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Bailey Automatics is Perth's Automatic Transmission Specialist.

Torque Converters

Torque converters are categorised by stall speed and diameter size. The stall speed (RPM) is the speed the engine can get to before the converter starts holding it back. When the engine can’t increase it’s RPM, the RPM will stall (or stop going up!) The stall speed is related to the engines ability to produce power and the torque converter holding the RPM back. 

So if we change the power output OR the change the converter this will change the stall speed. A high stall converter won’t stall at the same stall speed when changed from one engine to another if the torque produced by the engines is different.

Factory torque converters are 12-13 inch in diameter with a stall speed around 1600-1800 RPM. They are designed for fuel economy and drive-ability and certainly achieve this. However, when modifications are done to the fuel system, camshaft and other engine control systems problems can start to appear. It’s important to note that if you are planning on making modifications to your engine, especially performance modifications where you’ll be aiming to increase the torque curve to a higher RPM range so you’ll need to install a high stall converter.

So how do you choose a high stall converter?

As the diameter of a torque converter decreases the stall speed goes up
To allow engines with a lot of camshaft to idle better smaller diameter converters are needed to provide more slip.
As the torque converter and horsepower range is moved higher through the RPM range, the smaller torque converters with their higher stall speeds provide maximum torque multiplication where needed. You’ll need to make your converter selection with the help of a qualified professional because if your car’s set-up is mismatched your motor will stall easily.
That’s where Bailey Automatics comes in! We have many converter combination's to make your car or truck perform at its utmost potential.

Firstly how does a torque converter work?

A torque converter uses fluid coupling to multiply torque.
Some factory torque converters fall short in terms of specification when you are using your car for heavier duties than just street driving, for example towing or drag racing.
There are 2 types of torque converters-
1. Standard- single disc lock-up
2. Heavy duty converter which have 2 discs inside.
The torque converter must be correct for your application!
The heavy duty torque converter can handle tremendous torque without warping or deforming and will extend the life of the automatic transmission. Your automatic transmission will also be cheaper to operate with a heavy duty torque converter over the years. A highly modified engine will need a double disc clutch converter.

Lock up Torque converters

Lock up Torque converters have a clutch inside- the clutch grips together (controlled electronically) and allows better fuel economy by dropping the rpms down. When the clutch engages the converter locks the engine to the transmission input shaft so there is a direct connection between the motor and the transmission. It works like a fluid coupler, with an outside drum spinning, then the inside spins on the shaft of the transmission. This can produce tremendous heat and heat within the torque converter is bad for fuel economy! It can also transfer to the transmission or clutch and damage them by causing separation. The lock-up torque converter reduces the slippage which reduces heat which means better fuel economy.

What does it mean if my Torque Converter is shuddering…?

This is often described as a problem when your car is going through gears 1- 4 and a shudder is noticed when you hit fourth gear.
So that we can diagnose if this is a torque converter shudder we’ll need to know if the shudder goes away as you accelerate more and more.
If the shudder does go away as you increase your acceleration, the lock up lining on your torque converter is likely to be deteriorating and possibly on it’s way out.

How do Bailey Automatics test my Torque Converter?

You will need to bring the car in for a road test. We’ll check the oil level and look at your car’s history to see when you first noticed the shudder and how often the shudder is occurring.

From there we will run a scan tool on the vehicle. The on-board computer, ECU will register a code that tells us if there’s been a torque converter slip THEN we’ll take a drive to see if we feel the shudder.
When testing the oil level the smell of the oil will tell us if the lock up lining has gone on the torque converter which could be causing the torque converter to shudder.
If we catch it early a torque converter shudder could be an easily fixed problem such as needing to fix oil levels or repair the solenoid. The torque converter solenoid is in charge of controlling the fluid pressure to the torque converter. If the oil is too low it could be causing the shudder.
Alternatively we may have to pull the transmission out of the car to diagnose and fix, in minor cases a reconditioning of the torque converter will help. In this case we service the transmission- change the oil and filters and put the car back together! But if material from the torque converter has gone through the transmission we may need to complete a full recondition to fix the torque converter shudder.