RevMax 8 speed thermostat bypass

[crazykid1994]

A port is fluid leaving the transmission. B port is fluid returning to the transmission.
A port goes into the thermostat area

 

[caulk04]

Just a rough drawing for concept.
View attachment 235485

That's what I intend to do, just slightly differently. Rather than fit the diameter of the bore closely, my goal is to close it off at the face which appears to be how the factory thermostat does it.

 

[Different Drummer]

That's what I intend to do, just slightly differently. Rather than fit the diameter of the bore closely, my goal is to close it off at the face which appears to be how the factory thermostat does it.

So what you have in mind would fit the inside diameter of the larger upper ( Distal ) bore and sit like a lid over the lower bore. Is that correct?
I was thinking that by inserting the cylindrical shaped piece down into the lower smaller bore it would be more stable and would not have any extension into the upper bore where it might have an effect upon flow through the upper lateral wall inlet and outlet openings.
Either way I imagine would perform the function desired. One advantage to your way would be that you would not need to know the depth of the lower bore as it would not come into play.

Edit: Any chance there might be some pressure coming retrograde into that lower bore from the thermal exchanger? If there is I would then think that putting the plug down into the lower bore would be more desirable.

 

[Wild one]

That's what I intend to do, just slightly differently. Rather than fit the diameter of the bore closely, my goal is to close it off at the face which appears to be how the factory thermostat does it.

I'd thought about that idea to,but i still think you might want a step on the bottom under the sealing base to lock it into place.The plastic cap isn't an overly strong piece,and i'd be worried that lateral loads on a pin that long,might be determental to the life expectancy of the plastic end plug,and if it cracks or breaks in the middle of nowhere,you're basically hooped,and i don't know if that plastic endplug is a servicable piece if you do crack it.you might have to buy the whole assembly just to get the endplug.That's of course if you're going to use the original plastic cap,i don't think it'd be an issue with a brass endcap like the Rev Max kit uses though,but that's defeating the purpose of trying to do it relatively cheaply
Although if the sealing washer is a fairly snug tolarence fit in the bore,then lateral loads might not be an issue

 

[caulk04]

One of my concerns was fluid flow of the cooler became blocked but it appears that there's no accounting for that from the factory either.

From what I can ascertain, the smaller spring is there to absorb 'overtravel' from the thermostat which would otherwise put extreme pressure on the plastic cap/plug. Seems I need to add a spring to my plan between the cap and my part to keep everything in place and sealed off.

I'm also curious for those who have tapped/plugged those heater ports, how fluid would flow of they had not also removed the thermostat or if it would at all.

 

[caulk04]

The part I'm imagining would look something like a top hat on a stick.

 

[crazykid1994]

One of my concerns was fluid flow of the cooler became blocked but it appears that there's no accounting for that from the factory either.

From what I can ascertain, the smaller spring is there to absorb 'overtravel' from the thermostat which would otherwise put extreme pressure on the plastic cap/plug. Seems I need to add a spring to my plan between the cap and my part to keep everything in place and sealed off.

I'm also curious for those who have tapped/plugged those heater ports, how fluid would flow of they had not also removed the thermostat or if it would at all.

If you do not remove the thermostat and it stays blocking flow from going to the radiator it would have nowhere to go if you blocked the heater as well.

 

[caulk04]

If you do not remove the thermostat and it stays blocking flow from going to the radiator it would have nowhere to go if you blocked the heater as well.

Right, so there's no other bypass in the event of a clog somewhere.

 

[crazykid1994]

Right, so there's no other bypass in the event of a clog somewhere.

There should not be a clog in this setup. The filter should catch any sediment before being pumped through the radiator or heater. The only clog I could see is if something from the thermostat got jammed which would force fluid through either the heater or the radiator. I would rather not have it stuck going through the heater as that would lead to extremely high trans temps.

 

[caulk04]

I wouldn't expect a problem either, but it was something I thought of. Figured if there was a factory provision for it I didn't want to eliminate it.

