Rear end help. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bryanmartin · 09-05-2016, 12:48 AM

Hi all, I'm brand new to this forum, and I just picked up a 1965 C10 with which I'm going to do a custom build.

Right now I'm in the planning stages, and I admittedly know NOTHING about these trucks (eager to learn though!). It currently has a straight 6 and a three on the tree. I am looking at going with an LS motor, but I want to make sure the whole drive train can handle any power mods I throw at it.

My question is, what can you folks tell me about the rear end? What type is it? Is it strong? Weak? What are the popular upgrades to it? If my best bet is a rear end swap (e.g. GM 12-bolt or something), are there certain donor vehicles that work best? I know you all have been at this for awhile, so I see no need to reinvent the wheel.

Thanks!
Bryan

**66ChevyMax** · 09-05-2016, 01:54 AM

Most modern rear ends esp. posi units will handle the HP of an LS motor. Unless you do something crazy with your tires you won't have enough traction to cause a rear end problem in my opinion.

I installed an Eaton Posi 12 bolt and running 575hp currently.

bpmcgee · 09-05-2016, 08:15 AM

The three speed and straight six didn't have a ton of power, so expect to find really high gears in that rear end. I think if I recall correctly the '61 I have came with 3.93:1.

Investigate wether you can get the gears you want and if axle shafts are available for it before you decide to keep or swap.

B

vince1 · 09-05-2016, 10:52 AM

Is it not a 12 bolt now? Most common ratio was 3.73. That probably works with over drive. I currently have a 3.07 with straight through transmission.

**The Rocknrod** · 09-05-2016, 10:55 AM

You have a great set up in the 65. It's a 8.875" 12 Bolt Truck Rear End (12T). You can get all new internals from this guy (I did), he even carries the 5 lug axles (you have to ask him):
http://www.ebay.com/itm/GM-12-Bolt-T...PDZYWCBXVAa1Dw
You have the best panhard bar bracket on the frame for a longer bar already.
http://www.quickperformance.com/GM-1...-12T_c_54.html

bryanmartin · 09-05-2016, 11:48 AM

I suppose it could be a 12 bolt, I didn't think it would be. I would have looked, but it's in storage, oops. Thanks for the replies guys. Do you know how much power the 12 bolt is rated for?

**Captainfab** · 09-05-2016, 11:45 PM

All C10's from '63-'82 came with the truck 12 bolt. There is no reason to change the differential for something else. The 12 bolt will handle a lot of power. Of course how much will depend on how what tires you run and much money you want to put into it. In stock form a 12 bolt would easily handle ~400hp/tq. Your 12 bolt more than likely has 3.73 gears currently.

drmatera · 09-06-2016, 04:05 PM

sorry to hijack but are the leaf spring GMC rears of that model year range also have 12 bolts?

**Captainfab** · 09-06-2016, 11:47 PM

The GMC's from '63 to about 1970 typically have the Dana 44. The 12 bolt was an option on the later years of that range. I do know that from '73-'82 the GMC's had 12 bolts and from '83 up had 10 bolts.

Quote:

Originally Posted by drmatera

sorry to hijack but are the leaf spring GMC rears of that model year range also have 12 bolts?

drmatera · 09-07-2016, 12:12 PM

Thanks Captainfab, I went home last night and counted the cover bolts, only 10..

**Captainfab** · 09-08-2016, 12:41 AM

The Dana 44 that should be under your truck will have 10 bolts on the cover. It should look like this.

http://www.4wheelparts.com/Drivetrai...FUlrfgodYQ4Gjw

Quote:

Originally Posted by drmatera

Thanks Captainfab, I went home last night and counted the cover bolts, only 10..

