Building a Stage 2 ZF 8HP51 for the Toyota GR Supra

What does it actually take to assemble a Stage 2 8HP51? In this workshop video, Brian starts with a disassembled mild-hybrid 8HP51 on the bench and puts it back together step by step. The same 8HP51 family is familiar to Toyota GR Supra and BMW owners. This is a look at the sequence and the inspection points, not a substitute for the correct service information for your exact transmission.

The video's title calls out 1,200 WHP as the Stage 2 build rating. That is the shop's product rating, not a claim that this particular transmission or car was tested at that output in the video. Here is what Brian actually does on camera.

Start with the D clutch

Brian begins with the D clutch and P4 output planetary carrier. He sorts the return springs before assembly: the D spring is identified by its diameter, while the A spring has prominent teeth and is not interchangeable. He lubricates the replaced O-ring and molded lip seal, indexes the retainer, compresses the assembly and seats the snap ring. Before stacking the D clutches, he checks the piston circuit with air. The point is simple: confirm that the piston seals and applies now, while the assembly is still accessible.

Build the C and E hubs

Next are the C and E hubs, including ATS billet hub components in this Stage 2 build. A small but useful identification check happens before either goes together: the E-clutch return spring is shorter than the C-clutch spring. Brian lubricates the seals with assembly gel, compresses the hubs and installs their retainers, paying attention to the E hub's rounded snap-ring arrangement. Both assemblies get their clutch stacks before the geartrain goes back together.

Put the geartrain back in order

With the clutch hubs assembled, Brian moves to the P4 sun-gear basket and its bearings, then flips the basket and slides it into the output shaft. Bearings separate metal surfaces that rotate against one another; assembly gel helps hold the small parts in position during the stack-up. He works through the P2 carrier, checks the main-shaft circuit with air, and then adds the P2/P1 sun gears, P1 carrier and P1 annulus gear. Each piece has to seat correctly before the next one goes on.

Pump, A clutch and case stack

The final stretch covers the pump and A clutch, followed by the B piston and lowering the completed internal stack into the case. This is where careful alignment matters: forcing an assembly that has not settled into place can undo the work already completed. Brian notes a 150 in-lb pump-housing bolt torque in the video's description; always confirm fastener specifications against the service information for the exact unit in front of you.

What to take away from the build

• Identify the return springs and retainers before compressing the D, C and E clutch assemblies.
• Lubricate the seals, seat the snap rings correctly and air-check the circuits while they are still accessible.
• Keep the bearings in their proper positions as the P4 and P2/P1 assemblies come together.
• Use the service information for your exact 8HP51 variant when checking clearances, fasteners and final assembly.

For an owner deciding between rebuilding a core and having the shop assemble it, the full video shows the work behind the finished transmission. Watch the chapters above to follow each stage directly at the bench.