6 Speed T56 Trans Swap

T56 Swap Tips

The T56 6 speed manual transmission is an excellent choice for a wide range of applications. The popularity of this trans has led to many different models, improvements and aftermarket hop up parts. This trans is now available new as well as used and it has many features that make it an ideal choice for use when swapping out an automatic transmission in favor of a manual trans.

Why a T56 Transmission Swap?

There are many reasons for changing out an automatic trans in favor of a manual. People often cite things like better fuel economy, simpler installation, no need for external coolers and lines, racing use but most importantly the fun factor! While modern automatic transmission have made huge strides in performance there is still nothing like having full control of the transmission yourself. Once the basic skills of shifting and clutch operation are learned, driving with a manual trans is quite fun and with the T56 having 6 speeds instead of the more common 4 and 5 speeds, it is even more fun. It also has the advantage of better fuel economy and higher top end so there are many great reasons for doing a T56 swap.

Improved acceleration is another very important benefit of the T56 as the 2 overdrive gears allow you to run a much steeper rear end gear yet still get good highway mileage while cruising and higher top speed when the engine has enough power to pull the overdrive gears at higher engine rpms. Typical 3 and 4 speed manual transmissions have a 1-1 high gear ratio, so for each revolution of the engine, there is one revolution of the driveshaft. Overdrive refers to the output shaft of the transmission as being “overdriven” in relation to the input shaft. An example is if you have a .86 to 1 overdrive gear, when the engine is turning 5000 rpms, the output shaft of the trans, and hence the driveshaft is actually turning at 5700 rpms. This allows more vehicle speed in relation to engine speed which is where the fuel economy benefits come into play when cruising. Using that same logic, you can see how you can attain higher vehicle top end speeds with overdrive, but an important factor to take into account in that situation is that the engine has to work harder in order to “pull” the overdrive gears since the engine is seeing a higher load than in a 1 to 1 drive ratio situation.

One example of this, in a production car application, is the Dodge Viper. The 488 cubic inch V10 engine has plenty of torque and horsepower to work with. In a highway cruising application ( at posted speed limits of course), the 6th gear overdrive of the T56 allows the engine to spin at low rpms and provide greatly improved fuel economy compared to if you only had a 1-1 fourth gear to work with. At the other end of the driving experience though, since the V10 has plenty of power, it has the ability to take advantage of the overdrive gears to take the Viper to very impressive top end speeds when used on race tracks and other closed course competitions.

Potential T56 Trans Swap Projects

There are few limits on the type of vehicle that can benefit from swapping to a T56 model transmission. If you are starting with a vehicle that is already set up for a manual transmission, the job may be a bit easier but even if when the project is a vehicle originally equipped with an automatic transmission, the job can still be accomplished by most anyone with the desire, tools and some basic mechanical skills. If you do not want to perform the change over yourself, there are many shops that can handle the work for you.

Some things to consider in addition to the T56 6 speed transmission itself are the bellhousing, clutch assembly, clutch pedal and related linkage, flywheel, shifter, transmission cross member, driveshaft and the front yoke of the driveshaft. Another item that is often overlooked until it causes a problem, is the pilot area in the back of the crankshaft. you need to make sure that the back of your crankshaft is properly machined to accept the pilot shaft of the trans and also make sure a pilot bearing is installed. There are crankshafts that have been installed in cars that are intended only for use with an automatic transmission so are not machined from the factory to allow the input shaft or a pilot bearing to be used. Most aftermarket cranks have the ability to use either an automatic or manual trans, but always check the crank very early in the project.

The major parts of any transmission are heavy so please always practice good safety procedures, use solid stands or a lift to hold the vehicle and use hydraulic jacks to handle the weight of the transmission assembly in particular. It is best to perform this work with at least one person to help you due to the size and weight of these items.

T56 Swap Benefits Summary

  • Lighter weight, less rotating mass, greater torque handling in most cases
  • Better fuel economy
  • Ability to run lower rear end gear ratios for better acceleration, but still get good mpg and top end due to the 2 overdrive gears
  • Easier maintenance
  • Great flexibility, different transmission models, gear ratios and many aftermarket parts available

In closing, while it takes a good bit of work, a T56 swap can be accomplished by most anyone with the desire to do. The many benefits are well worth the investment in time and money and the resulting fun factor is off the charts. A separate article on T56 conversion kit information will be posted in the near future so stay tuned.

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