rotarywanker

After buying my 2007 RX-8 last year (had about 65k miles on it), one of the first things I did was change out the trans fluid to Red Line MT-90. Also changed the diff oil, although don't recall what I used (something recommended by folks on this forum, though).

Before making the change, the car shifted great, so there was no particular impetus to switch to red line. The Red Line seemed to work OK as well, although shifts seemed SLIGHTLY more labored and gear whine was SLIGHTLY more apparent.

Fast forward a year and 10k miles, and my car developed this difficult-to-explain 'hard shift' into 2nd. It doesn't grind, per se, but there is a sort of metal-on-metal resistance when I don't time my 1-2 shifts perfectly. I initially suspected the clutch master/slave, so I replaced those. After replacing the hydraulics and bleeding the system, the hard 1-2 shift was still there, so I lengthened the throw of my clutch slightly to see if that would help. Well, it did, quite a bit, but there was still an occasional hard 1-2 shift depending on how I timed it.

So I decided to change out my trans oil and have documented the process here. Per the strong recommendation of BHR, I used ENEOS 75W90. I bought 2 quarts which turned out to be EXACTLY the right amount for the change. Second bottle was literally empty by the time fluid started dribbling out of the fill plug hole.

The results of the change to ENEOS has been great so far. I've only clocked about 75 miles, but shifts are all much smoother/more effortless, and the hard 1-2 shift has disappeared. I also don't hear any more gear noise. We will see how it holds up over time.

Walk-through in next post.

rotarywanker

Step 1 - Gather your supplies. As i cite in the image, not everything here is required. I just like to use things like breaker bars to bust nuts loose when I'm in awkward positions (like laying under a car). Just makes things very easy. Thread sealant is also not a requirement - I just have a habit of using it on anything that has even the slightest chance of leaking and causing damage. Use it extremely judiciously, and don't put it on the end threads where it could come into contact with your trans fluid. New crush washers and a torque wrench ARE required. Use one or buy one if you don't have one.



Step 2 – Back your car onto a rather steep incline, secure it there, and yank the e-brake. Also put it in gear. Use wheel chucks if you can. Then jack up the front of the car to get it PERFECTLY level. If it isn’t level, you won’t get all of the fluid out and you may under/overfill your transmission with new fluid. I used a long bubble-level and placed it along the door sill as well as chassis to ensure my car was level. This is a pain but a must-do.
Also – don’t mind the ~700hp ~800 ft/lb Merc in the background









Step 3 – Locate your transmission drain and fill plugs. They are each 24mm (large) and located on the driver side of the vehicle. They are circled in this image.



Step 4 – Remove the fill bolt (upper) first. This is important. If you remove the drain plug first and drain the fluid out of the transmission, and later find out that the fill bolt is stripped or seized you will be stuck with a car that can’t be driven. Each of these bolts uses a 24mm socket. I use a wobble extension to make life easier.



Step 5 – Removal the drain plug (lower) and drain the transmission. Let it sit a good 15 minutes. Inspect the drain plug (magnetic) for debris and clean thoroughly with brake cleaner. Replace the crush washer and (optionally) add a small amount of thread sealant to the threads.





Step 6 – Replace the drain plug (just finger tight is fine for now) and start pumping in your new fluid. I use a pumping mechanism I purchased at an auto parts store years ago. It’s basically a requirement for our vehicles. Keep pumping until new fluid starts to slowly drip out of the fill hole. At that point, it is full and you are done. Wipe away any excess fluid from your transmission housing and reinstall the fill plug (with a new washer and, optionally, thread sealant). Finger tight is fine at this point.



Step 7 – Torque your drain and fill plugs to spec. I forget what the manual says – something like 35-47 nm. I went with 45nm.



Step 8 – Put your car back on the ground and drive. You’re done.

9krpmrx8

iTrader: (46)

https://www.rx8club.com/series-i-do-...acement-35115/

Youwonder

I need to do mine very soon, my 4th gear grind in high rpm

ASH8

Seriously, you do not need or use 'Thread Sealant' (Optional) on the diff or transmission fill or drain plugs.
Mazda do not and never have used it and that is why you have a crush washer which can be used more than once, as is, I am on my original crush washers and have changed trans and diff oils 4 times.
A torque wrench is a bit WOTT too and unnecessary.

rotarywanker

I torque every single nut/bolt to spec, if there is a spec. I'm certain one could get away with doing it by feel, but I like to be precise.