RevMax 8 speed thermostat bypass

[Wild one]

Put a 180 in my 2003 Dakota 4.7 in 2006, it's still in there...no problems.

Better buy yourself a lottery ticket,as you're one of the few that's had a Jet thermostat last,lol. They have a ****** rep on alot of the facebook pages. Maybe their earlier oddball 4.7 thermostats were okay,but in the Hemi world their rep leaves alot to be desired.

 

[Musky Mike]

Better buy yourself a lottery ticket,as you're one of the few that's had a Jet thermostat last,lol. They have a ****** rep on alot of the facebook pages. Maybe their earlier oddball 4.7 thermostats were okay,but in the Hemi world their rep leaves alot to be desired.

I wish I had that luck, I just bought a lotto ticket and didn't win. I didn't know their rep was that bad, but the t-stat is the only thing I ever bought from them, guess I got lucky. I hope a compony in the future make a low temp t-stat for the trans, that seems like the best solution.

 

[Wild one]

I hope a compony in the future make a low temp t-stat for the trans, that seems like the best solution.[/QUOTE]

That would be the ideal fix

 

[Wild one]

This video was already posted the other day by Differant Drummer,but i think it's a good addition to this thread to.There are updated bypass tubes available now that are a rubber encapsulated tube,doing away with the leak prone O-ring tubes

Dodge Ram 8 speed transmission heater assembly fluid leak repair - YouTube

 

[Wild one]

I'll also add the instructions for the proper fluid level check on the 8 speed for the guys who haven't seen them yet.You have to jack the rear wheels up in the air a fair ways to get the transmissions pan rail level

 

[Different Drummer]

Good-n-Tight is what i torque them to Shaun,sometimes 2 or 3 ugga-duggas works to,lol. I think down in either the Tech or DYI section the torque specs are posted for most common bolts on the trucks

We always called that "tractor tight".

 

[chrisbh17]

Anyone know what the driveshaft bolt torque is?


Sent from my iPhone using Tapatalk

Ever since my dad and I did a full tear down and restoration of a Corvette, I torque everything to spec after I re-assemble.

So:

"Install axle companion flange bolts and tighten to 115 N·m (85 ft. lbs.)."

You are also supposed to replace the bolts or clean them and re-apply thread lock (FSM specs Mopar blue but I assume its just relabeled LocTite)

 

[Different Drummer]

How about doing something as simple as placing a valve downstream of the 3 way Engine coolant valve? Between the valve and the transmission TCU. Something like a small ball valve.
This would stop hot engine coolant from reaching the TCU on the transmission. That together with the removal of the bypass mechanism in the TCU would seem to get optimal cooling. Hell, if you operated in extreme cold weather you would have the option to open the valve and let Engine coolant flow on through. Best of both worlds. Isn't that essentially what the blocking plate from RevMax is doing? You would still have Engine coolant to the cabin heater. The valve would receive it's instructions when to open and close, and would follow those commands. Just that no Engine coolant would flow to the TCU on the transmission. Seems too simple , I know. But why not?

 

[Wild one]

How about doing something as simple as placing a valve downstream of the 3 way Engine coolant valve? Between the valve and the transmission TCU. Something like a small ball valve.
This would stop hot engine coolant from reaching the TCU on the transmission. That together with the removal of the bypass mechanism in the TCU would seem to get optimal cooling. Hell, if you operated in extreme cold weather you would have the option to open the valve and let Engine coolant flow on through. Best of both worlds. Isn't that essentially what the blocking plate from RevMax is doing? You would still have Engine coolant to the cabin heater. The valve would receive it's instructions when to open and close, and would follow those commands. Just that no Engine coolant would flow to the TCU on the transmission. Seems too simple , I know. But why not?
View attachment 234027

So far i haven't found anybody who's running it just with the thermostat bypass in place,with the thermal heater unit still active.
The couple guys who are running the kit,are utilizing the plate,and reporting tranny temps in the 140'ish range.Before i get too worried about deleting the coolant flow to the thermal unit,i'm going to run it still hooked up,and see what happens with the temp and how long it takes the transmission to warm up. If it still seems too warm to me,i have a couple ideas to try. One is just disconnect the heater hoses to the thermal unit and tie them together,the other is very similiar to your idea,but use an old style cable operated heater control valve,and run it inside the interior ,so you can operate it from inside,and while going down the road.Your idea is good also with a manual ball valve under the hood.But till i actually see how things pan out with just the thermostat bypass,which won't be for awhile yet,i'm not going to worry to much about it,lol.My idea is to use something like this .

