GM 8L90 Transmission Problems, Symptoms & Fixes

The Stellantis family of brands — formerly known as FCA (Fiat Chrysler Automobiles) — includes Dodge, Ram, Jeep, and Chrysler . From heavy-duty truck automatics to refined 8-speed transmissions in SUVs and performance cars, Stellantis transmissions are powerful but often plagued by issues like torque converter shudder, valve body failures, overheating, and clutch wear. At DK Auto & Diesel Service in Magnolia, TX , we specialize in diagnosing, rebuilding, and upgrading Stellantis transmissions for towing, performance, and long-term reliability. Common Stellantis Transmission Problems • Torque Converter Shudder → especially on ZF 8HP variants (845RE, 850RE, 8HP75, 8HP95) • Valve Body & Solenoid Pack Failures → common on RE and RFE families (48RE, 545RFE, 68RFE) • Overheating → Ram trucks and Jeep SUVs towing in Texas heat • Harsh or Erratic Shifts → RFE family and ZF 9HP compact units • Clutch Pack Wear → 68RFE, 48RE, and Jeep ZF 9HP Stellantis / FCA Transmissions We Service Dodge Transmissions • 48RE (Ram/Dodge legacy Cummins trucks) • 545RFE (Durango, Ram gas, Jeep Grand Cherokee) • 68RFE (Ram Cummins 6.7L) • ZF 8HP (Stellantis 845RE / 850RE in Charger, Challenger, Durango, Chrysler 300) Explore Dodge Transmission Problems & Fixes → Ram Truck Transmissions • 48RE → Cummins 5.9L & early 6.7L (2003–2007) • 545RFE → Ram 1500/2500 (gas engines) • 68RFE → Ram 2500/3500 (6.7L Cummins, 2007.5–present) • Aisin AS69RC → Ram 3500/4500/5500 Cummins (2013–present) • ZF 8HP75 / 8HP95 → Ram 1500 HEMI & EcoDiesel Explore Ram Transmission Problems & Fixes → Jeep Transmissions • 545RFE → Grand Cherokee, Liberty • 68RFE (shared platform in some models) • ZF 8HP Variants → Grand Cherokee, Wagoneer, Wrangler (high torque versions) • ZF 9HP → Cherokee, Renegade, Compass (compact 9-speed) Explore Jeep Transmission Problems & Fixes → Chrysler Transmissions • 42RE / 46RE / 48RE legacy units → Chrysler Aspen, early SUVs • 545RFE → Chrysler Aspen, Pacifica (older) • ZF 8HP (845RE, 850RE) → Chrysler 300, Pacifica (newer models) Explore Chrysler Transmission Problems & Fixes → How DK Auto & Diesel Fixes Stellantis / FCA Transmissions We go beyond factory-level service by upgrading known weak points: Billet torque converters (multi-disc upgrades for Cummins & HEMI) Heavy-duty clutch packs, steels, & billet shafts (68RFE, AS69RC, 48RE) Valve body & solenoid pack rebuilds/replacements (Sonnax / TransGo kits) ECM/TCM tuning for smoother shifts, towing, & performance applications Auxiliary coolers for Ram trucks & Jeep SUVs in Texas heat Preventive fluid service with correct ATF (ZF Lifeguard / Mopar ULV / ATF+4) 24-month / 24,000 mile warranty Schedule Your Stellantis Transmission Diagnostic in Magnolia, TX Whether you drive a Ram 2500 Cummins, Jeep Cherokee, Dodge Challenger, or Chrysler 300 , trust DK Auto & Diesel Service for expert transmission diagnostics, rebuilds, and upgrades. Serving Magnolia, Montgomery, Conroe, The Woodlands, Tomball, Willis, and Spring.

