ZF8HP Jeep Grand Cherokee Slipping: Causes and Fix

When a Grand Cherokee owner says the transmission is slipping, the year and engine matter more than the word "slip." A 2015 V6 that flares on the 3-4 shift, a 2021 WL that will not shift past 3rd and will not back up, and a 2016 Hemi that bumps and flares after a battery replacement are three different jobs. FCA has published bulletins that cover all three, and only one of them says the fix is a hard part.

This post covers the WK2 Grand Cherokee from 2014 on and the 2021-up WL. It stays on slip, flare and lost-gear complaints, cheapest check first, using what FCA, ZF and Sonnax have published. For the wider list of eight-speed faults on these Jeeps, start with our ZF8HP Jeep Grand Cherokee common problems guide.

Recommended ZF 8HP parts for a slipping Grand Cherokee

An 8HP70 master rebuild kit for Hemi, EcoDiesel and SRT Jeeps with a burnt pack, an 8HP45 master rebuild kit for 845RE V6 Jeeps, and a pan, filter and ATF kit to set the level with the correct fluid. 850RE D clutch jobs use the FCA kit in the bulletin. Match the part to your sales code. Secure checkout on our own site.

8HP70 8HP75 Transmission Master Rebuild Kit BMW Jeep Dodge

$463.99View part

8HP45 Master Rebuild Kit

$340.99View part

ZF 8HP70 Transmission Pan, Filter & ATF Kit RAM/Jeep/Dodge

$254.99View part

Generation First: 845RE, 8HP70 or 850RE

FCA's bulletins split the Grand Cherokee eight-speeds by sales code, and the slip fixes split the same way. The early WK2 V6 (3.6L, engine code ERB) uses the 845RE, sales code DFL, which is Chrysler's build of the ZF 8HP45. The Hemi, EcoDiesel and SRT WK2s use the 8HP70, sales code DFD or DFK. Both are first-generation units.

The second-generation 850RE, sales code DFT, shows up in two places on this Jeep. FCA bulletin 21-009-25 Rev. A lists "2020 - 2022 (WK) Jeep Grand Cherokee" equipped with the 850RE, so late WK2s built with the DFT unit are in it. It also lists the 2021-2024 WL Grand Cherokee and Grand Cherokee L. That matters because the D clutch bulletin below applies only to DFT units. A 2016 V6 with the same symptom is a different diagnosis.

Read the code off the build sheet or the tag on the case. Gen 1 and Gen 2 valve bodies, clutch packs and rebuild kits do not interchange.

Match the Slipping Gears to One Element

The ZF eight-speed makes eight forward gears and reverse from four planetary sets, two brakes (A and B) and three clutches (C, D and E). Sonnax's "A New Path for ZF" lays out the apply chart, and every gear uses exactly three of the five elements. So the road test is the diagnosis: write down which gears slip and which hold, then find the one element every bad gear has in common.

Two patterns come up on Grand Cherokees. If the Jeep pulls fine through 3rd, then slips or flares into 4th and has weak or no reverse, every one of those ranges uses D. If it slips in 1st, 2nd and reverse but feels solid from 3rd to 6th, the A brake is the common element.

A flare on one shift that then holds in the next gear is different. The pack is holding once it is on, but the apply is late or soft. That points at fluid level, adaptations or valve body pressure, not friction wear. On the scan tool, log commanded gear against the actual input-to-output speed ratio. A ratio that sags during a shift and recovers is a timing or pressure problem. A ratio that never matches the commanded gear under load is a pack that is not holding.

Check 1: Set the Level the ZF Way

Low fluid shows up as slip before anything else. The pump draws air on hard launches, turns and braking, and line pressure drops right when a clutch needs it. These Jeeps have no dipstick, so the level is set at the fill plug inside a temperature window. ZF Service Information 50130 gives the procedure, and you need a scan tool reading transmission oil temperature:

1. Jeep level on the lift, in Park, parking brake on, loads off, no limp mode active.
2. Bring the oil to 30-50 C. Hold 2,000 rpm for 30 seconds to fill the converter, then return to idle.
3. Select P, R and D, then hold D1 and D2 for about 10 seconds each. Confirm the temperature is still 30-50 C.
4. Pull the fill plug. Add fluid until it runs out, wait for single drops, then install the plug: M18 x 1.5 at 35 Nm or M22 x 1.5 at 30 Nm, depending on which one is in the case.

