TCC Lockup switch

[Owly]

I plan on installing a TCC lockup switch on my 2000 Safari AWD Utility, as well as a transfer case lockout switch.

I've done the TCC lockup switch before on my 1997 C1500, and it has been extremely successful. I use it towing trailers, and just driving up the highway because the 4L60E uses the torque converter unlock as if it was an additional gear. This suppresses the unlocking of the TCC. If you need extra power for a hill, 3rd lock is better than 4th free........ better power and better efficiency.

Here's how it works:

Obtain a transmission harness from a junk vehicle....... you need the plug that goes into the passenger side of the tranny. Obtain a transmission internal harness & plug from a transmission rebuilder. This allows you to build a short piece of harness between the transmission and the vehicle wiring without cutting any wires. Two relays are used. One grounds the TCC wire from the transmission, locking it up, the other switches the wire from the ECM to a dummy load so the ECM doesn't see that it isn't connected to the TCC solenoid and generate an error code. Both are energized during manual lock up. Color codes are available on the net to show which wires do what. I built a little box under the hood with my relays and dummy solenoid. The ECM will still generate error codes occasionally if you have the TCC locked up and don't manual shift....... it will eventually figure out that something isn't right. I have a scan gauge and can cancel these errors on the rare occasions when they occur.

Step 2 is to install a very heavy spring in the PWM valve to disable it completely. These springs are available from most transmission rebuild shops. The 4L60E will slip clutches (by design), including the TCC clutch. I discovered this after installing my lock up switch. When the TCC wouldn't unlock, the TCC just dropped the pressure and let things slip...............not a good thing!! I will NEVER run a 4L60E without disabling this feature. Probably the worst feature in the transmission, it is designed to give those silky smooth stepless shifts, this valve will wear out the bore and cause pressure loss, resulting ultimately in complete transmission failure.

I have put 70,000 miles on my pickup since doing this, many of them pulling trailers that were far too much for a half ton pickup with 307:1 gears, a 4.3, and a 4L60E. 70K trouble free miles. I've scaled over 5 tons of scrap metal at the scrap yard during a clean up project, I pull vehicles, tractors, firewood, etc. Last year I finally did a transmission flush and filter change. The fluid was in excellent condition because it has never been hot. Torque converter slippage is what makes transmissions get hot!


Howard

[97CargoCrawler]

Very good info, Thank you!