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post #1 of 19 (permalink) Old 10-31-2018, 06:42 PM Thread Starter
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Hard Downshifts

I haven't been on in a while and just putting the Redline away for the winter but wanted to post this to see if anyone has experienced this. In September my wife and I drove from Maine to Niagara Falls, took the week and 4 nights away. A little over 600 miles over and no problems with one night on the way over. The car sat the first day in the parking lot 90 degree heat. We decided to go to a wine tasting so I reached in and just started the car (usually I turn the key to run for a few seconds before starting) to get the AC going. I noticed on the DIC it said check traction control. We took the top down and headed out, we almost got thrown through the windshield on the first downshift and noticed a short but not hard up shift. Drove about 15 miles with very hard down shifts the whole way and went to the wine tasting. When we came out I turned the key to run for a few seconds then started the car. It has been perfect since. 600+ miles home and a few short drives and it shifts and goes perfect. I am very happy about that but curious if anyone has had this happen.

Thanks, Steve
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post #2 of 19 (permalink) Old 10-31-2018, 07:03 PM
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I'm not an expert on the vocabulary for what you are experiencing, but I'll bet if you search for HARD DOWN SHIFTING, you will read about that issue and what needs to be done. The good news is it can be corrected for less than a hundred dollars and you can change the items with a screw driver. Good luck.
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post #3 of 19 (permalink) Old 10-31-2018, 07:39 PM Thread Starter
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I have read everything on the constant hard down shifts. As I said this happened only once and the DIC indicated check the Traction Control. After the next restart it has been perfect. Maybe just a computer thing or something just happy it's shifting correctly now.
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post #4 of 19 (permalink) Old 10-31-2018, 07:44 PM
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Originally Posted by Shameful1 View Post
I have read everything on the constant hard down shifts. As I said this happened only once and the DIC indicated check the Traction Control. After the next restart it has been perfect. Maybe just a computer thing or something just happy it's shifting correctly now.
Yes, it's a computer thing. If the computer doesn't know what's going on then it puts the transmission in a fail safe mode... which causes hard downshifts.

See this post: https://www.skyroadster.com/forums/f...ml#post1287527
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post #5 of 19 (permalink) Old 11-01-2018, 02:15 PM
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Mine needed a new solenoid and a new TCM.
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post #6 of 19 (permalink) Old 11-01-2018, 08:03 PM
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Do you have a CEL? I would change both the intake and exhaust camshaft solenoids. Their very inexpensive (about $40/each) and about 5 minutes to replace. Do some research on the hard downshifts and you'll find that a lot of people have replaced these and it will fix it. My guess is that one of them is starting to go and it's causing this issue. How often do you change your oil? My other word of advice is to check your brake fluid level (will cause your traction control light to come on!!). If it's a bit low, it's either leaking, or it's time to replace your brakes. While I don't have the post count here, I'm a regular on the Solstice forum....

Last edited by The_Ghost; 11-01-2018 at 08:05 PM.
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post #7 of 19 (permalink) Old 11-01-2018, 08:43 PM
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Yep, The_Ghost is a regular participant on the Solstice Forum and generally knows his stuff. I'd agree with him on this one.



.

Dave -
2006 Solstice NA #000741
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post #8 of 19 (permalink) Old 11-01-2018, 09:12 PM
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This is the first I have heard about the traction control light being related to the camshaft solenoids, or about hard downshifts being a temporary condition.

John
Lexington, KY
Sky NA 2007 Midnight Blue
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post #9 of 19 (permalink) Old 11-05-2018, 08:39 AM
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In the transmission succage thread we learned several things.

First is that the failure of the cam servo will cause the TCM to go into protection mode and you get hard downshifts.

Second was that the cam servo can and do "fail" intermittently. In fact, it took nearly a year of collecting clues to figure out that the servo did cause this hard down shift condition. The usual scenario is the driver experiences a random hard down shift followed by "normal" operation. Then another hard downshift. So they take it to the dealer and say "fix this". The dealer finds no codes and in test drives can not reproduce the fault so give the car back to the owner who drives the car for a week or a month and gets another hard downshift. It became clear over time that the cam servo can experience an intermittent failure to operate within the required parameters and the hard shift condition occurs, then the "problem" clears itself and the hard shift condition goes away.

Some have observed contamination on the screen on the oil input at the servo and assumed that the contamination was affecting the operation of the servo. Others have suggested that the servo can fail intermittently mechanically and then return to normal operation. Randomly.

Over the past few years, the vast majority of cases of hard downshifts reported have been solved by replacing the cam drive servos. My personal experience with multiple RMSSC cars that have seen hard downshifts is that in every case, replacing the cam servos solved the problem.

I have not personally learned of a TCM failure but recognize that it is a possibility. But as I said above, we have seen many instances of servo failure.
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post #10 of 19 (permalink) Old 11-05-2018, 08:43 AM
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We have begun to see TC and ABS failure warnings over the course of the past couple of years. They have all been a single occurrence that were reset by cycling the ignition. In at least one instance, we had multiple warnings on a cruise as we went over a mountain pass. My belief is that they are false warnings due to a condition related to the sensors resulting from aging of components. There have been no actual failures and in every instance normal operation was returned upon a restart.
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post #11 of 19 (permalink) Old 11-12-2018, 07:09 PM Thread Starter
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Thanks for the reply, I guess that makes sense, if it happens again maybe just a restart will fix it.
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post #12 of 19 (permalink) Old 11-12-2018, 07:16 PM Thread Starter
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Originally Posted by Rob the Elder View Post
In the transmission succage thread we learned several things.

First is that the failure of the cam servo will cause the TCM to go into protection mode and you get hard downshifts.

Second was that the cam servo can and do "fail" intermittently. In fact, it took nearly a year of collecting clues to figure out that the servo did cause this hard down shift condition. The usual scenario is the driver experiences a random hard down shift followed by "normal" operation. Then another hard downshift. So they take it to the dealer and say "fix this". The dealer finds no codes and in test drives can not reproduce the fault so give the car back to the owner who drives the car for a week or a month and gets another hard downshift. It became clear over time that the cam servo can experience an intermittent failure to operate within the required parameters and the hard shift condition occurs, then the "problem" clears itself and the hard shift condition goes away.

Some have observed contamination on the screen on the oil input at the servo and assumed that the contamination was affecting the operation of the servo. Others have suggested that the servo can fail intermittently mechanically and then return to normal operation. Randomly.

Over the past few years, the vast majority of cases of hard downshifts reported have been solved by replacing the cam drive servos. My personal experience with multiple RMSSC cars that have seen hard downshifts is that in every case, replacing the cam servos solved the problem.

I have not personally learned of a TCM failure but recognize that it is a possibility. But as I said above, we have seen many instances of servo failure.
Thank you for the explanation, car is put away for the winter but will certainly revisit this in the spring.
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post #13 of 19 (permalink) Old 11-14-2018, 08:34 AM
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Please let us know the outcome.
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post #14 of 19 (permalink) Old 11-23-2018, 08:44 AM
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I'm experiencing the same problem plus mine will downshift out of overdrive randomly at highway speed. So far I have replaced the 4-5 solenoid in the transmission, intake and exhaust camshaft solenoid and about to replace the MAP sensor.

2008 Redline Stage III
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post #15 of 19 (permalink) Old 11-26-2018, 11:48 AM
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if it is shifting randomly at highway speeds that is not the same failure mode addressed in the succage thread. That was hard downshifts on deceleration randomly.

You may have a "hard" failure in the TCM or BCM that can be diagnosed by a dealer. Find one who will look at the car without charging an arm and a leg and see what they say.
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