Hard shifting since tranny fluid change.... please help
 

used the search and did nont find anyone else posting this specifically....

So I had the tranny fluid changed (55,000 miles) and the diff fluid. MT-90.... & 75-90... it was fine for about a week now its starting to shift hard into second at lower rpm and the whine from the tranny is LOUD.... I checked the levels... its very concerning....

Anyone else have this problem? I am only having this problem since changing fluid... never grinded a gear prior never a hard shift... now its almost every time I go to second and it grinds third occasionally... WTF?

in the jeep I use half of a quart 100% petroleum in the transmission and half a quart in the diff.... added to standard transmission fluid and gear lubricant.... (lucas oil stabilizer is 100% petroleum)

Any concerns about doing the same in the rx-8?
Any one else had this problem with MT-90?

edit: I should add that it is fine until the tranny is up to temp. the first 5 minutes moving are fine but once the fluid warms up it starts being a PITA....

after poking around some more I am swapping to amsoil severe gear 75w90 for both asap.... sounds like others have had mt-90 ruin their gearboxes ... others swear by it.... apparently my Rex does not like it.....

Thanks Anyway.

I have heard of people having issues with nearly every type of transmission oil. Some have used Royal Purple (many of them using the wrong one!!!) and have reported issues and then recommended the switch to Redline. Then some people have claimed issues with Redline and have recommended switching to Amsoil. Some have had problems with the standard oil it came with. You get the idea. In some cases issues could be a coincedence with the timing of an oil change. Other times it could be directly related.

Although I have my opinion about oils in general and many don't agree with me, if there is every any question about what to use, always default with what the car came with. Whether or not it is the best to use is not the issue. It is known to work. Keep in mind that after a problem starts, it won't necessarily and probably won't go away with a different oil. It may help though.

I'm using the stuff you're going to use. Apparently GL-5 gear oil is not suitable for use in gearboxes because it's so slippery the synchro friction surfaces can't do their job properly, which explains why my higher gears keep trying to lock-in before they're fully synchronized. I'm planning to switch to MT-90 as soon as it arrives in the mail.

Also, GL-5 gear oil can damage brass synchros, because there are exposed sulfides on the ends of the oil molecules, and brass+sulfur=bits of copper sulfate flaking off the synchros and landing in the oil pan. They won't hurt anything, but it does eat away at the blocker rings. I don't think that's an issue with the graphite-coated blocker rings the RX-8 transmission uses, but it's something to consider nonetheless.

Thanks for the reply. I figured the gl-4/5 issue on my own after reading some more...

I swapped with Amsoil Synthetic Manual Transmission and Transaxle
Gear Lube 75W-90 API GL-4 (MTG)

all issues are gone...

thanks