Cintroen c3 al4 2003

[Kakjim23]

I have a 2003 Citroën C3 1.4 with an AL4 automatic transmission.

The transmission intermittently starts slipping, and the Sport and Snowflake warning lights come on. After turning the engine off and restarting it, the transmission can sometimes work completely normally again. There are also times when I can drive for about an hour without experiencing any problem at all.

A diagnostic scan reportedly showed “slipping clutch/brake.” However, the mechanic who performed the scan only spent about 5 minutes checking the car and did not inspect the transmission fluid, hydraulic pressure, solenoids, or valve body.

He told me that the transmission definitely needs a complete rebuild, costing around €3,000.

My question is: can a complete transmission rebuild really be diagnosed with certainty from a diagnostic scan alone? Could the same symptoms be caused by pressure problems, pressure-regulating solenoids, the valve body, or another issue that could potentially be repaired for significantly less?

I would especially appreciate an answer from someone with actual experience working on AL4/DP0 transmissions.

What tests would you recommend performing before concluding that a complete rebuild is necessary?

[mickthemaverick]

How many miles has the car done and has the transmission fluid ever been changed?

[ozvtr]

The transmission intermittently starts slipping, and the Sport and Snowflake warning lights come on. After turning the engine off and restarting it, the transmission can sometimes work completely normally again. There are also times when I can drive for about an hour without experiencing any problem at all.

Sounds like the main pressure regulator solenoid if the gearbox works fine after shutting the engine own and restarting.

A diagnostic scan reportedly showed “slipping clutch/brake.”

There are three clutch packs and two brake bands. Which one is slipping? Its a rhetorical question.

Could the same symptoms be caused by pressure problems, pressure-regulating solenoids, the valve body, or another issue that could potentially be repaired for significantly less?

The main pressure regulator is cheap and relatively easy to replace. It's the cause of a lot of AL4 failures. I would replace that and definitely change the fluid.

What tests would you recommend performing before concluding that a complete rebuild is necessary?

The AL4 is very compact and you need to literally pull the gearbox apart to get to anything! So while you are in there you would change the friction plates, seals and bands.
Another failure mode is that the brake band friction material can wear down and expose a rivet on the band causing the rivet to ride on the planetary gear drum instead of locking the drum. This also damages the drum!