Its an m6(car in sig) and its got 120000 on the clock. I know you dont really need to change your trans fluid with a manual but should i anyway? cant hurt.... I dont know if it has been changed before. i thought it would be a good idea to change all the fluids since it is a new to me car.

 

I just took the fill plug out and I saw that the fluid was very clean so I'm not going to do it for a while, if its dirty I would change it.

 

If you just bought it, I would change the fluid. Not much cash for peace of mind. Just because it's a manual doesn't mean the fluid doesn't need to be changed as much as an auto. The fluid has no filter, and its always picking up minute pieces of metal shavings and crud from the moving parts.

 

make sur you put the right fluid back in it.
I would not use synthetic either

 

why not use synthetic? should i not use synthetic in the rear diff either?

 

i bought some valvoline high mileage fluid but i had bought mobil 1 synthetic for the rear before this. I am basing these fluid changes off of this tutorial:
http://www.bfranker.badz28.com/fbody/lubeoil.htm

 

Do not use synth in the trans as the pressed paper blockers will swell causing problems.

The 98 posi calls for synth diff fluid so go ahead and use that.

 

I would change all the fluids, usually something I do in a used car that I just picked up, unless there are service records stating that the maint has been performed recently. When doing the rear differential fluid change, don't forget the small bottle of GM limited slip fluid as well.

 

i bought some rear end additive but it is not the gm brand but it says it is supposed to work in gm vehicles. Will this be ok?

 

It will be fine, but you may not even need it. I don't know if that car came with an auburn posi or a torsen.

Someone else should know AL!

 

i think its a posi since it leaves 2 tire marks hehehe....

 

98 is the last year for the Auburn so you should use the friction modifier.

 

You wont need the additive if you have the torsen