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G Force has the transmission swap essentials

Transmission Swap Essentials

What is a Transmission Swap?

Although it is a complex project, in straightforward terms, a transmission swap means replacing the transmission in your vehicle from the Original Equipment Manufacturer (OEM) or factory spec transmission to a different one that initially was not offered by the carmaker. Usually, when considering the subject of swapping a transmission, it refers to an automatic to manual transmission swap, or vise-versa. Although, it really applies to any change for automotive performance improvements. To get a better idea of what these advantages might be, let’s look at a conventional transmission swap for the 4L60, 700R4, or TH2004R.

 Evaluating Transmissions

Transmission Adapter Swap KitsWhile the pros are familiar to the veteran car enthusiast, the resemblances between transmissions might cause a less experienced to wonder which transmission to choose.

In this instance, the 4L60, 700R4, and TH2004R are all 4- speed automatic transmissions. However, a closer comparison of the two aftermarket transmissions to the OEM part reveals that the factory transmission cannot withstand high horsepower and does not offer electronic tunability, which is critical for optimal performance.

TH2004R versus 4L60E

The 4L60E transmission is computer-controlled. Therefore, adjusting torque converter lockout, shift points, and other tuning factors is as easy as making changes to a software program. In contrast, the TH2004R involves full disassembly to accomplish those same modifications.

In Search of Better Performance

Furthermore, the 4L60E can take higher output ratings. This transmission has a 360 ft lbs maximum torque rating versus the 250 ft lbs rating for the TH2004R. The benefit of the higher torque rating is that drivers get the ability to run higher horsepower. This power, along with easy tuning adjustability from the electronic controls, ultimately results in a faster quarter mile. If one needs a transmission to withstand more power, the 4l80e is even more robust and has an engine torque rating of 440 ft lbs.

How Does the 700R4 Differ from the TH200R4?

Both the TH2004R and 700R4 are from the same period and are remarkably similar. Both are four-speed transmissions, and a TV cable is used as their controller. Both transmissions are also more fuel-efficient alternatives to the TH350 or the TH400 transmission, mainly because they have additional overdrive gears, which increased fuel efficiency by 30%.

Possibly the most significant difference is gearing. The 700R4 transmission has a little shorter overdrive and longer gears compared to the TH2004R, which makes it more attractive to those looking for a transmission for drag racing.

Nevertheless, both transmissions are excellent aftermarket options because, recently, manufacturers have made these transmissions reasonably bulletproof. Ultimately, the 700R has more support in the automotive community due to the length of the production run. Documentation and support for this transmission add to its popularity and make it a favorite transmission swap for the enthusiast.

The 4L60 Compared to the 700R4

As noted earlier, GMs answered consumer demand for more fuel-efficient vehicles with the TH2004R and 700R4. The name of the 700R4 transmission changed in 1990, and it became the 4L60. This was unusual because it was only a name change. GM did not make mechanical modifications to the TH2004R/700R4 transmission at that time.

It was three years before engineers exchanged the traditional hydraulic shifting system for an electronic system, and 4L60E was introduced. The 4L60E allowed for a broader range of tuning options due to the new computer controls, making it a popular transmission swap option.

After that, General Motors launched a two-piece case that accommodates different bellhousings and made it a more adaptable transmission. Later revisions to design an even more robust transmission resulted in the 4L65E/4L70E. Eventually, even though the 4L60E and 700R4 have similar dimensions and internals, the 4L60E ended up as a more tunable, stronger, reliable, swappable, and popular transmission.

Choose the Transmission to Pair with Your Engine

Occasionally car enthusiasts take on a transmission swap project without also swapping the engine to enhance car performance. Sometimes the transmission conversion is part of a motor swap. While the transmission is frequently not the central consideration when completing an engine swap, the transmission merits careful thought. In the end, which transmission you choose influences your overall satisfaction with the results.

Even though it’s great to brag about the power behind your car’s engine, in the end, your ability to use that power is often more important. Without a suitable transmission, a high horsepower engine doesn't necessarily result in faster lap times. And it’s a good bet that if you're going through the work to trade your motor, you're doing it to increase power.