The Ford 10R100 10-speed automatic transmission is found in Ford F-650, F-750, and other medium-duty vocational trucks. Designed for high GCWR and commercial use, it’s engineered to handle severe-duty cycles — but it’s not invincible. Common issues include harsh shifts, torque converter shudder, and overheating under load. At DK Auto & Diesel Service in Magnolia, TX , we provide diagnostics, rebuilds, and upgrades for the Ford 10R100 to keep work trucks reliable on the job. Common Ford 10R100 Transmission Problems & Symptoms 1. Harsh or Erratic Shifting • Symptoms : ◦ Hard upshifts under light throttle ◦ Rough downshifts when slowing ◦ Delayed engagement into drive/reverse • Causes : ◦ TCM calibration for heavy loads feels rough when empty ◦ Valve body bore wear / solenoid sticking • Fixes : ◦ Custom programming to refine shift feel ◦ Valve body rebuild/replacement with heavy-duty kits ◦ Adaptive learn reset after service 2. Torque Converter Lockup Problems • Symptoms : ◦ Shudder at highway speeds ◦ RPM flare while towing uphill ◦ Converter fails to lock, reducing fuel economy • Causes : ◦ Converter clutch wear ◦ Fluid breakdown under heat • Fixes : ◦ Replace with billet heavy-duty torque converter ◦ Flush/refill with Ford-approved Mercon ULV ◦ Adjust lockup strategy via tuning 3. Overheating Under Severe Duty • Symptoms : ◦ Transmission over-temp warning ◦ Fluid turning dark or burnt ◦ Limp mode activation under heavy loads • Causes : ◦ Towing/hauling beyond cooling capacity ◦ Prolonged stop/go commercial use • Fixes : ◦ Install auxiliary coolers or larger-capacity cooler ◦ TCM tuning to reduce slip and increase line pressure ◦ More frequent fluid/filter service for fleets 4. Gear Hunting / Shift Flare • Symptoms : ◦ Constant gear changes under light throttle ◦ RPM spike between shifts ◦ Feels like slipping before gear applies • Causes : ◦ Programming prioritizes economy vs. durability ◦ Valve body or solenoid wear • Fixes : ◦ Custom tuning to reduce gear hunting ◦ Valve body inspection and upgrade 5. TCM / Electrical Issues • Symptoms : ◦ “Service Transmission” warning light ◦ Limp mode triggered under load ◦ Trouble codes (solenoid performance, pressure control errors) • Causes : ◦ TCM software corruption ◦ Faulty solenoid body assembly • Fixes : ◦ Replace solenoid body/mechatronic unit ◦ Update TCM software or apply custom tuning ◦ Relearn procedures after repair How DK Auto & Diesel Fixes the 10R100 We upgrade the 10R100 for fleet, vocational, and severe-duty reliability: Billet torque converters for heavy hauling Valve body & solenoid upgrades (Sonnax) Custom ECM/TCM tuning for commercial duty cycles Auxiliary cooler installs for extended life Preventive maintenance schedules for fleets 24-month / 24,000 mile warranty Schedule Your Ford 10R100 Transmission Diagnostic in Magnolia, TX If your 10R100 is shuddering, overheating, or shifting harshly , bring it to DK Auto & Diesel Service for a professional diagnostic and rebuild options. Serving Magnolia, Montgomery, Conroe, The Woodlands, Tomball, Willis, and Spring.

