The debate on Dex III vs Valvoline Dex/Merc for 4T65E

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Halfmoon, New York
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All, In your personal experiences (hopefully with the same or a similar GM tranny) have you found the Valvoline Dex/Merc to register lower on the dipstick? Back Story: I have a 2003 Century with 60K miles and a 4T65E. Fluid was original Dex III and was near top of cross-hatches. I used a mighty-vac pump, and measuring containers to make sure I put in the same fluid I took out. The reading is now at the bottom of the hatch mark. Checked after warm up, several drives, shifting through all gears, on same level surface. I wasn't sure if Dex/Merc's formula has a lower expansion point that could explain this. Thank you! James
 
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4
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Halfmoon, New York
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Originally Posted by Bottom_Feeder
If you've checked the level properly, is adding a smidge more fluid to get it where you want it on the stick not an option for some reason?
It is, but this is more than a smidge, and I just didn't want to be over-filling the transmission. For some reason I've always run into problems when the tranny has more fluid put in than what it originally had.
 
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I seriously doubt it. The coefficient of thermal expansion of any Group I, II or III hydrocarbon is going to be the same, and I looked up the values for a random PAO and it isn't that much different. But it doesn't really matter because whether one has a different coefficient than the other is irrelevant. Determining the proper fluid level of your transmission is what's important regardless of what brand you happened to buy. If the level is low when checked properly then it should be brought to the correct level for the proper operation of the transmission. And what exactly is the debate?
 
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Halfmoon, New York
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Originally Posted by kschachn
I seriously doubt it. The coefficient of thermal expansion of any Group I, II or III hydrocarbon is going to be the same, and I looked up the values for a random PAO and it isn't that much different. But it doesn't really matter because whether one has a different coefficient than the other is irrelevant. Determining the proper fluid level of your transmission is what's important regardless of what brand you happened to buy. If the level is low when checked properly then it should be brought to the correct level for the proper operation of the transmission. And what exactly is the debate?
The debate was whether or not Dex/Merc had a different expansion point than Dex III in the 4T65E or similar tranny's. Thank you so much for filling me in on this information, I'll add more.
 
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Hudson, NH
Its cold where you are, so thats probably why its staying lower. I would leave it a bit below the full hot line. Wait till summer to check again.
 
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Texas
Originally Posted by LeakySeals
Its cold where you are, so thats probably why its staying lower. I would leave it a bit below the full hot line. Wait till summer to check again.
THIS ^^^
 
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Halfmoon, New York
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Thank you.
Originally Posted by LeakySeals
Its cold where you are, so thats probably why its staying lower. I would leave it a bit below the full hot line. Wait till summer to check again.
 
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Unless you can measure the oil temp with some accuracy, it's difficult to compare the two fills. There's a temp sensor in the valve body you can read with some scanners, or an alternative is to look at the pan with a laser temp gun.
 
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