We've seen lots of enquiries lately about ZF 8HP transmissions - mostly race car builds, along with a few high-powered 4WDs.

It's not hard to see why. The 8HP has gone from a luxury car gearbox to one of the most swapped transmissions in motorsport.

Here's a broad rundown of what makes them worth considering, and what to sort out before you commit.

Why the 8HP is a good option

ZF launched the 8HP in 2008 in the BMW 7 Series. It's since been picked up by more than 20 brands and passed 15 million units built. When that many manufacturers land on the same gearbox, it's usually for good reason.

For a performance build, the appeal comes down to a few things:

• Shift speed. Full-throttle upshifts happen in a couple of hundred milliseconds. Quick enough that it holds its own against dual-clutch setups.
• Eight ratios, well spread. A tall enough overall spread to stay civilised on the road, but close enough between gears to keep an engine in its powerband under load.
• Torque capacity with headroom. Factory ratings are set conservatively for warranty purposes. In practice these boxes take a lot more than the sticker suggests, particularly where the tune manages torque properly through the shift.
• Sensible on the street too. For anything that still gets driven to and from events, it behaves like a normal automatic - which a sequential or a heavy clutch won't.
• Aftermarket support. Standalone controllers, adapter kits and hardware upgrades are widely available, so you're not on your own once it's in.

Fitment, options and torque ratings

This is where most enquiries need the most work, so it's worth being clear.

"8HP" is a family, not a part number

The variants are grouped roughly by torque capacity:

Those are ZF's numbers for factory applications under warranty. Real-world capacity is generally well above them — but they're still the right starting point when you're matching a box to a build.

Same variant doesn't mean same fitment

The bellhousing pattern, starter location and torque converter pilot depth are all specific to the original application. Two 8HP70s out of different engines won't necessarily interchange, and an adapter kit cut for one won't bolt to the other. Same family, different box.

What we see them in

Across the brands we work with, the 8HP turns up in a lot of BMW models, in longitudinal Audi applications, and in VW's Touareg and V6 Amarok — which is where a fair few of the 4WD enquiries come from.

Common donor engines and bellhousing patterns

Nearly every 8HP that ends up in a project car came out of a BMW, and which BMW engine it was bolted to matters more than the number on the case.

The bellhousing pattern, starter position and converter pilot depth are all set by the donor engine, not by the 8HP variant. So the model number tells you the torque rating — the donor engine tells you what will bolt to it. Two 8HP70s can have completely different faces.

Two donor patterns cover most of what turns up.

N57 engine donor — the common one

Shared with the N47, B57, B58 and S58. This is BMW's inline-six pattern, found behind the six-cylinder diesels and the modern B-series petrol sixes. It's the pattern most 8HP45, 8HP50, 8HP51, 8HP70, 8HP75 and 8HP76 boxes come with, and it has by far the widest adapter support of any 8HP.

If you're starting from scratch, this is the common box to build around. Off-the-shelf kits exist for:

• BMW — M10, M20, M30, S14, S38, M5x/S5x, M57N, N54, N55, S55, S65, S85
• Toyota — 1JZ/2JZ, 7M-GTE, 3S-GE/3S-GTE, 1UZ/2UZ/3UZ, 1UR/2UR, 2GR/3GR/4GR, 1GR-FE, 1GZ-FE, 1FZ-FE, 1HD/1HZ, 1KD/1KZ, 2TR-FE
• Nissan — RB, KA, SR20, VQ35DE, VQ35HR/VQ37VHR, VR38DETT, VG30DETT, TB48/TD42, VK56, FJ
• GM — LS, LT, small block, big block, Vortec
• Ford — Barra, small block 289/302/351, Cosworth YB, ST170
• Honda — K20/K24, F20/F22
• Mitsubishi — 4G63 (Gen 1 and Gen 2), 4B11
• Mazda — 13B/20B rotary, BP
• VW — 1.8T, VR6 3.2/3.6
• Volvo — Redblock, Whiteblock, SI6
• Mercedes-Benz — M117/M119, M156/M157, M10x/OM60x
• Others — Cummins 6BT, Ferrari F136 / Maserati GT, Saab B2x4

N63 engine donor

Shared with the N73 and N74 engine. This is BMW's V8 and V12 pattern — a different, larger face than the N57 — and it turns up on 8HP70, 8HP75, 8HP90 and 8HP95 boxes. The adapter range is narrower. It still covers the common swaps:

• BMW — M60, M62, S62, M70, M73, M5x/S5x (standard tilt), M57N, S65, S85
• Toyota — 1JZ/2JZ, 1UZ/2UZ/3UZ, 1FZ-FE
• Nissan — RB, KA, TB48/TD42, VK56
• GM — LS, LT, small block, big block, Vortec
• Ford — Coyote, Voodoo, Godzilla, small block 289/302/351
• Audi — ABZ 4.2 V8
• Mazda — 13B/20B rotary (8HP90/95 only)

Worth noting: the highest-capacity boxes (8HP90 and 8HP95) only come in the N63 pattern, so chasing maximum torque capacity means accepting fewer adapter choices.

