A few months back we detailed the buildup and testing of our street 4L60E trans with help from our trans man Jimmy Galante and parts from Sonnax and TCI Automotive. But that was only half the battle. Now it was time to slide our overdrive into place. But for older muscle cars there’s more to it than a straight R&R.
Because the 4L60E is an electronically controlled overdrive, it demands electronic watch-keepers like a stand-alone controller, TPS input, and converting the electronic signal into a useable speed display. Then there are the mechanical bits like the need for a shorter driveshaft and some floorpan mods. This may sound like a lot of effort. But it really isn’t much for any enterprising car builder looking for 21st century performance from a machine originally built four or five decades in the past.
Let’s start with installing the trans. Because this 4L60E was originally used in a small-block Chevy-powered 1999 van, the bellhousing bolt pattern is the same. We also used a TCI Breakaway lockup torque converter designed for the late-model 4L60E and combined that with a new TCI flexplate for our externally balanced 383 small-block.
We removed the old TH350 and temporarily bolted the 4L60E into place. Even without the crossmember in place, we noticed contact between the passenger side floor and the front servo cover. This necessitated sheetmetal massage. If this were a professional shop, we would have removed the carpet, cut the floor, raised it slightly, and welded an insert to fill the gap. Instead, we used a length of thick-wall tubing to use as a dolly to hammer a radius into the floor to create the necessary clearance for the servo cover and the 90-degree AN cooler fittings.
Because the 4L60E uses a 360-degree bellhousing face, the only place to access the converter bolts is through the starter motor hole, so we removed the starter and torqued the converter bolts to the TCI flexplate. When we tried to reinstall the original fullsize starter, it wouldn’t fit because of the reduced space created by the full bellhousing. Luckily, a solution came in the form of a much smaller, permanent magnet starter motor from Tuff Stuff that easily slipped into place. We have to classify this as a cost overrun we didn’t foresee in our original cost projection.
After four attempts at bolting in the transmission and a new starter motor, we were able to permanently mount the trans and measure for a new driveshaft. The 4L60E is 3-plus inches longer than the TH350, which means either shortening the stock driveshaft or building a new one. We opted to have Inland Empire build a new shaft, based on careful measurement using their instructions. We’re not going to publish our dimension because you should do your own. We followed Inland Empire’s instructions to ensure a proper fit.
When taking the measurements, it’s critical to place the rear axle at ride height. Because our two-post hoist allows the rear axle to droop, we first measured the stock ride height (rear axle centerline to the fender opening with the car on the ground), then placed the car on the hoist, removed the rear springs, and used a trans jack to set the rear axle at ride height. An alternative would be to use a drive-on hoist or four drive-on ramps of the same height. Inland says their steel 3.5-inch driveshaft is good for 500 hp on street tires.
While we were waiting for the driveshaft, we moved on to routing the custom AN cooler lines to the engine radiator. We elected not to install an auxiliary cooler ahead of the radiator because the converter is relatively tight and it’s a lockup. With the AN cooler lines routed using Earl’s fittings and lines, we then mounted the TCI EZ-TCU controller inside the passenger inner fender and routed the wires for the handheld unit into the interior. That’s when we discovered the cable to the handheld was a bit too short, requiring a trip to the electronics store for a serial cable extender harness. The handheld unit is powered by the cigarette lighter.
A move to the interior also presented a few minor challenges. The 4L60E offers no provision for a mechanical speedometer. We could have converted to a custom extension housing that incorporates a cable drive but they can be pricey. We also talked with Shannon Hudson at Redline Gauge Works about converting our stock speedo to electric drive.
Since our stock speedometer still worked well, he suggested SpeedHut’s new SpeedBox, which is an affordable brushless electric motor that spins a cable to drive the speedometer. The motor is commanded either by input from the 4L60E’s vehicle speed sensor (VSS) or from the included GPS antenna.
We bolted the SpeedBox in place and connected the wiring to tap into the input from the VSS. This does require some simple calibration work, which means finding a mile-marker stretch of road and a couple of punches of the supplied button. Or you can input the SpeedBox with the GPS, which requires placing a small black antenna on the dash. Both paths work great and the best part is we didn’t have to customize the dash to install an electric speedo and tach. For us, the SpeedBox was a no-brainer.
