How to Install a Stall Converter: Boost Your 5.7l Hemi’s Performance Step-by-step

Upgrading to a stall converter is one of the most effective modifications you can make to unlock the true potential of your 5.7L HEMI engine. By allowing the engine to reach a higher RPM before the transmission engages, a stall converter transforms your vehicle’s off-the-line punch and mid-range acceleration. Whether you’re building a weekend warrior, a track toy, or a daily driver that demands more snap, this guide will walk you through every step of the installation process with precision and safety as the top priorities.

Understanding the Stall Converter

A stall converter is simply a performance-oriented torque converter that has a higher “stall speed” than the factory unit. The stall speed is the RPM at which the converter begins to transfer torque to the transmission. A stock torque converter typically stalls around 1,200–1,600 RPM, which is ideal for fuel economy and smooth city driving. A performance stall converter for a 5.7L HEMI might be rated at 2,200–3,200 RPM, depending on your camshaft, intake, and overall power goals.

Why does this matter? When you launch from a stop, the higher stall speed lets the engine spin up into its power band before the vehicle moves. This means the engine is already making peak torque by the time the converter fully engages, resulting in a stronger, more violent launch. However, choosing the wrong stall speed can compromise drivability—too high and the car may feel “loose” in traffic; too low and you won’t see a benefit.

How It Works on a 5.7L HEMI

The 5.7L HEMI is known for its broad torque curve, but it also responds well to higher RPM because the cylinder heads and camshafts benefit from airflow velocity. A converter in the 2,400–2,800 RPM range pairs excellently with a mild cam or bolt-ons. For heavily modified HEMIs (e.g., supercharged or large cam), stall speeds around 3,200+ RPM may be necessary to keep the engine in the power band. Always consult your converter manufacturer and dyno data for the best match.

Choosing the Right Stall Converter

Before you even reach for a wrench, you must select a converter that suits your vehicle’s combination. Here are the key factors to consider:

Vehicle Weight and Gearing: Heavier vehicles or tall rear gears (e.g., 3.21:1) need a higher stall to get the car moving hard. Lightweight cars with 4.10:1 gears can use a lower stall.
Camshaft Profile: A cam with a later intake valve closing (IVC) event shifts the power band upward. Match the stall speed to the RPM where the cam starts making torque.
Intended Use: Street/strip converters often have a looser feel at low RPM, while dedicated drag converters are tighter for better consistency. For a daily driver, stay at or under 2,600 RPM.
Transmission Type: Most 5.7L HEMIs use a 545RFE, 65RFE, or A580 transmission. Ensure the converter is designed for your specific transmission bellhousing bolt pattern and input shaft spline count.

For expert recommendations, check out resources from Hughes Performance or Edge Racing Converters. They offer application-specific converters for the HEMI platform.

Tools and Materials Needed

Gather everything before you start—nothing kills momentum like a trip to the parts store mid-job. Here’s a comprehensive list:

Torque wrench (lb-ft and lb-in scales)
Deep socket set (metric: 10mm, 13mm, 15mm, 18mm; and SAE if needed)
Transmission jack (or a sturdy floor jack with a block of wood)
New stall converter (properly selected for your HEMI)
Transmission fluid – Use the correct type: Mopar ATF+4 or equivalent for most 5.7L HEMI automatics (check your service manual)
New transmission filter and pan gasket
Drain pan (at least 2-gallon capacity)
Safety glasses and mechanic’s gloves
Jack stands (4-ton capacity minimum; never rely on a hydraulic jack alone)
Breaker bar and extensions
Pry bar (for loosening tight components)
Rags and brake cleaner
Thread locker (medium strength) for converter bolts

Optional but Recommended

Flex plate inspection tool or mirror
Dial indicator to check converter depth
Engine support bar (if removing transmission crossmember)
Infrared thermometer for post-install temperature checks

Safety and Preparation Steps

Before you touch a single bolt, secure your workspace and vehicle. Follow these critical steps:

