I know rx7's take 80w gear oil but can I use 75w?

 

Yes

 

thanks

 

actually 80W is only used at below 0F (-18C), and 75W would be way way too thin.

90W is the recommended gear oil weight at above 0F.

If you are going to see colder weather, then a 85W90 or even a 80W90 would be okay. But straight 70W is way to light.

 

Wow i was just about to ask about some gear oil, anyone tried valvoline durablend 80w-90? FC gear boxes take 2 quarts right?

 

Redline Super light shock proof or Redline MT-90 would generally be what you wanted to use if you were going with a synthetic.

The Superlight is equivelent to a GL-5, while the MT-90 is a GL-4 (but works in the place of most GL-5 gear oil, when used in transmissions).

 

well i got the valvoline it was on ale for 2.50 a bottle, it's gl-5 so i guess iut should work, anything is bettern than at least 40,000 mile old oil right?

 

I think that 'anything' is not better, thats not good logic

Think water and sand :-p

 

Valvoline gear oils work just fine. Just make sure it meets all the specs you need, ie. gl5

 

When I changed my gearbox oil, I put 2.5 quarts in.

 

Ohh ****. So if one were to be using a redline synthedic 75w90 it should be removed and replace by a straight 90w sythetic?

 

I think you'll find straight 90w syn to be difficult to find. Most come 75-90, unless you go with a conventional 90w oil, likely not syn. If someone knows a good 90w only syn, that's redially avaliable please post and prove me wrong.