Transmission shifting on its own
09-23-10, 07:00 AM
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Transmission shifting on its own
HELP! I recently had the transmission on my SC 300 (165k) rebuilt. Since the rebuild sometimes when i'm driving down the road, the rpm will shoot up and it feels like the car is downshifting into a lower gear and it will stay there for a bit and then upshift and then downshift again (the rpm guage is going crazy at this point). I have taken it back to my mechanic, whom i've used for years, and he took it apart again and replaced the solinoid and put back together. I drove it for 4 days and it did fine! Perfect! and yesterday it started the downshifting AGAIN! Please help - any suggestions on what it might be would be greatly appreciated. He keeps thinking its something with the computer...??? As its still under warranty with him, I don't want to take it somewhere else. I am trying to keep her for another year at least, even though she is 15 years old, I love her and am not ready to part with her. Thanks in advance for your thoughts on this!!!
09-24-10, 08:02 AM
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Love the pic of the car - that could be me - my car is exactly like that one!!!
cc
09-24-10, 08:08 AM
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Well, I just put 4k in her - over a variety of problems - which about 2k was for the transmission - and he's rebuilt it twice now-just to be sure. I don't want to keep throwing money at her - and I am starting to believe it has something to do with the computer.
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09-24-10, 01:33 PM
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I would think if the transmission can shift properly but it chooses the wrong gear then its not a mechanical issue but an electrical one. now if it were to not shift into a particular gear i would check the solenoids. since yours is randomly selecting gears and your speedometer goes in and out I would check the sensors out first (i think there are 2 speed sensors).
Thanks for the comment, Your car must look pretty nice
09-25-10, 02:20 PM
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it could be a speed sensor issue, there are only a handfull of sensors that the ecu uses as an input for gear selection.
I would think if the transmission can shift properly but it chooses the wrong gear then its not a mechanical issue but an electrical one. now if it were to not shift into a particular gear i would check the solenoids. since yours is randomly selecting gears and your speedometer goes in and out I would check the sensors out first (i think there are 2 speed sensors).
Thanks for the comment, Your car must look pretty nice
I would think if the transmission can shift properly but it chooses the wrong gear then its not a mechanical issue but an electrical one. now if it were to not shift into a particular gear i would check the solenoids. since yours is randomly selecting gears and your speedometer goes in and out I would check the sensors out first (i think there are 2 speed sensors).
Thanks for the comment, Your car must look pretty nice
Ha, yes, she does look very nice!! That's one reason i'm trying so hard to get her fixed up instead of trading in! I'm almost positive he checked and replaced the speed sensors, but I'll have him check them again. That's the big problem, as you know, if its electrical, it could be anything!! thanks much for all the input!
09-25-10, 02:21 PM
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09-27-10, 06:22 AM
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Well, she's at the mechanic's now. I drove her over yesterday and she changed into 1st and 2nd fine - but just would not shift into 3rd. I just drove 40-45mph all the way over (33miles). A couple of times the rpms reved the engine up and then felt like it shifted up and down, then the speedometer felt like it was going down, speed wise...???? I could just never get her to go to third...??? I just don't know - I'm leaving it up to him! He's going to go through all the sensors, chips, electrical to see if he can find it, bless his heart! I wouldn't wish that on anyone! Thanks for all the help, if you think of anything else, let me know! And if and when we figure it out, I'll post...
11-01-10, 11:46 AM
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Just thought I'd send a thank you to those who responded and let you know - it turned out to be the computer. when my mechanic opened it up there was a burnt spot in the middle where something sparked and melted some components. He got me a really good deal on a used one and so far so good, she's running like a champ again!
11-01-10, 02:28 PM
#14
Just thought I'd send a thank you to those who responded and let you know - it turned out to be the computer. when my mechanic opened it up there was a burnt spot in the middle where something sparked and melted some components. He got me a really good deal on a used one and so far so good, she's running like a champ again!
do u mind me asking how many miles u have on your car and how long did the stock tranny last...thanks
11-01-10, 03:44 PM
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it was around 165,000 I got the transmission re-built. Is that what you asked, I'm not really car speak savvy...('stock tranny') - I ask because the milage was posted in the original post...