ZF-8HP overheat

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Scarylarry

Junior Member
Joined
Jan 19, 2022
Posts
27
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Location
sarasota fla
Ram Year
2014
Engine
5.7
I've never posted here before but just gotta share THIS. Trans running too hot, 220 + most of the time. First I added a 12x12 aluminum cooler, No help then a 24x18 W/fan and thermostate. No help. then I added a RevMax # 8HP70-500A. It's a bypass for the coolant preheater. Mounted low on the front driver side of the trans. I have not been able to get my trans over 130 deg f since.
About an hour to install and less than a 1/4 cup loss of fluid in the process. Oh yea and about $120.oo in the door.
 

crazykid1994

Senior Member
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Sep 21, 2013
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Florida
Ram Year
2017
Engine
Hemi 5.7
@Wild one i know this is one of your favorite subjects. Lol. Yup. Lots of people have bypassed the thermostat. There’s a guy on here that makes dummy plugs that replace the thermostat to block the heater off and direct full flow to the stock transmission cooler. I’ve done a full heater delete leaving the stock cooler and my trans makes it to 145° on hot days when I’m loaded down. Im actually looking at adding an in line thermostat again to bring my temps up to 145-150° all the time to help keep as much moisture out of the transmission fluid as possible. To cold and the oil absorbs moisture and turns acidic and wrecks the internal seals and stuff unless you stay on top of fluid changes and proper maintenance.
 

Wild one

Senior Member
Joined
Jan 17, 2016
Posts
13,917
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23,882
Ram Year
14 Sport
Engine
5.7
I've never posted here before but just gotta share THIS. Trans running too hot, 220 + most of the time. First I added a 12x12 aluminum cooler, No help then a 24x18 W/fan and thermostate. No help. then I added a RevMax # 8HP70-500A. It's a bypass for the coolant preheater. Mounted low on the front driver side of the trans. I have not been able to get my trans over 130 deg f since.
About an hour to install and less than a 1/4 cup loss of fluid in the process. Oh yea and about $120.oo in the door.
You spent alot of unneccessary money,lol.You should probably follow CrazyKids advice and install an aftermarket thermostat to bring the temps up slightly. I don't think Jesse is building his bypass anymore Khris,so you're pretty well stuck with Revmax's overpriced kit. You could of saved yourself alot of money on an unneeded external cooler/fan if you'd read through this thread first Larry. Khris and i both started out with Revmax's kit,then did things differantly,and a whole lot cheaper.BTW you're due for a tranny service on your 14's 8 speed if you haven't done one yet.ZF reconmends doing a service on the 8 speed between 80,000 kilometers (50,000 miles) and 130,000 kilometers (80,000 miles) or 8 years,which ever comes first,and you're at the 8 year mark with your 14

https://www.ramforum.com/threads/revmax-8-speed-thermostat-bypass.171776/

You might want to look into adding the 145 or 165 version into your cooler system.


Here's the instructions to do the fluid level check when you service the 8 speed.
 

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