Installing a high-stall torque converter such as the ProTorque 3500 is one of the most effective upgrades for unlocking serious horsepower in a performance vehicle. While a stock torque converter is designed for everyday driving, a 3500 RPM stall converter allows the engine to reach a higher RPM before engaging, letting the engine build boost or cammed power on the starting line. This guide provides a complete, step-by-step walkthrough for installing a ProTorque 3500 stall converter safely and correctly, with the potential for over 100 horsepower gains when paired with proper tuning.

Understanding Stall Speed and Torque Converters

The stall speed of a torque converter is the RPM at which the converter transfers power from the engine to the transmission under load. A stock converter may stall around 1800-2200 RPM; a ProTorque 3500 stall converter raises that window to 3500 RPM. This allows the engine to remain in its power band during launch, keeping the turbo spooled or the cam’s peak torque available. The result is dramatically improved acceleration from a standstill, especially for forced-induction or high-compression engines. Gains of 100+ horsepower are realistic when the converter is matched to the engine’s power curve and the vehicle is retuned.

Why Choose a ProTorque 3500 Stall Converter?

ProTorque is a respected name in high-performance torque converters, known for precision manufacturing and durability. The 3500 stall converter features a billet cover, triple-disc clutch, and furnace-brazed fins for maximum heat dissipation. It’s compatible with 4L60E, 4L80E, and other common GM transmissions, as well as many Ford and Mopar platforms. Before installation, verify that the ProTorque 3500 matches your transmission model and engine combination. Always refer to ProTorque’s official site for specific part numbers and compatibility.

Tools and Materials Needed

Having the right tools on hand prevents frustration and ensures a safe installation. Gather the following items before beginning:

  • ProTorque 3500 stall converter – pre-filled or with priming instructions
  • Socket and wrench sets – metric and SAE as needed
  • Torque wrench – for flexplate bolts and transmission mount bolts
  • Transmission jack or a sturdy floor jack with a transmission adapter
  • Fluid catch pan – large enough to hold old transmission fluid (8-15 quarts)
  • New transmission fluid – use the spec recommended for your trans (e.g., Dexron VI, Mercon V, or Type F)
  • Pry bar or large screwdriver – to rotate the flexplate
  • Safety glasses and gloves
  • Jack stands – never work under a vehicle supported only by a jack
  • Transmission dipstick funnel (or long flexible funnel)
  • Thread locker (medium strength) – for flexplate bolts
  • Shop rags and brake cleaner – for cleaning mating surfaces
  • Optional: transmission oil pump priming tool if the converter is not pre-lubed

Preparation Steps

Preparation is critical for a smooth installation. Follow these steps to ensure safety and efficiency:

  1. Park on level ground and engage the parking brake. Chock the rear wheels.
  2. Disconnect the battery (negative terminal first) to prevent electrical shorts and accidental starter engagement.
  3. Raise the vehicle securely on jack stands. Use ramps for the rear if necessary, but ensure the transmission pan is accessible.
  4. Drain the transmission fluid by removing the pan and filter. Allow the fluid to cool before handling. Dispose of old fluid properly.
  5. Remove the transmission crossmember and support the transmission with a jack. You may need to lower the transmission slightly to access the top bellhousing bolts.
  6. Remove the inspection cover on the bellhousing to expose the torque converter drain plug (if equipped) and flexplate bolts. On some vehicles, the starter must be removed first.
  7. Mark the flexplate and crankshaft orientation if you plan to reuse the flexplate. However, many high-horsepower builds benefit from an upgraded SFI-rated flexplate – consider replacing it now.

For detailed vehicle-specific procedures, consult the factory service manual or a reliable online resource like Hot Rod’s torque converter install guide.

Removing the Old Torque Converter

Removing the stock or previous converter requires careful alignment and attention to bolts that may be thread-locked. Follow these steps:

  1. Rotate the engine using a socket on the crankshaft bolt (or a pry bar on the flexplate teeth) to access each flexplate bolt. Use a 15mm or ⅝” socket depending on the converter.
  2. Remove the flexplate bolts one by one. Keep them organized – they may be different lengths if the flexplate is factory. Apply a drop of thread locker to each when reinstalling.
  3. Push the old converter back into the transmission bellhousing. It should slide freely – if it hangs, rock it slightly while pushing.
  4. Drain the old converter by orienting it so the pump drive hub is facing up, then pour out as much fluid as possible. This reduces mess when handling the converter.
  5. Lower the transmission jack slightly to gain clearance, then slide the old converter out from the transmission. Take care not to damage the pump drive teeth or transmission seal.
  6. Inspect the flexplate for cracks or excessive runout. If any damage is present, replace it – a catastrophic failure can happen at high RPM. Also check the pilot bore in the crankshaft for debris or wear.

Note: Some transmissions (like the 4L60E) have a pump that can be damaged if the converter is not fully seated during removal or installation. Always ensure the converter is fully disengaged from the pump before pulling the transmission back.

Installing the ProTorque 3500 Stall Converter

This is the most critical part of the installation. The ProTorque 3500 must be properly seated in the transmission oil pump to avoid costly damage.

