99 C70 coupe, slight hesitation on upshift, drain/fill time?

T1G3R · Post by **T1G3R** » 20 Jun 2014, 13:10

My 1999 C70 (HPT, 144k miles) has developed an occasional hesitation on upshift at low speed in stop/go traffic. I'm thinking it may be time for a drain/fill on the ATF. I'm a newbie when it comes to DIY auto care and would really appreciate advice on the right fluid and the right procedure to do this. I'd also be grateful for some straight talk on whether I should do this myself or have a mechanic do it for me. I've read some horror stories about an AT flush going really poorly, so I want to go slowly, do a few quarts at a time, and not screw up my car.

According to my research on here, this car has the AW50-42LE 4-speed FWD transmission. I've seen a lot of conflicting info on what the right fluid is-- which one is correct? And what's the right procedure for doing a drain/fill?

Thanks-- much appreciated in advance!

Post by **mecheng** » 20 Jun 2014, 13:25

Open drain bolt with 15/16" wrench, drain and refill with approx 3.5 - 4L of ATF Dextron III
Use a new crush washer, get from dealer

It is that easy, flush is not necessary and yes it could do more harm And yes it is a good idea to change the fluid, it will extend the life and shift smoother. It takes me no longer than 30 min including setup and cleanup. The flush is more of a complex job and not needed IMO.

T1G3R · Post by **T1G3R** » 20 Jun 2014, 13:32

Thanks. Is there a guide or picture to show where the drain bolt is? Where is the dipstick/fill area?

Also, I found this fluid recommended (the branded version of Mobil 3309, it looks like?). Is this acceptable to use?

Post by **mecheng** » 20 Jun 2014, 17:54

You said you have the 4sp, check your owners manual it should say dextron III. The 5sp auto uses different fluid, I think they were 2000 models that use mobile.

You can't miss the drain bolt. The filler dipstick is yellow on right hand side(drivers)

instarx · Post by **instarx** » 21 Jun 2014, 14:18

T1G3R wrote:Thanks. Is there a guide or picture to show where the drain bolt is? Where is the dipstick/fill area?

Also, I found this fluid recommended (the branded version of Mobil 3309, it looks like?). Is this acceptable to use?

Nope, it is not ok to use 3309 fluid. Dexron and 3309 are not compatible and cannot be mixed. The 3309 is for 5-speeds and your 4-speed does not use it. It might work if you did a complete flush, but you aren't going to do that. Get plain old Mobil 1 ATF (not 3309) or another Dexron III compatible fluid. They will be less expensive anyway.