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Old 10-15-2020, 08:10 AM   #21
gspman
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i have a 08 duramax ext cab, 4wd
undernormal not-towing, it hovers around ~70' above ambient air temp at hyway speeds.
towing my 5er, it is about ~90' above ambient. these are rough numbers because of variable's such as humidity and such.
But i know that if the temp gets much above the "average" then i need to be wary of things.
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Old 10-15-2020, 11:44 AM   #22
LCrabtree
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Temp Gage

Question: does your Trans Temp gauge have any indication of HOT v. Normal?

As another poster noted, you do want to run it warm / hot enough to drive out any moisture that has condensed inside the transmission. That said, anything under 230 seems to be magic for that era transmission. Almost all pickups have transmission coolers that incorporate the cooling system in some way. It is not unusual for a 'hot' transmission to heat up the engine coolant above normal operating temps. Without a trans temp gage, one can tell somewhat if the trans is within normal ranges by simply watching the engine temperature gauge. If it stays in normal range, chances are the trans is also within normal range.
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Old 10-15-2020, 02:01 PM   #23
rhagfo
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I don’t think fluids need to get to 212 degrees to remove moisture from oil. I don’t think my Aisin has ever been over 180, and there was no moisture in the fluid at the 30k drain and fill.
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Old 10-15-2020, 03:15 PM   #24
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Ford put the light bulb too close to the sensor.
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Old 10-15-2020, 05:22 PM   #25
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Quote:
Originally Posted by rhagfo View Post
I donít think fluids need to get to 212 degrees to remove moisture from oil. I donít think my Aisin has ever been over 180, and there was no moisture in the fluid at the 30k drain and fill.
Same here pulling over 17,000#.
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Old 10-16-2020, 07:19 AM   #26
LCrabtree
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Originally Posted by rhagfo View Post
I donít think fluids need to get to 212 degrees to remove moisture from oil. I donít think my Aisin has ever been over 180, and there was no moisture in the fluid at the 30k drain and fill.
True! Even at the ambient air temperature, in the open air, water will evaporate from an oil base; however, the warmer that the mixture is, the faster the water evaporates (don't overheat your cooling system just to accomplish this feat). Short trips are worse than long trips. Short trips will heat the mixture, but not long enough to drive the moisture out, and when you shut down more moisture condenses in the oil (mixture). Long trips heat the mixture and allow time for the moisture to evaporate before you shut it down.

In the "old days" we used to be 'leary' about buying a used car with low mileage from a 'little old lady who only drove it to church on Sundays' for this very reason. I suppose that technology has addressed some of these issues, but the science doesn't change.
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Old 10-16-2020, 07:51 AM   #27
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In 2012, GM only offered one rear end gear in the 2500 suburban. Off the top of my head I donít know what it is, but if you check inside the glove box there should be a label that has a bunch of 3 digit codes. Normally around the center or label is a GU code. Typically GU4, GU6 or GU8. You can google that code to see what your rear gear is, but I believe they are 3:08, 3:55, and 3:73 respectively.

As for trans temps. The owners manual will typically give you a normal range. I think youíll find 160 is normal warm temps. When towing heavy through mountains you will typically see trans temps around the same area as your coolant temps since the radiator is used for cooling trans fluid as well. As others have mentioned, I believe anything under 200 is fine. Short runs over a mountain pass above 200 is ok as well as long as it cools back down when the work load is reduced. I would get concerned if it jumped over 220-230 range or if it stayed in that range for extended periods even when work load is reduced such as going down the other side of a hill climb or running on flat.
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Old 10-16-2020, 07:53 AM   #28
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Originally Posted by bsmith0404 View Post
In 2012, GM only offered one rear end gear in the 2500 suburban. Off the top of my head I donít know what it is, but if you check inside the glove box there should be a label that has a bunch of 3 digit codes. Normally around the center or label is a GU code. Typically GU4, GU6 or GU8. You can google that code to see what your rear gear is, but I believe they are 3:08, 3:55, and 3:73 respectively.

As for trans temps. The owners manual will typically give you a normal range. I think youíll find 160 is normal warm temps. When towing heavy through mountains you will typically see trans temps around the same area as your coolant temps since the radiator is used for cooling trans fluid as well. As others have mentioned, I believe anything under 200 is fine. Short runs over a mountain pass above 200 is ok as well as long as it cools back down when the work load is reduced. I would get concerned if it jumped over 220-230 range or if it stayed in that range for extended periods even when work load is reduced such as going down the other side of a hill climb or running on flat.
I wish I could have said it this completely and succinctly.
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