The Ford 10R140 TorqShift 10-speed transmission is used in 2020+ Ford Super Duty trucks with the 6.7L Power Stroke and 7.3L gas engines. It offers smoother gear ratios and more torque handling than the older 6R140, but real-world issues include torque converter shudder, harsh shifting, and overheating when towing heavy loads. At DK Auto & Diesel Service in Magnolia, TX , we provide full diagnostics, rebuilds, and tuning solutions for the Ford 10R140. Common Ford 10R140 Transmission Problems & Symptoms 1. Torque Converter Shudder • Symptoms : ◦ Vibration/shudder at steady highway speeds ◦ RPM fluctuations under light throttle ◦ Feels like rumble strips when converter locks/unlocks • Causes : ◦ Converter clutch wear ◦ Fluid breakdown (Mercon ULV issues) • Fixes : ◦ Replace with upgraded billet torque converter ◦ Fluid flush with Ford-approved Mercon ULV ◦ TCM tuning to refine lockup apply strategy 2. Harsh or Erratic Shifting • Symptoms : ◦ Hard 1–2 or 2–3 upshifts ◦ Rough downshifts coming to a stop ◦ Delay engaging drive or reverse • Causes : ◦ TCM calibration quirks ◦ Valve body wear or solenoid sticking ◦ Adaptive learning errors • Fixes : ◦ TCM update or custom tuning ◦ Valve body rebuild/replacement with Sonnax upgrades ◦ Adaptive relearn procedure 3. Gear Hunting / Shift Flare • Symptoms : ◦ Constant gear hunting at light throttle ◦ RPM flare between gears (esp. 4–5, 7–8) ◦ Feels like slipping before gear engages • Causes : ◦ Programming prioritizing fuel economy over durability ◦ Valve body control issues • Fixes : ◦ Custom TCM tuning to reduce hunting ◦ Valve body inspection and upgrade ◦ Adaptive reset after repair 4. Overheating Under Heavy Tow • Symptoms : ◦ Transmission over-temp warning ◦ Burnt-smelling or darkened fluid ◦ Limp mode while towing uphill or in Texas heat • Causes : ◦ Converter slip generating heat ◦ Limited OEM cooler capacity under max tow • Fixes : ◦ Auxiliary transmission cooler install ◦ Shortened fluid service intervals ◦ Tuning to increase line pressure & reduce slip 5. Electronic / TCM Failures • Symptoms : ◦ “Service Transmission” light ◦ Limp mode activation ◦ Trouble codes (P0741, P2701, solenoid performance codes) • Causes : ◦ TCM software corruption ◦ Solenoid body assembly/mechatronic issues • Fixes : ◦ Replace solenoid body with updated version ◦ Reprogram with latest Ford calibration ◦ Adaptive relearn procedure How DK Auto & Diesel Fixes the 10R140 We strengthen the 10R140 for towing, work, and performance use : Billet torque converters & HD clutch packs Valve body rebuilds with Sonnax solutions TCM tuning to improve shift logic and durability Auxiliary cooler installs for hot Texas towing conditions Full rebuilds with upgraded steels and shafts 24-month / 24,000 mile warranty Schedule Your Ford 10R140 Transmission Diagnostic in Magnolia, TX If your 10R140 is shuddering, overheating, or hunting for gears , don’t risk a full failure. Bring it to DK Auto & Diesel Service for a professional diagnostic and rebuild options. Serving Magnolia, Montgomery, Conroe, The Woodlands, Tomball, Willis, and Spring.

The Ford 5R110W TorqShift transmission was used in 2003–2010 Super Duty trucks with the 6.0L and 6.4L Powerstroke diesel. Marketed as a 5-speed, it actually operates more like a 6-speed with a computer-controlled shifting strategy. While the 5R110 is known as one of Ford’s more durable heavy-duty transmissions, it still develops shudder, solenoid problems, and limp mode issues over time. At DK Auto & Diesel Service in Magnolia, TX , we provide complete diagnostics, rebuilds, and upgrades for the 5R110W. Common Ford 5R110 Transmission Problems & Symptoms 1. Torque Converter Failure • Symptoms : ◦ Shudder at highway speeds ◦ RPM flare when towing or climbing hills ◦ Loss of lockup function • Causes : ◦ Converter clutch wear (common in tuned/towed