seeOne popular transmission upgrade these days is in the form of GM’s electronically controlled overdrives, namely the 4L60e, 4L70e, and 4L80e transmissions. They’ll bolt to just about any small-block GM, especially LS-series engines, but when it comes to a small-block Mopar, Project Track Attack required something more than the basic 4L60e. It doesn’t bolt to a Mopar at all, and yet the overdrive choice from Ma Mopar — the A518 — is not exactly beefy enough for what we plan to do with our Plymouth.
For starters, we previously opted to install a low gearset in our TF727 to get a little better performance out of the hole since we also wanted the best of the other end of the performance spectrum: fuel mileage. Running a 3.23:1 rearend was great for fuel economy with our taller tires, and that low gearset helped us get up to speed just a little quicker.
Then, we decided to track the car with a 4L60e transmission. The drawback was our 4L60e had even lower gears than the TF727. We needed a solution, and Performance Automatic (PA) had the answer for us. But, instead of providing a stock-based transmission with different gearing, the Frederick, Maryland, transmission experts stepped up the performance factor for us by giving us better gearing by way of its Close Ratio Power Planet.
How Does Transmission Gearing Affect Performance?
The chart below shows how our gearing changed through the years to where it is now with this build. You can see the 4L60e went to a near-granny gear. With the gap between Second and Third gears on the track, we found ourselves coming out of turns either revving too high for 2nd or too low for 3rd — not quite in the powerband with the TF727. The 4L60e gearing took us further from our goals.
|Transmission||1st Gear||2nd Gear||3rd Gear||O/D|
|TF727 Low Gear Set||2.77:1||1.57:1||1:1||N/A|
|4L60e Close Ratio||2.84:1||1.55:1||1:1||0.7:1|
PA’s Close Ratio Power Planet took us from the previous wide-ratio to a much more performance-oriented, close-ratio gearset. Initially, when we weren’t on a tear trying to better lap times at Willow Springs, the combination of a low gearset and freeway gears gave us a little bit of both worlds. We could live with the 20 mpg we saw with our completely stock 318 Polyhead engine. Those gears gave us some oomph off the line, while the 3.23:1 rear gear gave us lower rpm and higher mileage.
Then we found ourselves at Willow Springs one day, and we weren’t doing so well, barely mustering a paltry 80 MPH down the front straight. By then, our Poly had been pumped up a little with a fresh build sporting dual quad fuel injection and ported & polished heads. But we still wanted something more suited to the new 408 stroker we had planned out, and also something that would allow us to get back closer to the 20 MPG we had seen a decade ago. We achieved better MPG with the 4L60e, thanks to the overdrive gear, and we knew we had a stronger transmission, but those gears – they weren’t right for our purposes.
These days, we’re happy with the overdrive. That doesn’t change at all, other than pushing a few more ponies with the new build — in the range of about 125- to 150-more horsepower. The Power Planet from PA allows us to stay closer to the powerband when racing out on the track. It equates to better on-street performance and a happier exit strategy for Turn 9 at Willow Springs.
The stock planet set for the 4L60e is a weaker four-pinion design. While it’s efficient and acceptable for the stock transmission, it’s limited in power capabilities and is often the cause for breakage or gear problems. The six-pinion carrier of the Power Planet provides a more robust set of planetary gears while closing in the gearing, allowing engines to stay within the powerband, improve performance, and provide consistent lap times. Staying within the powerband also allows longer pulls in First and Second gears, rather than the slow-motion pulls we saw with the wide gear ratio of the stock 4L60e gearing.
The carrier’s gears provide more durability for high-horsepower applications while being precision ground to OE specs. The captured bearing is a thicker late-design unit, and the thrust washers have a PTFE coated material, which is highly wear-resistant. Oil is directed to the pinion pins via lube channels. The overall unit requires no special tools or machining, yet can be disassembled for service and inspection. While we didn’t have any issues with our somewhat anemic Polyhead 318, the 408ci LA will be more than twice the power once we get done with it. So, we were ready to strengthen up the transmission and fix our gearing problem.
Stronger Internals Mean Better Power Handling
The gearing wasn’t the only place we made improvements over a stock 4L60e. When planning to do a gear swap, it’s a good idea to freshen up and go bigger and better with the rest of the transmission. This is where the team at PA came to the rescue to explain what they’ve done to beef up the transmission.
