I had used redline for the front diff... but would it be the same for the rear diff.? Synethic oil? To be honest, I forget.. I haven't done it in a while... but would redline be great for the rear diff.?

 

There is only a rear differential on a FC unless you have some custom made 4WD car.

Could you be confusing the Transmission with the differential???

In which case I recommend Redline MT90 gear oil for the tranny,

and Redline Shockproof gear oil for the rear end (an add some Red Line Limited-Slip Differential Friction-Modifier/Break-in Additive if you have a LSD- which if it is a 88 GXL from your sig; it should).

 

I use Redline MTL instead of the MT90 in the 5speed. I have used MT90 previously and both work great.
For the rearend, I using Mobil1 GL5 75/90. For automatics and power steering, I use Mobil1 ATF.

Don't remove gear oil until you remove fill plugs. Seems to be an issue with mechanical newbies.

As long as you use a synth gl4 in the transmission and synth gl5 in the rearend, you will have no problems. Stay away from cheap gearoils. Stay away from bottles labelled "blended".
Its unlikely that you will ever have to change the fluid ever again.

http://www.redlineoil.com/products.htm
http://www.amsoil.com/
http://www.royalpurple.com/
http://www.mobil1.com/

 

Oops, I guess you're right Icemark, I was. I dunno what got me to think the gear oil for rearend and front were the same. I guess I'm in the category for not knowing anything now, huh?

Anyway, thanks for the information. I know for a fact the rearend has not been changed since I got the car back in March '02. I changed the trannmission for the gears sometime in May, I believe.

 

I just put that Redline MT90 in my tranny recently and now my gearshift shaft (under the boot) is getting hotter than hell.....and I've noticed absolutely no noise reduction or difference in the way it shifts.

Anybody else notice the heat increase after switching to Redline?

 

Well, when I put redline synthetic gear oil in my tranny (not sure if it was MT90 or not) it didn't (that I was aware of) get hotter. I think, as of I know... it was hot before. When I first had put it in, I noticed a significant change in shifting, now... after a few months, it feels like it was before I had it put in.

 

Make sure your fluid is topped off.
That just means you need shifter boots. Had the same problem. Replace ALL the boots(inner/middle) and the problem goes away. Make sure all the insulation is reinstalled with the boot replacement. Usually you will also end up smelling the gear oil(also a tsp for gear oil smell). I also replaced the leather shifter boot. When it was torn(just a little), airflow would travel through it heating everything. The air was heated by the transmission.

Here are the pictures: The parts are usually on ebay.
http://mazdatrix.com/faq/ssinstal.htm
http://mazdatrix.com/g4.htm
http://www.mazdatrix.com/in-shift.htm
http://rx7boots.hypermart.net/

I have never noticed a noise reduction with the synthetics. But, I can definitely tell the difference with shifting. It depends on the condition of the xmission and synchros.