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Lenco Street Transmissions - Shifting Point
The Ultimate Race Transmission Can Now Be Used On The Street
Feb 1, 2001
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Lenco Street Transmissions - Shifting Point
Aside from its awesome appearance, the Lenco Street five-speed transmission offers Pro Street enthusiasts the capability of racing as well as driving their vehicles on the street.
The transmission is made up of sections, each holding a planetary gear set and an intermediate shaft. These can be easily removed and replaced in the case for changing ratios or servicing.
The planetary gear set in each housing is almost identical to that used in an automatic transmission. Three planet gears rotate around a central sun gear. Differences in gear sizing create different percentages in gear reduction.
When assembled, the planetary carrier holds the gears and clutch housing in place.
The clutch pack assembly is then held in place with a snap ring.
Floaters and clutch plates are installed in the carrier. Each carrier holds seven clutch discs and eight floaters.
The plates are measured with the center clutch hub in place and when the clearance is correct, a pressure plate and spring sit down on the clutch pack hub.
The shaft carries the sun gear that all the other gears rotate around. The outer gear on the shaft is what is engaged when the clutches are activated and keeps the gears from rotating.
This is the clutch pack assembly that's ready to be installed into its housing. Each assembly will have a different gear-reduction ratio that determines where on the transmission it will fit.
The sprag ring and sprag assembly are what keep the sun gear spinning in one direction until it is shifted.
The intermediate shaft is the connection to the other assemblies and is also made from hardened steel.
Part of the magic that allows the Lenco transmission to be shifted manually, is the radial plate. When the transmission's shift lever is moved the radial plate rotates and pushes against the pressure plate, actuating the clutch pack.
The ring is made from billet steel and sits over the entire planetary assembly.
Shown is what a complete planetary gear assembly looks like in the housing. Note the hardened steel intermediate shaft that is on every assembly.
With the intermediate shaft in place, the sprag is installed between the shaft and sprag ring.
A sprag lock, washer, and cover are then installed over the assembly.
The radial plate rides on this cam plate that pushes back against the pressure plate and clutch pack. Note the indentations in which the roller bearings of the radial plate ride in when it is not engaged.
Once everything is buttoned-up, the entire planetary assembly is bolted in place, behind other assemblies with different gear reduction ratios.
Although the reverser still uses a planetary gear set, it is operated with a slider rather than with the radial plate.
The fork actuates a slider gear over the rotating assembly that operates the planetary gear set.
The fork and lever is inserted into the housing. An arm with a detent is attached to the lever to actuate the fork.
The planetary gear set sits forward of the slider gears in the reverse housing.
Exploded view of the reverse assembly shows the planetary gear set, sprags, washers, thrust bearings, slider assembly and output shaft assembly.
The housing cover is then bolted onto the reverse housing and the assembly is finished.
Technicians check that the output shaft and the rest of the assembly rotate freely in one direction.
Once each planetary gear assembly is completed, it is bolted in the correct sequence to form the transmission, from the input shaft to the reverse assembly.
Our completed transmission has five planetary gear assemblies that make it a streetable five-speed that can handle 1,200 horsepower and 850 ft-lbs of torque.
At the front of the housing, a sprag plate and a very heavy-duty sprag surround the output shaft.
One of the only assemblies that is different in the Lenco transmission is reverse gear. This assembly not only engages the transmission into reverse but is also used for first gear and neutral.
In order for the Lenco technicians to determine which input shaft to install, they first have to know what type of bellhousing will be used. The one used in this application is a McCleod (PN 8630) big-block Chevy bellhousing.
For strength purposes, we decided to use the standard racing-style hardened shaft with a deep 10 spline.
The clutch for the Lenco must also be heavy-duty. We opted to use the McCleod (PN 64001-6) twin-disc clutch setup.
The twin-disc design has greater holding power than a single disc and features a zero-balance flywheel and separator plate.
Both discs and the separator plate fit on the flywheel and are made for the heavy-duty 10-spline input shaft.
The pressure plate is also unique to McLeod, as it has tremendous holding force, yet is not much harder to engage than a stock pressure plate.
Measuring the depth of the bellhousing determines the length of the input shaft.
Pushing in the clutch is just one of the operations of the Lenco transmission. The other is shifting. Each trademark shifter has a tower that fits into a boss at the top of each planetary gear assembly.
The tower is screwed in with shims to a depth that will allow the tower's plunger to actuate the radial plate in the assembly.
Rotating the tower in or out slightly from the boss adjusts shift pressure. A fishing scale is used to determine the amount of shift pressure.
The shifters are the trademark of the Lenco transmission, they are held in place with a shifter bracket that can be located in numerous places on the transmission.
Each shifter rod is made from billet aluminum and the linkage is cut to the required length. Heim joints are used to ensure a solid shift.
Since our engine and transmission are going to be set back in the cab, the shifter location was moved forward.
Driver position and the location of the transmission in the vehicle are key to the shifter's location.
Here you can see how stout the shift linkage is and the amount of spacing between each shifter for hassle-free shifting under acceleration.
Lenco uses a fork assembly to slide the gear in and out of position. Moving the slider forward engages the transmission into the first and forward gears. Sliding it back engages it into reverse, and in the middle is neutral.
The finished transmission ready to be installed in Truckin's World's Fastest Street Legal Pickup. We're sure it will work as awesome as it looks and can't wait to get in and pull the levers.
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