What gears do I have in my rear end? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

firedoger · 10-11-2013, 01:51 PM

I'm trying to figure out which gears I have in my rear axle. It's the stock axle. My Spids has this info:
1g8010 positraction axle.

Mike C · 10-11-2013, 10:03 PM

4x4? If so and original, will be a tag on the FRONT axle. Why GM didn't do that on the corporate rear axle, we'll never know.

What platform, engine, and transmission? Knowing that we can tell you what the base gear set would be. Less than 350 ci, 3:73 and with 350, 3:07 for the most part.

71swb4x4 · 10-11-2013, 10:12 PM

You should really count tire rotations vs drive shaft rotations or pull the cover, after 40+ years they could have been changed.

But I believe from the factory if you have a 350 you got 3.07's, with a 250 or 307 you got 3.73's. I think that's the way it was in 71 and 72 anyway. I could be wrong though lots of info floating around.

firedoger · 10-12-2013, 01:52 AM

It's a 4x4. It came with a 350 eng and th350. I'm the second owner and I doubt they where changed. Where would the tag be on the front axle?

Mike C · 10-12-2013, 11:44 AM

Probably 3.07, but 3.73 were optional. The tag is bolted onto one of the cover bolts and will have the gear ratio and/or number of pinion and ring gear teeth.

firedoger · 10-12-2013, 03:23 PM

Thx for the help. If I do have 3.07 that would explain why I don't have the acceleration I would think I should have from the line. Plus I'm running 33" tires which isn't going to help. It does well on the highway.

Chulisohombre · 10-12-2013, 10:38 PM

My came 350 and 3.73 gears stock. Best way is to pull the diff cover and look at the ring gear to get ratio. After 40 years it would be good to look in there to see if there are any problems. Plus new gear oil can't hurt anything either. Mine was also a posi unit.

2003 silverado · 10-13-2013, 06:12 AM

Pull the diff/ Change fluid/ 40yrs

firedoger · 10-13-2013, 01:34 PM

I pulled the covers and changed the fluids two years abo when I brought her home. I should have checked it then.

Chulisohombre · 10-13-2013, 06:03 PM

You can get close by the turn the driveshaft and count wheel revolution method. Other than that you can pull the cover again and reuse the gear oil if it looks good. Just silicone the cover back and refill.

cleszkie · 10-14-2013, 01:31 PM

It was my understanding that the models equipped with the 350/th350 combo got the 3.07 gears, and the 350/SM465 models got the 3.73 gears, unless specially ordered otherwise.

firedoger · 10-14-2013, 02:40 PM

I did the old turn the drive line tire rotation deal. My drive rotated three times per one full tire rotation. It was on the button. Looks like I have 3:07's. Dang It ! I was hoping for 3:73's.

Chulisohombre · 10-14-2013, 04:09 PM

That succks. To bad you didn't have the 3.73. With 33 in tires it worked ok still. When I stepped up to 35 I also went 3/4 ton and geared 4.10. Much happier now.

10-11-2013, 01:51 PM	#1
firedoger Registered User Join Date: Aug 2011 Location: Phoenix AZ Posts: 141	What gears do I have in my rear end? I'm trying to figure out which gears I have in my rear axle. It's the stock axle. My Spids has this info: 1g8010 positraction axle.

10-11-2013, 10:03 PM	#2
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,728	Re: What gears do I have in my rear end? 4x4? If so and original, will be a tag on the FRONT axle. Why GM didn't do that on the corporate rear axle, we'll never know. What platform, engine, and transmission? Knowing that we can tell you what the base gear set would be. Less than 350 ci, 3:73 and with 350, 3:07 for the most part. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

10-11-2013, 10:12 PM	#3
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	Re: What gears do I have in my rear end? You should really count tire rotations vs drive shaft rotations or pull the cover, after 40+ years they could have been changed. But I believe from the factory if you have a 350 you got 3.07's, with a 250 or 307 you got 3.73's. I think that's the way it was in 71 and 72 anyway. I could be wrong though lots of info floating around. __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

10-12-2013, 01:52 AM	#4
firedoger Registered User Join Date: Aug 2011 Location: Phoenix AZ Posts: 141	Re: What gears do I have in my rear end? It's a 4x4. It came with a 350 eng and th350. I'm the second owner and I doubt they where changed. Where would the tag be on the front axle?

10-12-2013, 11:44 AM	#5
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,728	Re: What gears do I have in my rear end? Probably 3.07, but 3.73 were optional. The tag is bolted onto one of the cover bolts and will have the gear ratio and/or number of pinion and ring gear teeth. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

10-12-2013, 03:23 PM	#6
firedoger Registered User Join Date: Aug 2011 Location: Phoenix AZ Posts: 141	Re: What gears do I have in my rear end? Thx for the help. If I do have 3.07 that would explain why I don't have the acceleration I would think I should have from the line. Plus I'm running 33" tires which isn't going to help. It does well on the highway.

10-12-2013, 10:38 PM	#7
Chulisohombre Registered User Join Date: Sep 2013 Location: Bangor pa Posts: 1,223	Re: What gears do I have in my rear end? My came 350 and 3.73 gears stock. Best way is to pull the diff cover and look at the ring gear to get ratio. After 40 years it would be good to look in there to see if there are any problems. Plus new gear oil can't hurt anything either. Mine was also a posi unit.

10-13-2013, 06:12 AM	#8
2003 silverado Registered User Join Date: Apr 2010 Location: West Chester Pa Posts: 965	Re: What gears do I have in my rear end? Pull the diff/ Change fluid/ 40yrs __________________ !972 K5 Blazer,Highlander,A/C a twin to the one I Had 1972 K/5 Blazer CST Highlander 15YR project 2003 Silverado Crew 2500HD (Daily driver) 1997 Ford focus (Beater) 2003 ford Taurus (student) 2014 Ford Fusion HYB (wife) 2003 Jetta ( Student)

10-13-2013, 01:34 PM	#9
firedoger Registered User Join Date: Aug 2011 Location: Phoenix AZ Posts: 141	Re: What gears do I have in my rear end? I pulled the covers and changed the fluids two years abo when I brought her home. I should have checked it then.

10-13-2013, 06:03 PM	#10
Chulisohombre Registered User Join Date: Sep 2013 Location: Bangor pa Posts: 1,223	Re: What gears do I have in my rear end? You can get close by the turn the driveshaft and count wheel revolution method. Other than that you can pull the cover again and reuse the gear oil if it looks good. Just silicone the cover back and refill.

10-14-2013, 01:31 PM	#11
cleszkie Registered User Join Date: Feb 2003 Location: Santa Ana, CA Posts: 2,191	Re: What gears do I have in my rear end? It was my understanding that the models equipped with the 350/th350 combo got the 3.07 gears, and the 350/SM465 models got the 3.73 gears, unless specially ordered otherwise.

10-14-2013, 02:40 PM	#12
firedoger Registered User Join Date: Aug 2011 Location: Phoenix AZ Posts: 141	Re: What gears do I have in my rear end? I did the old turn the drive line tire rotation deal. My drive rotated three times per one full tire rotation. It was on the button. Looks like I have 3:07's. Dang It ! I was hoping for 3:73's.

10-14-2013, 04:09 PM	#13
Chulisohombre Registered User Join Date: Sep 2013 Location: Bangor pa Posts: 1,223	Re: What gears do I have in my rear end? That succks. To bad you didn't have the 3.73. With 33 in tires it worked ok still. When I stepped up to 35 I also went 3/4 ton and geared 4.10. Much happier now.



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