Failing Alternator causing transmission shifting issues?

My vehicle (1999 Kia Sephia, 137000 miles) has had the brake and the battery indicator lights on, which from what I have read indicate an alternator problem. As my car was getting close to its last legs the shifts from one gear to the other as I was driving became harsher.

My question is, could a failing alternator cause the transmission to shift like that, and will that cause any transmission damage?

Yes it can. Electronic transmissions are computer controlled, the computer requires a minimum voltage to operate. If your charging system falls below this minimum voltage requirement the transmission will go into a limp mode. You need to get this fixed ASAP.


Why don’t you go to an auto parts store and get a free battery and alternator curb-side test? Then, if one of them needs replacing, you could take care of the problems of low voltage.

When I first experienced the problem yesterday, I setup an appointment to take it to my shop today. I would have yesterday, but I had to work the evening shift at work and was unable resolve it that day. I’m just glad my car was able to get me home, right after I got home my car refused to start or do anything, so I’m going have to have it towed there. I drove the car for less than a day and 40 miles , 5/6 of it highway so the transmission didn’t have to shift when I reached cruising speed, I just hope it wasn’t long enough to cause any permanent damage.

Thanks for your input.

You can save yourself a tow bill if: you recharge the battery, and then, see if it will start. If it does, you could drive it to the repairer; or, if you are confident that the alternator is bad, and you can do the job, replace the alternator.

I’ve got AAA, so the towing is taken care of… with an 11 year old car i know i’m going need a tow every now and then, they will probably try starting it up since that is their mode of operation. I’m in Buffalo, NY essentially all the work I do on my car stops as the first flake falls since I have no indoor garage.

Hi, Could you please tell us how this ended up? I’m having similar problems, just tell us what was the diagnostic finally specially for the transmission!

Hi Mike:
The author of this post, samdude1400, hasn’t logged into this site since June 2007, so I doubt he’ll be able to help you.

However, if you want to create a new post describing the problem you’re having with your vehicle, I’m sure many of us on this site will be more than happy to see if we can help.

Thank you.

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