Rich Carlton, the owner of Performance Automatic, tells us, “Internally, Raybestos Stage 1 Frictions were used in forward and overrun clutch packs for increased horsepower and torque handling.” He said these provide higher heat resistance and enhanced shift feel. He continued, “Raybestos GEN 2 High Static race frictions for the reverse input and low/reverse clutch packs were also used to handle increased power and torque.”
Kolene steels were used, which provide higher heat resistance and fatigue resistance, enhancing wear from 200 to 500-percent. “For the ¾ clutch pack, we used a Raybestos Z Pak to achieve increased torque and horsepower,” Rich continued. “It also eliminates coning under high stress.”
For more positive shifts and increased holding power, a performance 2-4 servo was installed. An upgraded valvebody kit to improve shift quality and feel was also implemented, along with a Raybestos Pro Series 2-4 band. A heavy-duty input shaft and drum with a reinforcement sleeve strengthen the input drum, which Rich tells us is prone to break. A cryogenic-hardened input shaft is used, and all of these upgrades rate the transmission capable of handling 650 to 700 horsepower.
Covering up all of these upgrades, we went with an aluminum pan with a drain plug. The aluminum pan helps dissipate heat better than the OE steel pan, which lacked the drain plug allowing for easier fluid services. The Raybestos Pro Series pan has a higher holding capacity, heat-treated anchors, and is resistant to extreme heat.
Service And Performance Of Our New Transmission
PA recommends using Dextron 3, 4, or 5 for the transmission. Also, the fluid level and condition should be checked monthly. Transmission service depends on how (and how much) the car is driven. With the way we track the car one week, then drive it long distances the following week, it’s in our best interest to follow through on these processes. Rich says, “At the very least, change the fluid once every year or two. Check the fluid after every race. If fluid starts to smell or change color, service the transmission at that time.”
Since we added a pressure sender to monitor our transmission, both on the street and the track, we figured we would see what kind of pressures we should see. Fortunately, our sender is tied into our Dakota Digital VHX gauges, via its BIM module, to warn of pressures that get a little too high or low. Rich stated, “With this transmission, you should see pressures around 65 to 75psi at idle. At full throttle, you should see pressures between 150 to 215psi.” He reminded us these all depend on the tune and settings of our TCI Auto electronic transmission controller.
Temperatures are controlled with our Derale transmission controller, which activates a dedicated cooling fan once the temperature reaches above 185-degrees. The fan is thermostatically controlled because the temperature needs to be between 170 and 200-degrees; above 225 is when most transmission fluids break down. “Transmission fluid is the lifeline of the transmission, so the cooler you can keep the temperature, the better it is,” Rich told us.
The installation isn’t the only important part of this upgrade. We called on Fragola Performance Systems to help us out with some AN fittings for the transmission cooler lines, and DEI for heat insulation sleeves to protect the tubes, hoses, and shifter cable from residual heat coming off the headers and exhaust.
So how does the new transmission perform out on the road? Can we detect a distinct difference? One problem we had before with the wide-ratio stock gearing was the confusion at low throttle — it almost seemed like we had granny gears for First. Unless we romped on it, the car wanted to be in Second gear at each intersection. With our new Performance Automatic 4L60e in place, shifts are smoother and not spread so far apart — that keeps us in the powerband from gear to gear.
From the intersections, there’s a definite shift into Second. As we approach the next light, it’s downshifting as we come to a stop. Of course, if you play around with the settings on the transmission controller, you’ll find it will react differently, so it’s imperative to make sure you go through all of the settings to see what works best for your driving style. It’s difficult for someone in an office half a country away to tell you what’s best for your vehicle, so the most you should expect are some starting points. From there, make some changes and see how the car reacts — away from regular traffic, of course.
We also took advantage of the bump-shift mode on our new Lokar Sport Shifter, providing electronic shifts at our discretion, giving us full control of our shifting needs. A couple of connections to our TCI Auto EZ-TCU transmission controller and manual mode was at our hands. We’ll follow up with more info about our Sport Shifter in an upcoming article, as well as another trip out to Willow Springs to put our new Performance Automatic 4L60e through its paces. Keep them in mind when you’re looking for a performance build for your Ford, GM, or Mopar. They’ll build one to suit your driving style with performance in mind.