Dear Auto Advisor.
I look forward to reading your column every Saturday hoping I will find someone who has the same problem as I. My 2007 Cadillac DTS has been doing this weird problem since it had 15,000 miles on it. What it does is shift hard when it comes out of overdrive. It does not do it every time and sometimes I may go 2 or 3 days before it does this weird shifting problem. I have taken to the dealership and they have looked for possible updates for the transmission control module and none were found. I read in past articles that you have “fixed” other transmission shift problem by reprogramming it. Sadly this is not the case of my Cadillac with 58,000 miles. Any suggestions would be appreciated before I trade this car in and buy a new one.
Mike the most overlooked item on today’s transmission is the fluid and filter need to be changed. The transmission fluid really needs to be changed every 50,000 miles. One of the problems I have seen over the years for rough shifting or harsh shifting is due to the transmission fluid be overloaded with impurities. The next common area is the transmission fluid friction modifiers and additives have evaporated or have depleted. The symptoms you are describing could very well be depleted additives in your transmission fluid. To help you determine if the additives have been depleted or overloaded look and the transmission fluid. Is it pretty and pink, or does it look darker than it should? Do you see bubbles on the dip stick after you drive it for a few minutes when you check the fluid? If you answer yes to any of these questions than a complete transmission fluid exchange along with a NEW TRANSMISSION FILTER is in order.
There is over 14 quarts of fluid in your transmission, changing just 4 or 5 quart is not good enough to make a difference in the long term shifting quality of your car. The other reason you want to replace all of the transmission fluid is your Cadillac came with Dexron 3 automatic transmission. GM (Government Motors) determined that this fluid breaks down too easy and should be replaced with Dexron 6 transmission fluid. Dexron 6 is a “full synthetic transmission fluid” (according to the US government) designed to replace the old Dexron 3 transmission fluid that your car came with.
So make sure that you change all the transmission fluid and the filter before you decide to trade your car in. The price you pay for this service is just a drop in the bucket to what it costs to replace your car.
Live long and prosper.
Tech Tip: Before you send your son or daughter back to school with their car, inspect the spare tire. Make sure that the spare tire has air and a couple of cans of “Fix a flat” (tire sensor safe version) in the
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