Your symptoms—whine under acceleration (especially at higher speeds) that vanishes when coasting, occasional shudder like hitting rumble strips, and black residue on the dipstick despite fresh fluid—point strongly to a failing torque converter, particularly the clutch or internal bearings wearing out. This is a common issue on the 42RLE transmission in Wranglers, often tied to heat buildup, partial lockup problems, or debris from clutch material circulating and causing contamination. The whine could be from worn needle bearings in the converter creating a whirring noise that changes with load, the shudder from the torque converter clutch slipping or engaging erratically, and the black stuff is likely clutch friction material or fine metal particles breaking down, which can show up even with low-mileage fluid if there's internal wear.
The shop's advice doesn't hold up based on typical 42RLE failures. A bad torque converter doesn't always make the vehicle undrivable—many people limp along with partial failures for thousands of miles before it gets worse, though it risks damaging the rest of the transmission over time by sending debris through the system. And yes, torque converter issues absolutely can contaminate the fluid; that's a classic sign, as worn clutches shed material, and damaged bearings or seals let particles mix in.
That said, don't jump straight to replacing the torque converter without confirming. Other possibilities like a failing transmission pump (which can whine under load from low pressure or wear), clogged filter, low fluid level, or even valve body issues could mimic this, though the combo of symptoms leans heavily toward the converter. The 42RLE is notorious for these problems in Jeeps, especially with stock setups pushing larger tires or in hot conditions.
Here's what I'd recommend stepping through before deciding on a replacement:
- Check fluid level and condition properly: Make sure the engine is running, transmission in neutral or park, and fully warmed up (drive it for 10-15 minutes). The dipstick should show full— even a slight low can cause whine and shudder. If it's low, top it off with ATF+4 only. But with black residue already, drain and replace the fluid and filter anyway (about 4-5 quarts for a pan drop). Inspect the pan magnet for excessive metal shavings; a little is normal, but chunks or a lot points to bigger internal damage.
- Scan for codes: Hook up an OBD-II scanner (or have a shop do it) to check for transmission-related trouble codes like P0740 (torque converter clutch circuit) or pressure solenoid issues. The 2005-2006 TJs sometimes have PCM (engine computer) glitches affecting the trans controller, which could contribute.
- Test drive and additives: If no codes, try a shudder-fix additive like Lubegard Instant Shudder Fixx or Dr. Tranny's (follow the bottle instructions, usually just pour in). Some folks report it quiets minor TC clutch issues temporarily. Pay attention to when the whine/grind happens— if it's tied to lockup speeds (around 40-50 mph), that's another TC clue.
- Get a second opinion: Take it to another reputable trans shop for a road test and pressure test. They can hook up gauges to check line pressure (should be 60-100 psi idle, higher under load) and see if the pump is weak or if there's a converter-specific fault. Avoid chain shops if possible; find one familiar with Jeeps.
If diagnostics confirm the torque converter, yes, replace it— but do it as part of a partial rebuild if there's debris, to flush the cooler and replace the solenoid pack or valve body if needed. A remanufactured TC runs $200-400, plus labor (total job often $1,000-2,000), but ignoring it could lead to a full trans failure down the line. If the trans is high-mileage or you've got mods like bigger tires, consider upgrading to a beefier aftermarket converter with better internals to prevent recurrence.
In short, the shop sounds off-base, and your initial hunch is likely right, but verify first to avoid unnecessary work. If you can share mileage, any mods, or if there are codes, that'd help narrow it further.