trucks) ◦ Overheating during heavy loads • Fixes : ◦ Upgrade to a billet multi-disc torque converter ◦ TCM calibration to optimize lockup strategy ◦ Cooler upgrades for towing applications 2. Solenoid Pack & Valve Body Issues • Symptoms : ◦ Harsh or erratic shifts ◦ Delay into drive or reverse ◦ Stuck in limp mode • Causes : ◦ Failed solenoid pack (integrated unit on 5R110) ◦ Valve body gasket leaks or bore wear • Fixes : ◦ Replace solenoid pack with new/upgraded unit ◦ Rebuild/upgrade valve body with Sonnax kits ◦ Perform adaptive relearn after repair 3. Overheating Under Load • Symptoms : ◦ Transmission temperature light or limp mode ◦ Fluid darkening or burnt smell ◦ Loss of pulling power on long grades • Causes : ◦ Towing heavy loads without sufficient cooling ◦ Stock calibration allowing converter slip • Fixes : ◦ Auxiliary transmission cooler install ◦ Synthetic fluid service ◦ TCM tuning to reduce slip under load 4. Input Shaft & Hard-Part Failures • Symptoms : ◦ Loss of drive in certain gears ◦ Metallic debris in fluid ◦ Sudden failure under heavy throttle/tow • Causes : ◦ Stock input shaft twisting/snapping with high power ◦ Clutch drum wear in high-mileage units • Fixes : ◦ Hardened input shaft installation (performance/towing builds) ◦ Full rebuild with upgraded drums and steels 5. Electronic / TCM Faults • Symptoms : ◦ “Transmission Fault” or limp mode ◦ Codes like P2703, P2704, or solenoid performance errors ◦ Erratic shift scheduling • Causes : ◦ TCM software corruption ◦ Faulty wiring or sensors • Fixes : ◦ Updated programming or TCM replacement ◦ Harness/sensor repair ◦ Full scan and adaptive relearn How DK Auto & Diesel Fixes the 5R110 TorqShift We strengthen the 5R110W beyond stock for tow, work, and performance: Billet torque converter upgrades Heavy-duty clutch packs & steels Solenoid pack replacement & valve body rebuilds Hardened input shafts for tuned trucks Auxiliary cooling installs for Texas towing 24-month / 24,000 mile warranty Schedule Your 5R110 Transmission Diagnostic in Magnolia, TX If your 5R110 TorqShift is slipping, shuddering, or overheating , bring it to DK Auto & Diesel Service for a complete diagnostic and upgrade plan. Serving Magnolia, Montgomery, Conroe, The Woodlands, Tomball, Willis, and Spring.

The Ford 6R80 6-speed automatic transmission was used in F-150 trucks, Mustangs, Expeditions, and other Ford vehicles from 2009–2017. It’s known as a reliable transmission when maintained, but many owners report shudder, flare, and erratic shifts as mileage increases — especially under towing or with poor fluid service. At DK Auto & Diesel Service in Magnolia, TX, we provide diagnostics, rebuilds, upgrades, and tuning solutions for the 6R80. Common Ford 6R80 Transmission Problems & Symptoms 1. Shift Flare (2–3, 3–4 Upshift) • Symptoms : ◦ RPMs jump during shifts ◦ Delay engaging the next gear ◦ Feels like slipping between gears • Causes : ◦ Valve body bore wear / solenoid leaks ◦ Line pressure issues ◦ TCM adaptive learning errors • Fixes : ◦ Valve body rebuild or replacement (Sonnax kits) ◦ Solenoid service/replacement ◦ TCM software update or custom tuning 2. Torque Converter Shudder • Symptoms : ◦ Vibration during steady cruise (40–60 mph) ◦ Feels like rumble strips or a “misfire” ◦ RPM fluctuations when converter locks/unlocks • Causes : ◦ Converter clutch wear ◦ Fluid breakdown (Mercon LV) • Fixes : ◦ Replace with upgraded torque converter ◦ Fluid flush with correct Mercon LV or ULV (depending on year) ◦ Tuning to optimize lockup apply strategy 3. Harsh or Delayed Shifting • Symptoms : ◦ Hard “bang” into gear (especially into reverse or 1st) ◦ Rough downshifts when slowing down ◦ Delay going into drive/reverse • Causes : ◦ Valve body gasket failure ◦ Worn accumulator pistons ◦ TCM calibration issues • Fixes : ◦ Valve body rebuild and gasket replacement ◦ Updated separator plates ◦ Adaptive learn reset after repair 4. Overheating Under Tow/Load • Symptoms : ◦ Transmission over-temp warnings ◦ Burnt-smelling fluid ◦ Limp mode when towing heavy • Causes : ◦ Insufficient cooling capacity for heavy towing ◦ Excess converter slip • Fixes : ◦ Add auxiliary cooler ◦ ECM/TCM tuning to raise line pressure and reduce slip ◦ Shorten fluid service intervals 5. Electronic / TCM Problems • Symptoms : ◦ “Transmission Fault” message ◦ Limp mode activation ◦ Trouble codes like P0731, P2701, P0729 • Causes : ◦ TCM failure or corrupted programming ◦ Solenoid body control module (mechatronic) issues • Fixes : ◦ Replace solenoid body (integrated electronics/valve body unit) ◦ Update programming with latest Ford calibration ◦ Relearn procedure after installation How DK Auto & Diesel Fixes the 6R80 We make 6R80s shift smoother, run cooler, and last longer : Upgraded torque converters for towing/performance Valve body & solenoid rebuilds with Sonnax kits TCM tuning for better shift pressure & timing Auxiliary cooler installs for heavy-duty use Heavy-duty rebuilds with improved clutches/steels 24-month / 24,000 mile warranty Schedule Your Ford 6R80 Transmission Diagnostic in Magnolia, TX If your 6R80 is slipping, shuddering, or overheating , don’t wait until it fails completely. Get a professional diagnostic at DK Auto & Diesel Service . Serving Magnolia, Montgomery, Conroe, The Woodlands, Tomball, Willis, and Spring.

The Ford 10R80 10-speed automatic transmission was introduced in 2017 and is used in the F-150, Mustang, Expedition, Ranger, and Bronco. While the 10R80 delivers efficiency and smooth power delivery, many owners report shift quality issues, torque converter shudder, and overheating — especially under towing or after tuning. At DK Auto & Diesel Service in Magnolia, TX , we provide diagnostics, rebuilds, and ECM/TCM tuning solutions for the 10R80. Common Ford 10R80 Transmission Problems & Symptoms 1. Harsh or Erratic Shifting • Symptoms : ◦ Hard 1–2 or 2–3 shifts ◦ Rough downshifts when slowing down ◦ Delay engaging drive or reverse • Causes : ◦ TCM calibration issues ◦ Valve body bore wear / solenoid sticking ◦ Adaptive learning errors • Fixes : ◦ TCM software update or custom tuning ◦ Valve body repair/replacement ◦ Reset/relearn adaptive strategy 2. Torque Converter Shudder • Symptoms : ◦ Vibration during steady cruise (40–60 mph) ◦ Feels like driving over rumble strips ◦ RPM surging when converter locks/unlocks • Causes : ◦ Converter clutch failure ◦ Fluid breakdown (Mercon ULV contamination) • Fixes : ◦ Replace with upgraded/billet torque converter ◦ Fluid flush with correct Mercon ULV ◦ Tuning to refine lockup strategy 3. Shift Flare / Gear Hunting • Symptoms : ◦ RPM flare between gears (esp. 2–3 or 5–6) ◦ Feels like slipping before gear engages ◦ Constant hunting between gears at light throttle • Causes : ◦ Valve body wear or separator plate issues ◦ TCM programming errors • Fixes : ◦ Rebuild valve body with Sonnax upgrades ◦ TCM recalibration or custom tune ◦ Adaptive reset after service 4. Overheating Under Tow/Load • Symptoms : ◦ Transmission over-temp warnings ◦ Fluid turning dark/burnt smell ◦ Limp mode while towing heavy • Causes : ◦ Converter slip generating excess heat ◦ Limited cooling capacity in stock form • Fixes : ◦ Install auxiliary cooler ◦ ECM/TCM tuning for higher line pressure & reduced slip ◦ Service fluid more frequently under towing conditions 5. Electronic / TCM Failures • Symptoms : ◦ “Transmission Fault” warning light ◦ Stuck in limp mode ◦ Trouble codes (P0741, P2701, P0777, etc.) • Causes : ◦ TCM corruption or failure ◦ Faulty solenoid body assembly (mechatronic unit) • Fixes : ◦ Replace solenoid body with updated unit ◦ Reprogram with latest Ford calibration ◦ Perform adaptive relearn procedure How DK Auto & Diesel