ENGINE FLARE DURING DOWNSHIFT ON THM 325/325-4L TRANSMISSION

ENGINE FLARE DURING 3-2 DOWNSHIFT ON THM 325 AND THM 325-4L TRANSMISSION (1981-1982 "E" and "K")

Certain 1981 and 1982 Eldorado and Seville models can exhibit an enaine flare (overrevving) condition during a part throttle or detent 3-2 transmission downshift. A "part-throttle" manuever represents less than 3/4 throttle (60 DEG throttle angle via diagnostics) while a "detent" downshift is available over 3/4 throttle. The part throttle engine flare is due to incorrect timing for the application of the intermediate band (2nd) causing the engine speed increase after release of direct clutch (3rd). The engine flare on a detent manuever is due to the transmission not completing the shift into 1st gear and then going to 2nd gear (3-1-2). Both conditions are most noticeable in the vehicle speed range of 25-30 MPH after the transmission has reached normal operating temperature (in 10-15 minutes). This condition can be diagnosed in both Drive and Manual Third selector positions.

This bulletin outlines specific service procedures required to correct this condition on each powertrain application. Depending on model year and engine/transmission combination, proceed as follows:

YEAR ENGINE TRANSMISSION MODEL SECTION OF BULLETIN ---- ------ ------------ ----- ------------------- 1981 4.1L V-6 THM 325 AG I 1982 HT4100 THM 325-4L AJ II 1982 5.7L Diesel THM 325-4L AL II 1982 4.1L V-6 THM 325-4L AM III

I. 1981 "AG" Model

To correct the flare condition on this model, a new design control valve assembly to transmission case spacer plate (P/N 8632998) is necessary. Install the plate with the transmission in the vehicle by using the following procedure:

1. Remove transmission oil pan and gasket.

2. Remove oil screen assembly and its "O" ring.

3. Remove throttle lever and bracket assembly, using care not to bend the throttle lever link.

4. Remove manual valve clip from valve and disconnect the manual valve link.

5. Remove the 10 mounting bolts noting the location of the two longer bolts that are used (refer to Figure 7B-25, page 7B-21, 1981 Service Information Manual).

6. Remove the valve body, gaskets, spacer plate and accumulator spring together. (Two check balls will be on top of the spacer plate).

7. On bench, remove original gaskets and spacer plate.

8. Install a new control valve assembly to spacer plate gasket marked "VB" (from P/N 8632988 kit) on the control valve assembly.

9. Orient the new spacer plate on top of the "VB" gasket, then install the new spacer plate to case gasket marked "C" (from P/N 8632988 kit) on top of the spacer plate.

10. Install the two check balls (#5 & 6) and accumulator spring in their proper locations (refer to Figure 7B-202, page 7B-61, 1981 Service Information Manual). Retain the check balls in place with petrolatum.

11. Place two guide pins into the transmission case and install control valve assembly.

12. Start control valve assembly to case attaching bolts (except at throttle lever and bracket location).

13. Remove guide pins and replace with bolts.

14. Install the manual valve link into the valve and secure with the clip.

15. Install throttle lever and bracket assembly.

16. Torque all control valve assembly to case attaching bolts to 15 N.m (11 ft. lbs.).

17. Install oil screen assembly with a new "O" ring (PIN 8635014).

18. Install transmission oil pan with new gasket (P/N 8632098) to case.

19. Torque oil pan to case bolts to 16 N.m (12 ft. - lbs.).

For warranty purposes, use Labor Operation Number T6059 at 1.2 hours.

This information updates the information in Serviceman Bulletin Nos. 81-50, 81-61, and 82-14.

II. 1982 "AJ" and "AL" Models

To correct only the flare condition at detent (25-30 MPH) on these models a service package with newly designed parts to rebuild the control valve assembly is necessary. Each package contains a 1-2 shift valve, Lo-1st detent valve and bushing as well as an instruction sheet.

Starting February, 1982 production, all THM 325-4L models were built with these new design parts. The following chart provides breakpoint information to identify those transmissions needing the service package (transmissions built prior to the listed serial numbers) as well as the part number to use based on model application.

