A transmission complaint deserves a diagnosis before a quote. Plenty of shifting problems come from a sensor, a solenoid, low or burnt fluid, a wiring fault or outdated software, and a rebuild will not fix any of those. RDI Power diagnoses and repairs diesel truck transmissions at our Brooksville shop, handles rebuilds and replacements when a unit is damaged inside, and tells you which of those your truck actually needs, with the evidence to back it up.
Transmissions we work on
Ford Super Duty
- E4OD (often written E40D): the 4-speed automatic behind 1990s 7.3L diesels, including early 7.3L Power Strokes
- 4R100: its successor, behind the 7.3L Power Stroke in 1999 to 2003 Super Duty trucks. Our comparison of the E40D and 4R100 covers both.
- 5R110W TorqShift: the 5-speed behind the 6.0L and 6.4L Power Stroke in 2003 to 2010 Super Duty trucks. See common 5R110W problems.
- 6R140: the 6-speed behind the 6.7L Power Stroke in 2011 to 2019 Super Duty trucks
- 10R140: the 10-speed behind the 6.7L Power Stroke from 2020 on. See why 10R140 problems should not be ignored.
Ram trucks
- 47RE and 48RE: the 4-speed automatics behind the 5.9L Cummins
- 68RFE: the 6-speed automatic behind the 6.7L Cummins
- Aisin: the heavy-duty automatic used in high-output Ram 3500 and chassis cab trucks
GM, medium duty, buses and motorhomes
- Allison 1000: the 5-speed and 6-speed automatics behind the Duramax in Chevrolet and GMC heavy duty pickups through 2019
- Allison 10-speed: behind the Duramax from 2020 on
- Allison medium duty automatics: in medium duty trucks, buses and diesel pushers
Manual transmissions and clutches
Manual gearboxes in heavy trucks, including 10-, 13- and 18-speed units, and the 6-speed manuals in older Ram and Ford Super Duty pickups, such as the G56, NV5600 and ZF 6-speed. Clutch replacement, adjustment, release bearings and flywheels are covered on our clutch repair page.
How we diagnose a transmission
1. Scan
We read stored and pending codes from the engine and transmission control modules, then watch live data while the truck drives: commanded versus actual gear, shift timing, torque converter clutch slip, fluid temperature and solenoid commands. Some complaints are software. A control module that needs an update or a relearn can shift badly on a perfectly healthy transmission.
2. Fluid analysis
Fluid level gets checked the way the manufacturer specifies, usually at a set temperature, because a cold reading can be off enough to matter. Then we look at the fluid itself: color, smell and what is suspended in it. Dark, burnt fluid points to heat and slipping clutches. Metal on the pan magnet tells us how much internal wear has already happened. Leaks get traced to the pan gasket, cooler lines, seals or the cooler itself; our guide to transmission fluid leaks explains the usual suspects.
3. Road test
We drive the truck under the conditions that cause the complaint, loaded or empty, cold or hot, climbing or cruising, and feel for flare, slip, harsh engagement, shudder and delayed shifts.
4. Pinpoint tests
Solenoid and sensor circuits, wiring, connectors and, where it applies, pressure tests. By the end we know whether the problem is outside the transmission, inside it, or both.
Repair, rebuild or replace
Repair
When the transmission itself is healthy, the fix is often outside it or bolted to it: a solenoid, a sensor, a wiring repair, a valve body, an external leak, a cooler line or a software update. These repairs cost far less than a rebuild and fix the actual problem.
Rebuild
When there is internal damage, the transmission comes out of the truck and gets torn down completely. Every part is cleaned and inspected to find what failed and why. Clutch packs, steels, seals, gaskets, bushings and filters are replaced along with any worn hard parts, and on units with known weak points, upgraded parts can make the rebuilt transmission stronger than it left the factory. The torque converter is addressed, and the cooler and lines are flushed or the cooler replaced, because debris left in a cooler will travel straight into a freshly rebuilt unit. Then it is reassembled to specification and reinstalled. For the full comparison, read transmission rebuild vs. replacement.