Fixes the 10R80 We correct weak points and tune the 10R80 for smoother, longer-lasting performance: Billet torque converter upgrades Valve body & solenoid repairs (Sonnax solutions) TCM programming and adaptive reset Auxiliary cooler installs for Texas towing conditions Heavy-duty rebuilds with upgraded clutches & steels 24-month / 24,000 mile warranty Schedule Your Ford 10R80 Transmission Diagnostic in Magnolia, TX If your 10R80 is shuddering, hunting for gears, or overheating , bring it to DK Auto & Diesel Service for a full inspection and upgrade options. Serving Magnolia, Montgomery, Conroe, The Woodlands, Tomball, Willis, and Spring .

The Ford 6R140 TorqShift transmission was introduced in 2011 Super Duty trucks and paired with the 6.7L Power Stroke diesel and 6.8L V10 gas engines. It’s a heavy-duty 6-speed designed for high torque capacity and towing, but it’s not without its weak points. Owners commonly report torque converter failures, valve body wear, and overheating under load. At DK Auto & Diesel Service in Magnolia, TX , we specialize in diagnosing, rebuilding, and upgrading the 6R140 for long-lasting reliability. Common Ford 6R140 Transmission Problems & Symptoms 1. Torque Converter Failure • Symptoms : ◦ Shudder or vibration during steady cruise ◦ RPM flare under load or towing ◦ Lockup not engaging smoothly • Causes : ◦ Converter clutch wear (especially on tuned trucks) ◦ Overheating from excess slip • Fixes : ◦ Replace with heavy-duty billet torque converter ◦ TCM tuning to optimize lockup strategy ◦ Fluid flush with Ford-approved Mercon LV 2. Valve Body & Solenoid Problems • Symptoms : ◦ Harsh or erratic shifts ◦ Delay into drive or reverse ◦ Codes for solenoid performance (e.g., P0776, P2701) • Causes : ◦ Bore wear in valve body ◦ Sticking solenoids ◦ Separator plate gasket failure • Fixes : ◦ Rebuild valve body with Sonnax upgrades ◦ Replace solenoids as needed ◦ Install updated gaskets & plates 3. Overheating Under Heavy Tow • Symptoms : ◦ Transmission over-temp warnings ◦ Burnt-smelling fluid ◦ Limp mode when hauling or climbing grades • Causes : ◦ Insufficient cooling capacity under extreme load ◦ High fluid temps from converter slip • Fixes : ◦ Auxiliary transmission cooler installation ◦ ECM/TCM tuning to raise line pressure and reduce slip ◦ Fluid service intervals shortened for heavy tow trucks 4. Gear Slippage / Limp Mode • Symptoms : ◦ Slipping in 5th or 6th gear under load ◦ Sudden loss of power with truck stuck in 5th gear ◦ “Transmission Fault” warning light • Causes : ◦ Burned clutch packs ◦ Drum or shaft failure in high-mileage/tuned trucks • Fixes : ◦ Rebuild with heavy-duty clutches and steels ◦ Upgrade to hardened shafts/drums for tuned applications ◦ Updated calibration to prevent repeat failures 5. TCM / Electrical Issues • Symptoms : ◦ Erratic shift scheduling ◦ Stuck in limp mode with codes ◦ “Service Transmission” warning • Causes : ◦ TCM software corruption or failed solenoid pack ◦ Harness or sensor malfunctions • Fixes : ◦ Replace solenoid body assembly (mechatronic unit) ◦ Reprogram with latest Ford software or custom tune ◦ Perform adaptive relearn after service How DK Auto & Diesel Fixes the 6R140 We strengthen the 6R140 for towing, work trucks, and performance builds: Billet & heavy-duty torque converters Valve body rebuilds with Sonnax upgrades Heavy-duty clutches, steels, and shafts Auxiliary cooler installs for towing in Texas heat ECM/TCM tuning to reduce slip and extend life 24-month / 24,000 mile warranty Schedule Your Ford 6R140 Transmission Diagnostic in Magnolia, TX If your 6R140 TorqShift is slipping, overheating, or going into limp mode , get it inspected before major failure. Bring it to DK Auto & Diesel Service for diagnostics and upgrade options. Serving Magnolia, Montgomery, Conroe, The Woodlands, Tomball, Willis, and Spring .

