FORWARD SPRAG CLUTCH/THM 700R4 NEW DESIGN CLUTCH

Beginning May 3, 1982, a new forward sprag clutch entered production replacing the forward roller clutch on all THM 700-R4 transmissions.

To minimize the number of service parts required in inventory, only the new forward sprag clutch parts are serviced as follows:

A. If any of the following parts require replacement on a transmission built with a roller clutch, order service package 8642947. (See Figure 1)

Hub, Overrun Clutch (ILL. No. 2) Race, Forward Clutch-Outer (5) Cam, Forward Roller (3) Gear, Input Sun (6) Roller Asm., Forward Clutch (4) Carrier Asm., Input-Complete (8)

NOTICE: Overrun Clutch Hub Retaining Snap Ring (ILL. No. 1) and Input Carrier to Race Thrust Washer (7) still available individually for service. (See B. below)

Service package 8642947 is a sprag conversion kit which contains the following parts: (See Figure 1)

Snap Ring, overrun Clutch Hub Race, Forward Clutch-Outer (644) Retaining (ILL. No. 638) Gear, Input Sun (658) Hub, overrun Clutch (639) Washer, Thrust (Input Carrier to Wear Plate, Sprag Asm. (640) Race) (660) Retainer & Race Asm., Sprag (641) Carrier Asm., Input-Complete (662) Forward Sprag Asm. (642) Instruction Sheet

B. The following individual part numbers can be used to service all transmissions which either were built with a forward sprag clutch after May 3, 1982, or have been converted with service package 8642947.

(a) 8647083 - Snap Ring, overrun Clutch Hub Retaining (ILL. No. 638) (b) 8647082 - Hub, Overrun Clutch (639) (c) 8647081 - Wear Plate, Sprag Asm. (640) (d) 8647085 - Retainer & Race Assembly (641) (e) 8647084 - Forward Sprag Assembly (642) (f) 8647090 - Race, Forward Clutch - outer (644) (g) 8647093 - Gear, Input Sun (658) (h) 8647095 - Washer, Thrust (Input Carrier to Race) (660) (i) 8647050 - Carrier Assembly, Input - Complete (662)

Service Information

1. Use the following procedure to assemble the forward sprag clutcht

(a) Place the forward clutch outer race (644) on table with the recessed face down.

(b) Hold the forward sprag assembly (642) (without brass retainer rings) (643) in your right hand. The crossbar notches in the sprag cage must point to the left as viewed in Figure 2.

(c) Install the sprag into the forward clutch outer race. Now, install a brass retainer ring (643) on the sprag case. When properly installed, the flanges of the retainer ring (643) will face the sprag cage. See Figure 2.

(d) Install the retainer and race assembly (641) into the sprag by pushing downward and rotating counterclockwise. (Figure 3)

(e) Turn the assembly over and install the remaining brass retainer ring (643) on the sprag cage.

(f) Install the wear plate (640) on top of the brass end cap. Place the overrun clutch hub (639) on the wear plate, (640) engage the tangs, and insert the snap ring (638) to retain it.

(g) Now, check for proper assembly as shown in Figure 4.

2. Some of the parts associated with the roller clutch are similar in appearance to the sprag clutch parts. If these parts are ever mixed, use the following information to identify which parts are roller design and which parts are sprag design. (lst design refers to roller clutch parts and 2nd design refers to sprag clutch parts)

(a) Overrun Clutch Hub (639) - See Figure 5 1st Design - Face of tangs was flat. 2nd Design - High spot on each tang.

(b) Outer Race Forward Clutch (644) - See Figure 6 1st Design - Lube hole in race. 2nd Design - Lube hole in shoulder.

(c) Input Sun Gear (658) - See Figure 7 1st Design - 1 lube hole and higher shoulder. 2nd Design - 4 lube holes and lower shoulder.

NOTICE: Do not mix any roller clutch design parts with sprag clutch design parts as they are not interchangeable. If these parts are mixed, premature wear will be experienced.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.