So, if that is your goal, and the factory transmission might not handle the added power, GM did not make mechanical modifications to the TH2004R/700R4 transmission at that time. it's time to consider a transmission swap too!

RCG-700 Crossmember to support your transmission swap

Check out our related articles and videos for more information regarding what GM transmission work with motor swaps such as LS, Vortec, or other GM small blocks.

Also, discover more about our RCG-700 Crossmember. It’s performance-engineered for swapping a TH2004R to a 700R4 transmission or 4L60 transmission in G-Body cars.


What is the impact of an engine swap on transmission alignment?

Proper Transmission Support is a Key Consideration

As we’ve already noted, motorsports enthusiasts have many choices for enriching the sport. From performance improvements to simple shine-and-go enhancements, the only boundary is your imagination. Whether you have an old school engine to swap into a newer chassis, or a recent engine and drivetrain to shift into a classic chassis the challenge keeps the "motorsports junkie" moving from one project to the next.

Because of the GM LS engine’s popularity, there is a huge demand for LS based performance products and the components needed to swap the electronically controlled powertrain. Let's take a closer look at transmission alignment using a LS swap as an example.

One of the most neglected parts of an LS engine swap in older classic or muscle cars is support for the transmission. You can read more about the basics of a Transmission Swap here.

G Force adjustable motor mounts

Numerous motor mount adapters for an LS conversion are generally engineered to allow engine placement at the stock bellhousing position. Most motor mounts allow movement forward 1 or 2 inches. Relocating the LS engine forward is frequently necessary for the exhaust headers and the cylinder heads to clear the firewall and other chassis components. Also, the electronic shift's various size and configuration options often mean the transmission mount is no longer positioned over the transmission crossmember.

The G Force Performance Adjustable LS motor mount adapter set allows the installation of a LS engine into early model GM vehicles that utilize a standard 3-bolt style motor mount. The mounts are adjustable to position the bellhousing in the original factory location, 1" forward or 2" forward. The G Force adapter is unique because the 3 locations are geometrically positioned to facilitate retention of proper driveline alignment, regardless of stock or forward position. Additionally, within each position, there is 1/2" of infinite adjustment for greater positioning flexibility.

A transmission crossmember from G Force Performance is, unless noted, designed for OEM or stock bellhousing location. For example, if you are bolting a 4L80E transmission behind your Big Block Chevy (BBC) in your 69 Camaro, the G Force Performance transmission crossmember for that application is based on the bellhousing positioned at the stock location behind the BBC. Find out why our customers choose a G Force Crossmember here.

Nevertheless, something like an LS swap that relocates the bellhousing location must be addressed. In some vehicles, this is accomplished by moving the crossmember the required 1 or 2 inches and drilling new holes.

However, a better option is an Adjustable Transmission Mount the G Force. Our mount accommodates the crossmember at the stock location, while the mount adjusts it forward between 1" and 2- 1/2".

In the larger context of an LS swap, these are only a few of the many things to consider. But a little advanced planning will go a long way towards making your conversion easier and more fun.

Answers to LS Conversion Frequently Asked Questions

How does a custom engine swap cost?

The cost differs based on the vehicles involved, the availability of materials, and the paid labor you require for completing the conversion. Prices vary from as low as $1,500 to higher than $12,000.

Is the engine I choose to swap dependent on what car I own?

Although technically it is possible to swap engines of different makes to nearly any car model, the cost is often a significant factor in your choice. To avoid wasting time and money, we recommend consulting a reliable engineer before beginning your LS swap. Depending on the performance you wish to achieve and your budget, the advice of an experienced professional, can save you a lot of headaches and expense down the road.

What is the best Transmission Crossmember for my LS Swap?

We get this question a lot! Although the answer may not be obvious, it is easy to determine. On our Products page, G Force has a robust filter where you can find what you need. First, select the Crossmember Part Type. Next, choose as many other criteria as required to find the correct part. The filter includes Transmission, Make, Model, Year, Transmission, Engine, and Platform. The available parts that meet your criteria are displayed. If more than one Crossmember fits your application, review the product details to determine the best option.

