There’s lots of talk about making horsepower these days. Sure, this is the golden age of horsepower but all that power does little good if the transmission fails to deliver the power to the tires. Today’s new cars have anywhere from six-, eight-, and now ten-speed(!) automatics. We decided the best compromise between old and new for our mild street car called for building an electronically controlled 4L60E four-speed automatic overdrive.
We did some research and discovered there are at least four different versions of the original 700-R4 that evolved into the 4L60E/4L65E/4L70E. For this story, we will concentrate on the electronic version 4L60E. While more expensive to retrofit into an older car, the electronic versions are much simpler to tune compared to messing with TV cables and mechanical governors. We found a used 4L60E out of a small-block Chevy-powered 1999 van for $200 and decided on a budget upgrade to handle roughly 500 hp.
This decision was shaped by the knowledge there are lots of performance upgrade parts from Sonnax and TCI Automotive. Here, in Part 1, we’ll go through the buildup with professional assembly from RaceTrans owner Jimmy Galante, who has over 20 years of experience with high-performance street and drag race automatics, and especially with the 4L60E. In Part 2, we’ll detail adapting this transmission into a 1964 El Camino and controlling it with a TCI EZ-TCU controller.
This story is not a step-by-step rebuild. Frankly, just rebuilding one of these transmissions is beyond the backyard builder. Instead, we will share a few important blueprinting points that Galante has learned through his years of building the 700-R4/4L60E family of transmissions.
Once Galante disassembled our Craigslist refugee, we discovered the front pump was scored heavily and the bearing that rides on the back of the stator shaft and on top of the input drum came apart, which created excessive endplay. The 3-4 clutches were toasted and a broken 3-2 downshift spring in the valvebody was among the other maladies. On the plus side, the main wiring connector was not damaged and all the plastic lock tabs on the main interior harness did not break off from excessive heat exposure, which saved us from the cost of a new harness.
Galante says that budget rebuilders replace the pump only if it is bad. But an under-performing pump can cause low line pressure that is the cause of multiple problems because automatics rely on hydraulic pressure to apply clutches and servos. After a complete disassembly and cleaning, Galante started by checking the clearances of our rebuilt front pump—even a slight change from 0.001- to 0.002-inch internal clearance is unacceptable. He also added Sonnax’s elevated pressure regulator spring and boost valve that are part of the Performance Pack for the 4L60E.
Sonnax offers an input housing reinforcement kit that prevents the housing from cracking where the input shaft presses in place. There are several potential problem areas associated with the clutches. A big issue is excessive backing plate flex when the clutches are applied.
If you can see spending another $500, Sonnax offers the Ultimate 3-4 Smart-Tech housing combined with a stronger input shaft. This drum increases the housing depth with 0.165-inch greater capacity to accommodate more clutches without sacrificing steel thickness. To eliminate deflection, the 3-4 housing uses a 15-bolt retaining ring cap that’s far stronger than the production snap ring. We elected to remain within our budget and go with the Sonnax Input Reinforcement kit instead, which is an improvement over stock.
Galante says that his experience with the 4L60E has taught him that a tight 3-4 clutch pack clearance results in excessive drag when the clutches are not applied in First and Second gears. In the first two gears, the drum spins but insufficient clearance can cause the clutches to glaze and prematurely fail. He sets his 3-4 clutch clearance dry at 0.060-inch using Sonnax return springs to ensure the clutches fully release. You will read posts on forums that insist these springs should not be used. That advice is, at best, uninformed. Galante says 0.045-inch is too tight even with the springs. Another critical improvement is adding Sonnax’s pump, rear stator support, and wider sun gear bushings that all contribute to increasing stability.
Many performance kits from Sonnax, TCI Automotive, and others include a wider reverse-input drum band that must be used with a new drum. With this wider band over a used drum, the band spans the worn portion of the drum. Imagine the band is like a bridge over a wide “gulley,” which is the worn portion created by the original band’s narrow contact point on the stock drum. This “gulley” allows only a small portion of the band to contact the drum, which will quickly cause it to fail. The solution is to always use a new reverse-input drum. We used a new GM piece that’s included in the parts list.
