4L78 Input housing / Drum assembly instructions
*Any questions call (219) 688-6680*
Always clean and blow out the input drum for any possible machining chips or debris. Handle the Billet cap with care, the threads on both the input housing / drum and billet cap are very fine and aluminum. We recommend after washing, immediately applying new Atf to the threads and performing all press work with the cap on the drum. Atf has proven best in making the threads glide with ease with no galling, sticking or any other adverse effects. *Note the use of heat from a small propane torch will make the aluminum expand and contract very quickly and very easily. If you have any issues we recommend using heat during assembly or disassembly.
*Note that the input housing and the input shaft have a “blind spline” used for lineup that both must be lined up before pressing. ***NEVER use a hammer*** Also *Note the input housing MUST be supported from the inside at the lube seal area to the press bed, failure to properly support the input housing will cause the drum to crack and void any and all warranty provided (cracks sometimes not visible to the naked eye) Apply loctite at splines as well as around the machined area of the shaft that seals into the input housing. Stop once the shaft stops- do not force beyond its stopping point. *Note you MUST blow out the input shaft feed oil passages, including lube passages thoroughly with air – as SOON as your done pressing. Failure to blow them out will result in hardened loctite in the ports possibly restricting oil flow leading to failure. Assemble internal pistons, springs and retainers just like oem. We recommend to always install new bonded pistons. Install overrun, and forward clutch packs as oem, including input sprag assembly.
Install bottom pressure plate, then your entire 3-4 clutch pack starting with a friction and ending with a steel plate
*Note, make sure your clutch stack ends in a STEEL. We understand this is UNlike most transmissions however this is MANDATORY. You do NOT run a friction against the billet end cap. The final steel puts the rotational forces into the input housing and not the cap. The billet cap takes strictly upward forces.
With clean oil on the threads, GENTLY start the billet cap onto the input housing. It usually starts best by turning counter clockwise slightly to aide in lineup. *** DO NOT FORCE THE THREADS *** they are shipped pre installed with oil and glide freely. Once 3-4 clutch pack is installed and desired clearance is set, install new load release springs into the oem retainers ( if you choose to use them ) *** Note- retainers must be inserted opposite of oem- springs will now ride against the bottom pressure plate. Run the cap down until the top of the drum and the underside of the cap start to touch and line up the 5 drum dimples to the end caps 5 holes perfectly. Then put a drop of loctite onto the supplied 5 Allen set screws and install them staggering them while running them up snug. Once snug make a final pass tightening them all to 35 inch pounds of torque. *Note if you’ve tightened and removed the set screws at any point, before reassembly take a fine file lightly across the top of the drum to clean off any high spots or burrs. Clean off any burrs on underside of cap as well, wash and relube before any reassembly.
***End play must be kept on the tight side on transmission assembly as clearances have been minimized to gain maximum clutch capacity. When using any thicker “Beast” style sunshell clearance must be verified.***