Jeep Changed This ZF Transmission Part in 2021 (JL & JT) — Here’s Why

Jeep made a silent change in 2021 to a critical component on the ZF 8-speed automatic transmission used in JL Wranglers and JT Gladiators — the transmission heat exchanger / transmission heater assembly. Most owners have no idea this change happened, but it can affect how the transmission warms up, how it cools under load, and why some early builds experienced overheating issues.

New Heat Exchanger (Mopar Part # 68485460AB): https://amzn.to/4a6E7t4

In this video, I break down the two cooling circuits shown in the Factory Service Manual:

✅ Engine Coolant Circuit (coolant ↔ heat exchanger)

✅ ATF Cooling Circuit (ATF → heat exchanger → front cooler → return)

I then explain what Jeep used before mid-2021 — a thermostat-controlled design on the ATF cooling loop — and what changed afterward with a revised, full-time-flow design.

I also cover real-world considerations, including:

• Clearance issues with aftermarket driveshafts
• Lift kits, skid plates, and exhaust modifications
• Why off-road articulation and towing can make this issue worse

If you have an earlier JL or JT, this is absolutely something worth verifying — and a good reminder to monitor transmission temperatures, especially if you tow or off-road.

🛠️ Factory Service Manual diagrams shown for education and verification

📌 Credit to the Jeep community discussions that helped surface this topic, especially the JL Wrangler Forum

CHAPTERS
0:00 Jeep’s Silent 2021 Change (JL & JT)
0:29 What the heat exchanger does (simple explanation)
0:51 The next 4 videos planned
1:16 The two transmission cooling circuits
1:49 Location of the heat exchanger and circuit routing
2:50 How the system actually works
3:35 What changed in 2021
4:05 Why Jeep made the change
4:53 How to tell which unit you have (visuals + part numbers)
5:23 Retrofit considerations + clearance warnings
6:07 Key takeaway + credits

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