A note on 8HP45 behind four-cylinders

8HP45s that came out of N20, N26 or N55 cars use their own smaller patterns again — not the N57 face. Kits exist (Subaru EJ/EZ/FA and Honda K-series among them), but don't assume an 8HP45 is automatically an N57-pattern box.

Other donor families

BMW isn't the only source. Jaguar/Land Rover and Audi 8HP55 boxes have their own patterns and their own kit ranges. 

Where to get kits

• DomiWorks (Sweden) — the widest range going, and they'll quote custom work if your engine isn't listed. View their 8HP adapter kits
• NZ Wiring (New Zealand) — local option, and they also handle controllers and looms. View their 8HP adapter kits

RWD, AWD and driveline options

The other thing to sort out early is which end of the box drives what.

RWD vs AWD from the factory

The 8HP was built in both rear-wheel-drive and all-wheel-drive form. The AWD versions — xDrive in BMW terms — carry a transfer case bolted to the side of the gearbox, feeding a front driveshaft as well as the rear.

In practice, AWD boxes are far more common in the used market. A lot of the donor cars were xDrive, so if you go looking for a second-hand 8HP you'll turn up plenty of AWD units and comparatively few RWD ones. Worth knowing before you set your heart on a straight RWD box.

Also worth knowing: BMW's xDrive transfer cases are on-road AWD units. They don't have a low range. For a genuine off-road build, that matters.

Converting AWD to RWD

This is the usual solution, and it's simpler than it sounds. DomiWorks makes a bolt-on conversion kit that replaces the transfer case with an adapter plate carrying a high-speed bearing and a new steel output flange. No machining, no case surgery.

Points worth knowing:

• Two output flange options — a 105mm PCD guibo flange, so a standard 8HP 105mm guibo bolts straight on, or a dual-pattern flange that takes a 1350 yoke or a Supra MKIV propshaft.
• Covers both transfer case patterns — the adapter carries the early and current BMW bolt patterns (ATC13-1 and earlier), so it suits most boxes.
• Includes a crossmember support bracket, plus extra holes for fabricating your own mount.
• Confirmed fitment on 8HP70 (N57 and N63), 8HP50, 8HP51, 8HP75, 8HP76 (B57 and S58) and 8HP90/95. The 8HP45 isn't confirmed.
• Measure your output shaft. Some N63 boxes have a longer shaft than others.

Land Rover-pattern and Dodge 8HP95 Trackhawk versions of the same kit are also available.

Keeping four-wheel drive

For the 4WD side — and this is where the high-power ute and off-road builds sit — you can go the other way and adapt a proper transfer case to the 8HP. Kits are available to mate an 8HP to:

• Land Rover LT230
• Nissan Patrol Y60/Y61
• Nissan Skyline R32–R34 GTR
• Toyota Land Cruiser Prado LC120/LC150 (VF4)
• Toyota HF2AV
• Jeep/Dodge NP231/241/242/243/246/249 and NP149
• BorgWarner BW4484

That's the combination most 4WD builders are after: keep the low-range transfer case and diffs you already have, and put eight closely spaced ratios in front of them.

Where we come in

We're a European vehicle specialist, not a performance transmission builder — so we'll be straight about what we're useful for:

• Parts sourcing. We dismantle European vehicles, so we hold used and second-hand 8HP transmissions and have seen enough of these go out the door to have a general knowledge of what works and what doesn't.
• Bolt-on parts. Because we dismantle complete vehicles, we can usually supply a shifter, cooling lines, transmission loom and other bolt-on components should you need them too.
• Getting the right part number. We've got expert catalogue and vehicle identification programs, so we can confirm variants, check supersessions, and make sure you've got the right box for what you're building.

If you're planning a build, chasing a specific part, or just want a hand confirming what you're looking at — get in touch. Send us what you're planning and the gearbox you're after, and we'll tell you what we can do.

SD European — European vehicle specialists, Hamilton.