Torque Converter Lockup

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Torque converter lock-up is engaged through a solenoid mounted inside the transmission. When the solenoid is energized it redirects the fluid flow back through the input shaft to put pressure against the clutch assembly allowing it to engage with the front of the torque converter. This takes the fluid coupling of the impeller, stator,. Torque Converter Lockup Kit, Wiring Kit, Vacuum Switch, GM, 200-4R, 700R4, Kit. Part Number: TCI-376600.

A torque converter, common to automatic transmissions only, is the equivalent to a clutch in a standard transmission. The torque converter converts the power from the engine, seamlessly and smoothly to the transmission instead of having a clutch to assist on take off as in a standard transmission.

  1. Torque converter lockup can have a major impact on how your engine performs. The torque converter is a part of the transmission, and you will notice that the engine will hesitate and be underpowered when it is locked up. There can be many different causes for certain engine problems.
  2. Curt addresses a common question: 'what is lock up, and do I need it?' He shows how lock up works between the transmission and torque converter, and explain.

BTW, if you don’t get a remanufactured torque converter with a remanufactured transmission, I would question the job and feel like the job was not complete. You don’t have to guess with a supplier of transmissions like

Nowadays all cars and trucks use a feature called lock-up in the torque converter.

By way of fluid coupling, the torque converter transfers the power to the transmission without a clutch or clutch pedal. It cushions the shifts as they occur and makes the transition of power very smooth as the automatic transmission shifts.

Torque converter lockup problems

What I wanted to discuss was not the technical details of how the actual parts work in a torque converter, heck most transmission mechanics don’t understand the theory behind it. Something else to throw out quickly is that very few transmission rebuild and repair shops rebuild their own torque converters. The amount of expensive equipment and the knowledge necessary to perform this is better off done by a torque converter remanufacturing specialist.

I wanted to briefly mention what the term lock-up means. Lock up is a feature introduced in about 1982 with the advent of the T-700R4 and T-200-C General motors transmissions. Simply put, since a torque converter is a fluid coupler it will always have a certain amount of ‘slip’ built into it. It is unavoidable due to fluid being the main component of the coupling action. This decreases gas mileage by 1-4 miles per gallon, the built in slippage, that is.

To eliminate the problem, an actual clutch disc has been built right into the torque converter. At a certain speed, usually about 45-50 mph a message from a computer sends a forceful ‘charge‘ of automatic transmission fluid to the converter, which applies the clutch plate inside and eliminates the small amount of built in ‘slippage’.

Darn good idea. A lot of updates and improvements have been developed over the years which has just about perfected the design. Obviously this is a desire-able feature with few drawbacks. The only legitimate drawback is if your son takes the car to the drag-strip and burns the converter clutch up.
Just joking, the drawback, which is negligible, is it produces more heat, therefore making maintenance using synthetic ATF more important and the installation of an external transmission cooler a good idea.

Once I link this post to some of the more technical posts on Blog, those posts will make more sense. Assuming any of my posts make sense. Let me know if you need more information or a better description. If you don’t tell me I can’t do a better job. Thanks and enjoy.

The lock up converter was introduced many years ago but due to the extra costs, it never gained popularity until the late 1970’s when the energy crisis demanded a more efficient operation of automatic transmissions. The GM 700-R4 & 200-4R transmissions utilize a lock up converter to help create a more efficient transmission.

It takes stress off the fluid coupling of the torque converter and it helps decrease the amount of heat being generated at higher cruising speeds. Many times it will seem as if the transmission has a 5th gear or extra over drive when the converter locks up since it will typically reduce engine speed by about 300 RPM.

When GM installed these transmissions in a particular vehicle they had a few different ways to activate the lock up for the converter. Sometimes it was just electrical and sometimes it was electrical and vacuum operated. This primarily had to do with what type of engine was being used with the transmission, as well as, under what circumstances the lock up needed to be turned on or off for maximum efficiency.

As these transmissions gained popularity as transplants into hot rods and customs it became necessary to figure out a way to get the lock up to function when the original equipment was no longer being used. The old school way was to tap into the case connector and manually turn it on or off via a toggle switch in the dash. That was all fine and good unless you forgot to turn it on or off.

There are several variations of lock up kits available on the market today. Some aren’t much more than the old toggle switch; some are much more advanced and include adjustable parameters to dictate how and when the converter lock up is activated.

Here at Bowler Performance we designed our lock up module with simplicity in mind. We wanted to create a lock up system that would work with any engine combination in any vehicle. It had to be simple to install, and most importantly it had to work without any interface from the driver.

Torque Converter Lockup Symptoms

The solution was a timing based module system that activates the converter only after the transmission has shifted into 4th gear. The basic operation is quite simple. When the transmission has shifted into 4th gear, the pressure in the valve body closes a pressure switch that then creates a ground input. Once the ground is established, that completes the circuit in the timing module which is receiving a +12 volt signal from the fuse panel.

This completed circuit activates a 10 second delay timer that when finished, connects the ground signal to the torque converter lock up solenoid, thus locking the converter clutch in. This connection stays active as long as the transmission is in 4th gear and the circuit is completed. Unlocking the torque converter is achieved by disconnection of the +12 volts, or the transmission downshifts out of 4th gear.

We also include a cruise control style brake switch that works perfectly to disconnect the +12 volt power to the lock up module when the brakes are applied. This pulls the converter out of lock up to allow the car to easily accelerate back up to speed before the lock up re-engages.

Lock Up Control Module for Sale

Torque Converter Lockup Solenoid

The entire lock up system can be installed by anyone with minimal mechanical skills. The internal components are all accessed by removal of the transmission pan and filter only. There are no special tools or procedures required. We include every component needed to connect the system and get it working properly. This ensures that regardless of if you have a newly re-built unit, or a unit that has been in service for years, you will be confident that the parts are correct for proper operation.