E30 1989 Convertible Automatic Transmission Oil

[billygates]

I've purchased this car with about 240,000 miles on it. The only thing I haven't done with it yet is change the transmission fluid. I've been reading that it might not be a good idea to change it and it can actually screw up the transmission. I have no records of when the transmission fluid was changed. What do you guys recommend? And if the transmission should be changed, what kind? What about the filter?

Thanks

[dohcdoh]

Dex 3 oil, new filter. Drain, change filter, clean magnets and pan, reinstall. Refill trans, run through gears, check level. Done.

[thejlevie]

The danger with changing the fluid on an automatic transmission that hasn't been properly maintained (fluid & filter changes every 50k) is that there may be a lot of deposits in the transmission. Transmission fluid contains detergents designed to dissolve that stuff, but those detergents become exhausted over time, which can allow deposits to build up in the transmission. Fresh fluid has, of course, a fresh detergent package which will start to dissolve any deposits in the transmission. If chunks of the deposits break off and circulate they can block small passages or the valves in the transmission.

In this case (240k) the transmission may not last much longer regardless of what you do. If you want to take a chance, change the fluid and filter, drive the car 500-1000 miles and repeat two or three times. If you are lucky the fresh fluid & detergents will clean up the transmission without causing any problems.