Caulk 8HP Thermal By-Pass Valve Installed!
My 2022 RAM 1500 has a “not wonderful” transmissionmission heater that assists in keeping the transmissionmission fluid too hot for my liking (185 deg F to 200 deg F). RAM identifies this Mopar 68463479AA Transmission Heater.
RAM 1500 stories abound about the thermostat sticking open and not fully closing after a period of use. Pictures in this post will also attempt to explain why the thermostat in the transmissionmission heater part stick(i.e. “fails”). When it does stick, the end user will generally experience a “slow creep” upwards in transmissionmission fluid temperature over time
. Obviously, this slow temperature creep of the ATF is not beneficial for those of us who desire to run a RAM1500 (also some Jeeps) 250,000 miles to 500,000 miles utilizing the original transmissionmission.
As such, I researched some other forums for my RAM and learned of a “thermal bypass valve” parts kit. Many RAM enthusiasts pointed myself in the direction of the Caulk 8HP Thermal Bypass Valve that is designed specifically for the ZF 8HP70 and ZF 8HP75 8-speed automatic transmissionmissions.
Caulk Thermal Bypass Valve
I read the manufacturer’s claims and decided I would take an $80 “gamble” on the thermal bypass valve with a new machined aluminum cap (replacing a plastic OEM ZF thermostat valve cap).
In reality, this valve is really a "delete" option that simply prevents the coolant loop from cycling coolant from the cooling system’s radiator back to a small liquid-to-liquid heat exchanger mounted on the side of transmissionmission (driver’s side).
After the thermal bypass valve thermostat guts are installed into the body of the transmissionmission heater assembly, transmissionmission fluid is sent to the transmissionmission cooler 100% of the time the motor is running. Post-modification, the transmissionmission temperature rises much more slowly and keeps normal transmissionmission fluid temperatures in the 140 deg F to 165 deg F range.
The idea here is to keep the transmissionmission fluid cooler when towing and driving 70+ mph (with and without towing trailer weight).
Hopefully this results in an extended transmissionmission service life and less lubricity loss as the transmissionmission fluid ages and is used/“burnt”over time). I shall see in the future, won’t I?
For those not desiring to read through the entire thread here, I will simply say “YES” ; the Caulk Thermal Bypass Valve does indeed work as advertised. I am impressed that this product actually performs as advertised.
The top two pieces in the above picture are the formal “kit.”
Below that, second row is the OEM pin and OEM snap ring. These two parts are reused.
On the bottom row are the original thermostat plunger, springs, and plastic cap. Over time, the plastic cap becomes worn from the brass of the original transmissionmission heater thermostat. Eventually the brass disc portion of this OEM part sticks into the “fingers” of the end of the OEM plastic cap. The net effect is that the thermostat cannot fully close (retract) from the plastic. At that point, you are continually cycling coolant into the transmission heat exchanger and it keeps heating.
Not a good thing for those of us that haul & tow heavy loads as well as not good for general summer driving.
My 2022 RAM 1500 has a “not wonderful” transmissionmission heater that assists in keeping the transmissionmission fluid too hot for my liking (185 deg F to 200 deg F). RAM identifies this Mopar 68463479AA Transmission Heater.
RAM 1500 stories abound about the thermostat sticking open and not fully closing after a period of use. Pictures in this post will also attempt to explain why the thermostat in the transmissionmission heater part stick(i.e. “fails”). When it does stick, the end user will generally experience a “slow creep” upwards in transmissionmission fluid temperature over time
. Obviously, this slow temperature creep of the ATF is not beneficial for those of us who desire to run a RAM1500 (also some Jeeps) 250,000 miles to 500,000 miles utilizing the original transmissionmission.As such, I researched some other forums for my RAM and learned of a “thermal bypass valve” parts kit. Many RAM enthusiasts pointed myself in the direction of the Caulk 8HP Thermal Bypass Valve that is designed specifically for the ZF 8HP70 and ZF 8HP75 8-speed automatic transmissionmissions.
Caulk Thermal Bypass Valve
I read the manufacturer’s claims and decided I would take an $80 “gamble” on the thermal bypass valve with a new machined aluminum cap (replacing a plastic OEM ZF thermostat valve cap).
In reality, this valve is really a "delete" option that simply prevents the coolant loop from cycling coolant from the cooling system’s radiator back to a small liquid-to-liquid heat exchanger mounted on the side of transmissionmission (driver’s side).
After the thermal bypass valve thermostat guts are installed into the body of the transmissionmission heater assembly, transmissionmission fluid is sent to the transmissionmission cooler 100% of the time the motor is running. Post-modification, the transmissionmission temperature rises much more slowly and keeps normal transmissionmission fluid temperatures in the 140 deg F to 165 deg F range.
The idea here is to keep the transmissionmission fluid cooler when towing and driving 70+ mph (with and without towing trailer weight).
Hopefully this results in an extended transmissionmission service life and less lubricity loss as the transmissionmission fluid ages and is used/“burnt”over time). I shall see in the future, won’t I?
For those not desiring to read through the entire thread here, I will simply say “YES” ; the Caulk Thermal Bypass Valve does indeed work as advertised. I am impressed that this product actually performs as advertised.
The top two pieces in the above picture are the formal “kit.”
Below that, second row is the OEM pin and OEM snap ring. These two parts are reused.
On the bottom row are the original thermostat plunger, springs, and plastic cap. Over time, the plastic cap becomes worn from the brass of the original transmissionmission heater thermostat. Eventually the brass disc portion of this OEM part sticks into the “fingers” of the end of the OEM plastic cap. The net effect is that the thermostat cannot fully close (retract) from the plastic. At that point, you are continually cycling coolant into the transmission heat exchanger and it keeps heating.
Not a good thing for those of us that haul & tow heavy loads as well as not good for general summer driving.
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