Other important upgrades include Sonnax’s Second and Fourth gear servos. These servos increase the piston apply area, which both reduces band slippage during upshifts while simultaneously increasing hold pressure. The Sonnax Corvette-style servo increases the servo apply area by 35 percent over the stock V-8 version.
We also selected a Sonnax SmartShell reaction shell that offers major durability improvements over the original failure-prone piece. Sonnax includes a thrust bearing that replaces the OE bushing along with a custom roller clutch race. Galante then pre-assembled the entire trans to check total endplay. He says that adding new drums demands this endplay be verified—a step that budget rebuilders often overlook. He prefers 0.020-inch for total endplay measured at the input shaft.
Moving to the valvebody, Sonnax offers a simple 2-3 shift valve modification that Galante says offers a significant improvement in durability. For performance driving with the Sonnax modification, placing the shifter in “D3” (rather than overdrive) applies the over-run clutch in the first three gears, which improves durability by not abusing the input sprag. In the OE configuration, the over-run clutch is only applied when the shifter is in “D3” after the transmission upshifts into Third gear.
With the trans assembled, Galante bolted it on his test stand along with the TCI Breakaway 12-inch lockup converter and TCI EZ-TCU electronic controller. We set up the configuration file in mere minutes and with 12 quarts of Lucas Sure-Shift ATF, the trans performed perfectly. We made some minor modifications to when the torque converter clutch (TCC) would lock up and also changed to a 5,600-rpm WOT upshift command.
There is another Sonnax upgrade that we didn’t use that you should know about. If the 4L60E has a major sore spot, it has to be its OE 3.06:1 First gear ratio. The problem surfaces when combined with a deep (4.10:1 and numerically higher) rear gear ratio that creates an extreme overall First Gear ratio. In this example, 3.06 x 4.10 = 12.56:1 overall First gear ratio. This is equivalent to a TH400 trans with a 5.05:1 rear gear (2.48 x 5.05 = 12.54:1). The fix comes from a taller Sonnax 2.84:1, six-pinion carrier. This reduces the overall First gear ratio although the rpm drop between First and Second is the same because of the new Second gear ratio of 1.55:1. The benefit to this becomes apparent because this taller Second Gear does reduce the rpm drop between Second and Third gears. This ratio mod isn’t cheap since it commands a near-$700 price tag.
After the run-in test, Galante was impressed with the line pressure at between 250 and 275 psi at WOT, so clearly everything is working well. So now that we know our trans works, all that’s left to do is bolt it in our El Camino and enjoy the experience of an electronically controlled overdrive. Next time, we’ll dial you in with what it took to make that happen.
01. The 700-R4/4L60E has taken a lot of abuse in trans circles, but by intelligently applying the right performance parts combined with a professional blueprinting/assembly, the 4L60E has all the makings of a solid street overdrive automatic.
02. We started by talking with Gregg Nader of Sonnax, who recommended a stack of Sonnax upgrade parts that included a heavy-duty input shaft, seven clutches, an input drum reinforcement kit (the piston and seal kit), and a new GM reverse-input drum to accommodate a wider Sonnax 2-4 band and a TCI Automotive rebuild kit (not shown).
03. Once the trans was disassembled and cleaned, Galante started with some of the smaller jobs, which included disassembling the rebuilt pump for proper machining. Tight clearances help produce the high pressures necessary for a performance application.
04. One 4L60E weak point is a failed sun gear shell. Sonnax has re-engineered this into the SmartShell heavy-duty reaction shell kit that is stamped with thicker material with heat-treated shell splines, a larger bearing, and a reinforced hub area with a welded collar.
05. Sonnax supplied a wider band that increases holding power but must be used with a new reverse-input drum. A new drum is necessary to ensure proper contact with the wider band.
