4L79 Input housing / Drum assembly Instructions
*ANY questions please call (219) 688-6680
Step 1
Clean input housing and Billet cap with care, the threads on both the input housing / drum and billet cap are very fine and aluminum. We recommend washing and 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.
Step 2
*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.
Step 3
Install 4L79 bottom pressure plate, then starting with a friction and ending with a steel plate, install the frictions and steels (8) of each.
*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.
Step 4
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.
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. Air check the 3-4 clutch and verify clutch clearances. Once your clutch clearance has been verified, slowly back the cap up counter clockwise until the 5 threaded holes line up with the 5 slots in all of the steel clutch plates. Drop a supplied spring into each of the five holes, then fully seat with the long end of your 1/8″ Allen wrench. With one hand apply a little bit of clockwise motion to the cap while pushing the springs down so that they slip just under the edge of the billet cap. Once all 5 springs are down and under the cap, continue turning the cap clockwise all the way until the 5 dimples in the input housing line back up with the 5 threaded holes in the billet top cap 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.
***Step 5***
***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.***
Step 6
Beware you are about to experience 3-4 clutch durability and 2-3 shifts unlike ANY other, at any throttle or power level.