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With the rapid increase in technology in the off road world, what worked just a couple of years ago is now outdated and wimpy. More horsepower, radical suspension, tougher terrain, and the desire to go over that terrain at faster speeds has created new demands on our drivetrain. Ultra4 style racing all over the globe has been a big factor in the leaps and bounds in technology and seeing what used to be thought of as indestructible drivetrain are now breaking like twigs at races all over the country and even on the trails.

But this article isn't about some uber high-tech Ultra4 race car. This article is about a Jeep. My Jeep. Over one million Jeep JK Wranglers have rolled off the assembly line since 2007. That's a lot of Jeeps. Anyone who does any sort of real off roading knows, the stock axles in a Jeep are ticking time bombs if you have anything larger than a 35" tire. It's not a matter of "if" you will break a drivetrain component, it's just a matter of "when" you will break.

So when I was putting together my parts list for what I envisioned as the "Ultimate" family rig, I knew I wanted an absolute bullet proof drivetrain. After researching all of my options and seeing what was working and what wasn't working, it became apparent that even a Dana 60 was not going to be adequate for my 4 door JK with 40" tires. Are you kidding me? A Dana 60 isn't tough enough? Go out in your driveway and take a peek under your 6,500lb tow rig. What rear axle is in it? A Dana 60? I didn't think so! Oh but this is a Jeep, not a 3/4 ton tow rig, right? Well guess what? A fully equipped 4 door JK loaded with camping gear can weigh in just south of 7,000lbs! Recently I was on Ultimate Adventure and was able to weigh my Jeep at a junk yard. To my surprise it weighed in at 6,600lbs with a full tank and camping gear!

So if a Dana 60 isn't enough, what is enough?
Dana 70s are child's play with their cute little 1.75" pinion and 10.5" ring gear. There's only one choice, the Dana 80! But wouldn't a diff that big smack every rock on the trail? The folks at Dynatrac have really stepped up the game with their latest offering - the Dynatrac Pro Rock 80. With only 1/4" less ground clearance than a Dana 60, you get a significant increase in strength. The photos below tell the story:

The Dynatrac ProRock 80 is a BEAST. Check out these stats:

  • 100% designed, manufactured and assembled in the USA
  • High clearance custom machined Dynatrac ProRock80® standard cut heavy duty nodular iron housing that is super smooth to effortlessly slide over obstacles
  • Heavy duty 4" diameter, 1/4" wall lightweight high rigidity chromoly axle tubes
  • 11.25" USA made standard cut ring gear 3.54 - 5.38:1
  • 37 spline pinion input shaft
  • Extreme housing rigidity to keep gears in proper mesh in any condition
  • Full floating, 40 spline Dynatrac "ProMax" 4340 Chromoly axle shafts
  • Most ground clearance of any axle using a 10.5" gear or larger
  • Dynatrac ProRock80 heavy duty full float nodular iron wheel hubs, chromoly heat treated spindles and serviceable bearings
  • Heavy Duty J8 Military 13.9" vented rotor disc brake assemblies

And my favorite part:

  • 1 year, unlimited mileage, "No-Fault" warranty

Armed with all of that data, I headed over to Dynatrac in Huntington Beach, CA, and watched them build my Dana 80 from a pile of tube to a brutally strong thing of beauty. Check out the photos below.


That's a big hunk 'o 4" chromoly tube!

Cutting the axle tubes to size

Dynatrac built chromoly full float spindles

Prepping tube for fitment into center section

Prepping tube for fitment into center section

Prepping tube for fitment into center section

Turning down the inside of the tube for a perfect press fit.

Turning down the tube for a perfect press fit. Note the step downs in the tube and spindle. Makes an easier press fit.

Spindle ready to be pressed into the tube

Pressing spindle into tube

Spindle ready for welding

Welding spindle to tube

Beefy!

Look at that cute little tape measure!

Pressing both tubes into center section at once

Drilling out plug weld holes

Plug welding the diff - not required but extra insurance

Smokin' hot!

Brake caliper mounts welded up

Washing all the grime off before paint and final assembly

Cleaning up surface of pinion for seal surface

Cleaning everything is key

Heating up the ring gear to make installation onto the locker easier

Easy does it


Working on the perfect pattern

Pressing in the chromoly wheel studs

Beefy full float hub

Greasing the serviceable wheel bearings

Ready to install

Pattern is dialed. Time for final assembly

Special oil ports for pinion

Let's check that pattern one more time

Seal it up!

Air locker line carefully tucked in there

Pressure testing the air locker for leaks

Looks good!

Installing pinion seal

Parking brake and even JK wheel/ABS sensors are all installed

Installing the hubs and 40 spline axle shafts

The signature Dynatrac diff cover - just bigger!

Whallah! The ultimate rear end!
 

Driving Impressions
I'd like to think I succeeded in building a pretty damn bullet proof family rig that can drive 1,500 miles on the highway in complete comfort yet run the toughest trails in the country. The day the Jeep was done we took it to Moab for Easter Jeep Safari. Shortly after that, we went down to the Hammers and ran all of the KOH trails including Sledge, Outer Limits, Spooners, climbing up the waterfall on the infamous "Back Door" trail, Resolution, etc. etc. After that we logged 1,500 miles on Petersen's 4 Wheel and Offroad's Ultimate Adventure with no issues. We recently returned from Colorado where we ran all the toughest trails at All 4 Fun including Carnage Canyon with zero problems and zero body damage!


Driving Carnage Canyon in comfort! Yes, there are passengers in the back seat.

The Dynatrac High Pinion ProRock 60 front end nicely compliments the rear ProRock 80

Conquering all the Hammer trails with no body damage in a full bodied Jeep requires top notch equipment

Here are a couple of video clips of the Jeep in action. The first video is climbing "Back Door"

Fully Getting It at Gulches Off Road Park in South Carolina  

Rear axle view of the same run above at Gulches Off Road Park

Climbing the muddy wall on Carnage Canyon

 

With only 1/4" less clearance than a Dana 60 and only 35 lbs heavier, I'll take the exponential strength and peace of mind knowing I can GET IT anytime I want without worry of breaking!

SOURCES
Dynatrac Products, Inc.
7392 Count Circle
Huntington Beach, CA 92647
Phone: 714.596.4461
Fax: 714.596.4449
http://www.dynatrac.com
E-mail:sales@dynatrac.com