Four Seasons 74828 Heater Valve, Heater Control Valves - Amazon Canada


Four Seasons 74627 Heater Valve, Heater Parts - Amazon Canada

NEW HVAC Heater Control Valve-Heater Valve Cable FOR Universal 3857131 | eBay

 

[Different Drummer]

So far i haven't found anybody who's running it just with the thermostat bypass in place,with the thermal heater unit still active.
The couple guys who are running the kit,are utilizing the plate,and reporting tranny temps in the 140'ish range.Before i get too worried about deleting the coolant flow to the thermal unit,i'm going to run it still hooked up,and see what happens with the temp and how long it takes the transmission to warm up. If it still seems too warm to me,i have a couple ideas to try. One is just disconnect the heater hoses to the thermal unit and tie them together,the other is very similiar to your idea,but use an old style cable operated heater control valve,and run it inside the interior ,so you can operate it from inside,and while going down the road.Your idea is good also with a manual ball valve under the hood.But till i actually see how things pan out with just the thermostat bypass,which won't be for awhile yet,i'm not going to worry to much about it,lol.My idea is to use something like this the lines as a temporary experiment.

Four Seasons 74828 Heater Valve, Heater Control Valves - Amazon Canada


Four Seasons 74627 Heater Valve, Heater Parts - Amazon Canada

NEW HVAC Heater Control Valve-Heater Valve Cable FOR Universal 3857131 | eBay

you also mentioned at some time placing a clamp across the lines as a temporary experiment. this would accomplish the same a placing a valve in the line. I was just thinking that it would be an easy process to place a valve in the line close to the 3 way diverting valve. It is pretty accessible.
I am anxiously awaiting the results from those of you who have removed the bypass plunger and spring in the TCU.

 

[Wild one]

you also mentioned at some time placing a clamp across the lines as a temporary experiment. this would accomplish the same a placing a valve in the line. I was just thinking that it would be an easy process to place a valve in the line close to the 3 way diverting valve. It is pretty accessible.
I am anxiously awaiting the results from those of you who have removed the bypass plunger and spring in the TCU.

I'm still going to see how it works first with just the bypass,if it's still to warm,i'll first try my idea of just using hose pinching clamps to restrict the flow to the thermal unit,if they work,then i'll spend the money to do it with a manual cable operated shut off valve,lol.I'm hoping CrazyKid gets his out for a drive this week-end and can give us an update on how the kit works with just the thermostat bypass in place. My trucks still parked for another couple months at least,it won't be coming back out,till the snow is gone and the salt is off the roads,i hate Canuck winters,lol

 

[crazykid1994]

Went out for dinner tonight. Truck barely got fully warmed up on the way home but usually my trans is in the 170s. Tonight my trans was at 159° by the time I got home. Outside temp is 66°. Oil temp was 192° and coolant temp was 190°. I have a 190° tstat. Should have better info tomorrow as long as weather holds out

 

[Wild one]

Went out for dinner tonight. Truck barely got fully warmed up on the way home but usually my trans is in the 170s. Tonight my trans was at 159° by the time I got home. Outside temp is 66°. Oil temp was 192° and coolant temp was 190°. I have a 190° tstat. Should have better info tomorrow as long as weather holds out

To me that almost sounds like it's just about spot on for temps ,i like the idea of 160'ish ,lol.Looking forward to how it pans out with a little longer drive Khristopher,gonna have to buy you lunch for testing it out for us,if i ever get down there again,lol.

 

[Barney556180]

Not trying to stir things up...

I was curious about the optimum 8Hp70 operating temperature. Did a search and the consensus from several authoritative sources cite 190°-195° F being the most efficient temp range.

This is typical:
https://r.tapatalk.com/shareLink/to...ing-temp?.43681/&share_type=t&link_source=app

“The 8HP70 runs quite a bit warmer than the 545rfe. Chryslers Dave Sowers said ‘We get benefit from bringing both of them [oil and transmission fluid] up to operating temperature faster. The primary benefit comes in the transmission. In colder climates, you could drive a vehicle for hours in the winter and the transmission might never reach that 190° (F) for the most efficient operation. So what we do is use some of that hot engine coolant through the heat exchanger to bring it up to 190° as quickly as possible, and that gives us efficient operation very quickly.’”

