2014 Jeep Grand Cherokee - P0734 Gear 4 Incorrect Ratio - Transmission slipping

Question

My Grand Cherokee is acting up when shifting from 3rd to 4th gear. It feels like it hits neutral for a second, the RPMs spike, and then it slams into gear or goes into limp mode. I have the ZF 8-speed automatic.

I've read these transmissions are 'sealed for life' but I'm at 110,000 miles and I've never touched the fluid. The code P0734 is consistently there. Could it just be low on fluid or is the whole trans toast?

ScannerSandy · Accepted Answer

✅ Confirmed fix: The transmission bridge seal (a small rubber rectangular seal between the valve body and the trans case) had flattened and cracked, causing a loss of hydraulic pressure to the 4th gear clutch pack. Replaced the bridge seal, the four sealing sleeves, and did a fresh filter/pan and ZF Lifeguard 8 fluid change. Shifting is now buttery smooth.

MountainMechMo · Answer

It's rarely just 'low' unless you have a visible leak. The 8HP45/70 units are very sensitive. Check the E-clutch values if you have a high-end scan tool. If the millisecond fill times are way out of spec, you have internal wear that fluid won't fix.

2014 Jeep Grand Cherokee - P0734 Gear 4 Incorrect Ratio - Transmission slipping

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