rear end gears?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

apachedaddy · 08-01-2008, 08:18 PM

did a search and didnt find what i was looking for. i have a 66 short wide it had a I6/3 speed but now has a 350/350 and really talks to me at 55mph. their is no build tag on the rear end. i know its a 12 bolt but short of pulling the cover would anyone have a guess on what the gears may be??? I was told if it has 3:73 or up i have to chang the carrier. i have been looking at them and am guess i need a 3 searies to run the 3:08 i would like to put in it. any help would be greatfull. o yeah it still has the stock 30 spline axels to boot.

72bigred · 08-01-2008, 08:54 PM

You can get a rough idea of what gear ratio by dropping your driveline jacking up the rear end and spinning the tire. Mark your tire, spin it one full rotation around counting how many times your yoke on the rear end spins.. If it spins lets say 'almost 4 times" then you can assume high 3.. 3.90 etc.. If it spins over 4 times then of course 4.10 etc.. Its a rough guesstimate. (this is of course if you have a posi)

If you have a slip then rotate the tire 2 full rotations and count how many times the yoke spins.

As far as a carrier.. Depends on what carrier you have and what gears you have.. Yes they have a range.. But for example I have an Eaton 3 with 4.56 gears from richmond in my chevelle.. Normally you would have to have an Eaton 4 to run these gears but some manufacturers make gears for different series.. If you look at the richmond site you will see some of the gears have the same ratio but two different part numbers.. You will see two 4.56 one for the 3 series and one for the 4..

Be safe

Skez

64c20crewcab · 08-02-2008, 12:49 AM

I looked up some info recently in the confusing assemby manual recently.
Saw this at the beginning of the book. Hope this helps.....

originalJD · 08-02-2008, 11:42 AM

It appears by that chart that a 66 C10 came with 4.11 gears only. Would that assumption be correct?

64c20crewcab · 08-02-2008, 12:47 PM

Thats my thought. The 66 12 bolt rearend in my garage is loaded with 4.11's.

I took the cover off, and drained the oil and counted the teeth on the r&p. Took the numbers and went to ringandpinion.com and used on of the calculators on that site.

Did not look for numbers or date on the carrier as indicated on the 1st page of the axle ID section. Under the title it reads: "Axle identification is stamped on differential carrier along with date of manufacture."

Also why did that person tell you that you needed to swap the carrier? If 4.11 is in you 12 bolt, you use the same carrier if swapping gears to 3.73. Or if running a posi for that matter. If wanting 3.42 or 3.08 gears - then a smaller carrier is required.

Some additiona info from another forum:
REAR AXLE IDENTIFICATION:

The production code number contains prefix letters and production date numbers. Axle identification is stamped on the differential carrier along with the date of manufacture.

Example: HB 0612 HB = 3.07:1 ratio, O6 = month built (June), 12 = day built(12th)

If your rearend came out from under a 66 C10, that tells me its a 1/2 ton truck and there are only three factory gear ratios for a 1/2 ton pickup, 3.07:1, 3.73:1 and 4.11:1. Here are the codes for each one.

JQ-4.11:1 HF-3.73:1 These are the only codes my book uses for 66 rearends
HA-3.73:1 HG-3.73:1
HB-3.07:1 HH-4.11:1
HC-3.73:1 HQ-3.73:1
HD-4.11:1

apachedaddy · 08-02-2008, 08:04 PM

i know for sure that the rpm it runs at 55 mph that the gears are not 307:1, i ordered a posie and 308:1 gears last night just have to wait for them to come in. i was also told that the smaller carrie can be used with the 373:1 and up gears with a shim plate. thanks for the great info all.

08-01-2008, 08:18 PM	#1
apachedaddy Registered User Join Date: Feb 2008 Location: pooler, GA Posts: 213	rear end gears?? did a search and didnt find what i was looking for. i have a 66 short wide it had a I6/3 speed but now has a 350/350 and really talks to me at 55mph. their is no build tag on the rear end. i know its a 12 bolt but short of pulling the cover would anyone have a guess on what the gears may be??? I was told if it has 3:73 or up i have to chang the carrier. i have been looking at them and am guess i need a 3 searies to run the 3:08 i would like to put in it. any help would be greatfull. o yeah it still has the stock 30 spline axels to boot.

08-01-2008, 08:54 PM	#2
72bigred Registered User Join Date: Jan 2008 Location: Spokane WA Posts: 254	Re: rear end gears?? You can get a rough idea of what gear ratio by dropping your driveline jacking up the rear end and spinning the tire. Mark your tire, spin it one full rotation around counting how many times your yoke on the rear end spins.. If it spins lets say 'almost 4 times" then you can assume high 3.. 3.90 etc.. If it spins over 4 times then of course 4.10 etc.. Its a rough guesstimate. (this is of course if you have a posi) If you have a slip then rotate the tire 2 full rotations and count how many times the yoke spins. As far as a carrier.. Depends on what carrier you have and what gears you have.. Yes they have a range.. But for example I have an Eaton 3 with 4.56 gears from richmond in my chevelle.. Normally you would have to have an Eaton 4 to run these gears but some manufacturers make gears for different series.. If you look at the richmond site you will see some of the gears have the same ratio but two different part numbers.. You will see two 4.56 one for the 3 series and one for the 4.. Be safe Skez Last edited by 72bigred; 08-01-2008 at 08:55 PM.

