8hp70 heater bypass

caulk04 · Feb 2, 2021

Starting this thread to consolidate some information that we've been discussing (https://www.ramforum.com/threads/revmax-8-speed-thermostat-bypass.171776/unread) on the topic of keeping the 8hp70 cooler than stock.

Here you'll see the thermostat assembly broken down into its individual components.

I have parts on order to make my own device to bypass the heater and flow fluid through the cooler up front all the time. You'll reuse the black plastic plug and the pin next to it. If someone was to purchase the brass plug from revmax, it should work as well but I don't have one to be sure.

I should have something made up this week, will update this post then. End game, I'd like to make these available to purchase but we'll see.

Wild one · Feb 2, 2021

caulk04 said:
Starting this thread to consolidate some information that we've been discussing (https://www.ramforum.com/threads/revmax-8-speed-thermostat-bypass.171776/unread) on the topic of keeping the 8hp70 cooler than stock.

Here you'll see the factory thermostat and it's related components as you'd remove them from the heater unit on the side of the trans. Shown is the general direction of flow with the fluid cold/cool and the thermostat closed.

View attachment 236117

Here you'll see the thermostat assembly broken down into its individual components.

View attachment 236120

I have parts on order to make my own device to bypass the heater and flow fluid through the cooler up front all the time. You'll reuse the black plastic plug and the pin next to it. If someone was to purchase the brass plug from revmax, it should work as well but I don't have one to be sure.

I should have something made up this week, will update this post then. End game, I'd like to make these available to purchase but we'll see.

The Rev Max plug is identical to the original plastic plug.If this works with the stock plug,it should also work with the Rev Max plug

caulk04 · Feb 3, 2021

So here's what I've come up with. The longer spring in the factory setup is there to compress the wax motor as it cools. They do not retract on their own. No need for that spring in my design.

The shorter spring is a damper of sorts so the extension of the wax motor does not become limited and put high stress on the plastic cap. That means the brass washer seals off flow and the spring keeps it there.

The only thing I need to confirm is that the depth I've figured is correct to seal and seat properly. I'll do that on my truck soon.

Installation will be quick and simple. Gain access to the thermostat housing, remove snap ring, remove cap and thermostat assembly. You'll keep the cap and the pin from the stock assembly but replace the thermostat with my bypass plug.

caulk04 · Feb 3, 2021

Here's a couple clearer shots of what I've made. I won't make any specific claims about how much more flow there will be over stock (revmax says 87%), but suffice to say there's less restriction at the cap.

Wild one · Feb 3, 2021

Now that's some good engineering Caulk,i like how simple your idea is. My hats off to you sir.

caulk04 · Feb 5, 2021

Installed the first one in my truck and it's all gone as expected so far. It fit in and compressed as I expected. Took a couple mile trip around the neighborhood to confirm no immediate issues, all good!

It'll be Monday before I go back to work for any good data, but I'll drive around some over the weekend for sure.

Different Drummer · Feb 5, 2021

caulk04 said:
Installed the first one in my truck and it's all gone as expected so far. It fit in and compressed as I expected. Took a couple mile trip around the neighborhood to confirm no immediate issues, all good!

It'll be Monday before I go back to work for any good data, but I'll drive around some over the weekend for sure.

What kind of ambient temperatures are you at where you live right now?

chrisbh17 · Feb 5, 2021

Different Drummer said:
What kind of ambient temperatures are you at where you live right now?

This, and what kind of transmission temperatures did you end up running?

caulk04 · Feb 5, 2021

In good time, I'll be driving it soon to find out. First drive was just to make sure I didn't miss anything and screw up royally.

Temps are mid 20's to teens overnight the next few days and by next weekend teens to 0 overnight. My truck is otherwise stock, including grille shutters.

Musky Mike · Feb 5, 2021

That looks great, you did an awesome job. I'm looking for a 20-30 degree reduction in temp, but being able to quickly and easily return to stock (I have an extended warranty). I would like to purchase one if it works out.

crazykid1994 · Feb 5, 2021

caulk04 said:
In good time, I'll be driving it soon to find out. First drive was just to make sure I didn't miss anything and screw up royally.

Temps are mid 20's to teens overnight the next few days and by next weekend teens to 0 overnight. My truck is otherwise stock, including grille shutters.

With grill shutters you have the benefit of helping the trans heat up but my concern is them not opening because the trans not reaching the programmed temp for the shutters to open. Otherwise that’s awesome and hope it works out well

chrisbh17 · Feb 5, 2021

crazykid1994 said:
With grill shutters you have the benefit of helping the trans heat up but my concern is them not opening because the trans not reaching the programmed temp for the shutters to open. Otherwise that’s awesome and hope it works out well

They should be based on the engine coolant temp....its affected by the trans temp, for sure, but I dont think enough that the coolant wont ever get up to temp enough to open the shutters.

Could be that the ultimate "non-intrusive" "fix" for coolant and trans temps is the bypass part in this thread + removing the inner AGS shutters (as long as you leave the outers connected the system will still work without throwing a CEL)

crazykid1994 · Feb 5, 2021

chrisbh17 said:
They should be based on the engine coolant temp....its affected by the trans temp, for sure, but I dont think enough that the coolant wont ever get up to temp enough to open the shutters.

