I recently picked up a 2003 C70 convertible (auto) around 6 months ago and have been daily driving it since then. It has a few issues (namely a lot of vibrations and noise when roof is up), and the issue I'm about to discuss, but otherwise it's been a great first car.

For the last few months, when I cold start the car, the transmission feels like it's 40% disconnected/slipping for the first ~1 minute of driving, then suddenly transitions to feeling 10% disconnected, and then when it reaches operating temperature it feels completely normal. However, recently, the 40% figure has begun to feel more like 90%, and the 10% figure now feels like 30%... I can floor it up to like 6000 RPMS and it barely moves the car to 15km/h (again, this only happens for the first minute or so).

Also, since I got the car, it's had this pretty strange (and I think related..?) issue (at operating temperature): Any time I take a right turn at any meaningful speed, it feels exactly as if I'd shifted the gear lever into neutral; then, around 2 seconds later, it abrubtly kicks back into gear. Also, when I suddenly brake, or take a left turn at VERY high speed, it seems to do a similar thing. This has also gradually become slightly worse, but not significantly.

Otherwise, there are no shift flares, the transmission shifts perfectly fine and at operating temp I don't THINK the clutches slip at all (apart from the sudden neutral thing).

I'm guessing either the transmission fluid level is low, the fluid itself has turned way too viscous or cooked (which might explain it working fine at operating temperature), or maybe the fluid pump is on its way out..???

So, any advice on how I could determine what the issue is? I can't find a transmission dipstick anywhere, and when I called the dealer the mechanic told me it's a sealed unit. I also can't find any tutorial for changing the fluid anywhere. And if the fluid itself and the level is fine, how could I check if the pump is going out? Is there another possible cause that I haven't thought of?

 

Yes your first step would be to check the trans fluid level. There is a dipstick on the front of the transmission. (facing the front of the car) It's usually covered up by the lower radiator hose, you have to move the hose out of the way sometimes burning the back of your hand.

Fluid level is critical - too much is just as bad as too little. Most important is to use the correct fluid - not some generic stuff from the local auto parts store. Fluid from Volvo is rebranded Aisin fluid. Toyota type T-IV fluid, and Jws3309 Mobile 1 is the same thing also.

The easiest fluid changes are a simple drain and fill. Pull the drain plug and MEASURE how much comes out. Usually 3.5 quarts to drain and fill. The new fluid is installed through the dipstick tube - yes not easy to get to. Many funnels are too large to fit in the tube - so work that out first. DO NOT take off what looks like a fill plug on the top of the trans, IT'S NOT A FILL PLUG (if you remove that bolt - you will lose 3rd gear)

Google "gibbons method" for discussions on various ways to change your trans fluid and only use the correct fluid.

 

Wow, thanks for making me aware of that, a few more days and I was probably going to remove that... XD

How did you find out what removing it does? Personal experience? Does 3rd gear come back after you put the bolt back?