I also got this back from the GDE folks when asking about the RevMax8:

“I would absolutely not install that bypass unit [RevMax 8] you’re mentioning. The longer the trans takes to warm up the more drag it will have internally until it does, also if it runs permanently cold due to their kit that is not good either and you’ll face poor shift quality due to the cold.”

I’m getting ZF Lifeguard 8 and a Dorman 265-850 pan installed this week. Then I’ll see where my temps are.

 

[Wild one]

Not trying to stir things up...

I was curious about the optimum 8Hp70 operating temperature. Did a search and the consensus from several authoritative sources cite 190°-195° F being the most efficient temp range.

This is typical:
https://r.tapatalk.com/shareLink/topic?share_fid=17770&share_tid=43681&url=https://www.ramforum.com/index.php?threads/Hemi-8-speed-transmission-operating-temp?.43681/&share_type=t&link_source=app

“The 8HP70 runs quite a bit warmer than the 545rfe. Chryslers Dave Sowers said ‘We get benefit from bringing both of them [oil and transmission fluid] up to operating temperature faster. The primary benefit comes in the transmission. In colder climates, you could drive a vehicle for hours in the winter and the transmission might never reach that 190° (F) for the most efficient operation. So what we do is use some of that hot engine coolant through the heat exchanger to bring it up to 190° as quickly as possible, and that gives us efficient operation very quickly.’”

I also got this back from the GDE folks when asking about the RevMax8:

“I would absolutely not install that bypass unit [RevMax 8] you’re mentioning. The longer the trans takes to warm up the more drag it will have internally until it does, also if it runs permanently cold due to their kit that is not good either and you’ll face poor shift quality due to the cold.”

I’m getting ZF Lifeguard 8 and a Dorman 265-850 pan installed this week. Then I’ll see where my temps are.

The cars use the same 8HP70 with-out the thermal heater,plus the 8HP75 behind the 6.4's in the 2500's doesn't use the thermal heater unit,and they're towing 7,000+lbs with the average tranny temp of 165/168'ish,and they're running down the road in the high 150's low 160's unloaded,so i'm leaning more towards 160 being closer to being the ideal temp. My wifes 6.4 Challenger takes 50 miles or more to hit 160 on the tranny temp if you're not beating on it,and will stay in that general ballpark as long as you're driving it decently. One other thing is you're supposed to check the fluid level at no more then 122F,which leads me to think that might be the temp were everything is close to operating temp parameters,otherwise they'd have you check the level at 185 if that was ideal operating temp. Personally i know my 8 speed operates better when it's under 168F then it does when it's at 180+,it'll hold 8th gear on hills better at 165 then it does at 180+.As soon as it hits the mid 170's,it starts wanting to shift out of 8th on the hills.Plus if you read what Sowers says and interpret it a bit,he's claiming most efficient,which means it's supposedly returning the best gas milege,he's not saying anything about that being the best temperature for the longevity of the transmission. They sell more 1500's then anything else,and the 1500's are consequently saddled with with more Cafe/EPA rules then any other vehicle in FCA's line up.Anytime somebody is talking "efficient" when it comes to vehicles i start to get a little leary as that word doesn't usually go with long life,lol

 

[crazykid1994]

Made it to 172° trans temp While cruising around town. Not sure that’s where it’s going to stabilize as it seemed to still be climbing slowly. Outside temp is 66° currently. Seems very odd that I’m in the 170° range with the thermostat removed.

 

[chrisbh17]

Made it to 172° trans temp While cruising around town. Not sure that’s where it’s going to stabilize as it seemed to still be climbing slowly. Outside temp is 66° currently. Seems very odd that I’m in the 170° range with the thermostat removed.

Not necessarily....like the thermostat for the engine coolant, I feel like its mostly there to keep heat in and help things warm up, but once its open it will never really close again.

So removing the thermostat portion of the trans thermo block doesnt "trap" heat, making it warm up slower (which you saw). But once its warmed up, if the thermostat was still present it would have been open the whole time anyway.

Now, for people like me that do a lot of short trips, slowing down the "up to temp" time will still keep the trans cooler, but the fully warmed up temp may end up remaining the same. That's why I was curious what would happen by just removing the spring/plunger. MAYBE the brass replacement would help draw a bit of heat away, but probably nothing noticeable.

 

[Different Drummer]

Not trying to stir things up...