Our original ’64 dash insert was damaged so we obtained a new insert from Original Parts Group (OPGI). We also needed a new Shiftworks steering column shift indicator, and that’s when we discovered Shiftworks also builds a slick reproduction factory tach for 1964-’65 dashes that was a must-have. Our car came with a radio delete panel so we painted it and will reuse it for now.
Next, we needed to connect the column shifter to the new trans. Shiftworks offers a Kugel Komponents universal rod that uses a stainless steel shaft with adjustable spherical bearings on both ends along with an adjustable aluminum quadrant that attaches to the 4L60E shift lever. It bolted up easily.
Once our 3.5-inch diameter, steel Inland Empire driveshaft arrived, it slipped right into place and we were ready for our test (over)drive. We knew the trans shifted great because we’d spun it through several cycles on RaceTrans’ test stand. In the car, we dialed in comfortable part-throttle shift points as well as WOT shift points at 5,700 rpm on the EZ-TCU handheld. Next, we set the torque converter clutch (TCC) lockup at 40 mph. We are going to try driving around town in Drive but keep lockup early to minimize heat buildup.
Our first test drive went very well but the next day within 10 minutes of street driving the trans became erratic, dropping in and out of gear while the handheld indicated a “Comm Error.” We tried several fixes with help from TCI’s Kevin Winstead. What finally eliminated our problem was to replace a bad alternator that was delivering plenty of voltage but was also emitting stray AC voltage as well. Alternators use diodes to convert AC voltage into DC and somehow some of that AC was causing controller confusion. This is caused because the VSS signal from the sensor is also an AC frequency output. Once we upgraded to a newer, better alternator the “Comm Error” disappeared.
With that problem figured out, we decided to dive into tuning our 4L60E. The EZ-TCU aggressiveness adjustment is separate from shift firmness. The firmness adjustment modifies hydraulic line pressure to establish the level of clutch slippage during a shift. The aggressiveness strategy modifies when the trans shifts. A higher number input into the ECU delays the part-throttle upshifts. Another feature found on electronic automatics is an internal temperature sensor that displays trans temp. Want more? The EZ-TCU can also control the 4L60E with paddle shifters. All these features are additional reasons that justify our decision to go with an electronic overdrive automatic.
Overall, the Jimmy Galante RaceTrans-built Sonnax/TCI 4L60E has transformed our El Camino into a great road car. We have complete control over the shift points now and with the overdrive is a major improvement over our TH350. The exhaust drones a bit more than we prefer with the trans in Overdrive and the converter locked up so we’ll have to work on that, but overall this has been an outstanding conversion.
Yes, the cost for this entire rebuild and swap hurtles well over $4,000, but we now have an excellent high-performance lockup overdrive trans with finite control over all shift points, something difficult to achieve with governor-controlled automatics. As an additional benefit, we expect fuel mileage to improve with the 30 percent lower cruise rpm. Now, with the trans in Overdrive and the converter locked up, our 70 mph engine speed loafs at just under 2,000 rpm—which is a solid 900 rpm lower cruise rpm.
Now it’s time to hit the road and enjoy the conversion since happiness is an overdrive automatic.
1. We’ve yanked the aging TH350 and this is the first of several test-fits of our RaceTrans-rebuilt 4L60E into our 1964 El Camino.
2. This is our RaceTrans-rebuilt 4L60E in one of several test-fits before it nestled into place in the El Camino for the final time.
3. The 4L60E requires a stand-alone controller that we selected from FAST.
4. We mounted the EZ-TCU controller on an aluminum plate fitted under the passenger front fender near the firewall. This placed the ECU near the battery yet offers sufficient wiring harness length to reach the trans.
5. A crucial consideration was torque converter selection. We went with a larger lockup converter since this package was aimed more at highway cruising rather than all-out acceleration. The 12-inch TCI Breakaway specs a stall speed roughly 800 to 1,000 rpm over stock.
6. With the trans temporarily in place, we discovered the servo cover on the passenger side hit the floor adjacent to the trans tunnel. We elected to use a dolly and hammer to bend the floor. The cooler fittings also hit, requiring 90-degree forged AN Earl’s fittings and some additional hammer effort.
