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THE ULTIMATE DANA 300
How To Build It With Parts From
JB Conversions & Onetime 4xProducts

By Jack Brinks

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The Dana 300 transfer case has a lot going for it. It has a strong, compact, cast iron case and is completely gear-driven. It can be “twin-sticked” relatively easily, allowing for a wider range of gearing options. In stock form, it offers a reasonable 2.62:1 low range, which is adequate for most off-road applications. However, if you have a taste for big engines, big tires and big rocks, just like other parts of your vehicle, you're going to need to make some upgrades.

JB Conversions LoMax 4:1 Gears:
The first upgrade most of us want to make is lower gears so we can crawl at lower speeds, allowing more control and better traction. We've already covered the LoMax in detail, so check out the previous Rockcrawler.com article on JB Conversions LoMax 4:1 gears at JB Conversions LoMax 4:1 Dana 300 kit. These heavy duty gears will definitely slow you down!

JB Conversions LoMax

Onetime 4xProducts Big Shaft Kit:
Now that we've dramatically increased the torque being transmitted to the tires, it's time to address the weakest link in the Dana 300 - the rear output shaft. The stock shaft has been known to give up the ghost when subjected to the kind of torture some of us put our rigs through. The Dana 300 Big Shaft Kit from Onetime 4xProducts solves this problem in a BIG way with a 32 spline output shaft and heavy-duty housing.

Onetime 4xProducts Big Shaft Kit

Check out the comparisons of the output shafts and housings. Size does matter! The Onetime 4X4 shaft is machined from 8620 heat-treated alloy. The shaft is a thing of beauty in itself, with precision machining and great attention to detail. Notice how the splined area does not extend into other areas of the shaft, which could reduce overall strength.

The first thing you'll notice about the housing, besides the size itself, is the 6-bolt mounting flange with two 3/8" dowel pin holes that have been integrated into it. You will also notice that each bolt hole has a machined face to reduce the possibility of cracking the housing when you torque down the bolts. The housing has been beefed up significantly, to not only to handle more torque, but to also accommodate a parking brake bracket without the need for any other bracing. If a parking brake is not used, a billet cap and seal are supplied with the kit.

JB Conversions Ultimate Dana 300
Shaft size comparison
JB Conversions Ultimate Dana 300
Housing size comparison

Onetime 4xProducts has designed a cable-operated e-brake kit consisting of bracketry, a caliper and a rotor. With longer, custom wheelbases and other modifications, this kit eliminates the need for longer cables that are difficult to find and tend to limit suspension travel. Its design allows even pressure to both sides of the rotor when engaged, greatly increasing braking efficiency and longevity. The one you see here is a prototype and actual production is about six months away. If you're interested (I'm in!), give Onetime 4xProducts a phone call at (205) 841-2493 or send them an email at sales@onetime4xproducts.com and let them know.

Onetime 4xProducts E-Brake Kit

JB Conversions HD Front Output Shaft: Another potential weak area is the front output shaft. Although normally not subjected to the abuse of the rear shaft, mainly due to weight transfer, upgrading the front shaft is definitely a good idea if you wheel hard or are competing. JB Conversions has designed a kit that includes a 32 spline shaft, new yoke, bearing, seal and small parts. Check out the comparison between a stock shaft and the JB Conversions shaft in the following photo.

Front Output Shaft Kit
JB Conversions Ultimate Dana 300

Because the shaft is much larger, the bearing must also be larger. This requires machining of the aluminum front bearing retainer housing accordingly to fit the larger, stronger bearing race. Instructions include detailed information your local machinist can use to do the job. The cost should run well under $100 and most-likely half of that amount, depending on hourly labor charges in your area. If you can't find a machinist who will work with you, JB Conversions has a local shop you can send your housing to for machining at a fair price.

JB Conversions Ultimate Dana 300
JB Conversions Ultimate Dana 300

 

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