8HP90 Pressure Control Solenoid, new and ready to install. Fits the 8HP90. Ships fast from the USA.
Searching for an 8HP90 pressure control solenoid usually means a big, high-torque car has started slamming into gear, slipping on the shift, or setting a line pressure code. The 8HP90 is the strongest of ZF's first-generation eight-speeds, rated for 900 Nm, and that load makes it unforgiving of a regulator that drifts. What ships on this page is not a lone solenoid: it is the complete new ZF-branded solenoid set shown in the photo, listed under ZF reference 1087 298 389 for the 8HP90 and the Audi 8HP55A. The line pressure regulator you are hunting for is in the box along with the regulators for every shift element, so you can renew the whole hydraulic control side in one pass.
There is no throttle cable or vacuum modulator in this transmission. The control unit sets system line pressure electronically through one variable-force regulator, and every clutch and brake gets its own regulator downstream of that. On BMW-style naming the line pressure part is EDS-7; Audi calls the same job EPC-SYS (N443) on its 8HP55 valve bodies, per the Sonnax identification guide. If line pressure comes up short, all five shift elements apply weakly and the clutches start to slip under the 8HP90's torque. If it sticks high, every engagement turns harsh. Because the element regulators (Audi N215 through N218 and N233, plus N371 for converter lockup) share the same fluid and the same hours, they tend to wear out together.
The leaking mechatronic connector sleeve is the classic ZF eight-speed pressure thief and produces the same complaints, so rule it out first using our ZF8HP common problems guide.
Start with the fluid: level checked at the specified temperature, and color and smell noted. Pull transmission codes with a tool that reads the transmission module and write down which regulator each one names. With the mechatronic out and the circuit board removed, the Sonnax ZF8-ZIP booklet gives about 5.0 ohms at 20 C (68 F) for these regulators and calls for an ohmmeter that tests under 0.6 volts. A regulator that reads open, shorted or far off spec, or one with a clogged inlet screen, confirms the fault. Our EPC solenoid diagnosis guide covers the full test, and Charger and Challenger owners can match symptoms in our Charger problems guide.
This set is listed for two first-generation units: the 8HP90 and the Audi 8HP55A. It is not for the second-generation 8HP95, which Transmission Digest shows uses different solenoid caps and moves the B and D regulators. Some high-output cars changed generations mid-run, so check before you order. Line the cap colors and connector styles in the photo up against the regulators on your own valve body, or send us your year and VIN and we will confirm it. Every eight-speed part we stock is on the ZF 8HP collection page.
Drain the fluid, drop the pan and remove the mechatronic unit. Change the regulators one at a time so each goes back into its own bore; the positions are not interchangeable. Look over each bore for scoring, fit fresh O-rings wetted with clean fluid, and torque the retainers evenly. A new connector sleeve costs little and is worth fitting while the unit is out. Most 8HP pans carry the filter, so a pan, filter and 8-liter ATF service kit covers the refill. Use ZF LifeguardFluid 8 only, such as our 7-liter Lifeguard 8 fill, set the level hot, then clear codes, reset adaptations and road test through all eight gears so the module relearns fill times. If a gauge is available, confirm line pressure after the repair.
| Fits | 8HP90 |
| Part type | Pressure Control Solenoid |
| Condition | New |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
It is the full new ZF-branded solenoid set shown in the photo, listed under ZF reference 1087 298 389. The line pressure regulator is included along with the regulators for each shift element and the converter clutch.
Yes, the 8HP55A is one of the two units this set is listed for. On Audi valve bodies the line pressure regulator is labeled EPC-SYS (N443). Compare the caps and connectors to the photo, or send your VIN to confirm.
No. The 8HP95 is a second-generation unit with different solenoid caps and relocated B and D regulators. It needs Gen 2 parts.
Yes. The pan has to come off to reach the mechatronic unit, and on most 8HP cars the filter is built into the pan, so a pan and filter service is the sensible pairing.
ZF LifeguardFluid 8. ZF's product data sheet limits these transmissions to LifeguardFluid 8 or 9, and a generic ATF can change how the new regulators control clutch pressure.
Yes. The control unit learned around the worn regulators. Clear the codes, reset the transmission adaptations with a capable scan tool and drive through every gear so it relearns.
