Hello, fans of speed and socket wrenches! This is Jarek again, and today landing on our bench is no ordinary car, but a true bestseller in Poland and Europe — a Ford Kuga (2.5L) with a 6F35 automatic gearbox. These gearboxes are usually known for reliability, but our customer, it seems, loved dynamic launches on the streets of Warsaw a little too much. And, as often happens, the gearbox said: “Enough!”
Chapter 1. Symptoms and diagnosis
The owner came to us with a standard set of complaints: noticeable jerks when shifting gears 1-2-3, clutch slip once the gearbox was warm, and worst of all — a clear burnt smell after short, dynamic drives.
We connected diagnostics. Pressure was normal. Temperature was normal. But a mechanic’s feel never lies. Disassembly showed we were dealing with the classic ailment of this transmission: “fatigue” of the friction clutch packs.
💡 What happened? The friction discs inside the packs wear, and their material gets into the oil, clogging the mechatronics (valve body) channels. That leads to incorrect operation, slip, and as a result of overheating the discs simply burned.
Chapter 2. The road to the heart of the automatic
Removing the 6F35 gearbox from a Ford Kuga is a job that takes patience. We had to work hard:
- Draining: the first step is draining the fluid. Instead of clean transmission oil, a real “coffee with grounds” ran out of the pan.
- Removal: we drop the subframe, disconnect the driveshafts, and hang the engine safely.
- Opening: the gearbox on the bench. We split it into two halves to reach the main culprit — the burned clutch packs.
When we saw the friction discs, there was no doubt: they had turned into carbon. The 3-5-R pack (gears 3, 5 and reverse) suffered especially, as it takes the greatest load.
Chapter 3. A recipe for rescue and longevity
Replacing only the burned discs is a half-measure. To give the gearbox a new life, we carried out a comprehensive rebuild:
- New friction and steel discs: a full repair set (Master Kit) using reinforced discs for better overheating resistance.
- Torque converter (hydrokinetic clutch): a mandatory procedure! We cut it open, replaced the lock-up clutch lining and welded it back. A dirty converter can kill a new gearbox within a few thousand kilometres!
- Valve body (mechatronics / “brain”): thorough cleaning, replacement of all valves (especially the solenoids) that had suffered from dust and metal filings.
- Filters and oil: a new internal and external filter and, of course, fresh transmission oil (we used original-spec Motorcraft Mercon LV).
Chapter 4. Test drive and summary
Assembly, installation in place, filling and precise oil-level adjustment. The most stressful moment arrives — the first start and adaptation.
First the gearbox goes through a learning process. We drove about 40 km in different driving modes.
The result: gear changes are smooth, completely unnoticeable, with no jerks at all. The Ford Kuga is breathing freely again, and most importantly — the burnt smell is gone.
📝 A takeaway for drivers: clutch replacement in an automatic gearbox is always a complex operation. If you feel the slightest slip, do not wait! Early, comprehensive repair of one clutch pack will save you from a very expensive replacement of the entire gearbox later.
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