I was curious about the optimum 8Hp70 operating temperature. Did a search and the consensus from several authoritative sources cite 190°-195° F being the most efficient temp range.

This is typical:
https://r.tapatalk.com/shareLink/topic?share_fid=17770&share_tid=43681&url=https://www.ramforum.com/index.php?threads/Hemi-8-speed-transmission-operating-temp?.43681/&share_type=t&link_source=app

“The 8HP70 runs quite a bit warmer than the 545rfe. Chryslers Dave Sowers said ‘We get benefit from bringing both of them [oil and transmission fluid] up to operating temperature faster. The primary benefit comes in the transmission. In colder climates, you could drive a vehicle for hours in the winter and the transmission might never reach that 190° (F) for the most efficient operation. So what we do is use some of that hot engine coolant through the heat exchanger to bring it up to 190° as quickly as possible, and that gives us efficient operation very quickly.’”

I also got this back from the GDE folks when asking about the RevMax8:

“I would absolutely not install that bypass unit [RevMax 8] you’re mentioning. The longer the trans takes to warm up the more drag it will have internally until it does, also if it runs permanently cold due to their kit that is not good either and you’ll face poor shift quality due to the cold.”

I’m getting ZF Lifeguard 8 and a Dorman 265-850 pan installed this week. Then I’ll see where my temps are.

No sense in me repeating what Wild one said. However, Just to embellish slightly. Transmission temperature has long been the bane of longevity in transmissions. Or, at the very least it degrades the fluid which in turn leads to the demise of the transmission. The temperatures that the ZF runs in the 1500 is higher than what most are used to in our vehicles. Especially us old dogs. ( to reiterate, it does not operate as hot in the 2500 RAMS or other passenger vehicles it is used in )
If someone ( ZF, FCA etc. ) can illustrate to me that running the ZF transmission at temps down around 160*F are detrimental to the health of the transmission I am all ears. However, what I am hearing is that it aids efficiency. I don't get a warm fuzzy feeling that the attempt at gaining efficiency has me the consumer as the intended beneficiary. In a truck that I may keep for years and well past warranty expiration date I will gladly give up a tiny bit of efficiency in trade for longevity of a very expensive replacement item.

 

[crazykid1994]

Not necessarily....like the thermostat for the engine coolant, I feel like its mostly there to keep heat in and help things warm up, but once its open it will never really close again.

So removing the thermostat portion of the trans thermo block doesnt "trap" heat, making it warm up slower (which you saw). But once its warmed up, if the thermostat was still present it would have been open the whole time anyway.

Now, for people like me that do a lot of short trips, slowing down the "up to temp" time will still keep the trans cooler, but the fully warmed up temp may end up remaining the same. That's why I was curious what would happen by just removing the spring/plunger. MAYBE the brass replacement would help draw a bit of heat away, but probably nothing noticeable.

If after a good solid drive the temp returns to the 180s I’ll probably reinstall the tstat to aid in faster warmup. Very amused though. I’ll have to see. It still warmed relatively fast due to not removing the coolant lines however it was a bit longer. If it remains in the 170 range I’ll be extremely happy, though being cooler out right now may change the temps too

 

[chrisbh17]

No sense in me repeating what Wild one said. However, Just to embellish slightly. Transmission temperature has long been the bane of longevity in transmissions. Or, at the very least it degrades the fluid which in turn leads to the demise of the transmission. The temperatures that the ZF runs in the 1500 is higher than what most are used to in their vehicles. Especially us old dogs. ( to reiterate, it does not operate as hot in the 2500 RAMS or other passenger vehicles it is used in )
If someone ( ZF, FCA etc. ) can illustrate to me that running the ZF transmission at temps down around 160*F are detrimental to the health of the transmission I am all ears. However, what I am hearing is that it aids efficiency. In a truck that I may keep for years and well past warranty expiration I will gladly give up a tiny bit of efficiency in trade for longevity.

Its kind of a balancing act.

Cooler temperatures are always better. But cooler fluid is (slightly) thicker, which will technically cause more friction and drag.

Now....do the 1500 transmissions run hotter because its better? Or because FCA wants to eek another 0.00000001 mpg out of them and so the hotter, thinner fluid helps with their goals at the cost of long term durability?

Personally I think its all about FCA making their CAFE targets....the fact they call it "lifetime fluid" makes me think they just want it to make it to the end of the warranty and to hell with the customer.