A/T - No Reverse/First Gear Only
Bulletin 84-7-3Date April '84
Ref. No. 84-171-7
SUBJECT: NO REVERSE, FIRST GEAR ONLY
MODELS AFFECTED: 1979-1984 REGAL, LESABRE, ELECTRA AND RIVIERA
Some 1979-1984 Buicks equipped with THM 200, 200C, 200-4R, 325 and 325-4L transmissions may experience a lack of engagement in reverse, second, third and fourth gear while operating properly in first gear. This condition can be caused by stripped input drum to rear sun gear splines (See illustration) and does not affect line pressure readings or cause worn clutch plates or bands.
The purpose of this bulletin is to inform technicians performing overhaul procedures for this condition that careful inspection of the input drum splines and planetary gear assemblies is necessary. Spline wear may not be completely obvious during disassembly since the splines may hold with hand torque but not with engine torque.
To inspect the splines properly, remove the snap ring used to retain the input drum to the sun gear shaft and remove the input drum from the sun gear If any wear is present, replace the sun gear shaft along with the input drum.