If you run a big engine and big tires, eventually it's going to happen - you're going to break the output shaft on your Dana 300 transfer case. It's just like what they say about rolling your rig over; it's not if...it's when! And, unlike an axle or a u-joint, an output shaft is not something you can fix easily on the trail! Don't get me wrong, this is a very reliable t-case, but it wasn't built to put up with high horsepower, high torque engines, low gearing, and big tires.

How big is big? Well, I think that's a relative question. I've read that the Dana 300 will stand up with tires up to 38 inches, but I think we need to look at the whole picture. I'm running a built 401, a T-18 transmission, and Dana 44's with Detroits, 4.88 gears, and 35" Swampers.

I know I'm pushing my luck on the diffs, but I carry spare front and rear axles, and I run standard 1310 u-joints, hoping they'll be the "fuse" in my drivetrain. So far, it has worked. And, I don't know about you, but I don't want to be a stick in the mud and break something I can't fix relatively quickly. That's the main reason I decided to upgrade my Dana 300 with Advance Adapters' 32 Spline Output Shaft.

The kit comes with everything you need, except for some good RTV sealer and medium strength thread-locking compound. I'm sure you'll be impressed by the quality of the parts, especially the massive new output shaft!

Doing the Conversion
When you first receive your kit, unpack it and verify that all of the parts are there. When I first checked parts against the list included with the instructions, I thought I was shorted. But, after reading carefully (good idea, right?), I realized that everything was there. Some of the parts had been pre-assembled by Advance Adapters, meaning, of course, less work for me.

I'm going to assume that you've already removed your transfer case from your vehicle and are ready to go. First, the bottom access cover has to come off.

Second, remove the rear output yoke. You should be able to tap it off with a small hammer.

Third, remove the front input shaft retainer. In my case, I had to remove my Advance Adapters clocking ring first. See "Clock It" from last month. The retainer has two grooves for prying it out evenly. Use them! The retainer and input shaft will come out as an assembly.

Next, remove the tailhousing. A minor point here, but AA's instructions don't tell you to remove the speedometer gear assembly, which you should do before removing the tailhousing.

The toughest part of this procedure is next. You must remove the output shaft tapered bearing from the shaft so that the shaft can be removed out the front of the transfer case. I had been told that with the yoke nut installed I could tap on the output shaft while having a friend pry the bearing in the opposite direction. WRONG!

AA says the best way to remove the bearing is with a puller, but I couldn't find one that would fit between the bearing and the case. After much frustration, I realized that I wasn't going to use the bearing again anyway. I promptly cut off the outer race and used the puller setup pictured to remove the inner race. (Thanks to Chris Sykes at Motor City Machine in Cypress, Texas) If I hadn't had access to this puller, I probably would have used my cut-off tool and a chisel to do the job. Make sure to clean up any metal pieces from the transfer case and your workspace.

After this, installation was fairly easy. Remove the new shaft from the new tailhousing assembly, making sure you retain the shim race to maintain proper end-play. This has been pre-set by Advance Adapters.

Also, make sure the pocket bearing in the new shaft (which supports the rear of the input shaft) is lubricated, as well as the shaft surfaces. I used good old Vaseline, but gear oil or even grease will work.

Install the shaft through the front of the t-case, through the slider hub, and through the gear. Next, install the thrust washer and bearing onto the shaft. AA says the bearing should be a "light press fit." Instead of pressing this bearing on (not an easy thing to do), I decided to solicit the help of a friend to hold the output shaft from the front while I used a small punch and hammer to carefully install the bearing. It worked like a charm.

Install the speedometer snap ring and then the speedo gear. Then install the shim race provided with the chamfer against the shoulder of the shaft. This shim is specific to this output assembly and keeps all the clearances where they need to be.

Using a very small amount of RTV sealer, install the new tailhousing. Although AA doesn't mention it, I had to use a small punch to lightly tap on the inner race of the rear bearing to convince it to slide down the output shaft.

Also, AA's instuctions say to install the tailhousing with the stock bolts, but they provide Allen head bolts to do this. Either way will work fine. Put a small amount of RTV sealer around the front retainer, line it up, and using a soft hammer to carefully tap it into position. Once it's bolted down, install the rear output yoke, splined rubber washer and torque the nut to 150 ft/lbs.

At this point, make sure everything rotates freely. If everything checks out, install the bottom access cover using RTV or a new gasket (which is not included), and using the new o-ring provided, then install the speedo gear assembly. Last, but not least, install the supplied vent fitting.

That's it. With the exception of installing the transfer case back in your vehicle, filling it with oil, and checking your driveshaft length, you're done. Since the AA shaft is 1/2 inch longer than stock, you may have to shorten your rear driveshaft accordingly, as I did. Some of you will not need to do this. Just be sure your driveshaft is not too long, or you could end up breaking things, like a friend of mine recently found out. His rear shaft was a bit too long, and over time, he actually broke the pinion in his Dana 44 rear differential! A good driveshaft shop can shorten any driveshaft for around $50.

Is this upgrade right for you? If you wheel hard and run large tires and/or horsepower, there's no doubt. I've had friends suggest I upgrade to an Atlas II transfer case, instead of wasting time and money on this upgrade. Don't get me wrong, I'd love to have the brute strength of an Atlas, but considering that I already had a perfectly good Dana 300, converting to the 32 spline output shaft was a lot less expensive and I really don't need the super low gearing for the kind of wheeling we do, which is mainly climbing hills and ledges that require a bit of momentum. Advance Adapters 32 Spline Output Shaft helps put my weakest link back where I want it, at the driveshaft u-joints, not inside my transfer case!

Jack Brinks is an avid four wheeler and contributor here at ROCKCRAWLER.com. Jack resides north of Houston, TX and frequents many events in the Southwest. Contact Jack at jb77cj7@aol.com