 

[Different Drummer]

I'd thought about that idea to,but i still think you might want a step on the bottom under the sealing base to lock it into place.The plastic cap isn't an overly strong piece,and i'd be worried that lateral loads on a pin that long,might be determental to the life expectancy of the plastic end plug,and if it cracks or breaks in the middle of nowhere,you're basically hooped,and i don't know if that plastic endplug is a servicable piece if you do crack it.you might have to buy the whole assembly just to get the endplug.That's of course if you're going to use the original plastic cap,i don't think it'd be an issue with a brass endcap like the Rev Max kit uses though,but that's defeating the purpose of trying to do it relatively cheaply
Although if the sealing washer is a fairly snug tolarence fit in the bore,then lateral loads might not be an issue

You have some sort of direct link into my mind. Both side load and direct pressure on that end cap was something I worry about. An upside down top hat in the lower bore would help. However, that involves more machining. Seems simpler to just bottom out into the lower bore.
I also like the end cap that came with your kit. However, I am not eager to by the entire kit to get the brass end cap.

 

[Wild one]

I wouldn't expect a problem either, but it was something I thought of. Figured if there was a factory provision for it I didn't want to eliminate it.

The internal passages and ports to the cooler lines are a good size,i think if you had something come out of the transmission,big enough to block them,i think the truck would be grinding to a halt in short order,as the tranny is starting to self destruct,probably very quickly at that,lol

 

[crazykid1994]

So far have 7 hours of driving. Highest trans temp is 122° at 77° ambient temp. Seems to have a 45-55° temp differential from outside at all times. Even with off-roading. Loving this. Shifting feels amazing.

 

[crazykid1994]

Forgot to update. Had 12 hours of total driving. Might have had 20 minutes total of engine off time spread throughout that. Everything is great. Trans shifted like butter. Hit 80° out. Trans temp was 127°

 

[chrisbh17]

Man those 120 numbers kinda scare me! Almost sounds TOO low.

In our cold weather Im not sure the trans temp would even get that high for me.

 

[crazykid1994]

Man those 120 numbers kinda scare me! Almost sounds TOO low.

In our cold weather Im not sure the trans temp would even get that high for me.

Given that a lot of people have short drives and the trans takes a bit to warm up I doubt many people get much higher. Not to include that older vehicles did not have a trans warmer and maintained low trans oil temps as well. I know the zf is a completely different setup. However, The cars do not include a oil warmer and would maintain low temps as well. Do I think an aftermarket bypass thermostat, like the HD trucks have, would be great in place of the stock thermostat housing unit with heater? Yes I do. That would be the best option and I would jump right on that boat if someone offered one. 160° would be great in my opinion. I do not think an aftermarket replacement thermostat to replace the stock thermostat will really do much given the thermostat does not fully block the heater from flowing and will continue to heat fluid beyond 160°. I do have to argue that a lot of people are nervous about the low temps. I have never experienced shifting issues in my truck at low temps when the truck is first started. And actually on that 12 hour drive my truck seemed to be more responsive on shifting. It shifted faster and when passing on the highway would drop right into gear and go. At 185° or 190° I always felt like it hesitated briefly when fully warmed up before down shifting.
Edit: speaking of which. Now that I’m thinking about it I really do wish someone would make a bypass style replacement for our trucks to replace the whole assembly. I’m seeing most dodge cars run 165-175° unless running a cooler bypass. BMW runs 195°-205° trans temps on their zf trans. The only thing I’m seeing with research on the fluid is expansion and viscosity change but the zf viscosity is designed to not change drastically from cold to OT. However it does expand quite a bit.

 

[crazykid1994]

@Wild one I asked mike and he said he’s averaging 140° but he’s got a 392 boosted so he’s definitely going to be hotter than I am.