09-05-2016, 12:48 AM	#1
bryanmartin Registered User Join Date: Sep 2016 Location: Puyallup, WA Posts: 3	Rear end help. Hi all, I'm brand new to this forum, and I just picked up a 1965 C10 with which I'm going to do a custom build. Right now I'm in the planning stages, and I admittedly know NOTHING about these trucks (eager to learn though!). It currently has a straight 6 and a three on the tree. I am looking at going with an LS motor, but I want to make sure the whole drive train can handle any power mods I throw at it. My question is, what can you folks tell me about the rear end? What type is it? Is it strong? Weak? What are the popular upgrades to it? If my best bet is a rear end swap (e.g. GM 12-bolt or something), are there certain donor vehicles that work best? I know you all have been at this for awhile, so I see no need to reinvent the wheel. Thanks! Bryan

09-05-2016, 01:54 AM	#2
66ChevyMax Senior Member Join Date: Oct 2011 Location: Wolfforth, Texas Posts: 976	Re: Rear end help. Most modern rear ends esp. posi units will handle the HP of an LS motor. Unless you do something crazy with your tires you won't have enough traction to cause a rear end problem in my opinion. I installed an Eaton Posi 12 bolt and running 575hp currently. __________________ Craig 1966 Chevrolet C10 - Supercharged LS3 1968 Chevrolet Camaro 1957 Chevrolet 2dr Hardtop "It makes sence if you don't think about it" Mesquite 1966 C10 - LS3 W/ Air Ride http://67-72chevytrucks.com/vboard/s...=1#post4989763

09-05-2016, 08:15 AM	#3
bpmcgee Registered User Join Date: Mar 2003 Location: Northern Illinois Posts: 2,181	Re: Rear end help. The three speed and straight six didn't have a ton of power, so expect to find really high gears in that rear end. I think if I recall correctly the '61 I have came with 3.93:1. Investigate wether you can get the gears you want and if axle shafts are available for it before you decide to keep or swap. B

09-05-2016, 10:52 AM	#4
vince1 Registered User Join Date: Jan 2013 Location: Calgary Alberta Posts: 1,164	Re: Rear end help. Is it not a 12 bolt now? Most common ratio was 3.73. That probably works with over drive. I currently have a 3.07 with straight through transmission.

09-05-2016, 10:55 AM	#5
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Rear end help. You have a great set up in the 65. It's a 8.875" 12 Bolt Truck Rear End (12T). You can get all new internals from this guy (I did), he even carries the 5 lug axles (you have to ask him): http://www.ebay.com/itm/GM-12-Bolt-T...PDZYWCBXVAa1Dw You have the best panhard bar bracket on the frame for a longer bar already. http://www.quickperformance.com/GM-1...-12T_c_54.html __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats? Last edited by The Rocknrod; 09-05-2016 at 11:05 AM.

09-05-2016, 11:48 AM	#6
bryanmartin Registered User Join Date: Sep 2016 Location: Puyallup, WA Posts: 3	Re: Rear end help. I suppose it could be a 12 bolt, I didn't think it would be. I would have looked, but it's in storage, oops. Thanks for the replies guys. Do you know how much power the 12 bolt is rated for? __________________ 1965 C10 - Got BIG plans for this little truck!

09-05-2016, 11:45 PM	#7
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,246	Re: Rear end help. All C10's from '63-'82 came with the truck 12 bolt. There is no reason to change the differential for something else. The 12 bolt will handle a lot of power. Of course how much will depend on how what tires you run and much money you want to put into it. In stock form a 12 bolt would easily handle ~400hp/tq. Your 12 bolt more than likely has 3.73 gears currently. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

09-06-2016, 04:05 PM	#8
drmatera Registered User Join Date: Aug 2016 Location: Nicholson, Ga Posts: 134	Re: Rear end help. sorry to hijack but are the leaf spring GMC rears of that model year range also have 12 bolts? __________________ 1981 K10 (4.8 / 4L60E swap) 1982 C10 (5.3 / 4L80E swap) 1985 C20 Suburban (454 / 4L80E)

09-07-2016, 12:12 PM	#10
drmatera Registered User Join Date: Aug 2016 Location: Nicholson, Ga Posts: 134	Re: Rear end help. Thanks Captainfab, I went home last night and counted the cover bolts, only 10.. __________________ 1981 K10 (4.8 / 4L60E swap) 1982 C10 (5.3 / 4L80E swap) 1985 C20 Suburban (454 / 4L80E)



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