# 3/4 ton rear end swap



## MTCK (Feb 13, 2000)

Here's an idea I've been thinking about. I've gone through a few 10 bolt rear ends, as I'm sure a few of you have, and I was looking at an early 90's 3/4 ton the other day, which was a light duty model and had six lug wheels. The rear end is the 9.5&quot; ring gear 14 bolt. Does anyone know if this would bolt up to my 83 1/2 ton's spring pads and shock mounts? What about running 15&quot; wheels on that rear end? All the ones that I have seen had 16's on them, but a fair amount of clearance between the break drum and rim. Are these rear ends very tough?


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## John DiMartino (Jan 22, 2000)

Hi HTCK,I have often thought of the same swap myself for someone who wants to beef up a 1500.My Uncle owns a modern salvage yard,and from walking it and my own experience and vehicles this is what I know about these rears:The 10 bolt has a 3750 lb rated capacity,12000GCWR (total truck and trailer it is rated to pull safely.)In 88 and newer 1500 P/U(5600-6200gvwr) the 10 bolt has 10x2.25 brakes,in the suburban 1500(6800gvwr 4x2,7200gvwr 4x4) it has a bigger set at 11.15 x2.75 shoes.These are both in 5lug or 6 depending on 2 or 4 wd.The 2500 P/U rear (LD) 6 lug has 4800 lb rated capacity,9.5" gear,is put in 7200 lb gvwr 2 and 4 wd which are basically a 1500 with a stronger rear and bigger brakes at 11.15x2.75.They are also put in 1500 4x4 with the HD chassis option (6600 gvwrXcab swb,6800 gvwrXcab lwb).I had one of these a 1994 and it is the beefiest 1500 you can buy.There is also a 5 lug version of this rear that is very rare,I am not 100% sure,but the only thing I have ever seen it under is the SS454 from 1990-1993.So it looks like GM swaps these at the factory to make upgrades for there own reasons.I have never measured,but the perches are prob. the same spacing.You may have to shorten driveshaft an inch or two,the yoke may be beefier and require a bigger u-joint and the wheel cylinders are 1" in diameter,slightly larger than yours,so a new proportioning valve may be needed.I have had a 1500 4x4,with 10 bolt,a 1500 4x4 HD chassis w/14 bolt and big brakes11.15x2.75,and now own a 2500 4x4 LD with 9.5 14 bolt.You will love the better brakes,I could stop better with 2000lbs in a 14 bolt truck than a 10bolt empty.The rear is much stronger,I have never seen one break,although they tend to clunk a lot more than the 10 bolt when they get high miles.For some reason all the 14 bolt LD's I have worked on have had cracked rear brake shoe linings after many miles.It seems like I change them for severe cracking long before they wear out.The only thing I left out was the E-brake,I'm not sure if the stock cables are long enough.Any swap is a lot of work and this one is worth doing if you are at the limits of the 10 and plan to keep it a while.Let me know if you need any more info.BTW I have an 84 S10 4x4,xcab with an '89 camaro 2.8Multi-Port FI,motor,complete with all accessorys and computer and EFI,The motor was a drop in,but the EFI was a lot of work,but well worth it.

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John D


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## John DiMartino (Jan 22, 2000)

I forgot to mention,if you want 15" wheels,use the SS454 axles with 5 lugs,then you can put the 2wd wheels on which are 15".The shock mounts on the C/K's are in the same location and the same part#at Napa or BigA.

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John D


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## jay (Nov 29, 2000)

mtck, if you're breaking 10 bolt axles,
a swap to a 14 bolt 6 lug rear will do
you no good.From what I understand they
use the same axles(diameter), you'll
get bigger brakes and a stronger diff though.
If you're doing hardcore wheeling you can't
beat a full floater.Keep in mind that you're
gonna lose ground clearence under any 14 bolts pumpkin.


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## John DiMartino (Jan 22, 2000)

I've had both axles out and they are not the same,the 14 has larger bearings,thicker shafts and flanges.That is why they have a 4800lb rating,a 10 has a 3750 lb.The most common failure in the 10 bolt is the carrier,which is much stronger on 14.Then R&pinion set,The axles rarely fail unless huge tires are used with lockers ,lots o power and no brains driving attitude.A full floater is the ultimate,but you might as well sell the 1500 and buy a 2500Hd or 3500.The cost and hassle of swapping both axles,and rims,tires,2hybrid driveshafts etc...will be more than the truck is worth.A simple swap that upgrades the axle for only a little more than the cost of a rebuilt 10 bolt is what MTCK,is looking for,it seems.BTW I know guys with 2500LD's that think all 3/4's are same.One guy runs a 2yd sander in one.,loaded it weighs 6000+.For ten years he has plowed with this with no problems+summer use hauling gravel,and mulch+towing trailer.His rear axle weight is 8000+,If that was a 10 bolt,it would've snapped axles and gears along time ago,so these are overbuilt for safety.I think this will be plenty strong for a 1500 truck.

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John D


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## jay (Nov 29, 2000)

hey john d., lots of info, wish i had
an uncle with a salvage yard. BTW i have
a 77 1/2 ton 4x4 with a 12 bolt rear and
a dana 44 front, drive it everyday to
work and hit the mountains for hunting
on weekends,drive sanely and never broke
a single part yet.the truck is 95% stock,
no lift, 32" tires, just a dual exhaust
and a b&m shift kit. anybody wanting a
shift kit in your auto, the B&M in RV/heavy
duty mode BANGS! pretty much. Wish i left it
stock. keep writing guys i enjoy the helpful
info.
jay


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## MTCK (Feb 13, 2000)

Bringing this post back from the dead.......... I have another question and figured by adding to this post it would be easier to see what I'm talking about. I've looked at several salvage yards, and am getting closer to doing this. The question I have is about brakes. I have all new rear brakes on my 10-bolt that I have now, and most of the axle's I've seen come without brakes on them. Are the bolt patterns that hold the backing plate to the axle housing the same on the LD 3/4 ton 6 lug as the 10 bolt? Another advantange to this move, is that I wouldn't have to mess with a different proportioning valve. Thanks in advance.

Marcus


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