I have a 2007 Volvo XC90 V8 AWD. I noticed driving on a flat highway the 6'th gear the ratio of SUV speed in miles per hour to the piston revolution speed in thousand rotation per minute is 40, especially between 60mph and higher. Now after a repair with modules replaced, the ratio has become lower at around 35 or even lower. Is this a problem? Is this controlled by the module? Should I bring the car back to the repair shop/dealer?

  • Welcome to the site! To clarify a few things: What year is your XC90? What do you mean by "8V"? Which modules exactly were replaced? – Pᴀᴜʟsᴛᴇʀ2 Feb 23 '17 at 21:26
  • @Pᴀᴜʟsᴛᴇʀ2: Thank you! I meant V8, 8 cylinders. I have corrected my question and added the year information. – Hans Feb 23 '17 at 21:29
  • So are you saying that the vehicle used to be at roughly 2500 RPM at 60 MPH and now after a repair its closer to 2000 RPM at 60 MPH? Just estimating based on your ratios, if I understood correctly. – Zshoulders Feb 23 '17 at 21:30
  • Again, which modules were replaced? – Pᴀᴜʟsᴛᴇʀ2 Feb 23 '17 at 21:31
  • @Zshoulders - I was reading this as 4000 before, 3500 after, though the OP states 40,000 before and 35,000 after. – Pᴀᴜʟsᴛᴇʀ2 Feb 23 '17 at 21:32

Yes, I'd take it back to the shop to see if there is something they missed. While 300 rpm at 60mph is not a huge difference, to me this is about the difference of when a lock up torque converter isn't locking up. This could be a programming issue which wasn't taken into account with the new CEM. While it isn't a huge issue, it will cause greater wear of parts and cost you in fuel mileage.

  • Thank you, PAULSTER2! Do you know what the optimal rpm of this SUV should be at cruise speeds of 60mph and at 80mph? The person (not a mechanic) talking to me said it had nothing to do with the module (and the code). Should I believe him? – Hans Feb 23 '17 at 21:54
  • No, I cannot say as I do. Your updated RPM range seems in the neighborhood of what I'd expect. Considering you have experience with how it ran before, I'd suspect you are correct in that now something isn't quite right. What I've stated is a best guess, but whatever the problem may be, I'd still take it back to the repair shop to get it looked over. – Pᴀᴜʟsᴛᴇʀ2 Feb 23 '17 at 21:56
  • If they insist that it has nothing to do with the module change, is there any recourse for me? Also should I bring up your guess when talking to them now before bringing the car back? – Hans Feb 23 '17 at 22:04
  • I would suggest you just tell them there seems to be an issue and describe what's going on. Tell this it isn't correct with how the vehicle used to drive. You may want to tell them the fears of this, such as the extra wear and the worsened fuel economy. I wouldn't tell them you got the information off the internet, as they will have a cow and tell you to go away. I wouldn't take "no" for an answer, though. Be firm but insistent. – Pᴀᴜʟsᴛᴇʀ2 Feb 24 '17 at 0:00
  • Thank you, PAULSTER2. I talked to the dealer and they asked me to take the car for a drive with them. I called a few Volvo dealers and mechanics other than the one I repaired my car at. They said if this was caused by the change of the module, nobody can do anything about it since all the code comes straight from the manufacturer. If that is the case, would you say that we need to rule out other possibilities than the module control? How would I get the dealership to check on other possibilities? – Hans Feb 24 '17 at 6:56

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