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Jerry Newton
Jerry Newton, Cadillac Technician
Category: Cadillac
Satisfied Customers: 4829
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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96 deville: started slipping out of overdrive..90k babied miles.

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96 deville started slipping out of overdrive. 90k babied miles. Is this likely internal(ie. TCC) or is there some wiring or connection which might be corroded and not providing enough current or voltage? No engine codes presently. Started after anXXXXX much of it in rain. If driving in 3rd and then shift to overdrive the rpms drop appropriately as it goes into od but then upshifts back into third. Thanks from Tom
These Cadillacs had issues with shift solenoids, they actually break in two from the pressure in the transmission. GM sells a kit with the solenoids and a little bracket that holds onto the solenoid to keep it from breaking again. Solenoids are located under the bottom pan, but you have to remove the lower valve body to service them. Expect to spend $300 or so to have a shop fix this. Even if they are not cracked/broken, I always begin by dropping the pan and looking at them to be sure.
Customer: replied 7 years ago.

Thank you JFN1 for your response. It sounds like you are fairly confident from hearing my description that this is in fact the problem. My next question would be that if in fact this is a compromised shift solenoid, shouldn't I be getting some sort of a computer code message regarding the problem?

Tom in Wisconsin

Yeah, you would think so, but honestly, I've seen them give trouble without giving codes. Like I said before, this is certainly the first thing I would look at. You say it started happening after a long drive, did it go away or is it still acting up, even when cool?
Customer: replied 7 years ago.

Started after a 1000 trip. Initially it seemed to jump in and out of od at highway speeds but today when I drove it refused ever to go into od at all. In addition, at low (40mph) city speed, it started to slip and rev a little while in od. I now am suspicious that continuing to drive (even at low city speed in 3rd) it is somehow making it worse. I think I will leave it parked for now until I can tear it apart. Thanks again and please add anything else you might have with regard to this problem.....for example if driving in 3rd with a bad od solenoid will start wrecking the other gears (solenoids) sequentially! Thanks and happy halloween! Tom in Wisconsin

If it's slipping in OD, then the thing to do is drive it in manual 3rd until you can get in there and fix it. Slippage causes damage that can only be repaired by removal and overhaul, so you definitely want to avoid that. You may already have damage that will necessitate overhaul, but removal of the lower pan and inspection of those solenoids is going to be the place to start, anyway.
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