Work on level ground: An uneven floor can cause the vehicle to shift dangerously.
Disconnect the battery: Remove the negative terminal to prevent accidental starter engagement or electrical shorts while working near the transmission.
Lift and support the vehicle: Use a floor jack to raise the front high enough to slide under. Place jack stands under the frame rails. For 2WD Rams or Chargers/Challengers, also support the transmission with a second jack or a transmission jack.
Allow the engine to cool: Transmission fluid and the converter itself retain heat. Let the vehicle sit for at least an hour after shutdown.
Drain the transmission fluid: Position your drain pan under the transmission pan. Loosen the pan bolts carefully—some fluid will spill. Remove the pan completely and pour out the remaining fluid.

If you’re working on a HEMI-powered Ram 1500 or a Challenger, note that the transmission crossmember may need to be partially lowered to access the torque converter bolts. Support the transmission with a jack before removing the crossmember.

Removing the Old Torque Converter

With the transmission pan removed and fluid drained, proceed to extract the factory converter.

Remove the transmission filter: Unclip or unscrew the filter from the valve body. This exposes the pump and converter hub.
Mark the flex plate and converter relationship: Before unbolting, use a paint marker to indicate the position of one converter bolt relative to the flex plate. This helps during reinstallation.
Access the converter bolts: Rotate the engine manually using a socket on the crankshaft balancer bolt (19mm or 21mm). You’ll see three or four converter bolts through the starter opening or through an access hole in the bellhousing. Some HEMIs have a removable cover plate on the bellhousing—remove that for direct access.
Unbolt the converter: Use a socket and breaker bar. The bolts are typically 10mm or 13mm and often have thread locker applied. Remove all bolts and set them aside in a labeled bag.
Slide the converter out: With the bolts gone, gently pull the converter toward the rear of the transmission. It may be tight; use a pry bar between the converter pads and the flex plate to break any adhesion. The converter should slide out of the pump hub. Place the old converter in the drain pan—do not reuse a used converter without professional cleaning.

While the converter is out, inspect the flex plate for cracks, warping, or missing teeth on the starter ring gear. Replace the flex plate if any damage is found. Also check the crankshaft rear seal for leaks.

Installing the Stall Converter

This is the most critical step. An improperly seated converter can destroy the transmission pump on startup.

Lubricate the converter hub: Apply a light film of transmission fluid to the pump drive hub and the front bushing bore of the transmission. Do not use grease.
Align the splines: Hold the converter level and carefully insert it into the transmission. Rotate the converter slowly until you feel it slide over the input shaft and stator splines. You should feel it engage and then drop into the pump.
Check the seating depth: Once seated, the converter should be at a certain distance from the bellhousing face (usually 0.125–0.200 inches depending on the transmission). Use a feeler gauge or a ruler. If the converter is not fully seated, it will not engage the pump properly and will hit the flex plate when you tighten the bolts. When properly seated, you can easily rock the converter with a slight rotational wiggle.
Bolt the converter to the flex plate: Rotate the engine so you can access each converter pad. Install the converter bolts using the marks you made earlier. Apply medium-strength thread locker (e.g., Loctite 242) to each bolt. Torque to the manufacturer’s specification—typically 45-55 lb-ft for most HEMI applications. Check your transmission service manual for exact values.
Verify rotation: After bolting, rotate the engine by hand again to ensure the converter turns freely without binding or rubbing against bellhousing.

If you feel resistance or hear scraping, stop immediately. Most likely the converter is not fully seated. Remove the bolts, re-seat the converter, and try again. Never force the converter into place.

Reassembling the Transmission

With the new converter installed, it’s time to button everything up.

