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Old 09-26-2008, 06:16 AM   #1
stillsmokin
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7200# rear axle (HO72) extreme application

Hi everyone, I'm new on this forum, but not new to old 4 wheel drives.



I have a 7200# axle (ho72) question thats a little different than most. I have seen many 7200# axles in hot gas sled pulling trucks. I have a 4.57 ratio7200# axle coming my way from a 67 2 wheel. If I were to put a 7200# axle under say a 92 dodge diesel (anticipating the pinion dislocating on the current dana 70U) how will it hold up? I was thinking of trussing the axle tubes, using a 14 bolt mini spool/welded to the carrier for reinforcement and 14 bolt axle shafts. Or can I get something even stronger? The yoke is too small for the dodge u joint so I need to do something there, think it's a 1410 joint.

It would be alot more cost effective vs. a dana 80 and would be more of the correct width and look for the dodge. Plus used parts are everywhere and fairly inexpensive which is not the case with a dana 80.

The 7200# axle is pretty similar to the 80. Both have 2" pinion shafts, they have similar sized axle shafts 1.5" although the 80 has 35-37 spline axles vs. the 30 spline 14 bolt shafts, the 80 has a little more in the ring gear and it's bolt circle is a little larger.
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Old 10-05-2008, 11:40 AM   #2
DieselEater
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Re: 7200# rear axle (HO72) extreme application

I'm running a 14-bolt in a 700ish HP super stock puller.....Unless you're making more than 800 HP and your rules allow it, you can't beat the 14-bolt!!! they're everywhere, the pinion style is stronger than the D80, they're cheap, and easy to get parts for, like yokes to match your driveline.

A........
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Old 10-05-2008, 11:49 AM   #3
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Re: 7200# rear axle (HO72) extreme application

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Old 10-05-2008, 10:55 PM   #4
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Re: 7200# rear axle (HO72) extreme application

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Originally Posted by DieselEater View Post
I'm running a 14-bolt in a 700ish HP super stock puller.....Unless you're making more than 800 HP and your rules allow it, you can't beat the 14-bolt!!! they're everywhere, the pinion style is stronger than the D80, they're cheap, and easy to get parts for, like yokes to match your driveline.

A........
Well a pinion design supported by 3 bearings is stronger than one with 2. But, in a diesel competition application we don't worry about HP, it is torque that shreds drivetrain components. The 14 bolts I have around here are 1.75" at the pinion splines. The dana 80 and 7200lb axle have 2" pinion splines, these cummins pulling engines produce 1400 torque fairly easily. The pinions on dana 60/70 axles just can't handle the torque surge and snap little little girl toys on street trucks. My new axle has to have a 2" pinion.

Nice truck by the way!
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Old 10-06-2008, 07:29 PM   #5
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Re: 7200# rear axle (HO72) extreme application

There are a large number of modified diesel 4x4's in our club, but, I've never looked to see what rears they are running??? Most are newer vehicles, so I'd say they are probably factory D80's.....

The H110 may be an option also, if rules allow.


A..........
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Old 10-08-2008, 12:24 AM   #6
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Re: 7200# rear axle (HO72) extreme application

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Originally Posted by DieselEater View Post
There are a large number of modified diesel 4x4's in our club, but, I've never looked to see what rears they are running??? Most are newer vehicles, so I'd say they are probably factory D80's.....

The H110 may be an option also, if rules allow.


A..........
The 80 wasn't available till 96 I believe, then it's standard behind cummins and v10 w/5 speed manuals. Every other dodge diesel came stock with a 70 or 70U.

I have a H110 third here but it's a 6.17 ratio, besides can't run it anyway (1 ton or smaller axle rule), I need to be at 4.56 anyway.

I did a little fooling around with the truck the other day, a friend did some video....

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69 GMC k2500, 427, 4 speed, Rockwell 221, 7200# rear, detroit, disk brake front, 5.13's
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Old 10-08-2008, 01:00 AM   #7
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Re: 7200# rear axle (HO72) extreme application

Im pretty sure i have been told the HO72 EATON comparable to the 14 bolt. The 14 bolt is a newer design that replaced the HO72. The only real problem with the HO72 is there is not really any aftermarket products. I run the HO72 but i have not had the hp to put it to the full test. With my planned 472 big block hopefully going in this comming spring i will see how she holds up.

