JeepWire on 4x4Wire

Superior Axle and Gear's New 4.88 Gears!

By: Randy L. Wheeler - 7/2000
Photos by Author and Vance Anderson

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Superior's new 4.88 Ring and Pinion

Superior Axle and Gear has been working feverishly over the past year to get these gears out of the design stage and into production. The long awaited 4.88 gears from Superior Axle and Gear have finally arrived! The 4.88 gears are currently available for the AMC Model 20, Dana 30 (standard and reverse cut), as well as the Dana 35. Up until now, the lowest gear set available for the Dana 35 was the 4.56. The new 4.88 gears should fill the need for those of us looking for something lower (numerically higher) than the standard 4.56 gear set. These new gears were developed specifically for those of us running 33 or 35-inch tires and lockers. According to Ron Stobaugh at Superior Axle Gear, they just got back from pre-running the Baja 500 race course in 2 Jeep TJ's, each equipped with 6 cylinder engines. One Jeep was equipped with only the new Super 35 Detroit kit, and the other Jeep was equipped with 35-inch tires, 4.88 gears and a Super 35 Detroit kit. Ron plans to take these same Jeeps on the Rubicon for the Jeepers Jamboree, then to Sierra Trek, and finally to Moab. They are not going to trailer these Jeeps to these events, they are going to be driving them. If this isn't a real life torture test, I don't know what is.

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The 4.88 gear (left)  compared to the 4.10 gear (right).

For my application, I'm driving a 2.5-liter, 1991 YJ equipped with 33-inch BFG MTs, stock transmission/transfer case, 4.10 gears, Dana 30 front end with a Lockright locker, Dana 35 rear end equipped with the older style Super 35 Lockright kit and a 4-inch lift. I considered installing a set of 4.56 gears last year, but when I heard that the 4.88's were coming out, I opted to stick with the 4.10 gears for the time being. The little 4-banger engine has sufficient low end torque, but on the freeway, my 5th gear was about as useful as a screen door on a submarine. The 4.10 gears and the 33-inch tires just weren't enough for me I needed a lower gear set.

I contacted owner Tom Grancey of Foothill Offroad of Auburn California and set up an appointment to have my gears and new Super 35 Detroit kit installed. Tom and his highly professional staff did an outstanding job installing these products. Foothill Offroad is an authorized dealer for Superior Axle and Gear products. They also have a complete fabrication shop and carry a wide variety of products for your 4x4. They specialize in custom axle buildups as well as installations and machine work.

Installing the new 4.88 gears was done in conjunction with the installation of the new Super 35 Detroit kit. The installation procedures for each axle are pretty similar, except that I elected to keep the Lockright locker in the front and just install the new 4.88 gear set in the Dana 30. The installation of the Detroit kit is covered in a separate article.

Overhaul Kit

Along with the 4.88 ring and pinion gears, I ordered new overhaul kits which included a Pinion nut, pinion seal, pinion and carrier shims, crush sleeve or shims, ring gear bolts, threadlocker, gasket or RTV, marking compound and brush, and new Timken pinion and carrier bearings.

Tom started the installation by putting the Jeep up on the hydraulic hoist and removing the tires. Starting on the rear axle, the existing Lockright locker was disassembled and the c-clips removed. Once the c-clips were out, the axle shafts were removed along with the carrier. Since a new Detroit locker was also being installed, there was no need to retain the carrier shims, bearings or axle seals. The new ring gear was installed onto the new Detroit locker. To remove the pinion shaft, loosen the pinion shaft nut while holding onto the pinion shaft yoke. Using a brass hammer, pound on the end of the pinion shaft until it pops out of the differential housing.

Installing the Pinion Gear.

Remove the pinion shaft bearing race and discard. Once the carrier and pinion shaft were removed, the case was thoroughly cleaned to remove any oil, grease and metal shavings. The new 4.88 ring gear was then bolted to the new Detroit locker. For the pinion gear, press the new pinion bearing into place, insert the bearing race and install the pinion gear. Install the new pinion nut and tighten to spec. Check to make sure the proper pre-load is set for the pinion shaft. Install the carrier back into the differential housing and check for pinion depth and backlash. New shims are included with the overhaul kit. You may need to try several shims to get the correct fit. Once everything is set up correctly, apply some marking compound to the ring gear and rotate the ring gear until the marking compound passes the pinion shaft in both the forward and reverse direction. The marking compound will show how the ring gear/pinion shaft wear pattern is.

Wear Pattern on the Ring Gear. Front Dana 30

If adjustments are needed, you may need to try different carrier shims or adjust the shims on the pinion shaft. This is the most difficult and the most critical process in setting up new gears. The wear pattern should look similar to the picture on the right.

For the front end, the same general procedures were followed. Remove the brake calipers along with the axle hub nut (1 7/16-in socket) and hub assembly from the steering knuckle. Remove the vacuum disconnect housing and shift fork and slide the front axle shafts from the axle housing. Remove the bearing caps and slide the entire carrier out of the differential. Remove the old ring gear and install the new 4.88 ring gear onto the carrier using the supplied ring gear bolts. Use locktight and torque to specs. The procedures for installing the pinion shaft, checking pre-load and backlash are detailed above. For additional information on disassembling the front Dana 30, refer to the Lockright installation article listed below in the Related links section.

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Comparison View of the 4.10 vs. 4.88 pinion shaft. Checking ring gear backlash using a dial indicator.
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View of the completed front Dana 30 Rear Dana 35 with new ring gear and Detroit locker installed.

The process of installing and properly setting up new gears really isn't that difficult, assuming you have some mechanical know-how, have the correct tools and a bit of patience. It took about 6 hours for a professional shop to install both sets of gears along with the new Super 35 Detroit kit. Plan on taking twice as long if you've never done this before. If you do plan on doing a gear swap yourself, I'd recommend contacting someone who's done it before and have them help you out. This is one project that can lead to severe carnage if not done correctly.

The difference the new 4.88 gears made is pretty remarkable, compared to the 4.10 gears I was running. My freeway RPM's are a bit higher, but at least I've got my 5th gear back. Every little bit helps with a 4 cylinder engine! With the 4.88 gears, my crawl ratio went from 43:1 (4.10 gears) to a respectable 52:1! Crawl ratio is calculated using the following formula:

Transmission 1st gear X Transfer case low range X Gear ratio
3.93 x 2.72 x 4.88 = 52:1 (4.88 gears)

I can't wait to get out on the trail and give these new products a thorough workout. I'm sure I won't be disappointed! For more information on the new 4.88 gears or the Super 35 Detroit kit, contact Superior Axle and Gear or Foothill OffRoad.

Contacts: Related Links