A/T - 700R4 No 4th, Late 4th, Falls Out Of 4th

TRANSMISSION: 700-R4

BULLETIN: # 043

SUBJECT: 4th Gear Complaints

APPLICATION: GM RWD

DATE: March 1991

NO 4TH, LATE 4TH, FALLS OUT OF 4TH

^ Reset TV cable:
^ Check manual linkage adjustment.
^ Check line pressure @ 1200 RPM:
^ Check pressure at 4th gear tap

If 4th gear pressure is zero go to step 1.
If 4th gear pressure is low go to step 2.
If 4th gear pressure is normal go to step 3.

STEP 1

A. Is this a truck with oversize tires? (This will reduce governor pressure.)

B. Check the governor.

C. Re-check VB bolts for proper torque, especially the stiffener plate.

D. Check the pressure regulator snap ring to be sure it's in its groove.

E. Air check into the exhaust hole at the 4-3 sequence valve (This will air check the 4th apply circuit of the servo).

F. Air check into the exhaust hole at the 3-4 shift valve (This will check the 4th gear switch, the 4-3 relay and sequence valves for stickiness, and check for a missing plug at the relay valve).

G. Air check the governor circuit: (This will check the governor circuit for leaks and checks for a stuck 3-4 shift valve).

H. Check for cup plug in tunnel being missing.

I. Remove valve body and check for the following: stuck valves, relay valve in backwards, plugs missing from MTV up and down valves, gaskets covering separator plate holes, check ball placement in case and 3-4 spring tension. (Should be 4-1/2 to 5-1/2 @ .675 in most vehicles.)

STEP 2





A. Remove pan and air check into the exhaust hole at the 4-3 sequence valve. (This will air check the 4th apply circuit at the servo including VB leaks.)

B. Remove servo and check seals, clearance, assembly errors, piston (for cracks), and pin bore for wear.

C. Check 3-4 accumulator piston for cracks or damaged seal and missing air bleed cup plug.

STEP 3

A. Remove pan and check servo exhaust hole for blockage by pan gasket or sealant (RTV).

B. Air check into 4th gear pressure tap. Air should come out the 4-3 sequence exhaust hole showing a clear circuit.

C. Block 4-3 sequence exhaust hole an air check again. The servo should apply.

D. Remove the servo and check to see if the servo pin is stuck in the second gear piston. Check for stripped sun gear shell. (Will also cause no 2nd and no reverse.)

BULLETIN RECAP:

^ If 4th gear pressure is zero, the shift was not made. Step 1 will check the items that could keep the shift from being made.

^ If 4th gear pressure is low, (below line pressure) then the shift happened but their is a leak in the circuit Step 2 will check for leaks.

^ If 4th gear pressure is normal then their is a mechanical problem. Step 3 will check for mechanical problems.