ZF warns that underfill damages the transmission and that anything set above 50 C will be low once the extra pushes out the overflow. Write down how much it took. If a Jeep that flares on hard right turns took most of a liter, that is your diagnosis, and the next job is finding the leak at the pan, cooler lines or fill plug. FCA's bulletins call for Mopar ZF 8&9 Speed ATF, part number 68218925AB. The 21-009-25 Rev. A parts list calls for 10 of them on a D clutch job. ZF's own fluid is LifeguardFluid 8. Its data sheet recommends a change at 150,000 km (about 93,000 miles), and sooner for towing, heat or unknown history. A lot of Grand Cherokees tow, so plenty of them are due well before that.

Check 2: Adaptations, Especially After a Battery or Repair

This one catches a lot of people on Gen 1 Jeeps. FCA bulletin 21-012-14 Rev. B explains that the 845RE and 8HP70 store a learned value for every clutch in "adaptation memory cells": the fill time in milliseconds and the fill pressure in millibar or psi, each with a counter showing how many times the TCM has updated it. Those cells are set to zero on every new or replaced transmission, on a replaced TCM, and whenever someone clears them with a scan tool. Until they relearn, FCA says shift quality may not meet the customer's expectations. In practice, that means flares and bumps that feel like slip.

The bulletin gives you numbers to check. FCA says the filling counter should ideally be at least 12 (6 on the 8HP70) and the fast filling counter at least 4 (2 on the 8HP70). A counter at zero means that cell has never been updated. So when a WK2 comes in flaring after a recent repair, pull the A through E filling counters before anything else. If they are near zero, the transmission has not learned yet. Clearing them again will not help.

FCA's fix is a structured drive. Warm the oil to at least 30 C (86 F). From a stop, accelerate on light, steady throttle to 45-50 mph so it shifts 1st through 8th, brake lightly to a stop, and check the Neutral-to-Reverse engagement. Rate each shift from 1 to 10. Any shift under 5 gets the Adaptation Drive Learn procedure in the bulletin. On 2014-2015 V6 Jeeps, FCA also requires the 845RE Quick Learn (bulletin 21-030-14 or later) before the evaluation. One more rule from the same bulletin: after an overhaul, the adaptation cells must be cleared, unless the mechatronic itself was replaced.

Software matters too. Bulletin 21-027-15 Rev. A covers 2015 V6 Jeeps that set P0734 (gear 4 incorrect ratio) along with P1DCD and P1B13 when nothing is actually wrong, and the fix is a TCM reflash. On a 2022 WL, bulletin 21-015-23 covers a Jeep that shifts back and forth between 1st and 2nd in Selec-Speed Control. FCA lists TCM software as the cause, with a 0.2-hour reprogram. Before you condemn a pack over a ratio code, check the calibration level. Flash with a charger holding 13.2-13.5 volts.

Check 3: The 850RE D Clutch Bulletin (2020-2022 WK, 2021-2024 WL)

On a DFT Grand Cherokee, this is the slip complaint that matters most. FCA first released it as 21-039-24 in May 2024, revised it through Rev. H, and replaced it with 21-009-25, now at Rev. A (February 1, 2025). The entry rule is strict. The Jeep must have the MIL on and one or more of these codes:

• P0733-00: gear 3 shift incorrect ratio.
• P1DA8-00: incorrect gear ratio, clutch A, B or D defective.
• P1D92-00: incorrect gear ratio, clutch 4 defective.

Owners may also say the transmission slips when shifting, the vehicle will not move in reverse, or it will not shift higher than 3rd. Check those against the apply chart. D is applied in 4th through 8th and in reverse, so a failing D clutch takes away exactly the gears that need it and leaves 1st through 3rd working.

The repair is a D clutch replacement, not a transmission. The output shaft D clutch repair kit is 68676891AB for a 4x4 WL, 68676890AB for a 4x4 WK, and 68676894AB for RWD WD, WK and WL. FCA allows 7.3 hours on the WL and 7.9 on the WK, plus 1.0 hour for 4x4/AWD, 0.2 hours for the skid plate and 1.0 hour for the TCM adaptation procedure. The procedure pulls the converter and, on 4x4 Jeeps, the extension housing, and for the WL 4x4 it adds a new O-ring on the output shaft.

