The Boss Hog 4540HD is a Night Stalker series lock-up towing torque converter for the GM 6L80E and 6L90E automatic transmissions behind LS engines, on the two-step input shaft. It adds roughly 200 to 300 RPM of stall over stock and is one of the lightest weight converters on the market, built to strengthen the factory weak points with new Torrington-style encased bearings and an oversized extreme-duty lock-up. It uses a factory 12.5 in core, a 12.125 in bolt circle, a 36-spline input shaft, a 36-spline modified heavy-duty stator, a hardened chrome moly impeller hub, and a factory 1.703 in crank pilot. Every unit is leak and pressure tested, digitally balanced, and made in the USA.
- Series: Night Stalker (Towing / HD)
- Transmission: GM 6L80E, 6L90E (LS, lock-up)
- Stall Speed: 200-300 RPM over stock
- Core: 12.5 in (factory)
- Bolt Circle: 12.125 in
- Input Spline: 36
- Stator: 36-spline modified heavy duty
- Lock-Up: Oversized extreme-duty
- Impeller Hub: Hardened chrome moly
- Bearings: Torrington-style encased
- Crank Pilot: 1.703 in (factory)
- Bolt Size: 10mm x 1.5 (Class 10+)
- Anti-Balloon Plates: No
- Balance: Digitally balanced
- Towing Note: Needs transmission cooler to exceed 30,000 GVW
- Build: Leak & pressure tested; made in USA
- Part Number: 4540HD
WARNING: This product can expose you to chemicals including lead and lead compounds, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.
FAQ
What transmission does the Boss Hog 4540HD fit?
It fits the GM 6L80E and 6L90E lock-up transmissions behind LS engines, on the two-step input shaft.
How much stall does it add?
The 4540HD adds roughly 200 to 300 RPM over the stock stall. Advertised stall varies with your vehicle setup.
Is this a lock-up converter?
Yes. It uses an oversized extreme-duty lock-up.
Is it built for towing?
Yes. It is a heavy-duty towing unit; use a transmission cooler to exceed 30,000 GVW.
What are the key fitment specs?
It is a 36-spline input with a 12.125 in bolt circle, a 12.5 in factory core, and a 1.703 in crank pilot.
Which Boss Hog series should I choose?
Boss Hog groups these converters by build level. Night Stalker suits stock to mild combinations, Street Bandit is the step up once you have upgraded two or more items such as intake, heads, headers, exhaust, cam, or gearing, and the Out Law racing series is for power adders like nitrous, a supercharger, a turbocharger, or a trans brake.