The Ford 4R70W transmission family (including the 4R70E and 4R75E variants) was used in F-150 trucks, Expeditions, Mustangs, Crown Victorias, and other RWD Fords from the mid-1990s through the mid-2000s. These units are generally reliable, but they’re also known for slipping, OD band failure, and solenoid issues — especially when neglected or under heavy loads. At DK Auto & Diesel Service in Magnolia, TX , we diagnose, rebuild, and upgrade 4R70W-family transmissions to handle both daily driving and towing. Common Ford 4R70W / 4R70E / 4R75E Transmission Problems & Symptoms 1. Overdrive Band Failure • Symptoms : ◦ No overdrive (4th gear won’t engage) ◦ Slipping at highway speeds ◦ Check engine light with OD codes • Causes : ◦ Weak OD band and servo piston wear ◦ Heat and high mileage breakdown • Fixes : ◦ Replace band with upgraded heavy-duty version ◦ Servo bore repair kits (Sonnax solutions) ◦ Full rebuild if clutches/bands are burned 2. Torque Converter Issues • Symptoms : ◦ Shudder during highway cruising ◦ RPM flare at steady throttle ◦ Whining noise in gear • Causes : ◦ Worn converter clutch ◦ Fluid breakdown • Fixes : ◦ Replace with upgraded torque converter ◦ TCC solenoid replacement ◦ Fluid service with Mercon V 3. Solenoid & Valve Body Problems • Symptoms : ◦ Harsh or erratic shifts ◦ Delay going into drive or reverse ◦ Trouble codes (P0750, P0755, etc.) • Causes : ◦ EPC solenoid failure (common) ◦ Valve body wear or gasket failure • Fixes : ◦ Replace EPC, TCC, and shift solenoids as needed ◦ Rebuild/upgrade valve body with new gaskets and plates ◦ Install shift kit for firmer, more reliable shifts 4. Overheating & Fluid Breakdown • Symptoms : ◦ Burnt smell from fluid ◦ Slipping in multiple gears ◦ Early clutch/band failure under towing • Causes : ◦ Inadequate cooling for trucks used in hot climates or heavy tow • Fixes : ◦ Add auxiliary cooler ◦ Shorten service intervals ◦ Use upgraded Mercon V fluid 5. Mechanical Hard-Part Failures • Symptoms : ◦ Loss of reverse or forward gears ◦ Loud clunks when shifting ◦ Transmission won’t move at all • Causes : ◦ Forward clutch drum cracking (common in high-mileage units) ◦ Input shaft wear • Fixes : ◦ Full rebuild with upgraded drums and shafts ◦ Install hardened input shafts on performance/towing builds How DK Auto & Diesel Fixes the Ford 4R70W Family Our rebuilds address weak points and extend service life: Heavy-duty OD bands & clutches Hardened input shafts for trucks/performance use EPC & shift solenoid replacements Valve body rebuilds with Sonnax upgrades Auxiliary coolers for towing in Texas heat 24-month / 24,000 mile warranty Schedule Your 4R70W / 4R75E Transmission Diagnostic in Magnolia, TX If your 4R70W is slipping, shuddering, or won’t go into overdrive , bring it to DK Auto & Diesel Service for a full diagnostic. Serving Magnolia, Montgomery, Conroe, The Woodlands, Tomball, Willis, and Spring.

