Changing the rear axle...again - The 1947 - Present Chevrolet & GMC Truck Message Board Network

LeesTruk · 08-29-2018, 05:10 AM

When I first got my C10 (I6, 4spd, 12 bolt 2:73), I knew I was gonna convert it to LS/4L60E. So I bought an axle from an '86 C10 and was told it was a 3:42. Wrong!! Turned out to be a 3:08. Went ahead and used it anyways. Definitely a good hiway gear, but I still wanted a little more gear. Well, after a long search, found a 3:42 axle from an '86 GMC 1500 4x4 (try finding a 3:42 from a 2X4...good luck with that, especially in New England). Anyways, I pulled the cover, checked the ring and found the numbers 41/12 stamped into it. Yes!! 3:42!! But... while looking at the gears for wear/broken teeth, I found a side gear spider with more craters than the moon. Was thinking, if I gotta fix it anyhow, why not pull the carrier and install a posi unit. Anyone have 1st hand knowledge of the Eaton TrueTrac (#912A556), and is this a decent choice for a street truck/toy? Thanks

**Warrens69GMC** · 08-29-2018, 08:03 AM

Easy Peasy -
www.car-part.com

Rich84 · 08-29-2018, 09:42 AM

Lee..You sure are right about all the 4x4s in the yards. I found a newish Auburn unit with 3.73's in a 89 Suburban. Some say they are not the best but its fine for a cruiser. It's 30 spline so I had to change the axles too. 88 and up trucks are 30 spline so they were easy to find.
Wow those Eatons are expensive.

DieselSJ · 08-29-2018, 01:35 PM

Truetrac is an excellent choice for a street driven truck. You will not be disappointed.

SBTork · 08-31-2018, 10:08 AM

Quote:

Originally Posted by DieselSJ

Truetrac is an excellent choice for a street driven truck. You will not be disappointed.

x2

LeesTruk · 09-01-2018, 05:04 AM

Thanks , Gents. I've ordered a unit from the local speed emporium and should have it next week

Rich, I had looked at the "later" year rears, but knew of the different axle spline count. My intent is to use the axles/brakes from my current rear to convert from six lug to five lug to save on money. I know the 30 spline axles are stronger than the 28, but for what I use the truck for, I don't think I have a problem. I'll let the next "keeper of the keys" worry about it

08-29-2018, 05:10 AM	#1
LeesTruk Registered User Join Date: Mar 2015 Location: Manchester, CT Posts: 433	Changing the rear axle...again When I first got my C10 (I6, 4spd, 12 bolt 2:73), I knew I was gonna convert it to LS/4L60E. So I bought an axle from an '86 C10 and was told it was a 3:42. Wrong!! Turned out to be a 3:08. Went ahead and used it anyways. Definitely a good hiway gear, but I still wanted a little more gear. Well, after a long search, found a 3:42 axle from an '86 GMC 1500 4x4 (try finding a 3:42 from a 2X4...good luck with that, especially in New England). Anyways, I pulled the cover, checked the ring and found the numbers 41/12 stamped into it. Yes!! 3:42!! But... while looking at the gears for wear/broken teeth, I found a side gear spider with more craters than the moon. Was thinking, if I gotta fix it anyhow, why not pull the carrier and install a posi unit. Anyone have 1st hand knowledge of the Eaton TrueTrac (#912A556), and is this a decent choice for a street truck/toy? Thanks

08-29-2018, 08:03 AM	#2
Warrens69GMC Registered User Join Date: Jan 2003 Location: Safford,AZ Posts: 3,626	Re: Changing the rear axle...again Easy Peasy - www.car-part.com Attached Images __________________ 1969 307, t350 1950 Chevy Wagon 1978 Big 10 1967 C10, 250,3-OTT

08-29-2018, 09:42 AM	#3
Rich84 Registered User Join Date: Mar 2012 Location: Woodbury, Ct. Posts: 1,708	Re: Changing the rear axle...again Lee..You sure are right about all the 4x4s in the yards. I found a newish Auburn unit with 3.73's in a 89 Suburban. Some say they are not the best but its fine for a cruiser. It's 30 spline so I had to change the axles too. 88 and up trucks are 30 spline so they were easy to find. Wow those Eatons are expensive.

08-29-2018, 01:35 PM	#4
DieselSJ Registered User Join Date: Jun 2016 Location: Phoenix, AZ Posts: 574	Re: Changing the rear axle...again Truetrac is an excellent choice for a street driven truck. You will not be disappointed. __________________ 87 R30 CC Dually, TBI 454, NV4500, zero rust barn find 87 Jeep Grand Wagoneer, 6.5 turbodiesel, 700R4

09-01-2018, 05:04 AM	#6
LeesTruk Registered User Join Date: Mar 2015 Location: Manchester, CT Posts: 433	Re: Changing the rear axle...again Thanks , Gents. I've ordered a unit from the local speed emporium and should have it next week Rich, I had looked at the "later" year rears, but knew of the different axle spline count. My intent is to use the axles/brakes from my current rear to convert from six lug to five lug to save on money. I know the 30 spline axles are stronger than the 28, but for what I use the truck for, I don't think I have a problem. I'll let the next "keeper of the keys" worry about it

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