Dug out an Allison trans filter I've had since the early 90"s and found it had developed a number of small rust spots. They clean up pretty well with penetrant and a scuff pad, but not sure if I want to use it now.
Are they really much better than the GM/Delco filter as I had been told years ago?
Any opinions/experience?

 

Nothing to offer about which brand is better. I'd source a new quality one, in over 30 years the materials have started to degrade.

 

I can't speak for the Allison filter, but I've never heard from anyone that there was a problem with a GM filter..

 

Yeah, guess I'll play it safe and throw in the AC/Delco filter this afternoon.

 

I build mainly race or high performance transmissions, so this may not be relevant.

The cheap parts store filters with the fiber filter media are very restrictive. I have had countless people complain about pump whine when starting the engine cold. Once it warms up, the fluid thins enough the whine goes away.

I don’t understand why this is a fairly recent problem, the 400 has been around since 1964, why did filter media change? If it ain’t broke, don’t fix it.

It’s something to keep in mind. A stock transmission with stock line pressure might be fine. If you find you do have cold pump whine that wasn’t there before, install the “Allison” filter with the screen filter media.