Allison 540/545 still popular among rebuilders
Many members have problems with the Allison 540/545 converters.
Do to the fact a great percentage of the cores are destroyed, rebuilders resort to using GM TH400 cores. Although similar in design and most parts being interchangeable, a few items are overlooked. It is suggested that a flanged impeller hub must always be used in conjunction with either the original type Allison bearing or at least the standard late model GM bearing with appropriate adaptor.
If the 400 turbine is to be used, it is suggested to use a turbine reinforcement plate in the front of the turbine. Also, if the TH400 front cover is to be used, instead of the OEM Allison cover, an anti-balloon plate should be installed. You will notice that the original OEM Allison cover is slightly heavier than the TH400. The use of the balloon plate will prevent bearing failure which occurs so often. If you decide to use the TH400 impeller, it should be furnace brazed, and the fin angle should be adjusted to match that of the 540/545.
The 545 has a lower fin angle than the 540 and should not be confused. Using the wrong impeller will result in poor performance and a dissatisfied customer.
For information on bearing adaptors, contact Sonnax. For more information on the turbine reinforcement ring, contact Dennis at Midwest Converters, 1-800-554-2668.
Found in issue 03, 2004