Fits: GEN III Swap Builds
ZF 8HP90 Transmission Mock-Up Skeleton
Dodge Hellcat ZF 8HP90 8 speed automatics are fantastic transmissions and becoming very popular in drivetrain swaps into classic Mopars. The US Car Tool ZF-8HP90 Transmission Mock-Up skeleton can help you with modifications needed to fit these big porky transmissions into your classic Muscle car.
The HP90 is a bit longer than the HP70, (29.5" for the HP90 vs 28.25" for the HP70) and is rated to handle 664 lb-ft of Torque.
It is much easier to use this 5 lb mock-up skeleton during the test fit and mock-up phase instead of trying to wrestle a 275 lb transmission in and out of your project hot rod. And we made sure to add all the bumps, lumps and protrusions that are on the actual transmission (even the vent fitting) to minimize surprises when fitting this transmission into a car originally designed for a much smaller transmission. And we reproduce the Guibo yoke bolt pattern on the 94mm bolt circle so you can mockup and check your driveline angles.
The US Car Tool mock-up skeletons come flat packed for the most economical shipping, they go together fast using supplied 1/4-20 fasteners and can be quickly disassembled for storage. We make them from 5052 Aluminum, so they are rough and tough, providing years of service while being lightweight.
ZF 8HP90 Gear Ratio's
1st at 4.71
2nd at 3.14
3rd at 2.10
4th at 1.67
5th at 1.29
6th at 1.00
7th at 0.84 (overdrive)
8th at 0.67 (Really Overdrive)
Comparing these ratio's to a Mopar 727 3-speed automatic shows why these new 8-speed automatics are so popular for swaps. The 1st gear in a 727 is 2.45. That shows the ZF-8HP90 has almost double the gearing in 1st gear vs the 727. That's the same as swapping your 3:23 rear end gears for a set of 6:20's, so the ZF-8HP90 swap will help you accelerate like crazy.
And along with great acceleration (and torque multiplication), look at 7th and 8th - two overdrives ! The same transmission that helps you accelerate like crazy, provides highway cruising and fuel economy underheard of before. In a 3:23 geared muscle car with 27" tall tires you would be turning 2800 rpm's at 70 mph. Swap in a ZF-8HP90 and you can do that same 70 mph with your engine spinning a miserly 1800 rpm in 8th gear.
And that is having the best of both worlds. So Gen3 Hemi swap the world, but remember to bring along the 8-speed automatic and make room for it, there is zero chance the ZF-8HP90 fits under the factory Transmission Tunnel on your classic muscle car.
