Installing Used Ring-and-Pinion Gears

[Socalflofam]

Hello

i found a good deal on a differential carrier with the gears I need for my front Dana 30. 
I installed new gears in the rear no problem. 
 

what is the process for installing used gears if you don’t have access to the backlash , gear pattern, and rotational torque of said gears when they were in the original case?

Appreciate in help I can get. 

[Moses Ludel]

Socalflofam...As you hint, used gears can be a challenge.  Factory axles are set up with the pinion gear head depth being the primary reference point.  This is because axle housing differential centerlines can vary slightly.  The most important and critical step is setting the pinion depth in your Dana 30 axle housing.  The official way this can be done is with the factory gear setting arbor and scooter block tools ($$$$) shown below or with a universal pinion depth gauge available in today's tool market. 

On your Dana 30 axle, however, there is a much easier approach that Spicer and Dana have used for years:  adjusting the pinion depth using the pinion gear head "+/-" readings and making pinion height/depth shim stack thickness adjustments.  The readings on each of your pinion gear heads will determine the shim thickness change needed to adjust the height of the pinion gear head for your original axle housing.  You will add or subtract shim thickness from your original axle's pinion shim stack.  Assuming that your original pinion gear is factory set correctly, the chart recommendations will work.

Look at your original pinion gear head markings and the markings on your "new/used" pinion gear.  The chart in a shop manual shows how you need to adjust the shim thickness.  You will measure your original pinion depth shim stack, use that figure as a base, and add or subtract shim thickness for the pinion gear you are installing.  The head of each pinion gear should have markings like you see below.

This chart is for a Dana 30 low pinion front axle in the 1998 TJ Wrangler shop manual.  Use a manual for your year and model Jeep front axle.  As for the pinion bearing preload, know the distinction between a crush sleeve pinion shaft and a shim preload pinion.  You should follow the manual to do a safe and thorough job:

Above are pages with details on the pinion gear markings and the chart for adjusting the shims.  Use a factory service manual chart for your Jeep model and year.  This manual happens to be 1998 TJ Wrangler, which uses a semi-floating Dana 30 front axle and a crush sleeve for pinion bearing preload adjustment.  The original CJ Dana 30 pinion bearing preload is adjusted with shims.  Assembly steps are different for crush sleeve versus shim adjustment pinions.  For CJ Jeep models, use a factory shop manual or my book.

This is the factory method for installing a pinion gear in a new or empty (used) axle housing.  The goal is to set the pinion depth to match the exact centerline of the differential carrier bearings.  This tool set is expensive, and there are current aftermarket pinion depth gauges that are much less costly.  (If investing in an aftermarket universal depth gauge, read reviews on the quality and accuracy of the tool;  some tools are inaccurate.)  When the pinion gear head markings are not available, this is how to set the pinion depth.  Obviously, it's much easier and usually accurate enough to simply use the original shim stack's thickness (measured carefully with a micrometer), the gear head markings and the adjustment chart.  Build a shim stack to adjust the "new/used" pinion position.  You'll confirm the accuracy with a gear tooth contact pattern test.

The pinion bearing rotational torque is a setting achieved by installing shims or a new crush sleeve (depending upon whether the axle uses pinion bearing preload shims or a crush sleeve).  Once the pinion depth is clearly established, bearing preload can be adjusted by measuring the rotational torque of the pinion and adjusting as necessary. 

Warning:  When using a crush sleeve (later axles), do not overtighten the bearing preload .  If overtightened, you will need to install another new crush sleeve if you crush a new sleeve too far.  Never back off the pinion nut to readjust the rotational preload on an overtightened crush sleeve.  To avoid this, crush the sleeve very gradually to specification and stop.  When the axle uses shims (like CJs do) to adjust the pinion bearing preload, you can set up the axle with "dummy bearings" while adjusting the shim stack thickness.  (See my articles at the magazine and YouTube video on AAM axle rebuilding for details on how to make dummy bearings.)  This eliminates the risk of damage to the new bearings and shims.  The new bearings will be installed once the right preload shim stack thickness has been determined.

Once you have the pinion depth accurately adjusted and the pinion bearing preload/torque adjusted correctly, the two other measurements are the ring gear backlash and carrier bearing preloads.  I cover each of these steps in my Jeep CJ Rebuilder's Manual: 1972-86 (Bentley Publishers).  Use my book or follow the factory service manual steps for your Jeep model and year.  You want both the carrier bearing preload and backlash to be on factory specification.  I trial fit the carrier bearing preload shims and backlash using "dummy bearings" that can be made from original bearings in good condition.  Before pressing new bearings onto the carrier flanges, dummy bearings can be slid onto the carrier flanges with finger pressure.  Details are in my books and also at the 4WD Mechanix Magazine's coverage of the Dana 30 axle build.  The magazine's coverage of the Dana 30 is the YJ Wrangler and XJ Cherokee high pinion versions;  the CJ and TJ are low pinion axle housing designs:  https://4wdmechanix.com/?s=Dana+30.  As for high versus low pinion axles, many concerns and service steps overlap.  For assembly work, use the manual for your axle type.

Used gears pose one significant concern:  getting the tooth contact pattern identical to the gear set's previous installation.  To do this, and I have done it successfully, you use gear tooth marking compound and do a tooth contact pattern.  I make sure there is resistance between the pinion gear and ring gear by making a "tourniquet" with shop rags and wrapping it around the pinion yoke.  This drag requires rotating the ring gear slowly with a box end wrench on the secured ring gear bolts.  The result is a more accurate marking compound impression.  Especially with used (donor) gears, the ring-and-pinion gear backlash and tooth contact pattern must match the original gear mesh.  Shop manuals provide charts on how the tooth contact patterns should look...If you neglect this step, the gears will be noisy and fail in service.

This is your best approach to setting up a "good" used/matching gear set in a different axle housing...Make sure the used gears are the same design and fit as your original ring-and-pinion gears.  Use new ring gear bolts (with Loctite), new seals, new shims as needed and new bearings.  These are parts included in a gear set installation kit.

Moses