Transmission Fluid Issue? Amsoil 80W90. Gears won't engage, shifter heavy when cold?
 

I had Amsoil 80W90 filled in my transmission a few weeks ago. I've driven the Z twice since then. And both times the transmission has acted the same way when cold: hard to engage 1st and 2nd when cold and shifter feels heavy (like churning thick butter when wiggled side-to-side).

Before with the OEM fluid, wiggling the shifter was always the same, hot or cold. Now, even when the car is off, you can feel a bit of weight in it, until the transmission warms up and it feels normal.

Engaging 1st and 2nd when cold requires to really push the shifter in. Never had this problem before with OEM. OEM fluid 1st was a bit notchy, but not enough for me to complain about - it never bothered me before. Today, after about 1.5 miles of local driving, at around 1-2MPH I tried to engage 1st, and it just didn't want to engage. It felt like it locked me out of the gear, so I tried to push and I felt a vibration in the knob and I heard a noise very briefly (my music was on, but it sounded like a quick grind).

I immediately stopped trying to force it in, put it back in neutral and tried again, and the gear went in just fine. The grind couldn't have been more than a millisecond, but still, it pissed me off. I've never grinded a gear before.

So is it the transmission fluid? Once it warms up, it's perfectly fine. And stays perfectly fine even after the car's been off for 4-5 hours. Is the fluid no good for our cars? Could it be a bit low?

Could the problem be the weight is too thick? Amsoil 75-90 Synthetic stuff is whats recommended for the Z. The 80-90 is probably too thick when cold which is was causing you issues.

Our transmissions use 75w-85 or 75w-90, and must be GL-4 service class.

That's what I thought too.

Alright, I'm gonna' drain this sh*t out tomorrow.

Back to OEM.

Car is driving normal again. Sat for 7 hours, I took it around the block, no issues anymore.

Even though it may not seem like a big difference in weight, the Amsoil 80W90 is NOT for the Z.

I'm still new to the Z crowd but coming from the MX-5 world, the top GL-4 fluid is the Ford Motorcraft Full Synthetic Manual Transmission Fluid. It's $18 per quart at your local Ford dealer or online but it's a lifetime fluid and the performance gets better the longer its in.

:confused: whaaaaaa

:iagree::icon14:

"Motorcraft Full Synthetic Manual Transmission Fluid XT-M5-QS" from Germany which is a 75w90 GL-4. It's very popular with the Miata/Mazdaspeed and Focus crowd amongst others. Has an enormous following and positive results. Probably the best GL-4 fluid around.

Just Google it for more info and testimony. It's one of those "ad nauseum" topics that is so well established, forums hate seeing new threads about it.

It has an immediate effect with many people having notchiness problems but it is also a lifetime fluid meaning simply that you don't flush it out after a few thousand miles. You leave it in for good and it keeps getting better over time.

I have it in my Miata 6-speed which shares the same Aisin tranny as the S2000 and never looked back. I just got my Z recently and am going with the Motorcraft in that too. I'm not affiliated with Motorcraft, haha, just swear by it from experience.

Info:
https://www.fcsdchemicalsandlubrican...ission%20Fluid

Interesting....