Editor's Note: Some modifications never become outdated, especially those that are simple bolt-on improvements that can be done with junkyard parts. We still get questions about swaps and conversions we did over five years ago. This is one of them. And it's the third installment of our Timeless Tech series.
If your Dana Spicer 18 transfer case is worn out and howling like a ballad from an '80s hair-metal band, it's probably the intermediate shaft and bearings crying for mercy. When the bearings and gears get real sloppy, the transfer case will even pop out of gear. Highway driving accelerates the wear. If you continue to run it this way, you'll be rewarded with a wonderful chain reaction that crunches all of the gears in the transfer case.
Most transfer cases are a straight-through type. When they're shifted into two-wheel drive, the intermediate shaft and bearings are free-spinning. The 18 is a side-drive, so the intermediate gear is always under load. This makes the bearings and shaft extremely prone to wear. Replacing the original pieces with low-quality import jobbies results in short bearing and shaft life.
We installed a cheapie shaft in one of our transfer cases and pulled it out after a mere 2,000 miles only to find it already had grooves worn into it. We began to wonder if it had even been hardened. Novak offers quality hardened shafts for all three Spicer 18 sizes and the 1 1/4-inch Dana 20 shaft that will also fit into a Dana 300.
We showed the total rebuild of a Spicer 18 in "The Best Transfer Case Ever" (Sept. '00), so we'll just show the basics of installing one of Novak's shafts. You could conceivably swap out the intermediate shaft and bearings while the transfer case is in the vehicle. However, we removed the whole assembly for easier access.
On the left is a 1 1/8-inch...
On the left is a 1 1/8-inch intermediate shaft that we let go way past its prime. It's an import unit that we managed to squeeze about 6,000 miles from before the whole transfer case went bang. The bearings had worn out of the cages and were in very sad shape. The shaft on the right is from the same manufacturer, and after 2,000 miles of use, it's showing unacceptable wear.
Once the bearings and the...
Once the bearings and the shaft wear, the intermediate gear will no longer run parallel to the rest of the gears. The gears won't mesh properly and even more noise will emit from the transfer case until all of the gears start chucking teeth like a 98-pound hockey player.
The 3/4-inch and 1 1/8-inch...
The 3/4-inch and 1 1/8-inch Spicer 18 transfer cases use caged bearings. They only need to be lightly lubricated with grease or gear oil prior to installation. The 1 1/4-inch transfer cases have 48 independent rollers that need to be held in place with thick grease prior to assembly.
Here's another low-buck jobbie-check...
Here's another low-buck jobbie-check out the dents in the shaft. Is someone making these things out of rebar? We've had poor-quality shafts damaged in shipping, so how are they supposed to survive inside a transfer case?
The Novak shafts come with...
The Novak shafts come with bearings, thrust washers, some other small parts, and are several times harder than the import junk we're used to. A harder shaft will last longer.
All of the Novak shafts have...
All of the Novak shafts have O-rings on both ends to eliminate oil leaks. Smear grease on the O-rings to prevent them from being cut or chewed up during installation.
Grease the thrust-washer mating...
Grease the thrust-washer mating surfaces in the transfer case to hold the thrust washers in place. You can also grease the bores so the O-rings slide in easily.
Once you have the washers...
Once you have the washers in place, you can use the new shaft and an old one to keep them there while installing the intermediate gear.
Here's another sweet bonus....
Here's another sweet bonus. Most aftermarket intermediate shafts are too long, and they interfere with the transfer case adapter. This often causes oil leaks unless you grind the adapter for clearance. Novak makes the shafts just long enough to sit flush with the case.