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General Motors’ transmissions’ 1982–1989 Turbo-Hydramatic TH700-R4, 1990–1991 4L60, 1992–2000 electronic 4L60E, 2001–2005 4L65E, and the 2006-and-newer 4L70E were all designed to replace the tried-and-true TH350.
The 4L60E is basically a digitally controlled 700-R4. The first 700-R4 was built as a Corvette four gear automatic with overdrive. This was back in 1982. This initial version was designed with a bolt-on extension housing and employed a throttle-valve cable that was installed to signal engine load to the transmission via throttle position, instead of using engine vacuum. Almost all the transmission specialists including those at Gearstar.com agree that the improperly adjusted throttle valve cable is the cause of most aftermarket 700-R4 failures.
Since old transmissions used lower grid ratios, have a different valve body, offer the extra 4th gear and are supplied with a lock-up torque converter. In 1995 the 4L60E was provided with a pulse-width modulated torque converter lock-up control.
The year following that one, the case was redesigned with a bolt-on bell-housing and six-bolt tail-shaft and a change to the solenoid. The 2001 model featured improvements in the torque capacity and it was renamed 4L65E. The main improvements of interest to hot rodders are the 4L65E’s 5 pinion carrier that replaces 4 opinions. The extra opinion helps to spread the load, allowing this new transmission to handle more torque. Additionally, a better 3 to 4 clutch, improved input shaft and a deeper pan for more fluid were added.
In 2006 there was another name change to 4L70E for the four-speeds found in GM rear-drive 1⁄2-ton trucks and SUVs. This is the same transmission as a 4L65E but with a speed sensor located in the pump, which was totally redesigned.
Once they’re made strong enough, the only problem that occurs in the 4L60E family is the wide ratio between 1rst and 2nd gear which is 3.06:1 to 1.62:1). As Mark Walk at Gearstar says, “It leaps like a deer.” While many modifications are available for these transmissions, there is little that can be done to shorten up the first gear to second gear shift
Transmission builders like Gearstar can modify a 700-R4 or 4L60 or 4L65E or 4L70E automatic to withstand different levels of torque and horsepower thresholds. Modified transmissions are rated at “levels” from Two on up. A Level Two can withstand up to 450 hp, Level Three up to 500 hp, and Level Four to 650 hp. The breakdown of these modifications go into each of Gearstar’s upgrades and can be found on their website which is Gearstar.net
The General Motors electronic four-speed automatics are strong, can be easily upgraded and are in abundance to find. After a certain period of time, one can reach the limits that a 4L60E or a 4L65E transmission is designed to withstand, which is about 700 hp at Level 4.
Thus, from all the three choices automatic 4l65e transmission is the best and is the most efficient as well as the most versatile choice.