The first step is what makes this bulletin useful outside a dealer: "Are DTCs P0733, P1DA8 or P1D92 present?" If not, the bulletin does not apply. Earlier, Rev. A of 21-039-24 had the tech pressure-check the D clutch circuit with the clutch air pressure test before pulling the transmission. A shop without the dealer procedure can still air-check D on the bench to confirm it before ordering parts. The bulletin also warns that any time the transmission is reconditioned or replaced, the TCM Adaptation Procedure has to be run. Skip it and a fresh D clutch job comes back flaring.

Check 4: A Brake Burn-Up and Worn Valve Body Bores

If the slip lines up with the A brake (1st, 2nd, 7th, 8th and reverse), think backing plate. Sonnax calls A clutch failure a chronic problem across the ZF8 family, 845RE and 850RE included. It traces the failure to a weak OE backing plate that flexes during apply, wears the pack unevenly and builds heat. The symptoms Sonnax lists are no reverse, reverse slip, gear ratio codes and slipping gears. Its billet plates are 35577-45 for the 845RE and 850RE and 35577-70 for the 8HP70 and 8HP75. If a WK2 is already apart for a burnt A pack, put the stiffer plate in so it does not come back.

If the complaint is a flare on certain shifts with clean fluid at the right level and adaptations that have learned, look at the valve body. On Gen 1 units, Sonnax's ZF8HP45/ZF8HP70 valve body layout ties bump shifts, flare shifts, burnt clutches, lost gears and ratio codes to worn clutch holding valve bores (kit 35740-20K, five locations). It ties harsh or soft shifts and erratic line pressure to the pressure regulator valve (35740-01K). Our ZF8HP valve body wear guide covers the bench checks.

If the pan has clutch material in it and the fluid smells burnt, stop working the valve body. The pack is gone, and the job is new frictions and steels, plus the backing plate upgrade if A was involved.

The Order I Work a Grand Cherokee Slip Complaint

1. Read the sales code: DFL, DFD/DFK or DFT.
2. Save every code. Do not clear adaptations on the first visit.
3. Road test with the scan tool logging gear ratio. Mark which gears slip and find the common element on the chart.
4. Set the fluid level at 30-50 C and write down how much it took. If it was low, find the leak.
5. Check the A-E filling counters. Near zero after a repair or battery job means the Jeep has not learned yet, so run the bulletin drive cycle.
6. Check the TCM software against current flashes, with a charger on the Jeep.
7. On a DFT Jeep with P0733, P1DA8 or P1D92: air-check D, then replace the D clutch.
8. A brake slip: rebuild with the heavy-duty backing plate. Shift flares with clean fluid and learned adaptations: valve body bores.
9. After any internal repair, run the adaptation procedure.

Frequently Asked Questions

Why is my Jeep Grand Cherokee transmission slipping?

The most common causes on the eight-speed are a low fluid level, adaptations that have not relearned after a repair or TCM reset, TCM software, and on 850RE Jeeps a failing D clutch. Set the level at the fill plug with the fluid at 30-50 C before condemning anything. Then note which gears slip, because each gear uses three of five clutches and the shared one is usually the culprit.

Is there a TSB for Grand Cherokee 8-speed slipping?

Yes. FCA bulletin 21-009-25 Rev. A covers 2020-2022 WK and 2021-2024 WL Grand Cherokees with the 850RE (sales code DFT). It requires a MIL with P0733, P1DA8 or P1D92, lists slipping on shifts, no reverse and no shift above 3rd as complaints, and the repair is replacing the D clutch followed by the TCM adaptation procedure.

Why does my Grand Cherokee shift badly after a battery or transmission repair?

The 845RE and 8HP70 store learned fill time and fill pressure for every clutch, and those values are reset to zero when the transmission or TCM is replaced or the cells are cleared. FCA bulletin 21-012-14 Rev. B says shift quality may not meet expectations until they relearn, and gives a drive procedure: warm to at least 30 C, accelerate gently to 45-50 mph through all eight gears, and run the Adaptation Drive Learn on any shift rated under 5.

How much does the Grand Cherokee D clutch repair take?

FCA allows 7.3 hours to inspect and replace the D clutch on a WL and 7.9 hours on a WK, plus 1.0 hour for 4x4 or AWD, 0.2 hours for the skid plate and 1.0 hour for the adaptation procedure. The 4x4 WL kit is 68676891AB. It is a clutch repair, not a transmission replacement.