08-02-2008, 12:49 AM	#3
64c20crewcab Registered User Join Date: Jun 2008 Location: North SD County Posts: 631	Re: rear end gears?? I looked up some info recently in the confusing assemby manual recently. Saw this at the beginning of the book. Hope this helps..... Attached Images __________________ ..............................._________ ......___________//___[[___{\ _____ ...../__(_(O)_)___/____/____/_(O)_/ 1964 C20 Long Stepside 3 Door Crew Cab - Armbruster-Stageway Conversion Y2K INDN Chief "ONE OF A KIND, NOT ONE OF THE CROWD" Aug 2010 - Front end frame cleanup & engine swap done!!! June 2011 - Rear end bagged Sept 2011 - Rebuild motor top end Sept 2012 - Parked and slowly working on it. Aug 2013 - Front end bagged - finally! Aug 2014 - Stepside swap conversion done. Finally ready to start bodywork! Have a few KEWL ideas... Here is my build thread: http://www.67-72chevytrucks.com/vboa...d.php?t=335427

08-02-2008, 11:42 AM	#4
originalJD James Join Date: May 2008 Location: Dayton, WA Posts: 455	Re: rear end gears?? It appears by that chart that a 66 C10 came with 4.11 gears only. Would that assumption be correct? __________________ Never crush'em. Restor'em or recycle'em. The payoff is always worth it in the end. http://viewmorepics.myspace.com/inde...lbumId=1709080 http://s258.photobucket.com/albums/h...e_top_view_all

08-02-2008, 12:47 PM	#5
64c20crewcab Registered User Join Date: Jun 2008 Location: North SD County Posts: 631	Re: rear end gears?? Thats my thought. The 66 12 bolt rearend in my garage is loaded with 4.11's. I took the cover off, and drained the oil and counted the teeth on the r&p. Took the numbers and went to ringandpinion.com and used on of the calculators on that site. Did not look for numbers or date on the carrier as indicated on the 1st page of the axle ID section. Under the title it reads: "Axle identification is stamped on differential carrier along with date of manufacture." Also why did that person tell you that you needed to swap the carrier? If 4.11 is in you 12 bolt, you use the same carrier if swapping gears to 3.73. Or if running a posi for that matter. If wanting 3.42 or 3.08 gears - then a smaller carrier is required. Some additiona info from another forum: REAR AXLE IDENTIFICATION: The production code number contains prefix letters and production date numbers. Axle identification is stamped on the differential carrier along with the date of manufacture. Example: HB 0612 HB = 3.07:1 ratio, O6 = month built (June), 12 = day built(12th) If your rearend came out from under a 66 C10, that tells me its a 1/2 ton truck and there are only three factory gear ratios for a 1/2 ton pickup, 3.07:1, 3.73:1 and 4.11:1. Here are the codes for each one. JQ-4.11:1 HF-3.73:1 These are the only codes my book uses for 66 rearends HA-3.73:1 HG-3.73:1 HB-3.07:1 HH-4.11:1 HC-3.73:1 HQ-3.73:1 HD-4.11:1 __________________ ..............................._________ ......___________//___[[___{\ _____ ...../__(_(O)_)___/____/____/_(O)_/ 1964 C20 Long Stepside 3 Door Crew Cab - Armbruster-Stageway Conversion Y2K INDN Chief "ONE OF A KIND, NOT ONE OF THE CROWD" Aug 2010 - Front end frame cleanup & engine swap done!!! June 2011 - Rear end bagged Sept 2011 - Rebuild motor top end Sept 2012 - Parked and slowly working on it. Aug 2013 - Front end bagged - finally! Aug 2014 - Stepside swap conversion done. Finally ready to start bodywork! Have a few KEWL ideas... Here is my build thread: http://www.67-72chevytrucks.com/vboa...d.php?t=335427 Last edited by 64c20crewcab; 08-02-2008 at 12:54 PM. Reason: more info

08-02-2008, 08:04 PM	#6
apachedaddy Registered User Join Date: Feb 2008 Location: pooler, GA Posts: 213	Re: rear end gears?? i know for sure that the rpm it runs at 55 mph that the gears are not 307:1, i ordered a posie and 308:1 gears last night just have to wait for them to come in. i was also told that the smaller carrie can be used with the 373:1 and up gears with a shim plate. thanks for the great info all.



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