For the 5 spd. transmission:
Park the car on a flat surface, jack it up, placing it on jack stands to get space for your body
On the transmission's driver side, there's a square bolt on the middle, it's the filler bolt, after removed, put your finger in and if you feel the fluid is ok; otherwise it needs some, refill until it starts coming out, put the bolt back and clean the area.
check out the below. http://www.techguys.ca/howto/index.html
automatic has a dipstick under the hood. manual should have a plug on the side of it.
Miata owners typically replace the transmission fluid with 2 quarts of MTL Redline Synthetic Gear Oil.
To check the automatic transmission fluid in a 1990 Mazda Miata, start the engine and let it warm up for a few minutes. With the engine running, locate the transmission dipstick, which is typically found near the back of the engine bay. Pull out the dipstick, wipe it clean, reinsert it, and then remove it again to check the fluid level; it should be within the marked range. Additionally, inspect the fluid's color and consistency; it should be a reddish color and not smell burnt.
How to check the transmission fluid in a 1995 Mazda 626
Fill the transmission filter with transmission fluid before you put the new transmission filter on. You probably will not need to add any transmission fluid.
To change the transmission fluid on a 1991 Mazda Miata, first, ensure the vehicle is on a level surface and secure it with jack stands. Remove the transmission drain plug to drain the old fluid completely, then replace the plug and torque it to the specified setting. Next, remove the fill plug and use a funnel to add new transmission fluid, ensuring you use the correct type specified in the owner's manual. Finally, check the fluid level and replace the fill plug securely.
In a 2006 Mazda Miata, the transmission fluid dipstick is located on the driver's side of the engine bay, near the back of the engine. It is typically found near the transmission itself, often with a yellow or colored handle for easy identification. If you're having trouble locating it, refer to the owner's manual for a visual guide.
You add fluid the same place you check the fluid level.
You do it from under the car. Through the filler plug. Jacking the car on a level surface, remove the filler bolt (square bolt in the middle of transmission on driver's side) and put your finger into the hole, if you feel the fluid it's OK; otherwise, refil
Mazda recommends 75w-90 weight oil for the manual transmission, changed at 30,000 mile intervals. See http://www.miata.net/garage/maint.html for more information
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