Ever since I appropriated an '89 S-10 from a family member, I've been trying to restore it while still driving it back and forth to work. Although the truck runs fine thanks to the complete tune-up I performed, the 170,000-plus miles of wear and tear on the motor are starting to create a problem.
Leaving from a stop, the truck does fine pulling through the rpm range. Once it shifts into Second gear and starts to pull is when the issue shows up. As the motor gains rpm and hits about three grand, something starts to pull it down and no matter how much I push on the throttle the truck still slows. If I lift off the gas and then slowly reapply pedal pressure, it will finally reach cruising speed. After a little research, I figured out what was happening. The converter was locking up at the top end of Second and in Third and loading the motor. If my motor was fresh this probably wouldn't be an issue, but since my 4.3L V-6 is worn out the extra load induces detonation and the knock sensor starts pulling back the timing. GM found locking the converter in multiple gears would increase mpg and decrease heat on the transmission but probably didn't account for worn-out motors.
Thankfully, during my search I also found a solution to this little problem in the way of JET Performance and its 700 R-4 Lockup Delay Module. This little black box simply plugs into the transmission and stops the lockup in Second and Third gears but still lets it lock up in Overdrive. After I installed the module, the truck pulled nice and even all the way through Second and Third. This allows me to get up to cruising speed without the knock sensor getting involved. I'm not sure if this did anything to my mpg because I haven't seen any recordable difference, but the truck is definitely much faster, even with a worn-out motor.
JET makes the modules for fullsize and S-series trucks and Blazers from '88-'92, so if you're driving one of those and want a little more pep this might be worth the $63 investment.
What's in the box
Above is the JET 700 R-4 Lockup Delay Module that prevents converter lockup until Fourth gear, eliminating unwanted converter locking and unlocking in Second and Third gears. It features a little sealed black box and the proper plugs for the '88-'92 trucks equipped with a 700 transmission.
 The Install 1. Installation...  The Install
1. Installation is as simple as it gets because the module goes in between the factory plug on the trans. The most time-consuming part was getting the truck jacked up enough to squeeze my fat gut underneath it. Man, I need to diet. |  2. So there it is after installation...  2. So there it is after installation and a few well-placed zip ties. The box is not heavy at all, and the factory wire harness will be able to support it without a problem. | |
The Final Word
The S-10 drives much better than before and definitely has more pep in its step. Instead of the torque converter locking up and loading the tired motor so much that it pings, it spins freely and doesn't engage the knock sensor. I have to say this was worth every bit of the 63 bucks I spent on it. Another nice thing I found about this module is it stops the trans from hunting for gears at light throttle while cruising.