ZF Transmission question - temps

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BenchTest

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I've observed a very repeatable trend and I'm curious if others have. This also may be a design build for this transmission? My fluid runs mid to upper 180s when ambient temps are below 60. As ambient temps increase, my fluid cools to low 170s. Is this an intentional temperature regulation to keep fluid thinned at lower temps for flow properties and fuel economy (thinner fluids are easier to move, less drag)?
 

crash68

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With the ZF transmissions if the transmission temperature is staying at or below the coolant temperature it's working as intended. If the temperature is spiking really high over the coolant temp, the TMU on the side of the transmission will probably needs to be replaced.
 

HEMIMANN

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With the ZF transmissions if the transmission temperature is staying at or below the coolant temperature it's working as intended. If the temperature is spiking really high over the coolant temp, the TMU on the side of the transmission will probably needs to be replaced.

Thermostat bypass kit?
 

Wild one

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I've observed a very repeatable trend and I'm curious if others have. This also may be a design build for this transmission? My fluid runs mid to upper 180s when ambient temps are below 60. As ambient temps increase, my fluid cools to low 170s. Is this an intentional temperature regulation to keep fluid thinned at lower temps for flow properties and fuel economy (thinner fluids are easier to move, less drag)?

The 8 speeds use their own thermostat,it's in the TMU on the side of the transmission as Crash stated.They have been known to give trouble. For now i wouldn't worry to much about your's,but if the transmission starts to regulary run above 200F in the summer,you might want to look into either replacing the Thermal Management Unit on the side of the transmission,or pull the thermostat out and replace it with one of Caulk04's thermostat bypasses.The thermostat is a pellet style thermostat,similiar to the engine thermostat,so it doesn't really change opening temps in relation to ambient temps,as much as it does to fluid temps. Your's could be acting up a bit,but as long as the transmission temps don't sky rocket,i wouldn't worry to much about it yet,but you might want to keep an eye on the transmission temp from here on in.
How many miles are on your truck,ZF reconmends doing a transmission service on the 8 speed between 50,000 (if you tow alot) and 80,000 miles or 8 years which ever comes first
 
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BenchTest

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The 8 speeds use their own thermostat,it's in the TMU on the side of the transmission as Crash stated.They have been known to give trouble. For now i wouldn't worry to much about your's,but if the transmission starts to regulary run above 200F in the summer,you might want to look into either replacing the Thermal Management Unit on the side of the transmission,or pull the thermostat out and replace it with one of Caulk04's thermostat bypasses.The thermostat is a pellet style thermostat,similiar to the engine thermostat,so it doesn't really change opening temps in relation to ambient temps,as much as it does to fluid temps. Your's could be acting up a bit,but as long as the transmission temps don't sky rocket,i wouldn't worry to much about it yet,but you might want to keep an eye on the transmission temp from here on in.
How many miles are on your truck,ZF reconmends doing a transmission service on the 8 speed between 50,000 (if you tow alot) and 80,000 miles or 8 years which ever comes first
Pan/filter was replaced at 54k miles and I currently set at 65k. Was behaving in this manner prior to trans service. It's temperature swings have stayed the same prior/post trans service. I serviced the trans as a preventative at 54k, not due to any performance related issues.
 

CanuckRam1313

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Highly recommend the @caulk04 transmission bypass cooler mod!
I've got one in my truck, in my step-daughters truck, and a third on order for an acquaintances truck, too.

Do a transmission fluid and filter change at the same time as well. I'm seeing trans temps decreases of up to 30deg with this mod.

My trans runs great now, and I will be doing a 60K to 70K oil & filter change interval moving forward. That reminds me.... I'm near due for another fluid and filter change....
 

Wild one

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Pan/filter was replaced at 54k miles and I currently set at 65k. Was behaving in this manner prior to trans service. It's temperature swings have stayed the same prior/post trans service. I serviced the trans as a preventative at 54k, not due to any performance related issues.

Did you follow these directions,especially the part about leveling the pan rail.
 

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indept

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Highly recommend the @caulk04 transmission bypass cooler mod!
I've got one in my truck, in my step-daughters truck, and a third on order for an acquaintances truck, too.

Do a transmission fluid and filter change at the same time as well. I'm seeing trans temps decreases of up to 30deg with this mod.

My trans runs great now, and I will be doing a 60K to 70K oil & filter change interval moving forward. That reminds me.... I'm near due for another fluid and filter change....
Do you have a link?
 
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