Courtesy of ALLDATA
In cold temperatures, thermal contraction causes a shrinking of the transmission case. In high temperatures, thermal expansion causes the case to expand. These temperature changes affect the amount of pre-load on the transfer driven shaft bearings. In some cases, when bearing pre-load is near the limit of specification, this thermally induced pre-load change may cause damage to the bearings and result in a high-pitched noise from the transmission.
The following Subaru models equipped with the 5MT manual transmission may exhibit this condition: 2000-‘09 Legacy and Outback; 1999-2014 Forester; and 1999-2014 Impreza (Including WRX).
Subaru offers an updated extension case featuring the addition of a “dish plate.” The machining depth of the extension case has been increased to accommodate the new dish plate. (Fig. 1)
When used along with a selective thrust washer, the spring tension of the dish plate helps to maintain a consistent amount of pre-load on these bearings throughout varying temperature conditions. Here are the measurement and repair procedures.
Measurement Procedure
Measure height “W” between transfer case sealing surface and taper roller bearing outer race on the transfer driven gear. (Fig 2)
With the bearing outer race, dish plate and thrust washer removed, measure depth “X” of the bearing bore of the extension case. (Fig. 3)
Calculate the required thrust washer thickness “T” using this formula: X – W = T and then select the thrust washer with the closest value from the table in Fig. 4. Example: [X] 1.05 mm – [W] 0.20 mm = 0.85 mm or 0.0335 inches. You would use shim No. 803050067 according to the table.
Service Procedure
Once the proper thrust washer has been selected, assemble the new extension case as shown in Fig. 5.
NOTE: Both outer races of the transfer driven shaft bearings are hand-fit to their bores and are not press-fit. Turning the outer races slightly will make their installation easier.
NOTE: Always install a new output oil seal before transferring the original metal dust cover over to the new extension case.
IMPORTANT: If the transfer driven shaft bearings are damaged or have failed, thoroughly clean and inspect all of the internal components of the transmission before reassembly. In very severe cases, where metal contamination damage is extensive, a complete transmission replacement may be required. When reinstalling the transfer driven shaft, put a small amount of bearing grease on both roller bearings, then rotate the shaft in the outer races to distribute it evenly.
NOTE: When you are replacing the extension case, shorter case bolts must also be installed due to the thinner retaining bolt boss areas of the new extension case (16 mm vs. 20 mm).
Written by the ALLDATA® Community Automotive Diagnostic Team, a select group of automotive experts dedicated to helping technicians fix hard-to-repair vehicles more efficiently. To meet the team, visit http://support.alldata.com/alldata-community. © 2014 ALLDATA LLC.
