I’ve been searching all over online about transmission fluid drain and fill. I recently got a 08 g37 with a appointment 131,500 miles on it. I check the fluid and it’s a light brown color and I know it’s shouldn’t look like that. But here’s where I’m concerned, i don’t know when the fluid was serviced so is it too late or should still go for the drain and fill. Is it smarter to do one drain and fill and another drain and fill the next 500 or 1000 miles or just go for a 3-5x drain and fill?

 

I'd go ahead and do the 3-5x drain and fill. Then just check on it at the 1000 mile mark. If it still looks good, check it at every engine oil change.

You might also want to do the differential(s) (and transfer case if your is an X) fluid change as well. There should be a DIY for it in the DIY Section.

 

mines a G37S. That’s the plan to do a 3-5x drain and fill but I’m going back and forward with the one drain and fill. Since I don’t know when the fluid was changed I don’t want mess up the transmission

 

If I'm not mistaken, the '08 has the 5-speed auto with a dipstick, so this will be a far simpler process than dealing with the 7-speed's under-pan drain and fill plugs, and lack of a dipstick.

 

yea mines has the dipstick. It’s just the concern about new fluid mess up the tranny since I don’t know when it was serviced. Either doing one drain and fill will be lot safe than doing 3-5x drain and fill.

 

I'd still do the 3-5x drain and fill.

You said that you didn't know when/if it had be done by a previous owner, so even if it had been done, a full fluid change is only going to cost you the price of the new fluid. You would them have a Known Full Service Date & Mileage.

By doing the 3-5x drain and fill you have a better chance of removing more of the possible things (that might be in the current fluid) that can cause problems.

By doing the 1 time and checking at 500 or 1000 miles, you'll be possibly leaving things that could cause you problems. Then all of the old fluid will also be fully mixed with the new fluid, so now when you check it at the 500 or 1000 miles and if the fluid still looks bad, what are you going to do? Another 1 time drain and fill? Then at the next check it's still looks dirty, you're going to do a 1 time drain and fill for the third time (then forth time, then fifth time..etc.....) Why?

Why possibly leave contaminates in the transmission with the 1 time drain and fill, when doing the 3-5 drain and fill will remove more of the possible contaminates that a repeated 1 time drain and fill over 2, 3, 4 or more times would remove?

Bottom line, it's your car, money & time.

 

You’re right why go through the hassle of checking it over and over again when doing a 3-5x drain and fill will surely leave out almost all the old fluid out and brand new in. Then I don’t have to worry about it till the next 30,000 miles or so.