T53 Bearing Changes
The T53 engine has gone through several variations of bearings from un-pinned to pinned and also vendor manufacturing issues and vendor changes. These changes have been addressed over the years by the issuance of several different service bulletins. The main changes have been with the #1/2/3/4 main line bearings by way of re-designs and vendor changes:
1. The #1 and #4 bearings are both Thrust Ball Bearings. They have gone through various changes but the final change hasbeen to eliminate the silica/bronze cage that was susceptible to metal generation and the presence of bronze colored particles in the oil and filters. This has been eliminated by the introduction of SB0179/0180 with the introduction of P/N 1-300-663-01 bearing.
2. The #2/3 bearings are both Radial Rollers Bearings. The original 1-300-176-xx bearings were un-pinned outer race bearings. With the upgrade of service bulletins these bearings were upgraded to the 1-300-584-xx bearing which had a pinned outer race. The 1-300-176-03 became the the 1-300-584-01 and the 1-300-176-04 became the 1-300-584-02. The pinned outer race was introduced at the same time the bearing housing for the bearing was modified with the introduction of the corresponding slot to prevent bearing race movement and subsequent metal generation. The 1-300-584-02 was later replaced by the 1-300-665-01 as the 1-300-584-02 had a tendency to premature failure as it was designed with one extra roller which weakened the roller cage causing metal generation. the 1-300-665-xx series remains the latest bearing as there has been a vendor change.
3. Another change was to the #21 (Power Shaft Roller Bearing) was the introduction of the 1-300-082-03 bearing, which was the original replacement to the 1-300-082-01/02. An alternate to the 1-300-082-03 is the 1-300-664-01 that was introduced when an alternate vendor was approved by Honeywell.
4. Another major bearing change was introduced into the Accessory Drive Carrier by way of the removing the separate support bearings and replacing them with the 1-300-658-01/02 and 1-300-672-02. This was under SB0093 and SB0110 in order to eliminate most of the areas of metal generation that could occur in the Accessory Drive Carrier. The spare drive gear was also eliminated at this time which was a problem for Bell 204 operators. This drive gear elimination caused them to come up with an alternate starter installation as this gear drove the cooling fan that was mounted to the spare pad.