TRANSMISSION MODEL SERIAL NUMBER SERVICE PACKAGE P/N ----- ------------- ------------------- AJ 82-AJ-22392 8635932 AL 82-AL-7111 8635931

Using certain specific service procedures in the Automatic Transmission 325-4L Section of the 1982 Service Information Manual, the following on-car checks should be performed before the service package is installed:

1. Remove the intermediate servo assembly following the service procedures on page 10, step 19. Inspect the inner and outer intermediate servo pistons and seals for wear, cracks, burrs, etc. using tbe procedure on page 54 under the heading "The Intermediate Servo Piston-Inspection". If no substandard conditions are found, install the intermediate servo assembly to the transmission using the procedure on pages 55 and 56 under the heading "Reassembly".

2. On car, remove the transmission oil pan and inspect the D-2 signal pipe for any looseness. Refer to Figure 7 on page 6.

3. Remove the transmission oil filter and inspect for foreign material, neck to case fit, "O" ring integrity, etc.

4. Remove the control valve assembly on-car by using the following procedure:

A. Disconnect the wire leads at the case electrical connector and at the pressure switch(es) and remove the D-2 signal, the reverse signal and overrun pipe retainers and pipes (Figure 7, page 6).

B. Remove the throttle lever and bracket assembly (Figure 16, page 9) as well as the remaining control valve assembly attaching bolts and disconnect the manual valve in order to remove the control valve assembly from the transmission. Use care to not drop the manual valve as damage may occur. Remove the control valve assembly and gasket. One check ball (#6) is located between the valve body and gasket.

5. Inspect the control valve assembly to spacer plate gasket for nicks, tears, scoring, etc.

6. On bench, disassemble and inspect the components of the control valve assembly following the procedure on pages 56, 57 and 58 under the headings "Disassembly" and "Inspection".

Make certain there is no foreign material present in the control valve assembly components and that all retaining and/or roll pins have the correct fit and location.

If the above six steps have not revealed any substandard conditions that could cause the flare, reassemble the control valve assembly using the appropriate service package and following the procedures on pages 58 and 59 under the heading "Reassembly". At step #11, be sure to install the new design 1-2 shift valve, Lo-1st detent valve and bushing into the control valve assembly (Refer to Figure 221, page 57, items #12, 13 and 14).

In order to replace the gaskets (from P/N 8635919 kit) for the accumulator housing as well as each side of the spacer plate, proceed as follows:

7. Remove the TCC solenoid assembly attaching bolts, solenoid and "O" ring seal (Figure 9, page,7).

8. Remove the 1-2, 3-4 accumulator assembly attaching bolts, housing, gasket and 1-2 accumulator spring. The Drive 3 (D3) check ball (#11) will be in the accumulator housing (Figure 18A, page 9). At this point of disassembly, the spacer plate will not be attached to the case. Use care when removing the spacer plate from the transmission case as there will be nine check balls on top of it. (Refer to Ilustration #1 on page 2 of this bulletin.)

9. Clean and air dry the transmission case passages.

10. Install two guide pins into the case as shown in Figure 224, page 61.

11. On bench, orient and install a new case to spacer plate gasket marked "C" (from P/N 8635919 kit) on top of the spacer plate. Using Illustration #1 on page 2 of this bulletin, properly position the nine check balls onto the spacer plate. Retain the check balls in place with petrolatum.

12. Install spacer plate on transmission and retain temporarily using a small bolt from the accumulator housing. Install this bolt in any bolt hole near the center of the spacer plate.

13. Position a check ball (#11) in the accumulator housing (Figure 18A, page 9).

14. Place a new gasket (from P/N 8635919 kit) unto the accumulator housing and position the housing into the transmission. Temporarily hold in place with 2 of the appropriate bolts. Do not torque at this time.

15. Install the TCC solenoid with a new "O" ring (P/N 8630052) in its proper location on the accumulator housing. Finger tighten the two attaching bolts to hold the solenoid and wiring harness in place. The small bolt that was used to temporarily hold the spacer plate in place (Step #7 above) may now be removed.