Replace
A remanufactured transmission can be the better call when the case is damaged, when parts costs approach the price of a remanufactured unit, or when getting the truck back in service quickly outweighs the savings of a rebuild. We do not recommend used transmissions for work trucks; you are buying someone else’s unknown history.
The decision comes down to the severity of the damage, the age and condition of the truck, how long you plan to keep it and your budget. We walk you through each before any work starts.
Brooksville’s rolling ground and loaded trailers
Brooksville does not fit the flat-Florida picture. The city sits on rolling ground between roughly 100 and 180 feet above sea level, and while those are modest hills, a truck pulling a loaded gooseneck feels every one of them. Climbing under load raises fluid temperature, especially when the torque converter unlocks and slips to multiply torque, and it works the clutches and shift pressures harder than cruising on level highway does. Heat is the enemy of automatic transmission fluid, and Florida summers add their own share.
That is why towing trucks here benefit from fluid service at sensible intervals, an auxiliary cooler that is clean and flowing, and a transmission temperature gauge the driver actually watches. When the temperature climbs higher than it used to on the same load, treat it as an early warning worth a call.
Signs it is time to come in
- Slipping, flaring between gears or engine speed rising without the truck gaining speed
- Harsh, late or delayed shifts, or a long pause before it engages drive or reverse
- Shudder at steady highway speed, often torque converter related
- A transmission temperature warning, or fluid that smells burnt
- Fluid spots under the truck
- A check engine or transmission warning light
The longer a slipping transmission is driven, the more expensive the repair gets. Our article on signs your truck needs a transmission rebuild goes into each one.
Tuned and modified trucks
Added engine power goes straight through the transmission. A tune that raises torque can push clutch packs and the torque converter past what they were built to hold, and slipping or flaring that shows up after a tune is common on diesel pickups. Tell us about any tuning or modifications before we diagnose. If you plan to keep the extra power, a rebuild can include clutches, converter and other parts chosen for the torque the truck actually makes.
Heavy trucks, buses and motorhomes
Bigger trucks bring different transmission work. On manual heavy trucks that usually means clutch adjustment and replacement, shift problems, gear oil leaks and worn driveline parts behind the transmission. On Allison-equipped medium duty trucks, buses and diesel pushers, it means fluid and filter service on schedule, shift diagnosis with a scan tool, and tracking down leaks and cooler problems. Many of these vehicles run thousands of hours of stop-and-go or idling service, which is hard on fluid even when the mileage looks low. Older Ford and Ram automatics such as the E4OD, 4R100 and 47RE are now decades old, so worn clutches, tired solenoids and hardened seals are expected wear rather than surprises.
How a rebuild goes
When a transmission needs a rebuild, the unit comes out of the truck and comes apart completely. Every part is cleaned and inspected, and the clutch packs, bearings, seals and gaskets are replaced along with any worn hard parts the inspection turns up. The valve body and solenoids get checked, the unit goes back together to factory specifications, and after installation we road test it with the scan tool connected and run any relearn the transmission module needs. The digital inspection shows you photos of what we found inside.
Warranty
Transmission labor at RDI Power carries our 3-year/36,000-mile labor warranty, and fleet repairs under RDI Fleet carry a 2-year/24,000-mile warranty. Before you approve a rebuild or replacement, we explain what the parts or unit warranty covers so there are no surprises later. If you are weighing whether a rebuild is worth it on an older truck, our article on rebuilt truck transmissions lays out the tradeoffs.
Keeping a transmission alive
Heat kills automatic transmissions. Towing and hauling in a Florida summer pushes fluid temperatures up, and fluid that has been cooked stops protecting clutches and bearings. Use the severe service schedule if your truck works hard, keep the cooler clean, fix leaks early and watch the transmission temperature reading if your truck has one.
If your truck is shifting wrong, slipping or leaking, bring it to our Brooksville shop or request service online. We will diagnose it first and give you a straight answer on repair, rebuild or replacement.