Chrysler A604
Ultradrive Problems & Cost

Chrysler launched the A604 in 1989 under the Ultradrive name. It was the first fully adaptive electronically controlled automatic in a mass-market front-wheel-drive car, and that is exactly why it developed a bad name. There is no mechanical governor and no throttle valve cable on this transaxle. The transmission control module reads speed sensors and throttle position, then commands every shift electrically through a solenoid pack. If the electronics are unhappy, the transmission is unhappy, even when every clutch inside it is perfect.

Chrysler later renamed it the 41TE under its four-character scheme, and the same basic unit carried on for decades in Caravan and Town & Country minivans, Neon, Stratus, Cirrus, Sebring, PT Cruiser, and Journey, with the 40TE, 41AE, and 42LE as close relatives. Later production units are meaningfully better than 1989 to 1993 units — the early failures were largely a fluid specification problem that Chrysler fixed.

If you have one running today, most of the failures you will hit are electrical or hydraulic, not catastrophic. Diagnose before you condemn.

Problem 1 — Solenoid Pack Failure

The solenoid pack is the number one A604 repair. It sits on top of the valve body behind the side cover, contains the shift solenoids plus the pressure switches the TCM uses to confirm what gear actually engaged, and it is the single component doing the most work on this transaxle.

Symptoms

• Sudden drop into limp mode — second gear only, with park, reverse, and neutral still working
• Harsh or delayed 2-3 or 3-4 shift, or a shift that never happens at all
• Check engine light with solenoid or pressure switch codes in the P0750 to P0760 range
• Fault that appears when the transmission is hot and clears after it sits overnight — classic degrading solenoid pack
• No 4th gear / no overdrive with no slipping sensation

Diagnosis

Pull codes with a scan tool that reads Chrysler transmission modules, not just generic powertrain codes. The pressure switch data is what separates a solenoid pack from a clutch failure: if the TCM commands a gear, the pressure switch reports the correct state, and the vehicle still does not shift, the problem is mechanical. If the pressure switch state does not match the command, the pack is the suspect. Check the fluid before anything — low fluid produces identical symptoms.

Cost

Solenoid pack itself runs $130 to $300 in 2026 depending on brand and whether you buy the OE-level unit. Labor is 1.5 to 2.5 hours plus fluid and a gasket, so $400 to $750 installed at an independent. Dealer pricing lands $700 to $1,100.

Do not skip the quick-learn. After a solenoid pack replacement the TCM has to run its clutch volume relearn procedure with a bidirectional scan tool, and the pinion factor has to be correct. Skip it and the car shifts badly on a brand new part, which is how good solenoid packs get blamed and thrown away.

A604 / 41TE solenoid packsScan tools that run Chrysler quick-learn →

Not sure whether you need a solenoid pack or a full valve body? Valve body vs solenoid pack, explained. Pricing across Chrysler platforms: cost to replace a transmission solenoid pack.

Problem 2 — Limp Mode (Limp-In)

Limp-in is not a failure by itself. It is the TCM's response to a fault it cannot drive around. You get second gear forward, plus park, reverse, and neutral, and the car will move but will not shift. Understanding that saves people thousands of dollars, because a $30 sensor and a $3,000 rebuild produce the exact same driving symptom.

The four things that actually cause it

• Speed sensor mismatch. The TCM compares input and output speed sensor signals continuously. If the calculated ratio does not match the commanded gear within tolerance, it commands limp. This is the most common cause and the cheapest fix.
• Solenoid pack electrical fault. Open or shorted solenoid circuit, or a pressure switch that disagrees with the commanded gear.
• Low or degraded fluid. Low line pressure means slow clutch apply, which reads as a ratio error to the TCM.
• Loss of TCM communication or power. Corroded connector, chafed harness, bad ground, or a failing TCM. Chrysler harness connectors of this era corrode; inspect before you buy modules.

The five-minute triage

Check fluid level and smell it. Pull codes. Cycle the key three times — if limp clears on a restart and comes back at the same road speed or the same shift, you are looking at a speed sensor or a solenoid pack. If it never clears, look at wiring and power/ground first. Only after all that does anyone open the transaxle.

The same diagnostic logic applies to the later 41TE variants: 41TE transmission problems and cost.

Problem 3 — Input and Output Speed Sensors

These two sensors are the cheapest fix on the entire transaxle and are responsible for a large share of the A604's undeserved reputation. They thread into the case, they are accessible from above or from the wheel well on most applications, and they fail from heat cycling and connector corrosion.

Symptoms

• Limp mode that appears at a consistent point — a particular speed or a particular shift
• Erratic or dropping-out speedometer on applications that take vehicle speed from the output sensor
• Ratio error codes in the P0715 to P0725 family
• Symptoms that get worse as the transmission heats up

Diagnosis

Watch input and output rpm live on a scan tool while driving. A dropout, a spike to zero, or a signal that goes ragged as temperature climbs is a bad sensor. Before you replace either one, pull the connector and look at the pins — green corrosion on the terminals is common and a $6 connector repair beats a $40 sensor that will not fix it. Also confirm the sensor tip is clean; a magnetic tip loaded with clutch debris gives a weak signal and is itself a warning about what is happening inside.

Cost

Sensors are $18 to $45 each. Most people replace both while they are in there. Labor is half an hour to an hour, so a shop bill of $110 to $220. As a DIY job it is a socket, a new O-ring, and a few ounces of fluid. This is the first thing to check on any limp-mode Ultradrive.

41TE input and output speed sensors

Problem 4 — The ATF+4 Requirement (Do Not Get This Wrong)

This is the single most important thing on this page. The A604 requires ATF+4. Early units specified ATF+3 (and before that, Chrysler 7176 fluid); ATF+4 supersedes those and is what you buy today. It is not a suggestion and it is not a marketing exercise.

