General Bellhousing Alignment Instructions
In order to properly install an American Powertrain transmission, we require you to have proper bellhousing alignment with the engine block. Even with brand new components this is an important step for smooth shifting and minimal wear.
Bellhousing alignment is crucial for proper clutch function and reliability of the related components. Due to manufacturing tolerances of engine blocks and bellhousings, it is possible for the transmission centerline and crankshaft centerline to be misaligned. The result of this misalignment may be hard shifting, pilot bearing wear, transmission mainshaft bearing wear and failure of clutch disc hub.
First, check bellhousing for bore concentricity. Install magnetic base to flywheel or pressure plate, then install the indicator to measure the bellhousing bore(shown above). Rotate the crankshaft and mark down the indicator readings (marking the bellhousing works well). The maximum out of concentricity is .005″.
Next, the bellhousing face should be checked for parallelism to the back of the block for proper bellhousing alignment. Install the indicator(as shown above). Rotate the cranksahft and mark down the readings – be sure to push the crankshaft against thrust bearing for accurate measurement. The maximum out of parallelism is .002″.
To correct off-center condition, select the offset dowel pin pair that is closest to one-half of the indicator reading. For example if the reading is .016″, 1/2R = .008″ so use .007″ dowels. If the reading is .024″, 1/2R=.012″ so use .014″ dowels.
The bellhousing was offset toward the top of engine and slightly to the left, as viewed from behind. To align the bellhousing, install two .014″ offset down pins with the maximum offset positioned roughly at the 5 O’clock position.
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After reading this if you’re still scratching your head or have a question or to, please feel free to reach out! We deal with this every single day and can walk you through the process.
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