The next thing to think about is the LS engine swap itself and how the drivetrain location will be affected. Often in a swap, the engine is relocated forward between 1" and 2" for sufficient clearance to the firewall. The original early generation V8 engine has the cylinder heads offset forward from the back of the engine block. However, the cylinder heads on a LS engine maintain a rearward position with the right-side cylinder head flush to the back of the block requiring the drivetrain to shift forward.

How far do I move my LS engine forward? 

Engine position isn’t a “one size fits all” question —several variables from the vehicle configuration to which components have been chosen for the project impact that answer. But there is a solution that allows making allowances for all of these variables. It is the G Force Performance Model: GF-LS-MMA LS Conversion Adjustable Motor Mount Adapter Set.

This adjustable mount set lets you position your LS engine in the stock OEM location or forward 1 to 2 inches without removing the engine to change the position. Simply remove the clamping bolts, slide the engine to the optimum location, and then reinstall the clamping bolts.

Once I've installed my LS engine with the G Force GF-LS-MMA  Adjustable Mounts—what about my Transmission Crossmember?

G Force adjustable transmission mount

The first thing to consider is—do you need a new Transmission Crossmember? You may already have a crossmember that provides clearance for your large diameter exhaust. However, since you have installed your LS engine with your repositioned drivetrain, your transmission mount may now be in front of the transmission crossmember. The good news is that if your offset is between 1” and 2-1/2”, you can keep your existing crossmember by installing the G Force GF-GMATM  Adjustable Transmission Mount.

But, what do you do if you do not have the correct transmission crossmember for your build, or you’ve installed a transmission that positions the transmission mount rearward of your transmission crossmember?  

If that is the case, finding the right G Force Transmission Crossmember for your build is the best option. The first consideration is to determine which transmission you are using in your build. Next, you must take into account that, unless otherwise noted, all G Force Transmission Crossmembers are designed to support your transmission at the OEM or stock bellhousing location.

Therefore keep in mind, it is necessary for some LS engine conversions that you may need both a G Force Transmission Crossmember and our Adjustable Transmission Mount for proper installation and alignment of the drivetrain. Our Adjustable Transmission Mount, LS Motor Mounts, and our full line of Transmission Crossmembers are now available and are proudly American-made.

What do I need to know as I prepare for my swap?

We have several articles you may find helpful, and we're constantly adding more. So check our blog page frequently. Here are a few about LS Swaps-

LS Swaps with Products from G Force

G Force Performance Products is a top supplier of transmission adapter kits and crossmembers for LS swaps. With our parts, you can be confident in the quality and reliability of the components you choose for upgrading from stock parts or swapping components into your vehicle. In addition to our adapter kits and crossmembers, we have adjustable transmission mount replacements, bellhousing adapters, flywheels, exhaust parts, bolt kits, and more!

If you are interested in LS swaps, check out the following products:

Z32 Transmission Conversion Kit: Nissan 300z V8 LS Swaps Kit

Z32 transmission adapter swap kit

You can connect a Nissan 300Zx, 5-speed transmission to an LS engine with our Z32 Kit: Nissan 300z V8 LS Swap Kit. Notably, these kits will give you the ability to run a manual transmission with a powerful LS engine. Z32 transmissions can handle 700 horsepower with ease. Also, they are reliable and easy to find. As a matter of fact, you can acquire a Z32 from classified ads and salvage yard for around $300.

Our Z32 Kit: 

Nissan 300z V8 LS Swap Kit fits naturally-aspirated 300zx transmissions with twin-turbo or naturally-aspirated plate/clutch setups from 1990 to 1996 exclusively. This LS Conversion/Swap Kit includes:

  • Custom Steel Flywheel
  • 3/8 Steel Powder Coated Adapter Plate
  • Pilot Bushing Adapter
  • Mounting Hardware

Additional Details:

  • Includes stock 300zx pilot bushing and steel adapter
  • 300zx starter on the side of transmission
  • Incompatible with twin-turbo Z32 transmissions
    • The twin-turbo Z32 has a much larger bellhousing, so the starter is farther from the flywheel ring gear. As a result, the starter will not engage with the flywheel.
  • 300zx pressure plate/clutch and throw-out bearing.
    • Compatible with naturally-aspirated or twin-turbo pressure plate/clutch discs.