Install a new filter: Push the new filter into the valve body until it clicks or seats firmly. Many HEMI transmissions use a filter with a rubber O-ring—lube the O-ring with fluid.
Replace the pan gasket and pan: Clean the mating surfaces. Place a new gasket on the pan or use a reusable silicone gasket. Tighten bolts in a crisscross pattern to the manufacturer’s torque (usually 12-15 lb-ft).
Reinstall the transmission crossmember (if removed). Torque the crossmember bolts to spec.
Reconnect the battery.
Refill with transmission fluid: Pour in the recommended ATF+4 through the dipstick tube. The exact amount depends on transmission and cooler capacity—expect 4-6 quarts initially, but you will need to add more after startup.

Testing the Installation

Testing is not optional. A simple fire-and-forget approach can damage your transmission.

Initial Start-Up and Check

Start the engine and let it idle. Immediately check for fluid leaks around the pan, bellhousing, and cooler lines.
With the engine running and parking brake firmly engaged, cycle through all gear positions (P, R, N, D) pausing 5 seconds in each. This fills the converter.
Check the transmission fluid level on the dipstick with the engine at normal operating temperature and in Park. Add fluid as needed to reach the “HOT” line.
Listen for unusual noises: a whine from the converter, a clunk, or a metallic rattle. Any abnormal sound means something is wrong—shut down immediately and investigate.

Stall Test (Optional but Recommended)

A stall test confirms the converter is functioning at its rated speed. Perform this in a safe, open area. Do not overheat the transmission.

Warm up the transmission to operating temperature.
Block all wheels and set the parking brake firmly.
Push the brake pedal hard with your left foot. With your right foot, press the accelerator to the floor and note the RPM. Release the accelerator as soon as the RPM stops climbing (usually within 2-3 seconds).
The indicated RPM should be within 200 RPM of your converter’s advertised stall speed. If it’s significantly lower, the engine may be underpowered or the converter may be too tight. If it’s much higher, the converter may be slipping excessively.

Do not perform a stall test for more than 5 seconds at a time. Allow 30 seconds of cool-down between tests.

Road Test

Take the vehicle for a gentle test drive. Gradually increase throttle loads. Verify that the transmission shifts normally through all gears. The converter should lock up properly (if equipped with a lockup clutch). Heavy throttle launches should result in stronger acceleration. Note any vibrations or harsh shifts.

Troubleshooting Common Issues

Even with careful installation, problems can arise. Here are the most frequent issues and solutions:

Symptom	Possible Cause	Solution
Converter not locking up	Incorrect converter, wiring issue, or TCM tuning	Verify converter has lockup piston. Check harness and torque converter clutch solenoid. Tune the transmission controller for the new converter.
Vibration at highway speeds	Converter imbalance, flex plate runout, or improper seating	Check converter seating depth. Inspect flex plate for damage. Dynamic balancing may be needed.
Transmission overheating	High stall converter generating extra heat, cooler inadequate	Upgrade to a larger external transmission cooler with a fan. Use synthetic ATF+4. Monitor temps with a gauge.
Fluid leaks from bellhousing	Front seal damaged or converter hub score	Inspect front seal; replace if torn. Check converter hub for wear. Re-seal with proper installer tool.
Harsh or delayed shifts	Low fluid, incorrect stall speed, or valve body issues	Recheck fluid level. Consider a transmission tune. If the stall is drastically different from stock, recalibrate shift points.

For deeper troubleshooting, forums like RamForum.com and HEMITest.com have dedicated sections for transmission and converter issues with the 5.7L platform.

Conclusion

Installing a stall converter in your 5.7L HEMI is a rewarding upgrade that completely changes the character of your vehicle. By understanding the principles of stall speed, choosing the right converter, and following the detailed installation procedure outlined above, you can achieve a dramatic improvement in acceleration without sacrificing reliability. Remember to always prioritize safety, double-check your fluid levels, and give your transmission proper cool-down after aggressive runs. If at any point the job seems overwhelming, don’t hesitate to consult a professional transmission shop—protecting your investment is worth the peace of mind.

With your new stall converter in place, get ready to feel the difference every time you leave a stoplight. Your HEMI will thank you.