TM 10-3930-671-24 1. Put   directional   control   level   in   FORWARD   (or REVERSE), as applicable, depending upon truck position to barrier. 2. To test all clutch assemblies in the transmission, check stall speeds and vacuum with transmission in forward and reverse. 3. Check stall speed at full throttle. Slowly push the accelerator   pedal   to   its   maximum   travel   (fully down) position and hold while doing test. Stall  tests  should  be  a  part  of  all  engine  tune-ups  and must  be  carefully  conducted  and  analyzed  to  pinpoint specific problems. Stall   tests   must   include   RPM   and   hydraulic   pressure measurements  to  accurately  diagnose  specific  problem areas. Engine  speed  checks  with  engine  under  load  are  made to     also     determine     whether     major     components     or systems-other than the engine-are causing problems. Full Throttle Stall Speed Chart TMD 27 Engine 2100 rpm, nominal Range: 2000 2500 rpm Analysis of Stall Test NOTE • If  stall  speed  is  low,  do  not  automatically blame    the    torque    converter.    Carefully check   engine   condition.      Frequently   an obstruction, e.g. carbon plugging, in the air intake or exhaust system is the problem. • When  high  stall  speed  is  found,  perform transmission pressure tests (see following) to help isolate the problem area. 1.    Operation at nominal stall speed is an indication that: a) Engine performance is good (correct). b) Torque converter is operating correctly. c) Transmission  clutch  packs  are  operating correctly (not slipping). 2.    Below  normal  stall  rpm  is  typically  1500  -  1800 rpm. Low stall rpm is an indication that the: a) Engine performance is faulty (needs tune- up or repair). b) Hydraulic  pump  is  defective  or  return  line is blocked. Repeat hydraulic bypass test. c) Transmission  and  torque  converter  are  in satisfactory     condition     (performance     is correct). F-90