Street Cruiser Series (Level 1) 4L70E
Our Street Cruiser Series transmission is the finest built mild street/performance automatic transmission in the industry. These transmissions are tough and built to handle whatever you dish out. We incorporate all the updates and modifications to compensate for the problems and issues they were born with from the factory. We believe you will not find a better performance transmission anywhere!
Below are the details of our Street Cruiser (LEVEL 1) built Transmission, which is suitable for applications up to 450HP.
First, each core transmission is disassembled and carefully inspected. The case and hard parts are then cleaned thoroughly and re-inspected for cracks, wear, or other damage before we begin. The case is specially prepared and a coating of and heavy duty, heat resistant, oil based enamel is baked on, creating a hard and durable glossy finish. The seals in the case are replaced and assembly begins.
The rear planetary assembly and bearings are meticulously inspected and assembled into case along with heavy duty reverse frictions and steels. At this time, the center support and sprags (one way rollers) are installed after being inspected for stress cracks and damage. Also, a special anti-clunk device is installed to replace the OEM spring, if needed. This prevents the support from tearing through lugs in the case and reinforces the case.
Next, the sun gear is inspected and modified to improve lubrication to the rear planetary assembly. This allows oil to escape from between the bearing and the gear it rests against; which feeds additional lube to the planetary gears. This is a huge improvement, and it virtually eliminates one of the most common points of failure for this type of transmission. In fact, contrary to common opinion, the rear planetary assembly in these transmissions is not, in any way, weak by design. Their failure is almost exclusively due to a lack of lubrication. When you see one with a damaged rear planetary, it will almost always be accompanied by the blue-black signs of excessive heat. Simply put, the planetary assemblies with good lube DO NOT FAIL, even in the most demanding environments.
We then replace the sun shell with a strengthened heavy duty unit. This unit far exceeds the factory component and is able to withstand the rigors of either the street or the strip.
Next, we re-inspect the front planetary assembles – measuring clearances and making sure everything is within our own rigid specifications before installing it and inserting the output shaft. The front sun gear is then modified for improved lubrication, as the rear sun gear was, and installed. Then, end play is set for the output shaft.
For the input drum, we re-inspect it before installing new rubber seals and a neoprene lubrication seal. We install new heavy duty overrun friction plates, a heavy duty input sprag assembly, and carbon composite forward friction plates. These forward frictions have a superior holding capability as well as improved ability to withstand extreme heat; compared to the OEM friction plates. Since these friction plates must hold the power of your vehicle in every forward gear, they have to be tough enough for the job.
Finally, we replace the 3-4 clutch set with 8 Borg Warner performance friction plates and heavy duty steel plates. This combination is very strong.
As we move on to the reverse input drum, it is assembled, seals replaced, and the band surface area is resurfaced to accept the max duty carbon performance 2-4 band. This band has reinforced band-apply-area and pin lug to prevent pull through. This stronger 2-4 band will hold the torque during that tire chirping shift into second at full throttle in your performance machine.
We also install the corvette servo for maximum “apply pressure” in second gear. This is the largest GM offering and is plenty for most applications.
Now we move on to the pump. It is inspected and modified to provide maximum lube to the planetary sets. We install a boost valve suitable for the application. The vanes in the pump are carefully inspected for wear and replaced as needed, steel pump rings are installed. The pump bushing is replaced with a Teflon bushing, and notches are made in pump surface to prevent its movement, even in the most demanding high RPM or towing situations. This effectively eliminates front seal blow out. In addition, the front seal is installed with a special adhesive and seal retainer to eliminate any possibility of problems occurring. The pump is the heart and soul of any automatic transmission, and we make sure it’s a healthy one.
The last section is the valve body. For this, we use all we have learned over the years. What we have learned is, although most shift kits have certain distinct advantages, no one kit has all the best modifications… some parts we liked and others we didn’t. We took the best parts of each and, utilizing our own experience, created a set of modifications that is superior to all the others. We do not block accumulators, since the reason they exist is to prevent excessive shock to the transmission and drive train. With our transmissions, you will always have a solid, firm shift that will be linearly progressive. That means at light throttle you will feel a nice bump, letting you know the car or truck has shifted. As throttle is increased, the shifts will become more pronounced to the point of tire chirping in high performance vehicles or a firm shift at full throttle in a towing/hauling situation. It will not cause whiplash just cruising with your significant other or your grandmother around town, but will turn heads when laying it on the line.
We also eliminate the partial lockup function GM mistakenly engineered into the 4L60E transmission, thus eliminating converter shudder, premature converter clutch failure, and the well known code 1870, which causes high “line pressure,” no fourth gear, and teeth cracking shifts at low throttle. Lockup is either OFF or ON, not slipping off-and-on as it did with the factory PWM working. This does not affect performance, but it does have the added advantage of increasing low speed fuel efficiency, which at today’s fuel prices is like getting a bonus. In addition, this mod along with others allows us to use later valve bodies on older units to improve performance and increase interchangeability and reliability.