Originally Posted by DWR

I purchased a 2007 C70 with 99k miles just under a year ago. I did have the car inspected and was well aware of the transmission issues and the car did have some minor downshift issues between 2nd and 3rd gear when I bought it. Otherwise the car was immaculate and exceptionally well maintained.

The car was already significantly discounted (IMO) and I used the inspection report to knock another $1200 off the price. I've driven the car for roughly 20,000 since I bought it with varying transmission issues. Shortly after purchase it threw a service transmission urgently warning and I took it to my mechanic (not Volvo specific but very good) and he replaced a knock sensor and the car ran great for about 2500 miles before slowly reverting back to a pattern or great driving for 100-200 miles and then progressively worse slippage until the "urgent transmission service" triangle and check engine light reappear.

The car drops into limp mode and then after it's been parked the triangle disappears but the check engine light stays on. After roughly 100 miles of driving the check engine light goes off and the car drives normally for another 50-200 miles before the cycle starts again.

What is unusual (at least I haven't seen it here elsewhere) is that the the triangle of death is often preceded or followed with a "low bulb failure" and once with a "stop lamp failure" warning??

My mechanic has been very hesitant to recommend anything further since he feels that it's as likely as not to be an issue outside of the transmission itself.

I did notice a thread here where is seems that the electric throttle body (do I have that right?) was sending a code to the transmission generating a transmission warning and limp code??

The car runs great and the transmission works perfectly about 50% of the time. I love the car and have no issue spending money on a rebuilt transmission if that is actually the issue but I have a hard time believing that a genuine transmission related issue would be so intermittent.

Any thoughts on the best way to proceed would be greatly appreciated...

Originally Posted by hichamaziz

hi have you checked the transmission fluid level and the color of the fluid?

Originally Posted by mt6127

sorry to hear your frustration. seems there was some confusion about your post due to it being added to a prior thread. Generally on these cars there's three things in play - the transmission computer - which gets information from various sources about engine and road speeds (so a wonky ABS module can show as a transmission fault), the valve body, which have electronic switches (solenoids) to shift the gears and the wet clutches which transfer power. The point of looking at the fluid is that if there's black or brown, that means something produced too much heat (like a slipping clutch) or has bits of clutch floating around. That means its rebuild time. If you have hard shifting it can either be a computer issue (either bad data in or old software) or it can mean the valve body isn't switching gears correctly (a solenoid uses magnetism to move the switch so if its sticky or has a short, it will cause missed or hard shifts). Seems your mechanic has some vested interest in not telling you he was aware of this issue. I don't think you messed up - this is not a caveot emptor or owner awareness issue - your mechanic should have read fault codes to clue him in on possible causes. So what to do next? You can either find a transmission shop with special tools/skills to diagnose and repair or consider finding a replacement transmission from a yard. car-parts.com is a good resource for searching and pricing used parts like transmissions.