If you’ve got a Ram Heavy Duty truck with a 6.7L Cummins—or you’re shopping for one—you’ve likely faced the big transmission question: Aisin or 68RFE? And it’s not just a badge thing. It’s a real, practical fork in the road that determines how much power you can push, how well your truck shifts, and just how frustrated you’ll get when it’s time to upgrade.

Let’s break down the pros and cons of both, dig into the current state of aftermarket support, and talk about why so many experienced owners choose to build a 68RFE over trying to tame an Aisin.

Who Gets What?

• The 68RFE comes standard in most Ram 2500s and many 3500s with the standard-output Cummins.
• The Aisin AS69RC is reserved for Ram 3500s equipped with the High Output Cummins engine—rated at 400 hp and 1,000 lb-ft of torque from the factory.

It’s easy to assume the Aisin is “better” because it’s only offered behind the big-torque engine. And while the Aisin is technically stronger out of the box, the conversation changes fast once you start thinking about modifications.

Built for Work, But Not for Tuning

The Aisin AS69RC was designed in Japan for medium-duty commercial trucks. It’s heavy-duty, yes—but it’s also heavily controlled. The TCM (transmission control module) is locked down tight, making tuning almost impossible.

You can’t command higher line pressure, change shift strategy, or truly dial in the transmission unless you go through an expensive and limited standalone conversion—or run it stock and hope it plays nice.

Many owners report clunky shifts, long delays between park/reverse/drive, and strange behavior under towing or throttle—especially when the truck is tuned but the Aisin is not. And because it’s not widely supported by tuners like EFI Live or HP Tuners, your options for solving those problems are limited.

The 68RFE: Not Perfect, but Proven

The 68RFE, on the other hand, is Chrysler’s in-house transmission—originally based on the 545RFE platform. It’s had a rocky history, especially in early models, but the aftermarket has embraced it. In a big way.

You’ve got full TCM tuning support. You’ve got converters, coolers, billet shafts, upgraded valve bodies, and dozens of rebuild paths and power levels. And once you address its known weak spots—namely the torque converter and clutches—it becomes a surprisingly capable transmission.

In fact, many seasoned builders now say a well-built 68RFE can handle more abuse than a stock Aisin—and drive better doing it.

Aisin: A Tough Nut to Crack

Here at Alligator Performance, we’re working closely with our partners on developing true Stage 2 and Stage 3 Aisin upgrades. But we’ll be straight with you—it’s a tough nut to crack.

Parts are expensive. Cores are scarce. And tuning? The TCM isn’t giving up its secrets easily, so unless you’re willing to go full race setup? (and race setup budget…) The 68RFE is the winner.

There are shops beginning to offer upgraded Aisin rebuilds, and we’re watching all the options the specialists are developing—but we’re not going to call something “bulletproof” until we’ve seen it take the hits and come back swinging. So if you’re holding out for a truly tunable, proven Aisin solution, just know it’s a work in progress—not a solved problem.

Head-to-Head Breakdown

The Smart Move for Builders?

If you’re out of warranty—or getting close—and you’re planning to tune or tow regularly, you’re not wrong to buy a non-HO truck and focus on building the 68RFE. Especially if it’s a 2020-2024 model with low miles and no issues.

That platform gives you:

• Full tuning control
• Affordable rebuild options
• Flexibility to upgrade in stages
• A huge support network from shops and fellow owners

For all its factory torque, the Aisin is still frustrating to work with if your goal is to tune, modify, or push the platform hard. And until the aftermarket catches up, it’ll stay that way.

Which One Should You Choose?

Go Aisin if:

• You plan to keep your truck stock or very lightly modified
• You tow extremely heavy and want a factory HO Cummins
• You’re okay with limited tuning options and clunky shifts

Go 68RFE if:

• You plan to tune, upgrade, or push power
• You want aftermarket flexibility
• You’re out of warranty and ready to build your truck your way

Thinking of building your 68RFE the right way?

Alligator Performance carries everything from complete transmissions to converters, coolers, valve bodies, and more—handpicked for 6.7L Cummins trucks running the 68RFE. Whether you're replacing a worn-out stocker or building for 700+ horsepower, we’ve got your back.

Shop 68RFE Upgrades at Alligator Performance

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Final Take

Both transmissions have their place—but only one is truly buildable right now.

If you’ve got a 68RFE and it’s starting to show signs of wear, you’re in a great position. Build it right, and you’ll have a transmission that shifts crisp, holds power, and stays cool under pressure.

If you’ve got an Aisin? We’re not leaving you out in the cold. Alligator Performance is testing solutions and working closely with trusted builders to crack the Aisin challenge. We’re not done yet—but we’re not giving up either.

Ready to start your build? Let’s talk converters, coolers, and complete transmissions. We’ll help you choose the right path—no guesswork, no regrets.

Pros & Cons on your 2019-2025 Ram Cummins Transmission