The Ultradrive's adaptive clutch control and its converter clutch were designed around a specific friction curve. Dexron, Mercon, and the universal multi-vehicle bottles that claim to cover "all makes" have a different friction modifier package. Put the wrong fluid in an A604 and you get torque converter shudder and harsh, hunting shifts within a few hundred miles, followed by real clutch damage. A very large share of the early Ultradrive failures that built this transmission's reputation were exactly this: shops topping them off with whatever ATF was on the shelf.

Rules to follow

• Buy fluid that is licensed to the ATF+4 specification, not fluid that says it is "suitable for" or "recommended for" ATF+4 applications. There is a difference and it is printed on the bottle.
• Do not add a friction modifier bottle to a conventional ATF and call it ATF+4. It is not the same fluid.
• If the wrong fluid has been in it, a full exchange plus a filter is the fix — do it before the shudder becomes clutch damage.
• Service interval: a drain, filter, and fill every 30,000 to 50,000 miles. These transaxles reward fluid maintenance more than almost anything else on the road.

Cost

A pan drop with filter and gasket takes 5 to 6 quarts. Fluid runs $8 to $12 per quart, filter and gasket kit $18 to $35. DIY total $70 to $120. At a shop, $180 to $300.

ATF+4 licensed transmission fluid41TE filter and gasket kits →

More on the spec and the naming confusion around it: the ATF+4 spec explained.

Problem 5 — Internal Wear: Clutches, Converter, and Pump

When an A604 does fail mechanically, it follows a pattern.

• Overdrive and underdrive clutch packs. These carry the most load and burn first, usually after a period of slipping that was ignored. Symptom is slipping in a specific gear that gets worse hot, and a burnt smell in the fluid.
• Torque converter lockup shudder. Often fluid-related and fixable early. Once the lining is gone, the converter is replaced — and it should always be replaced during a rebuild, never reused.
• Front pump and bushing wear. Produces low line pressure across the board, which shows as universally soft, late shifts rather than a single bad gear.
• Valve body bore wear. Aluminum bores wear oval over decades of use. Symptom is inconsistent shift quality that a solenoid pack does not fix. On a high-mileage unit this is why a solenoid pack sometimes disappoints.
• Cooler line and cooler debris. After any internal failure, the cooler and lines are full of clutch material. If they are not thoroughly flushed or replaced, that debris goes straight into the rebuilt unit.

Rebuild vs Replace — 2026 Pricing

The honest math

Most vehicles still running an A604 are worth less than the rebuild. A $3,000 rebuild in a $2,500 minivan is not a repair decision, it is a sentimental one. Before you authorize anything past a solenoid pack, price the vehicle.

The cases where a rebuild does make sense: a clean low-mileage car the owner plans to keep, a body in good shape with no rust, or a situation where the alternative is a car payment. In those cases insist on updated parts, a new converter, a thoroughly flushed cooler circuit, and a proper quick-learn on delivery.

The case where a salvage unit makes sense: almost never. These units are all old now, and you have no idea what fluid the last owner ran. If you go that route, replace the solenoid pack and do a full fluid and filter service before it ever sees load.

DIY vs Shop

Reasonable at home

• Input and output speed sensors — hand tools, under an hour, biggest bang for the buck
• Fluid, filter, and gasket service — a pan drop, nothing exotic
• Solenoid pack — doable, but you need a bidirectional scan tool for the quick-learn afterward or do not start
• Connector and harness repair — often the actual fix, and a soldering iron is cheaper than a module
• Reading codes and live speed sensor data before you pay a shop for a diagnosis

Send it to a shop

• Valve body replacement — possible in the vehicle, but bore wear diagnosis takes experience
• Torque converter — transaxle out, which is a full FWD driveline job with axles and subframe
• Any rebuild — clutch clearance setting and endplay shimming on this unit needs the specs and the tools
• Anything with metal or heavy clutch debris in the pan — you are past repairing and into replacing

FAQ

Is the A604 the same as the 41TE?

Yes. A604 was the original engineering designation, Ultradrive was the marketing name, and 41TE is the later Chrysler naming convention for the same transaxle. The 40TE, 41AE, and 42LE are close relatives sharing most internals and the same solenoid pack design.

What does limp mode mean on an Ultradrive?

The TCM has found a fault it cannot compensate for and has commanded limp-in: second gear forward, plus park, reverse, and neutral. The usual triggers are a speed sensor mismatch, a solenoid pack fault, low fluid, or lost TCM communication. It is a symptom, not a diagnosis.

How much does an A604 solenoid pack cost to replace?

The pack is $130 to $300, and $400 to $750 installed at an independent shop with fluid, gasket, and the quick-learn procedure. If you have a bidirectional scan tool it is a reasonable DIY job.

Can I use Dexron or a universal ATF in an A604?

No. It requires ATF+4. Dexron, Mercon, and most universal multi-vehicle fluids have the wrong friction package for the Ultradrive's converter clutch and adaptive control, and you will get shudder and harsh shifts quickly, then real clutch damage.

Is it worth rebuilding an A604 in 2026?

Only if the vehicle is worth it. A rebuild is $2,000 to $3,200 and a reman unit installed is $2,600 to $4,000. On a minivan worth $2,500 the math fails. On a clean, low-mileage car you intend to keep, a proper rebuild with updated parts and a new converter is reasonable money.

Why did the Ultradrive get such a bad reputation?

Three reasons, in order: the wrong fluid was routinely put in them in the early years, the fully adaptive electronic control was new and shops did not know how to diagnose it, and the early 1989 to 1993 production had real teething problems that later revisions addressed. A late-production, properly maintained 41TE on the correct fluid is a reasonably durable transaxle.