ZF 6HP26 Master Rebuild Kit with Clutches, T18302A

If your BMW 550i, 750i, X5 or X6, Jaguar S-Type, XJ or XK, or Land Rover Range Rover or Discovery is flaring between gears, slipping once the fluid is hot, or leaving ATF on the driveway, and the case is already coming out, this is the kit to open on the bench. The T18302A package pairs the full 6HP26 overhaul seal and gasket set with a new set of friction clutch plates, so one box covers the rubber and the frictions for a complete rebuild. It replaces ZF overhaul kit reference 1068298051 and ships at about 14.4 lb.

What the master rebuild kit does in a ZF 6HP26

The 6HP26 is ZF's high-torque first-generation six-speed, built around a Lepelletier gear train: a simple planetary feeding a Ravigneaux set, with three rotating clutches and two brakes doing the shifting. Every one of those five shift elements is applied by a piston sealed with molded lip seals and fed through Teflon sealing rings on the shafts. The converter clutch is designed to run with a controlled slip, so the fluid in these units sees a lot of heat over its life. That heat is what hardens the rubber and glazes the frictions at roughly the same rate. Renewing only one of them leaves the other as the next failure, which is why this kit carries both. In the box you get the case and pump gaskets, the lip seals, the bagged piston and clutch seal sets, the solenoid seal set, the sealing rings, the small O-rings and a new friction set.

Symptoms that point to a full rebuild

• Engine flare on the 2-3 or 3-4 upshift that gets worse as the transmission warms up
• Slip under throttle in one or more gears, often with a clutch or gear ratio fault stored
• Dark, burnt-smelling fluid with friction material on the pan magnets
• Leaks at the pan gasket and the mechatronic connector sleeve at the same time
• On Jaguar and Land Rover 6HP26 and 6HP28 units, codes in the P0729-P0735, P0783 and P2702-P2704 range, which a JLR bulletin tied to wear of an internal lead-free bush

How to confirm before you buy

Rule out the cheap faults first. On BMW cars, unplug the transmission connector and look for oil on the pins: a leaking mechatronic sleeve causes communication faults and failsafe mode that can look like internal failure. Check the fluid level the ZF way (described below), then read clutch adaptation values with a scan tool. If adaptations are maxed out and the pan shows friction material, the clutches are done and a rebuild is the fix. Our BMW 5 Series 6HP problems guide walks through the BMW faults, and the ZF6HP rebuild cost guide lays out what a full overhaul involves so you can decide between doing it yourself and farming it out.

Fitment

The kit is listed for the ZF 6HP26, 6HP26A and 6HP28, the longitudinal rear-wheel and all-wheel drive family, across roughly 2002-2011: BMW 3, 5, 6 and 7 Series, X5 and X6 (550i and 750i builds included), Jaguar S-Type, XJ and XK, and Land Rover Discovery and Range Rover. Read the ZF tag on the side of the case before ordering. The 6HP19, 6HP21 and 6HP32 use different clutch stacks, and Sonnax notes that the 6HP26 is a first-generation unit while the 6HP28 is second-generation, with valve body parts that do not interchange. If in doubt, send us the year and VIN and we will check it. Browse every ZF six-speed part on our ZF 6HP collection page.

Install notes

• Soak the new frictions in ATF before stacking them, and set each pack's clearance with the selective snap ring as you build it. Air-check every drum once it is sealed.
• The listing describes the frictions and the overhaul seal set. It does not include steels, the filter, the mechatronic or hard parts. Reuse steels only if they are flat and unscored.
• Size the Teflon sealing rings so they sit flush before a drum goes over them. A proud ring shaves on assembly and cross-leaks pressure.
• BMW's sleeve bulletin calls for the connector to sit no more than 3 mm from the case. At 7-8 mm the sleeve is not seated and the connector will drop out intermittently. If yours leaked there, fit a new 6HP26 sleeve and connector seal kit.
• With the mechatronic out, this is the time to address worn solenoids. Our ZF 6HP26 seven-solenoid set fits the same unit.
• Refill with ZF LifeguardFluid 6. Follow ZF's procedure: idle at 650-950 rpm, cycle the gears, then set the level at the fill plug with the oil between 30 and 35 C, and never above 50 C.

Does the T18302A kit fit both the 6HP26 and the 6HP28?

It is listed for the 6HP26, 6HP26A and 6HP28. Confirm the ZF tag on your case first. The 6HP26 is a first-generation unit and the 6HP28 is second-generation, so valve body parts differ even though this seal and friction kit is listed for both.

Are steel plates included?

The listing describes the friction clutch plates and the full overhaul gasket and seal set. Steels are not described as included, so measure and inspect your originals and replace any that are blued, scored or out of flat.

What else should I buy with it?

A new mechatronic sleeve and connector seal set if the unit leaked at the plug, a filter, fresh ZF LifeguardFluid 6, and solenoids if the old ones are worn. The valve body and torque converter are separate.

Which fluid goes back in after the rebuild?

ZF LifeguardFluid 6 is ZF's specified fill for the 6HP family. BMW's own sleeve bulletin lists its long-life fill as Shell M-1375.4. Fill until it runs from the fill hole, cycle the gears at idle, then set the final level with the oil at 30-35 C.

Do I need to reset adaptations after the rebuild?

Yes. Clear the old clutch adaptation values with a capable scan tool and let the unit relearn through a gentle drive cycle. Old adaptations were built around worn clutches and will make the new ones shift harshly.

• ZF6HP Rebuild Cost: What You're Actually Paying For
• ZF6HP BMW 5 Series Common Problems and Fixes
• ZF6HP Jaguar Common Problems and Fixes
• ZF6HP BMW 5 Series Shift Problems: Diagnosis and Fix