The ZF 8HP transmission is one of the most widely used 8-speed automatics in the world. In the Stellantis (formerly FCA/Chrysler) lineup, it’s found under several names: • 845RE → Dodge Charger, Dodge Challenger, Chrysler 300, Jeep Grand Cherokee (V6) • 850RE → Jeep Grand Cherokee, Dodge Durango, Ram 1500 (gas engines) • 8HP75 → Ram 1500 5.7L HEMI, Jeep Grand Cherokee (higher torque version) • 8HP95 → Ram 1500 EcoDiesel & high-output variants (highest torque rating) Although praised for smoothness and fuel efficiency, these transmissions suffer from torque converter shudder, harsh shifts, overheating under tow, and mechatronic unit failures. At DK Auto & Diesel Service in Magnolia, TX , we repair, rebuild, and tune ZF 8HP / Stellantis 845RE, 850RE, 8HP75, 8HP95 transmissions for trucks, SUVs, and performance cars. Common ZF 8HP / Stellantis Transmission Problems & Symptoms 1. Torque Converter Shudder • Symptoms : ◦ Rumble-strip vibration at 40–70 mph ◦ RPM fluctuations at highway cruise • Causes : ◦ Converter clutch wear ◦ Incorrect or degraded fluid • Fixes : ◦ Replace with upgraded converter ◦ Flush/refill with ZF Lifeguard 8 or Mopar/Stellantis-approved ATF ULV ◦ Update TCM calibration 2. Harsh or Delayed Shifts • Symptoms : ◦ Hard 1–2 or 2–3 shifts ◦ Jerky downshifts when stopping • Causes : ◦ Valve body wear ◦ Mechatronic unit failure • Fixes : ◦ Rebuild valve body with Sonnax/ZF upgrades ◦ Replace mechatronic/solenoid unit ◦ Reset adaptive strategy 3. Overheating (Ram/Jeep Truck Applications) • Symptoms : ◦ Over-temp warnings under tow ◦ Burnt-smelling fluid • Causes : ◦ Limited cooling capacity ◦ Converter slip under load • Fixes : ◦ Install auxiliary cooler ◦ Service fluid every 30k–40k under towing use ◦ Custom tuning to increase line pressure 4. Gear Hunting / Shift Flare • Symptoms : ◦ Constant gear changes at steady cruise ◦ RPM flare before gear engagement • Causes : ◦ Fuel economy-biased TCM programming ◦ Valve body cross leaks • Fixes : ◦ TCM tuning for refined shift logic ◦ Valve body repair/replacement 5. Mechatronic Unit Failures • Symptoms : ◦ “Service Transmission” warning ◦ Limp mode activation • Causes : ◦ Electronics integrated into valve body fail • Fixes : ◦ Replace solenoid/mechatronic assembly ◦ Perform relearn procedure How DK Auto & Diesel Fixes the ZF 8HP (Stellantis / FCA) We service all Stellantis/FCA versions of the ZF 8HP: 845RE, 850RE (cars & SUVs) 8HP75, 8HP95 (Ram trucks & Jeep applications) Torque converter replacements & upgrades Valve body & solenoid/mechatronic repairs ECM/TCM tuning for smoother shifts and towing Auxiliary cooler installs for Ram/Jeep trucks 24-month / 24,000 mile warranty Schedule Your Stellantis / FCA ZF 8HP Transmission Diagnostic If your ZF 8HP / Stellantis 845RE, 850RE, 8HP75, or 8HP95 is slipping, shuddering, or overheating, bring it to DK Auto & Diesel Service for a professional diagnostic.  Serving Magnolia, Montgomery, Conroe, The Woodlands, Tomball, Willis, and Spring.