06. When using a stock 3-4 drum, Sonnax prefers to run the stock 4L65/70 number of seven clutches. Galante says his experience dictates using the Sonnax return springs but with a total clutch stack clearance of 0.060-inch. Clearance can be adjusted with different thickness snap rings.
07. Here, Galante installs the Sonnax return springs, which help produce clearance when the clutches are not applied in First and Second gears. The springs keep the clutches separated when the clutch is released and prevents drag.
08. Hydraulic pressure is critical for any performance-built automatic. Sonnax supplies a stronger pressure regulator spring (left) in the Performance Pack, and we also added the Sonnax Boost Valve kit (right). The Sonnax boost valve uses O-rings to better seal the valve to the body for stable pressure under load.
09. We also used larger Sonnax Second and Fourth gear servo kits. The Second gear kit shown here (left) has 18 percent more apply area (the area surrounding the raised center) than the OE Corvette servo to create a more positive 1-2 and 2-3 shift.
10. With several new parts, Galante always checks input housing endplay to the back of the pump during pre-assembly. There is a select-fit washer for this clearance, and initially he measured 0.050 but tightened this to a more-preferred 0.020-inch.
11. Final assembly doesn’t take nearly as long as all the pre-assembly checks. Galante has a three-page checklist he follows all along that helps him keep track of what has been accomplished. We counted and his 4L60E checklist has 92 separate steps!
12. With the trans assembled, Galante has built his own test stand powered by a small-block Chevy and using a narrowed 9-inch with Wilwood disc brakes to create the load. The dashboard includes both full trans line pressure and cooler line pressure readings. This trans idles in gear with 210 psi of line pressure. We were surprised to see as much as 160 psi of pressure in the cooler lines in overdrive. This is why high-quality hoses and fittings are necessary.
13. To test the trans, we had to also connect and configure the TCI EZ-TCU controller. Here, you can see that the trans is in overdrive with the torque converter locked up at 96 mph at 2,700 rpm. The PM marker is not indicated, which means the trans is in Economy Mode rather than Performance Mode (PM).
|Used 4L60E transmission||N/A||Junkyard/Craigslist|
|Sonnax 4L60E Performance Pack||HP-4L60E-01||Summit Racing|
|Sonnax Rear Stator Support Bushing||77002BT-01||Summit Racing|
|Sonnax Heavy-Duty 2-3 Shift Valve||77754-41||Summit Racing|
|Sonnax 4th Gear Super-Hold Servo||77767K||Summit Racing|
|Sonnax 2nd Gear “Corvette” Ratio Servo||77701-04K||Summit Racing|
|Sonnax Input Drum Reinforcement Kit||77733-51K||Summit Racing|
|Sonnax Transmission Band “Red”||77700-01||Summit Racing|
|Sonnax HD Input Shaft||77733-10S||Summit Racing|
|TCI Master Racing Overhaul Kit||379110||Summit Racing|
|Front Pump Assembly, Rebuilt, PWM||N/A||RaceTrans|
|GM New 4L60E Input Drum||N/A||GMPartsDirect|
|Misc. Small Replacement Parts Needed||N/A||RaceTrans|
|Labor - Custom Blueprint and Assemble||N/A||RaceTrans|
|Approximate Cost For Transmission: $2,429.98|
|TCI Flexplate SB Chevy, Ext. Bal.*||399373||Summit Racing|
|TCI Slip Yoke*||967300||Summit Racing|
|TCI EZ-TCU Controller*||302820||Summit Racing|
|TCI TPS Cable Conversion*||377400||Summit Racing|
|TCI Breakaway Torque Converter*||242800||Summit Racing|
|Fragola -6 AN Cooler Adapter Fittings (2)*||481670-BL||Summit Racing|
|Lucas Sure-Shift ATF, 12 qts*||10052||RaceTrans|
|Sonnax Smart-Tech Input Housing*||77733-06K||Summit Racing|
|Sonnax 2.84:1 Input Carrier*||77284-K||Summit Racing|
|TCI 4L60E Trans*||371016||Summit Racing|
|*Parts not used in the buildup of this transmission but included because we know you like part numbers!|