A/T - 700R4 TCC Lock-Up Kit Precautions
TSB 86-14 (Mar)SUBJECT: 700 R4
Caution must be taken when using the GM Kit # 8642970, to raise the TCC lock-up speed (Fig - Items A, B, & C).
Numerous reports are indicating variances in the lock-up speeds from one kit to another. These kits were designed for use on the early diesel models only. Some shops are trimming a coil from the spring in the kit, and the 2-3 shiftspring to make shift pattern changes on a gas model.
NOTE THE FOLLOWING PRECAUTIONS
1. The converter clutch must be applied in 4th. Normal cooler flow is high in this unit - about 1 gallon in 30 seconds. Even this high flow is not sufficient cooling for the extreme heat generated by the converter when stalling in overdrive. The early lock-up was designed to keep the unit running cooler.
Severe overheating WILL OCCUR if the vehicle is loaded and the converter is not locked-up in 4th. Note: Solenoid failure is also a common cause of such overheating.
2. L-6, U-8, and Diesel models, with the kit installed, will no longer lock-up between the 1-2 and the 2-3 shift. Trimming a coil from the 2-3 shift speed will lower the 2-3 shift speed, and narrow the gap between the 1-2 and the 2-3 shifts. It may be necessary to trim a coil or more from the kit spring to get lock-up before over-drive.
3. 4 Cyl. and V-6 models have lockup after 3rd. Trimming a coil from the 2-3 shift spring will only stack the 2-3 shift on top of the 1-2 shift. Again, be sure lock-up is before overdrive. The high stall converters in these models generate even more heat.
4. '85 and '86 computer controlled vehicles have plugs in the valve body (Figure - Items E & F) to let the computer control lock-up. Many owners are complaining of "lock-up too early", and shops are installing the kit in place of the plugs. BOTH "E" & "F" must be changed to achieve transmission controlled TCC again. To date, the only source for valve "D" is to rob an earlier valve body.
IN SUMMARY:
EACH unit must be test driven well to determine that modifications are satisfactory. Valve body calibration changes from year to year, and lock-up kit variations, make it difficult to predict the outcome every time. "Over-counter" sales can be risky when the installer doesn't understand what to look for, or doesn't care to spend the extra time for a thorough test drive. Sometimes what feels better to a customer, is not what is better for the transmission.