Transmission and Drivelines
High Performance Transmissions
High-performance transmissions are used to improve vehicle performance.
Typical upgrades include replacing the transmission with one that:
Shifts faster
Keeps the engine within its power range
Type of transmission upgrade depends on the intended use of the vehicle.
Transmissions are often replaced because the original cannot support increased engine power after an upgrade.
Cost of a replacement transmission depends on:
Type
Brand
Power rating
Examples of high-performance transmissions include: Jerico, Liberty, Tremec, and Lenco.
Jerico Transmission
Usage
Jerico transmissions are used in various racing applications, including:
Road racing
Drag racing
NASCAR racing (most notable)
These applications require quick-shifting transmissions capable of handling high engine horsepower.
Features
Jerico transmissions are available in 2, 3, 4, and 5-speed versions.
Clutch is required to engage the transmission from a stop.
Uses dog rings with large engagement teeth on the slider and speed gear.
Features include:
Pistol grip shifter or air shifter system
Air shifter can automatically shift at a preset engine speed.
Integral coolant pump
Circulates transmission or rear axle fluids to a cooler.
Dual-stage pump can circulate both transmission and axle fluids simultaneously.
Jerico Transmission Configuration
Configuration Types
Jerico transmissions are rear-wheel drive manual transmissions.
All models require a clutch to engage the transmission from a stop.
Once engaged, the driver can shift gears without using the clutch.
Air-operated shifter changes gears automatically at a predetermined engine RPM.
This feature is referred to as a clutchless design.
Benefits and Drawbacks
Benefits of Jerico transmissions:
Increased horsepower delivery to the rear wheels
Faster and more precise shifting
Customizable to suit each vehicle
Uses straight-cut gears (instead of helical-cut) to handle higher engine power.
Downside: Straight-cut gears produce more noise during rotation.
Main drawback: High cost of the transmission.
Liberty Transmission
Liberty transmissions are manual performance transmissions.
They are rated based on engine horsepower.
Commonly used in drag racing and circle track racing due to the need for precise shifting.
Gear changes are either lever-operated or air-operated.
Types
Liberty transmissions also offer a clutchless design like Jerico.
Uses two countershafts to split engine power, allowing operation with higher horsepower engines.
Typically available in 3, 4, or 5 speeds.
Lighter than many other performance transmissions.
Custom-manufactured to fit vehicle needs.
Commonly used in:
Circuit racing
Drag racing
High-performance powerboats
Benefits and Drawbacks
Benefits of Liberty transmissions:
Increased horsepower delivery to the rear wheels
Faster and more precise gear changes using lever or push-button shifts
Customizable to fit each vehicle
Drawback: Typically high cost
Tremec
Tremec transmissions are used as standard equipment in many OEM vehicles worldwide.
High-performance Tremec versions are available for vehicles where the replacement transmission is a straight bolt-in.
Internal components of the high-performance Tremec transmission are modified to handle higher engine power and torque.
Types
Tremec transmissions are available in 4-, 5-, and 6-speed variants for rear-wheel drive vehicles.
Used in a range of vehicles, including:
High-performance cars
Light-duty trucks
Heavy-duty trucks
Benefits
Benefit of Tremec high-performance transmissions:
Direct bolt-in replacement, making installation easier.
Can reuse stock brackets, crossmembers, and clutch system.
Comparison to other aftermarket transmissions:
Other upgrades often require modifications to crossmembers, clutch system, and brackets.
Lenco Transmission
Lenco transmissions are used in super high-performance race cars and supercharged boats.
Two-speed transmission can handle up to 3000 horsepower.
Available in manual and automatic versions:
Manual: two-speed planetary gearset transmission
Lenco stacks individual gearboxes together to increase gear ranges, up to five speeds.
Shifting options include: individual lever shifters and air shifters.
Drivelines
Driveshaft
High-performance or racing driveshafts are built to vehicle specifications.
Key specifications include:
Vehicle class, weight, and type
Engine power output
Top speed of the vehicle
Driveshafts are commonly made from aluminum, steel, or chrome-moly to reduce weight and increase strength.
Smaller driveshafts reduce rotating weight, improving performance.
Caution: Driveshafts that are too small may twist or break under stress.
Rear Axle Shaft
High-performance rear axles are lighter and stronger than standard axles.
Typically made from steel or chrome-moly materials.
Performance axle shafts use more splines at the shaft ends to:
Engage the differential side gear
Provide greater holding power
More splines distribute the load, reducing stress and making the axle less likely to break or strip.
Carrier
Racing/high-performance axles use a removable carrier.
Technician can perform adjustments with the carrier removed from the vehicle.
Makes ring and pinion changes and adjustments easier.
Manufacturers modify racing carriers to withstand the high stress from large engine power.
Axle Housing
Racing/high-performance axle housings are stronger than standard housings.
Axle tubes are usually welded to the housing on solid axles to prevent separation.
Trusses connect the middle of the axle tubes to the center housing to prevent bending under harsh driving conditions.
Axle housings can be shortened or lengthened to fit the specific vehicle configuration.
Ring and Pinion
Racing ring and pinion gearsets are made of steel.
Manufactured to withstand high horsepower delivered from the engine.
Gear ratios are changed as needed to suit different racing tracks.
Helps keep the engine operating in its optimal power range.