7. We also had to relocate our stock crossmember rearward slightly to accommodate the 4L60E. Early El Caminos use flat mounts welded to the boxed frame so we had to drill one new hole in the old mount and fabricate an extension with a second hole and weld it in to create a crossmember mount extension.
8. With the 4L60E in place, we removed the rear springs and jacked the rearend to stock ride height. Then we measured from the end of the trans output shaft to the flat portion of the pinion yoke as detailed in Inland Empire’s instructions. We sent Inland the info and they produced a great 3.5-inch steel driveshaft that slid right in place. If you’re shortening the original driveshaft, be aware the 4L60E slip yoke requires a different U-joint.
9. Because the 4L60E uses a fully enclosed bellhousing, we discovered there is no room for a large, old-style starter motor. This required a smaller, permanent magnet starter motor from Tuff Stuff, which fits much better, offers plenty of starting power, and sounds cool.
10. The original radiator in the car was junk so we updated to one of Holley’s new Frostbite aluminum radiators. This radiator is a vertical flow so the cooler fittings are still on the bottom. We used high-pressure Earl’s braided steel -6 AN lines and fittings to connect the trans to the cooler and ensure a durable, leak-free connection.
11. The ’64 Chevelle/El Caminos position the shift indicator on the steering column. We replaced the factory piece with a Shiftworks overdrive version along with an adjustable column shift linkage designed by Kugel Komponents. Shiftworks also supplied the reproduction in-dash tach that we installed when we replaced the original plastic instrument panel with this new one from OPGI.
12. Any modern electronic overdrive trans requires throttle position sensor (TPS) input. We added a Holley TPS kit to our 600-cfm electric choke Holley to deliver accurate information to the trans. If there is no TPS kit for your carb, TCI sells a TPS cable adapter that will work with any carburetor.
13. We mounted the SpeedBox inside the glovebox and routed the new speedo cable directly out the side to the speedometer. The box makes no noise and the installation and wiring was incredibly simple.
14. Because our engine uses an HEI distributor, the EZ-TCU requires this tach signal module to condition the HEI’s noisy rpm signal. This is the same module used if you are using a FAST EZ-EFI throttle body fuel injection system.
15. We configured the EZ-TCU to set WOT shifts at 5,700 rpm and then experimented with different part-throttle upshift speeds, firmness, and aggressiveness until we created a pattern that we preferred. All of this only took a few minutes with simple keystrokes.
16. With the trans installed and tuned, we took the El Camino out for several test drives. Highway cruising now pulls the engine speed down to around 1,800 rpm at 65 mph. That might be worth 1-2 mpg on the highway, helped by the lockup converter.
|TCI Flexplate SB Chevy, Ext. Bal.||399373||Summit Racing|
|Sonnax Slip yoke||12051HP||Summit Racing|
|TCI EZ-TCU controller||302820||Summit Racing|
|TCI TPS carb conversion||377400||Summit Racing|
|TCI Breakaway torque converter||242800||Summit Racing|
|Fragola -6 AN cooler adapter fittings||481670-BL||Summit Racing|
|Lucas Sure Shift ATF, 12 qts||10052||RaceTrans|
|SpeedHut SpeedBox||G-SNDR-SB-22||RedLine Gauge|
|Holley TPS for Holley carb||534-202||Summit Racing|
|Shiftworks column shift indicator||S139||Shiftworks|
|Shiftworks Kugel column adapter||KK02||Shiftworks|
|Shiftworks 4L60E shift adapter||4LEKit||Shiftworks|
|Shiftworks in-dash tachometer||S510-1||Shiftworks|
|Pioneer trans mount||622378||Summit Racing|
|Earl’s 90-degree AN fittings (4)||809006ERL||Summit Racing|
|Earl’s -6 male to 1/4 pipe adapters (2)||981606ERL||Summit Racing|
|Earl’s -6 AN hose, 10-ft length||410006ERL||Summit Racing|
|Frostbite alum. 3-row radiator||FB-113||Summit Racing|
|Tuff Stuff perm. Magnet starter motor||6510NB||Summit Racing|
|Inland Empire Driveshaft, steel 3.5”||SK-31-35-83C||Inland Empire|