The Build Process

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Your brand new transmission was once someone else's core before it was rebuilt.  All cores are torn down in our shop, with every part inspected for wear and damage.  It is during this process that the failure mode of the core, if any, is determined, and this is usually reported back to the originator for information.  At BSA, we have many pallets and racks full of 4r100 parts.  Any part that is found to be damaged or defective is scrapped and replaced.

We have invested tens of thousands of dollars in cleaning equipment to ensure your new transmission is absolutely spotless, inside and out.  

We feel that since the customer can't see how beautiful it is INSIDE the transmission, we better make the outside beautiful too.  But more importantly, the paint provides protection from corrosion.

A variety of cutting and grinding machines do all the work - machines that can cut anything from a small valve piece in repetition to a large torque converter.  We use custom jigs wherever possible to facilitate the rough machining of multiple parts one after another, so we usually wait until we have about 12 or more of each OEM part before we rough machine them in bulk.  Finish machining is done during assembly in order to meet our own clearance specifications.  This greatly increases build time, but it is worth it!

Individual subassemblies and the completed unit are sent through several different electrical, vacuum, pressure and hydraulic tests to verify things like piston motion, return to rest, seal integrity, solenoid action, and circuit conservation.

There are a few different videos on the youtube channel demonstrating them.

With the machines we have, we make all of our own special tools.  This includes bushing removers and installers, pullers, slide hammers, spring compressors, alignment pins, assembly fixtures and more. We employ all of them throughout disassembly and assembly.  Custom tooling is probably the biggest secret of any manufacturing shop, and this picture is a fraction of the special tools we use for each transmission build.  All clutch pack clearances are maintained within a specific range for each pack to ensure longevity of the friction material, reduced slippage, as well as quicker engagement.

This is the rewarding part!  During assembly, we use Vaseline, TransLube and Synthetic ATF (MerconV compatible).  All frictions, bearings and seals are soaked in the ATF.  Translube is used sparingly and Vaseline is used only in one place.  Translube has a tack to it, so it is good for holding things in place.  But you don't always want that tack.