16. Position the Lo-1st check ball (#6) in the control valve assembly. Using Figure 226 on page 63 as a reference, the check ball goes into the cavity in the lower, right hand corner marked "LO 1ST". Retain in place with petrolatum. (The check ball is not shown in the Service Manual Illustration. Omitting it will cause oil flowing to the lo/reverse clutch to be unregulated during Manual Lo transmission operation causing an abrupt shift into manual low.)

17. Place a new control valve to spacer plate gasket marked "VB" (from P/N 8635919 kit) on top of the control valve assembly.

18. Install the control valve assembly to the case using the two guide pins as locators. Start two attaching bolts to hold in place. (Use Figure 240, page 66 for correct attaching bolt length for each location).

19. Install the manual valve link into the valve (it may be necessary to remove the push on nut to install the link).

20. Install the throttle lever and bracket assembly (Figure 235, page 64).

21. Referring to Figure 236, page 65 install the oil pipes and wiring in their proper locations. Use the following sequence:

A. Install the solenoid screen in the converter clutch signal pipe hole at the control valve assembly. Install the coverter signal pipe.

B. Install the overrun clutch pipe.

C. Install the reverse signal pipe.

D. Install the D-2 signal pipe.

E. Install the six pipe retainers with attaching bolts in their proper location. Make sure all pipes are fully seated.

F. Install the electrical wire connector(s) to the pressure switch(es). Use the clips and attaching bolts to properly route the wiring. Secure the harness leads at the transmission case connector.

22. Install remaining control valve assembly to case and accumulator housing to case attaching bolts in their proper location and torque all these bolts to 15 N.m (10 ft. - lbs.). Refer to Figure 240, page 66.

23. Clean, air dry, inspect (and if necessary replace) oil screen assembly (P/N 8635923) with a new "O" ring (P/N 1363951).

24. Clean, inspect and install the transmission oil pan with a new gasket (P/N 8635014). Torque all these bolts to 16 N.m (12 ft. - lbs.).

For warranty purposes use Labor Operation Number T6059 at 2.8 hours.

III.. 1982 "AM" Model

To correct the part throttle and detent flare conditions on this model it is necessary to install a new control valve assembly and spacer plate (both available in kit P/N 8635938), a new design accumulator housing kit (P/N 8635935) and a new Torque Converter Clutch solenoid (P/N 8635922).

Before any new design parts are installed, perform the on-car checks in Section II, Steps #1 through #5 only of this bulletin. Before reinstalling the intermediate servo assembly to the case, install the new design servo cushion spring provided in the control valve kit (P/N 8635938).

After they have been performed, install the new service packages on-car by following the procedures in Section II, Steps #7 through #24 of this bulletin with the following exceptions:

A. At Step #13, the original 1-2, 3-4 accumulator housing will be replaced by the new design accumulator housing. It will be necessary to utilize the 4th clutch pressure switch, and accumulator pistons from the original housing when building up the new housing. To accomplish this, proceed as follows:

1. Remove the 4th clutch pressure switch from the original accumulator housing and install on the new housing from service package (P/N 8635935). Torque to 7-14 N.m (15-10 f t. - lbs.).

2. Remove the 1-2 and 3-4 accumulator pistons and springs from the original housing. Using the 5mm longer piston pins from the service package (P/N 8635935), assemble the new accumulator with the original pistons. Use Figures 3 and 4 of Serviceman Bulletin #T 82-92, Group 7, Number 44 for a reference. Install the 1-2 and 3-4 accumulator springs provided in the 8635938 control valve kit. The 1-2 accumulator spring is the heavy spring.

B. At Step #15, install the new design TCC solenoid (P/N 8635922) along with a new "O" ring (P/N 8630052).

C. At Step #16 install the new design control valve assembly and spacer plate (from P/N 8635938 kit) onto the transmission case. It is not necessary to disassemble and rebuild the control valve assembly as outlined in Section II, Step #6.

D. Install the new TV boost valve and bushing into the case (provided in the control valve kit 8635938).

For warranty purposes, use Labor Operation Number T6059 at 2.1 hours.

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.