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Old 10-08-2008, 01:12 AM   #8
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Re: 7200# rear axle (HO72) extreme application

BTW NICE CUMMINS! i kinda like the pre 94 cummins trucks. See ya sat in broken bow if your coming.
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Old 10-09-2008, 11:43 AM   #9
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Re: 7200# rear axle (HO72) extreme application

Nice dodge. I have a few good threds book marked on upgrading the eaton here are some good ones may help you out some.

http://www.pirate4x4.com/forum/showt...ght=eaton+1410

http://www.pirate4x4.com/forum/showt...ht=1410+flange

http://www.pirate4x4.com/forum/showthread.php?t=250006
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Old 10-10-2008, 08:51 AM   #10
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Re: 7200# rear axle (HO72) extreme application

Quote:
Originally Posted by FROSTBITE406 View Post
Im pretty sure i have been told the HO72 EATON comparable to the 14 bolt. The 14 bolt is a newer design that replaced the HO72. The only real problem with the HO72 is there is not really any aftermarket products. I run the HO72 but i have not had the hp to put it to the full test. With my planned 472 big block hopefully going in this comming spring i will see how she holds up.
From what I've been able to find out, the difference between the ho 52 and ho72 is that the ho72 has an adjustable deflection bushing directly opposite the pinion gear, so the ring gear cannot deflect away. I would say the ho52 is comparable to a 14 bolt, and the ho 72 is just a bit better. I've been colecting these rear ends for a while now, and have picked them up from 3/4 ton to 3 ton trucks. I do believe, like all things that are built too good, they just stopped making them because they were way stronger than needed. I don't know how they would hold up in major extreme use, but I would use one over a 14 bolt or dana 70. I am not familiar with a dana 80.
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Old 10-10-2008, 10:49 AM   #11
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Re: 7200# rear axle (HO72) extreme application

Nice truck!
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Old 10-10-2008, 10:47 PM   #12
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Re: 7200# rear axle (HO72) extreme application

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From what I've been able to find out, the difference between the ho 52 and ho72 is that the ho72 has an adjustable deflection bushing directly opposite the pinion gear, so the ring gear cannot deflect away. I would say the ho52 is comparable to a 14 bolt, and the ho 72 is just a bit better. I've been colecting these rear ends for a while now, and have picked them up from 3/4 ton to 3 ton trucks. I do believe, like all things that are built too good, they just stopped making them because they were way stronger than needed. I don't know how they would hold up in major extreme use, but I would use one over a 14 bolt or dana 70. I am not familiar with a dana 80.
According to the 68 chevrolet overhual manual the difference between the 7200# and 5200# axles is the brake size. The manual also implies these are not actually "eaton" units rather, scaled down single speed eaton designs that GM produced. The "eaton brand" designation is used at 18,000 pounds and heavier in the manual. The "HO72, HO52" is not a GM axle designation by the way, apparently somebody invented this over time, and they are NOT 12.5" either, that would be the 11,000# unit. The 5200/7200# axle are 10.125" ring gear. I believe the load bolt design is simply a later design revision. These load bolt third members have additional oiling passages for the revised tapered roller pinion bearing vs. the ball roller/no load bolt/no oil passage earlier version. GM quit producing them due to "high production" costs but it is becoming apparent now the quality of materials used was definately top notch, so the costs were well worth it. Yet the offroad magazines have yet to even list it as a high strength axle, it's amazing these people still get a paycheck.

I just heard in a conversation how a ford puller down the road ran a 14 bolt for a few months last year because he kept breaking axle shafts in a dana 60. Then, he found more power and twisted off the pinion in the 14 bolt, He then went with a 5200/7200# axle and he is now twisting the driveshafts off at the middle of the stubshaft, they wanted advice.
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92 Dodge, Cummins, SLED PULLER, 5'' hood exit, NV4500UHD, dual disk clutch, Borg Warner S400 charger, GM 7200#/14B hybrid rear

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69 GMC k2500, 427, 4 speed, Rockwell 221, 7200# rear, detroit, disk brake front, 5.13's
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Old 10-10-2008, 10:55 PM   #13
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Re: 7200# rear axle (HO72) extreme application

Quote:
Originally Posted by FROSTBITE406 View Post
BTW NICE CUMMINS! i kinda like the pre 94 cummins trucks. See ya sat in broken bow if your coming.
I was going, but the 8500# diesel class was so heavy I figured I'd just finish the truck all the way this winter. These old trucks are weighing heavy at 6400#s with the 10 disk changer, spare tire, and the kitchen sink. I only have 1550 lbs of iron to hang. Maybe they'll do one this spring again and get that weight down to the fairly standard 7800 or 8200# classes.
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92 Dodge, Cummins, SLED PULLER, 5'' hood exit, NV4500UHD, dual disk clutch, Borg Warner S400 charger, GM 7200#/14B hybrid rear

Dads...

69 GMC k2500, 427, 4 speed, Rockwell 221, 7200# rear, detroit, disk brake front, 5.13's
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