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Discussion Starter #1
Guys
I live in the Canary Islands and there are no other Cadillacs here but mine, the problem is that mine will now only change gear at high speeds. I have changed the oil and filter, also she now has no kick down either. As I am not a mechanic but have a little know-how, can anyone help, please?

Regards
Gary Hagger
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
Your transmission has an externally mounted vacuum operated modulator valve. Check to see that it holds a vacuum.

"When you have a bad modulator valve, some or all of the following symptoms will begin to manifest themselves:
  • A whistling sound (from a leaking diaphragm)
  • White smoke coming out of the exhaust (from a leaking diaphragm)
  • Early or late shifting.
  • Hard shifts (usually causing the car to jerk)
  • A rough idle."
 

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2014 SRX Luxury
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93 Posts
Your transmission is a 400 turbo. It has a governor, electric kickdown switch, and a vacuum modulator. The first place I would look is to the electric downshift switch and disconnect it. If it has internally closed then the transmission would want to stay in passing gear all the time. The second place to check is the modulator. These can get bent and not function. Before that make sure the vacuum line to the modulator is not leaking as again with no vacuum the transmission wants to be in passing gear all the time. The third issue could be the governor. It is behind a round hat looking cap on side of transmission. It can get stuck with debris and malfunction. Look at the governor last as they rarely fail.

Hope this helps...
 

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Discussion Starter #4
Your transmission is a 400 turbo. It has a governor, electric kickdown switch, and a vacuum modulator. The first place I would look is to the electric downshift switch and disconnect it. If it has internally closed then the transmission would want to stay in passing gear all the time. The second place to check is the modulator. These can get bent and not function. Before that make sure the vacuum line to the modulator is not leaking as again with no vacuum the transmission wants to be in passing gear all the time. The third issue could be the governor. It is behind a round hat looking cap on side of transmission. It can get stuck with debris and malfunction. Look at the governor last as they rarely fail.

Hope this helps...
Thanks to you both.
Sorry to sound stupid but as a builder I find motors a mystory, can you tell me where they are and where can I find pictures.
 

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96 FWB
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353 Posts
In top 5 duckduck hits with 'service for 400thm'

First duckduck hit with '400thm troubleshooting'

Considering the cost it seems a very good investment. ::smiles::
 
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