Aisin Warner U540E

Transmission general data

The 4-speed FWD automatic transmission U540E was designed by Aisin in 2000 on the basis of the famous A4LB-1, which went out of fashion by that time. The transmission A4LB-1 also was modified in 2002 and a new modification can be found on different cars worldwide.

This automatic transmission has two names - U540E (according to Aisin Co), and Daihatsu gave different names to its sub-modifications: A4Q, A4P, A4L, A4G, ..., depending on the car model. The U540E was upgraded with several hydraulic control solenoids, the valve body and electrics, and the new filter for the valve body.

Technical issues and repair guidelines

This transmission is very reliable as the most of Aisin transmissions. For many years of operation, it only requires change of oil and filter replacement, however it can cover the distance of 150-200 thousand kilometers even with an old filter. For the overhaul of this carefully adjusted transmission, specialists usually order the repair kit of gaskets and seals, which is mainly needed for reassembly of contaminated valve body and replacement of worn out rings causing the burning of frictions.

The kit of all friction clutches is usually ordered together with the repair kit. Frictions get burnt for various reasons, but one of the most popular ones is related to insufficient oil pressure, caused by:

1. worn-out teflon and rubber rings

2. dirty wedging valves of the valve body

3. dirty valves of solenoids

4. faulty electrics of the solenoid or wiring of solenoids

5. clogged filter

This transmission can be rarely met in repair services, all spare parts for this transmission are considered to be rarity and there is no much statistics related to its repair.