Nine-piece solenoid set for the ZF 8HP70 mechatronic unit, replacing OE 1087-298-388 when shifts flare, bang or drop into limp mode.
A Hemi Ram 1500, Grand Cherokee or Charger with a first-generation ZF eight-speed that slams the 1-2 shift, hangs before engaging Drive, flares between gears or falls into limp mode is usually telling you the solenoids on the mechatronic unit are worn. This set replaces ZF solenoid kit 1087-298-388, the common part for the Gen 1 8HP45, 8HP70 and 8HP90. Every piece is remanufactured and flow tested, so you replace the wear items without paying for a complete mechatronic unit, and it carries a 3-month warranty.
The 8HP70 is the heavier-duty member of the Gen 1 family, used behind the bigger engines where the 8HP45 (Chrysler's 845RE) would be at its limit. It has no conventional shift valves for each gear. Instead, five shift elements are each fed by their own electronic pressure regulator, and the transmission computer blends one element off while bringing the next on. Sonnax's identification guide shows that Chrysler and ZF use the same letters for the same positions: Chrysler's SOL A through SOL E are ZF's EDS-1 A, EDS-3 B, EDS-5 C, EDS-6 D and EDS-4 E, with SOL TCC (EDS-2) for converter lockup, SOL LPS (EDS-7) for line pressure and SOL Park (MV-1). When one regulator's valve wears or its screen loads up with debris, the clutch it feeds gets too much or too little pressure, and every shift that uses that clutch suffers.
Start with software. Chrysler released TCM reflashes for these same complaints; bulletin 21-018-15 covers harsh and inconsistent shifts and delayed reverse-to-drive engagement on the 2015 Grand Cherokee SRT with the 8HP70, so have the dealer or a capable scan tool check your calibration first. Then confirm fluid level at temperature and look for leaks at the mechatronic connector sleeve, a known source of pressure loss. If the codes and shift complaints stay after an update and an adaptation reset, solenoids are the likely cause. Our ZF8HP pressure control solenoid guide walks through the tests, and the Grand Cherokee 8HP problems guide and Charger shift problems guide cover model-specific faults.
The listing calls out OE 1087-298-388 for the 8HP45, 8HP70 and 8HP90. That makes it a Gen 1 part. Transmission Digest's Chrysler ZF8 identification guide explains that Gen 2 units (8HP50, 8HP75, 8HP95 and Chrysler's 850RE) use different solenoid caps and swap the B and D positions, so they will not take this set. Because Chrysler changed generations at different times on different models, check the tag on your transmission or send us your year and VIN. The set is listed as nine pieces; the photo shows three orange-capped and four cream-capped regulators, a black-bodied solenoid, a green-connector solenoid and the parking-lock actuator rod, so lay your old parts beside it and match caps and connectors. More parts for this transmission are on our ZF 8HP collection page.
Drain the fluid, remove the pan, unplug the connector sleeve and lift out the mechatronic unit. Change one solenoid at a time so no position gets swapped, fit new O-rings wetted with fluid, and put a new connector sleeve in while it is apart. The pan should be replaced rather than reused; our 8HP70 fluid and filter service kit covers the filter and fluid, and the aluminum 8HP70 pan is an option for Ram and Charger owners. ZF approves only LifeguardFluid 8 or 9 for these units. Fill through the side plug following the factory procedure for your vehicle; Chrysler's dry-fill figure is 9 liters, but an in-car service takes less and must be leveled at temperature. Clear codes and run the adaptation relearn before the road test. If shifts are still firm after new solenoids, a ZF8HP valve body shift kit addresses worn regulator valve bores.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
If the truck has the Gen 1 8HP70, yes. Ram moved to Gen 2 units later, so check the transmission tag or send us your VIN and we will confirm before you order.
Yes. Chrysler issued TCM reflashes for harsh shifts and delayed engagement on these transmissions. Rule that out first, then replace solenoids if the problem and codes remain.
The listing counts nine solenoids. The photo also shows the parking-lock actuator rod. Compare the caps and connectors with your old set before installing.
ZF approves only LifeguardFluid 8 or 9 for this family. Use that or the factory 8-speed fluid your owner's manual names, and set the level at operating temperature.
Yes. Clear codes and run the transmission adaptation reset with a capable scan tool, then drive it gently through all gears so the computer can learn the new parts.
