my transmission hasn't been shifting smoothly lately and i don't know if the pervious owner ever changed the tranmission fluid.

i was just wondering what tranmission fluid do you all recommend?

i have heard good things about red line but then i have also heard bad things like synthetic transmission fluid is bad for the internal parts of the transmission. which do you all recommend.

 

also what is the differnce in gl4 transmission fluid and gl5?

 

Read this: https://www.rx8club.com/series-i-tech-garage-22/change-tranny-oil-19006/
I changed mine to RedLine MT90 for tranny and 75W90 for rear diff about 100 miles ago. I hope it's good stuff but I did not notice any difference from before and after like others are saying.

As far as GL4 vs GL5 I am no expert but I think GL4 lacks Sulfur that might damage synchro. Here is a qoute from the RedLine website on MT90: "Safe for brass synchros, as it lacks the reactive sulfurs found in most GL-5 oils that cause damage"

While you are changing that change the rear diff too. On my car the rear diff was much more dirtier than tranny.

 

Some GL-5 are ok but for peace of mind, get some Redline MT-90.

 

Im no expert ether but I have used Royal Purple’s Synchromax, RedLine MT90 and Eneos 75w-90 transmission fluids, and the one I like is Eneos.
Here is BHR's Blackstone Oil Test of Eneos 75w-90 Transmission Oil
http://blackhaloracing.com/technical...abs-eneos-uoa/

 

thanks for the info good stuff.