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A lip seal is designed to ride lightly on the torque converter hub making it critical that the seal be concentric to the bushing. A seal that is not concentric results from 1) An after market bushing being offset by the way Ford manufactured the bell housing, or 2) Excessive clearance in the bushing bore allowing the hub to shift off center. Another contributing factor is a warped face on the bell housing that mounts to the block. This warpage causes the bushing and seal centerline to shift out of alignment with the crankshaft centerline. This can also prevent proper alignment of the converter to the flexplate during assembly, forcing the torque converter hub to runout during operation. In more extreme conditions, runout of the hub caused by the misaligned assembly rubs hard on one side of the bushing. This causes wear to the bushing bore and hub, creating the excess clearance. The failure from these conditions usually appears in less than five thousand miles. All of these conditions lead to the same result. The lip seal material can be very abrasive to the steel hub of the torque converter. This creates a tendency for excess wear of the hub and seal. The seal can no longer hold its fit to the hub. A clearance between the hub and seal forms a leak pathway. The torque converter hub, bell housing seal, and bushing are destroyed. In more extreme cases, the hub in the bushing generates a large amount of heat build up which burns the transmission up sooner. Most Transmission shops report that leaks were ignored or not noticed by the vehicle owners until a low fluid level was reached which burned up the transmission. Shops have tried to leave the original factory bushing in since it was machined concentric to the seal. However, we have found in some cases the clearance of these original bushings were worn resulting in the torque converter shifting to one side causing excessive wear on components, and ultimately premature failure.
An additional problem has been identified resulting from warpage. The original bushing is machined in place by Ford which assures alignment. The bell housing is then installed at the factory. While in service, stresses are introduced to the bell housing. This stress is released when the bell housing is removed for rebuilding. This was proven in tests on bell housings with the original OEM bushing having acceptable clearance to the torque converter hub and showing no signs of uneven wear. These transmissions failed in less than five thousand miles. Inspection of the bushing showed rubbing and wear on one side of the bushing bore. It was found that runout was caused by a warped block mounting face causing misalignment to the crankshaft centerline. This was supported by the wear patterns in the direction of the misalignment.
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Precision technologies LLP is providing a valuable service to its customers. With our service, we bore the bushing concentric with the seal and machine the block mounting face to correct misalignment of the seal and bushing bores to the crankshaft centerline. Installation of the bushing is carefully done with special tools that apply even pressure while inserting it into its proper location. This ensures that the bushing is not cocked in the bore preventing spinning of the bushing under operating conditions. The seal bore is indicated to less than .001". The bore size of the bushing is machined to exact tolerance to maintain an optimum minimal design clearance. The bores fine surface finish is achieved through the use of state-of-the-art ceramic tooling. No abrasives are applied to the bushing that could imbed into the bushings material and cause wear of the torque converter hub. During operation, the machined bore allows the hub to float on a thin film of fluid over a wide contact area reducing friction and heat generation. An after market bushing bore size and shape vary with the amount of interference and imperfections in the shape of the bore into which it was installed. The hub contact area is also affected by these factors. A bushing machined in place to exact clearance and alignment to the axis offers a very precise starting point for building the transmission and ensures a long service life.
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The standard charge to remanufacture an A4LD bell housing is $40 ( plus shipping and handling) Pump face resurfacing is extra. The cost of a new bell housing from Ford is approximately $345.00. For more information contact PrecisionTechnologies at (864) 503-3100 or email us at ptechllp@bellsouth.net
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