335i trans pan leak 1 500x333 2008 BMW 335i (E9x) Transmission LeakWhat does a transmission leak repair look like?

This BMW came to Autoscope when the client noticed some drips of red fluid under their 335i.  Red fluid normally indicates transmission fluid and upon examination we saw the leak coming from the rear of the transmission pan.  When the transmission is leaking from the pan it is necessary to replace the transmission pan, the pan gasket, and the transmission fluid.  On some vehicles the transmission fluid filter, and possibly the gasket, are incorporated into the pan itself.

For this BMW 335i the transmission fluid filter and gasket are part of the pan so it is replaced as one unit and then the new transmission fluid is added.  This repair is common because the transmission housing is an aluminum alloy and the pan is made from plastic.  Each time the car is operated the transmission and the pan get warm, however since they are made from different materials they expand and contract at different rates.  Over time this causes the pan to leak transmission fluid.

We only use BMW’s OEM transmission fluid for this service or repair, as is true with all the services we provide.  BMW will tell you that they use a “lifetime fluid” however we have seen numerous transmissions fail due in part to the transmissions not being serviced.  We do recommend that all automatic transmissions have a fluid and filter change at regular intervals starting at 50k miles.  One item of note, some service providers will offer a transmission fluid change without changing the filter.  This is strongly discouraged since it would be similar to changing your engine’s oil but leaving the dirty filter there and is it is not a proper service.

In the photos you will see the leak coming from the transmission pan, the inside of the old pan and the inside of the new pan, which includes the filter.  You will also see the bottom of the inside of the transmission where the solenoids and valves are visible.  The colored parts are the solenoids and the round metallic parts are the valves – both work to transfer fluid within the transmission to select the proper gear.  The tube going into the transmission is the transmission being filled with fluid to the proper level.

If you have questions, or need help with your E9X, contact us!

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