Just bought a 91 FC NA and I wanted to know what’s the first mods I should do or what I should swap out also any recommendations for fluids such as coolant diff oil etc. thanks I’m advance!

 

Welcome! I also am a new 91 FC NA owner. Great questions. Looking forward to the board's advice.

 

Welcome. Let's start with this. Make sure all of the maintenance has been performed on the car. All fluids, belts, hoses vacuum lines, etc. Make sure any leaks are addressed and then when the car is able to handle a little extra power or suspension stiffness, then consider what you hope to achieve with the car. My first mods would be reliability focused and then I would concentrate on adding a little power.

 

Thanks I appreciate that I just ordered a bunch of parts like spark plugs & wires and also some hoses and a new radiator the car drives really well and I’ve had no issues with it there seems to be a small coolant leak somewhere but I will pressure test the car to find out where it’s coming from and address it. Do you have any recommendations for diff oil and manual trans oil to use? Thanks!

 

You're welcome. As far as oils, I think everyone has their own opinions on what to use. I have had really good luck using Motul gear oil as well as Redline and Amsoil gear oils. Switching over to Motul in my 944 as well.

 

Ive never heard of Motul oil but I will forsure look into it I heard a lot of good things about Redline oils too but just wanted to get someone’s input before deciding. Thanks for the response

 

Happy to help. They sell Motul on Amazon among other places. Its priced pretty well there to be honest. And I've always loved Redline fluids as well. I've used Redline for many years before trying Royal Purple, which I found to be just ok and then I switched to Amsoil and then have tried Motul and have really loved the results from each.

 

Welcome to forum

 

Thanks I appreciate that if you have any tips on how to keep my car maintenance well or any suggestions I’ll be happy to read about them. Thanks in advance

 

Nice glad to see that you’ve experimented with all these brands and that you’ve shared your experience with all of them. What viscosity and quarts does the diff take as well as the manual trans?

 

The manual transmission takes 2.65 quarts of 75W90 or 80W90.
The rear differential takes 1.35 quarts of 75W90 or 80W90

 

Cool so I can pretty much buy 4quarts of motul 75w90 and add it to the diff and tranny right?

 

Yes you can. The Motul is a great choice!! I always buy one quart extra, just to be on the safe side and to have extra in case I need it. But it's not completely necessary.

 

That is true I might just buy the gallon off of amazon and get both things done do you recommend replacing the plugs and gaskets for the diff and tranny?

 

The crush washers should be replaced on both the trans and diff any time the plugs are removed.

 

Hey I have a question so I was driving my rx7 and then noticed a bunch of coolant coming out I pressure tester it and the radiator was cracked I replaced it and the car was fine then the car was having trouble starting up and I think it was because it was flooded with gas I finally got it to start a lot of smoke came out for about 4mins from the exhaust and it smelled like gas but a little different not sure if it was the smell of the premix I was adding the next two days I was driving it and then it started overheating I pulled over let it sit I then pressure tested it and the upper radiator hose clamp came loose I tightened it and pressure tested again and the car kept its pressure I drove it for 25mins then noticed it overheating again at resting idle when I continued to drive the temperature would drop ima pressure test it again and see if there’s any leaks. What do you think could be making it overheat if no leaks are detected?