I got 178k miles on my transmission. I previously did a 6qt flush of the fluid with Nissan matic J fluid at 100k.
Now I got a case of Amsoil ATF Fluid sitting in the garage that I want to do a flush with, but don't know if I should. Don't want the new fluid to wash out the sludge build up and render my transmission unusable.
Do you think that will be a problem?
Or should I just drain few qts and fill with Amsoil? Do those two mix ok or will I have an even bigger problem?

I currently don't have any issues with transmission, just want to keep up the freshness of the fluids.

 

I had a Nissan dealership do mine at around about 6 years ago I think the mileage was around 52K. I then did it myself around 127K with 9/12 qts. of fluid last year. I haven't had a problem since relating to the transmission and I'm at around 140K I think.

 

First I wouldn't use the Amsoil and would stick to Jmatic as recommended by Nissan. I don't know of any issues personally with other fluids but I have heard there have been when other ATF's have been used.
Second if you have only done a flush in the past I would pull the pan and replace the filter. Based on the mileage you should not have an issue with sledge if you drive normally.

I flush mine every year and change the filter every 30,000 miles but then I drive my car hard and it gets hot even with a added cooler.

 

I miss wrote when I said replace the filter as our filters are not replaceable. I went clean the filter.

 

Just throw some 20w50 in there and call it a day. Haha

 

I have no problem using Amsoil. It meets and exceeds Matic J (which is Matic S now) fluid requirements. The concern I have is with possible mixture of the two.
According to some internet research there should not be any problems as long as the chemicals and additives in the fluids do not cancel or react with each other. In most cases it's not the case unless you are using something exotic. Matic S supersedes Matic J because of the few additives that are not found in Matic J. S is basically J with couple more additives.
How do you clean the filter?

 

I think he means he cleaned the textile screen in the transmission.

 

Correct