Z33 Conversion Kit: Nissan 350z V8 LS Swaps Kit

Z33 transmission adapter swap kit

Our Z33 Kit: Nissan 350z V8 LS Swap Kit will connect a Nissan 350Z 6-Speed Transmission to a Gen III or IV LS Series Chevy Small Block Engine. Are you looking to buy a transmission that can handle the power of an LS engine without breaking the bank?

The Z33 is the perfect conversion kit for you. In addition, these transmissions are reliable and easy to acquire.

The Z33 Kit: Nissan 350z V8 LS Swap Kit works with transmissions available in Nissan 350Zs from 2003 to 2008. For example, this LS Swap Kit includes:

  • Custom Steel Flywheel
  • 3/8 Steel Adapter Plate with a Powder Coated Finish
  • Pilot Bushing and Adapter
  • Hi-Torque Starter Adapter
    • (Use your current Hi-Torque Mini Starter or purchase one separately.)
  • Mounting Hardware

Additional Details:

  • Billet steel flywheel kit of about 30 lbs.
  • Direct bolt-on flywheel: No required adapters or spacer bushings.
    • (Some conversion kits use lighter aluminum flywheels, but 30-pound steel wheels are ideal for 90% of all builds.)
  • Flywheel works with any OEM or aftermarket 350Z clutch assembly.
  • Stock 350Z pilot bushing with a machined steel adapter included.
    • No transmission modifications required
    • Some heavy wall bell-housings may need a clearance trim for the flywheel ring gear—polish away .06 inches over a small area about the size of a stamp.
  • LS blocks require the removal of a small casting boss for clearance for your high-torque starter.
    • Small modification with a hand grinder—instructions included.

An LS swap is a complicated venture. Each swap requires making a modern engine made for a specialized purpose and engineering a solution to use it in a configuration for which it is not built. Consequently, every individual component that makes the motor work must be adapted for the new platform.

In other words, each LS swap is different according to the new application. The possible stumbling blocks encountered are case-specific. However, here is a list of some of the items you should consider before starting a swap project.

Components needed in any LS swap:

    1. Motor Mounts
    2. Transmission Crossmembers
    3. Driveshaft
    4. Shifter linkage modification
    5. Throttle cable modification (or in the case of drive by wire, electronic throttle pedal adapter, and CAN BUS electronic adapter)
    6. Oil Pan
    7. Front end accessories
      1. This includes: water pump, alternator, AC compressor, tensioners, belts and associated mounting brackets, and shims.
    8. Wiring Harness
    9. ECU
    10. Exhaust
    11. Intake
    12. Cooling Components
      1. Cooling hoses, fans, radiator,
    13. Fuel Components
      1. Fuel lines, pump, fittings, fuel return lines, fuel rail
    14. Oil filter relocation
    15. Clutch Lines
    16. Within this list of components, it is easy to see where our products fall in line with solving the complex LS conversion problem. For example, for conventional LS swaps, we offer transmission crossmembers and some motor mounts for specific swaps. On the other hand, the adapter plates that we sell were designed to resolve specific problems for customers—customers who want to swap a particular transmission and motor into any platform.

Even though our kits might allow customers to choose various transmission and motor combinations, it does not fulfill all aspects of a customer's desire to swap these specific motor and transmission combinations into specific platforms or cars. Paring these adapter plates with transmission crossmembers or motor mounts would allow them to be considered “LS transmission adapter swap kits” as opposed to “LS Swap components.”

Parts with Intent

Our customers choose G Force parts for swapping transmissions and motors because of installation ease and time savings. All of our parts are road and track tested to deliver reliability, strength, and quality at a competitive price.


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