Could be that the ultimate "non-intrusive" "fix" for coolant and trans temps is the bypass part in this thread + removing the inner AGS shutters (as long as you leave the outers connected the system will still work without throwing a CEL)

It uses engine coolant and trans temps both. Mine are fully deleted and I have no cel. I’m also running a 190 tstat so my temps are all around lower. For those who want to remain stockish yes I agree with you

caulk04 · Feb 5, 2021

crazykid1994 said:
It uses engine coolant and trans temps both

Can confirm. After a short drive to town the engine coolant would rise to 201-203 then drop quickly to 192 while the trans was still around 100. Nothing at all alarming, but a notable difference in behavior.

Funny that revmax says nothing about that with their kit.

Wild one · Feb 5, 2021

caulk04 said:
Can confirm. After a short drive to town the engine coolant would rise to 201-203 then drop quickly to 192 while the trans was still around 100. Nothing at all alarming, but a notable difference in behavior.

Funny that revmax says nothing about that with their kit.

Rev Max's instructions also leave alot to be desired too.As there's no way you can run either Option 1 or Option 2 with-out over heating the tranny.
I'm very impressed with what you've done Caulk.I'd already bought the Rev Max kit and modded my truck before you had this out,but if i was doing it again,i'd spring for your plug long before i'd do it the way i did,lol. The only benefit to doing it the way Crazy Kid and i did ,was completely deleting the heat exchanger off the side of the tranny and cleaning it up,but for the work involved,it's not really worth it.
Like i said before my hats off to you,that's some good engineering you did.

I thought vehicle speed was also a factor in the shutters operation,along with the temps,aren't they supposed to close up at speed if the temps are with-in the factory temp parameters

crazykid1994 · Feb 5, 2021

Wild one said:
Rev Max's instructions also leave alot to be desired too.As there's no way you can run either Option 1 or Option 2 with-out over heating the tranny.
I'm very impressed with what you've done Caulk.I'd already bought the Rev Max kit and modded my truck before you had this out,but if i was doing it again,i'd spring for your plug long before i'd do it the way i did,lol. The only benefit to doing it the way Crazy Kid and i did ,was completely deleting the heat exchanger off the side of the tranny and cleaning it up,but for the work involved,it's not really worth it.
Like i said before my hats off to you,that's some good engineering you did.

I thought vehicle speed was also a factor in the shutters operation,along with the temps,aren't they supposed to close up at speed if the temps are with-in the factory temp parameters

I think they close similar to how the mds functions to increase fuel economy by blocking airflow into the engine bay when at speed. And I agree. I would not do what I did over again. Pain in my butt.

crazykid1994 · Feb 5, 2021

caulk04 said:
Can confirm. After a short drive to town the engine coolant would rise to 201-203 then drop quickly to 192 while the trans was still around 100. Nothing at all alarming, but a notable difference in behavior.

Funny that revmax says nothing about that with their kit.

Like wild stated. Rev max doesn’t really give much data and honestly lacks some really important as well. I really like your idea and would spring for that had I not already deleted the heater completely. I like your design quite a bit.

Wild one · Feb 5, 2021

crazykid1994 said:
Like wild stated. Rev max doesn’t really give much data and honestly lacks some really important as well. I really like your idea and would spring for that had I not already deleted the heater completely. I like your design quite a bit.

We were a couple days early Khristopher.There's times a kick my ass for being impatient,this is one of those times,lol

caulk04 · Feb 6, 2021

More data for yinz.

This is at the end of my normal drive to work, plus a couple miles then back home a couple hours later. 24miles each way, 60mph cruising, back road ish. Normally the trans is 165 by this point, levels out at 176 if I drive a little further.

The PCM seems to keep the grille shutters closed to warm up the trans, then opens it if the coolant crosses 203-205. The trans levels out here at 110-115 and the coolant settles down as well, seems the PCM is ok with the trans at this temp and stops trying to force it hotter with the shutters.

I'm quite happy with it as is. There is nothing wrong, in my mind, with the trans running at this temp and I can only assume it'll be a little warmer once temps return to a hospitable level.

View attachment 236716

View attachment 236717

chrisbh17 · Feb 6, 2021

caulk04 said:
More data for yinz.

This is at the end of my normal drive to work, plus a couple miles then back home a couple hours later. 24miles each way, 60mph cruising, back road ish. Normally the trans is 165 by this point, levels out at 176 if I drive a little further.

The PCM seems to keep the grille shutters closed to warm up the trans, then opens it if the coolant crosses 203-205. The trans levels out here at 110-115 and the coolant settles down as well, seems the PCM is ok with the trans at this temp and stops trying to force it hotter with the shutters.

I'm quite happy with it as is. There is nothing wrong, in my mind, with the trans running at this temp and I can only assume it'll be a little warmer once temps return to a hospitable level.

View attachment 236716

View attachment 236717

View attachment 236718

View attachment 236719

With results like that, let me know if/when you are selling them

8hp70 heater bypass

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