Most folks immersed in the world of early Jeeps have heard of Herm Tillford, aka, Herm the Overdrive Guy. In fact, those in the early Jeep inner circle know right away what you're talking about when you say something like, "I used Herm's steering kit," or, "I had Herm rebuild my T-case and overdrive." And although the company is technically called ATV Manufacturing, anybody who has visited Herm's website at hermtheoverdriveguy.com has probably come to associate the moniker with a wide selection of specialty conversion drivetrain, steering, and braking parts for early Jeep vehicles.
We have a buddy who recently put an injected 5.0L Ford engine in his '66 CJ-6. With the newfound power, we figured the 19-spline rear shafts didn't stand a prayer of lasting more than a couple of feet into the first rock garden that he visited. A couple of years ago the solution would've been to stab a Warn full-float conversion kit in the offset Dana 44. However, Warn recently ceased production on those kits. Thankfully, ATV Manufacturing has stepped up with its own full-floating axle kits for '49-'70 Jeep CJs with the offset Dana 44 rear axle. Now you can once again ditch the problematic and weak two-piece shafts and tapered hub assembly in favor of stronger, more durable 19- or 30-spline full-floating shafts.
Herm offers his floater kits in so many different versions we don't have the space to list them all in this story. You can buy just the 19- or 30-spline shafts (no 10-spline shafts are available), 27-spline drive flanges or locking hubs, complete 19- or 30-spline conversion kits with or without hubs or flanges, or you can even buy any component individually if you're building your own floater kit or trying to fix an older aftermarket kit. We went with Herm's full-mambo 30-spline conversion kit. And since we were converting from the Jeep's current 19-spline shafts, we needed a new 30-spline carrier. In addition to weekend warrior duties on the trail, this Jeep serves as a daily driver, so a mild-mannered Eaton Detroit Truetrac differential got the nod as part of our conversion package. Follow along as we power-proof an early Dana 44 in our driveway in a leisurely afternoon.
At top is the 30-spline Eaton Detroit Truetrac differential and a Lube Locker diff gasket. Shown underneath is ATV Manufacturing's new Full-Float Axle Kit, which includes a mix of brand new and refurbished genuine Spicer components. Herm has discovered some quality issues on certain aftermarket replacement parts that aren't up to his exacting standards, so he prefers to go through the extra steps of obtaining and refurbishing used parts where he feels necessary. Our kit included brand new shafts, bearings, seals, hubs, and drive flanges. The spindles were refurbished genuine Spicer parts that were machined to fit the ID of the housing bore.
We first checked the backlash on the old 19-spline diff, then removed the old bearings to get at the shim packs noting which side they came from. Like most Eaton product we've used lately, we were able to get a perfect backlash reading by simply transferring the shims to the same side on the new Truetrac, then installing the carrier bearings. The Lube Locker is a reusable gasket that requires no sealant and does a great job sealing the factory stamped sheetmetal diff cover.
With the axle stripped down past the drum backing plates, we first installed the outer axle seal for the new 1.31-inch 30-spline shafts. We coated the outside diameter of the seal with Permatex Aviation Form-A-Gasket and then installed it using a seal driver tool.
The shafts must be installed before the spindle because the 1.31-inch, 30-spline end that indexes the carrier is too large to fit through the spindle. We greased the seal surfaces and then slid the new shafts home, taking care not to nick the new seals.
Using the original backing plate T-bolts, install the spindle over the shaft (not shown) and then install the backing plate over the spindle. We added a bit more Permatex Aviation Form-A-Gasket to the rear of the spindle around the bore index just to be on the safe side.
With the spindle and backing plates bolted on, we then drove the new races and lubed and installed the new bearings and seals into the hubs. The hubs were then installed using the new lock washers and nuts supplied with the kit, and we set the bearing preload just like you would on a front axle.
Both the 19- and 30-spline axle kits include shafts with 27-spline ends, so most common 6-bolt locking hubs and drive flanges can be used. Our buddy flat tows his Jeep to the trail, so we installed a used pair of Warn locking hubs seen in the lead photo. But for heavy-throttle use, he'll swap the hubs out to these drive flanges from Herm. Now the Jeep's early Dana 44 is more than ready to deal with a rip-snorting 300hp engine and 33s or 35s without worry.