  1. Clean the pilot hub of the new converter with brake cleaner. Apply a thin coat of transmission assembly lube or petroleum jelly to the hub and the pump drive tangs.
  2. Check converter depth before installation. Measure from the flexplate mounting pad on the converter to the front face of the transmission bellhousing. This distance should be approximately 1/8” to 3/8” less than the distance from the flexplate to the bellhousing face – this ensures the converter will not bottom out and can move slightly with thermal expansion. Consult ProTorque’s instructions for specific measurements.
  3. Install the converter onto the transmission input shaft. Align the notches in the converter tangs with the pump drive. Push the converter straight in while rotating it slightly. It should seat with a noticeable “clunk” or slight resistance.
  4. Verify full engagement: With the converter fully seated, the distance from the bellhousing face to the converter’s flexplate mounting pads should be uniform. You should be able to spin the converter by hand with some resistance from the pump. If it spins freely or feels obstructed, the converter may not be fully engaged – remove and reinstall.
  5. Install the flexplate bolts in a star pattern. Torque to the manufacturer’s specification (typically 35-45 ft-lb for small bolts, 65-85 ft-lb for larger). Use thread locker on the bolts.
  6. Rotate the engine to verify that the converter does not rub against the bellhousing or flexplate. Listen for any grinding or binding.
  7. Reinstall the inspection cover and ensure it clears the converter weights (if any). Some high-stall converters have external weights that require clearance.

Pro Tip: If you’re installing a ProTorque converter with an anti-ballooning plate (common in high-horsepower builds), verify that the plate is oriented correctly and does not interfere with the flexplate bolts.

Common Mistakes to Avoid

Many installation failures stem from improper converter seating. Avoid these pitfalls:

  • Forcing the converter – If it doesn’t slide fully into the pump, stop and recheck alignment. Forcing can damage pump seals.
  • Ignoring converter fill – A dry converter can cause immediate pump failure. Follow proper priming procedures.
  • Reusing old flexplate bolts – Over-torqued or stretched bolts can snap. Replace them with new ARP or OEM bolts.
  • Skipping the converter drain – Mixing old ATF with new fluid can compromise friction modifiers and cause shift issues.

For further troubleshooting, the Super Chevy torque converter installation article offers additional insight from experienced transmission builders.

Reconnecting the Transmission and Refilling Fluid

With the converter installed and secured, reassemble the transmission and refill the fluid.

  1. Raise the transmission into position and install the bellhousing bolts. Torque them to factory spec (usually 30-40 ft-lb).
  2. Reinstall the crossmember and transmission mount.
  3. Connect the transmission cooler lines (if removed) and check for kinks.
  4. Install a new transmission filter and reinstall the pan with a new gasket. Torque pan bolts to spec in a cross pattern.
  5. Fill the transmission through the dipstick tube. Use a funnel designed for transmission fluid
  6. Prime the converter – The ProTorque 3500 may come pre-filled with fluid, but if not, you must add approximately 4-6 quarts directly into the converter before installation (check manufacturer instructions). If you installed a dry converter, add fluid after the transmission is bolted but before starting the engine. Often, pouring fluid into the dipstick tube while the transmission is still on the jack will fill the converter as it sits. However, the safest method is to fill the converter per ProTorque’s specs.
  7. Start the engine and allow it to idle. Immediately check the fluid level and top off. Cycle the gear selectors (P to R to N to D) while holding your foot on the brake to circulate fluid. Recheck level. The engine should be at operating temperature for an accurate read.

Important: Do not race the engine or perform a full-throttle launch until the transmission fluid has been properly cycled and the converter has been heat-cycled a few times. The clutch friction material in the converter needs to break in.

Final Steps and Testing

After refilling and priming, perform these final checks and tests:

  1. Reconnect the battery (positive first, then negative).
  2. Check for leaks at the bellhousing, transmission pan, cooler lines, and dipstick tube. Tighten any suspect fittings.
  3. Lower the vehicle to the ground.
  4. Test drive gently – Drive at low speeds, letting the transmission shift normally. Listen for unusual whining or shuddering. Pay attention to the RPM vs vehicle speed relationship.
  5. Perform a stall test (if your tuner approves): With the vehicle in gear, foot firmly on the brake, slowly increase throttle until the engine RPM stops rising. The converter should flash to approximately 3500 RPM. Do not hold it at stall for more than 5 seconds to avoid overheating.
  6. Monitor transmission temperature – High stall converters generate more heat. Consider adding an external cooler if your vehicle lacks one, especially for street-driven cars that may see stop-and-go traffic.
  7. Reset the ECU/TCU if needed. Many modern transmissions have adaptive learning that may need to be reset after a converter change. Use a scan tool or follow manufacturer procedure.

If you experience vibrations or a slipping feeling, recheck converter seating and flexplate alignment. A minor misalignment can cause premature pump wear. For tuning guidance specific to stall converter upgrades, visit EFI University’s tuning resources.

Performance Gains and Tuning Considerations

A ProTorque 3500 stall converter alone will not deliver 100+ horsepower – it simply enables the engine to work in its powerband. To realize the full potential, you must pair the converter with engine modifications (camshaft, headers, forced induction) and professional tuning. The converter allows the engine to launch at 3500 RPM instead of 2000 RPM, which means your turbo is already spooled or your cam’s peak torque is instantly available. On a dyno, this can translate to 0-60 MPH times dropping by a full second or more, depending on traction.

When the converter is matched to your engine’s torque curve, the effective horsepower at the wheels can increase significantly – up to 100 HP in some street/strip builds. However, the drivability trade-off is lower fuel economy and increased heat during stop-and-go driving. Plan your transmission cooler and driving habits accordingly.

Conclusion

Installing a ProTorque 3500 stall converter is a straightforward project for an experienced DIY mechanic, but it demands precision and patience. By following this step-by-step guide, you can avoid common mistakes and achieve a reliable installation that unlocks the full potential of your engine. When combined with proper tuning, the 3500 stall converter can transform your car’s acceleration, delivering the “kick in the pants” that serious enthusiasts chase. Always consult ProTorque’s official instructions for your specific converter model, and do not hesitate to seek professional help if you are uncertain about any step of the process. The rewards are well worth the effort.