 

[Wild one]

Given that a lot of people have short drives and the trans takes a bit to warm up I doubt many people get much higher. Not to include that older vehicles did not have a trans warmer and maintained low trans oil temps as well. I know the zf is a completely different setup. However, The cars do not include a oil warmer and would maintain low temps as well. Do I think an aftermarket bypass thermostat, like the HD trucks have, would be great in place of the stock thermostat housing unit with heater? Yes I do. That would be the best option and I would jump right on that boat if someone offered one. 160° would be great in my opinion. I do not think an aftermarket replacement thermostat to replace the stock thermostat will really do much given the thermostat does not fully block the heater from flowing and will continue to heat fluid beyond 160°. I do have to argue that a lot of people are nervous about the low temps. I have never experienced shifting issues in my truck at low temps when the truck is first started. And actually on that 12 hour drive my truck seemed to be more responsive on shifting. It shifted faster and when passing on the highway would drop right into gear and go. At 185° or 190° I always felt like it hesitated briefly when fully warmed up before down shifting.
Edit: speaking of which. Now that I’m thinking about it I really do wish someone would make a bypass style replacement for our trucks to replace the whole assembly. I’m seeing most dodge cars run 165-175° unless running a cooler bypass. BMW runs 195°-205° trans temps on their zf trans. The only thing I’m seeing with research on the fluid is expansion and viscosity change but the zf viscosity is designed to not change drastically from cold to OT. However it does expand quite a bit.

Both of my wifes last two 8HP70 equipped Challengers take forever to get above 140F.I can drive from my place to the city at 75 mph on an 75F day,shut the cars off for 20 minutes,then turn around and drive back home at the same speeds before the tranny hits 140F.It's roughly a 20 minute trip each way. I agree about the shifting,as long as my tranny temps are under 165F my truck shifts good,as soon as it hits 168+F it won't hold 8th gear as well as it does at 160F. I think anything above 122F is probably okay,as that's the max temp for checking the fluid level. There's also lots of cars that get operated during the winter,for relatively short drives,and they never seem to have many transmission issues in the cold.I've got 2 buddies that use their 8HP70 equipped cars year round up here,with nary an issue with either cars transmission,and the one guy drives maybe 10 minutes at most when it's -25C or colder,car sits for close to 9 hours at his work,where he remote starts it,while changing out of his work clothes,then jumps in it,and he has been known to beat on the car leaving work,lol.

 

[Wild one]

@Wild one I asked mike and he said he’s averaging 140° but he’s got a 392 boosted so he’s definitely going to be hotter than I am.

He drives the **** out of that truck too,lol

 

[chrisbh17]

Given that a lot of people have short drives and the trans takes a bit to warm up I doubt many people get much higher. Not to include that older vehicles did not have a trans warmer and maintained low trans oil temps as well. I know the zf is a completely different setup. However, The cars do not include a oil warmer and would maintain low temps as well. Do I think an aftermarket bypass thermostat, like the HD trucks have, would be great in place of the stock thermostat housing unit with heater? Yes I do. That would be the best option and I would jump right on that boat if someone offered one. 160° would be great in my opinion. I do not think an aftermarket replacement thermostat to replace the stock thermostat will really do much given the thermostat does not fully block the heater from flowing and will continue to heat fluid beyond 160°. I do have to argue that a lot of people are nervous about the low temps. I have never experienced shifting issues in my truck at low temps when the truck is first started. And actually on that 12 hour drive my truck seemed to be more responsive on shifting. It shifted faster and when passing on the highway would drop right into gear and go. At 185° or 190° I always felt like it hesitated briefly when fully warmed up before down shifting.
Edit: speaking of which. Now that I’m thinking about it I really do wish someone would make a bypass style replacement for our trucks to replace the whole assembly. I’m seeing most dodge cars run 165-175° unless running a cooler bypass. BMW runs 195°-205° trans temps on their zf trans. The only thing I’m seeing with research on the fluid is expansion and viscosity change but the zf viscosity is designed to not change drastically from cold to OT. However it does expand quite a bit.

Even in the cold my shortest trip would still get the trans to 140-ish. Definitely higher than 120.

And yes, trans fluid expands so I would be concerned the expansion thats taken into account during engineering and design might not quite be there at a fluid temp of 120. And keep in mind during a day like today where its 30F outside, I probably wouldnt even hit 120.