a highway gear with 16" rims and factory tires. The only one I've seen was a 4wd, a light 3/4 ton pickup. It's interesting to note that this is the only ratio not available aftermarket - must not have made many.
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Plus a mess o' tractors

Last edited by D13; 01-30-2010 at 09:35 AM.
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Old 02-01-2010, 10:31 AM   #9
Winston301
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Re: RPO code GQ1

I thank everyone for their input. Me & a buddy dug it out from the snow drift & figured it out. Even with the 6.2 it has 4.11 gears. I'm not sure why 4.11 would be the standard ratio for that setup. I don't see someone changing both front & rear gears but I guess it is a possibility it could have happened.

Again, Thanks for all the input!
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