New '17 8 speed trany temp?

[tsielski]

Finally here is a pic of the bore that the TBV fits into. It is forward facing as the heater is mounted on our Rams. I would have already removed mine, but getting to it, particularly that snap ring is difficult as a lot of stuff needs to be removed to gain access on 4x4 models, not as much on 2x models.
That hole in the top of the bore is the return for the ATF from the trans cooler. It is blocked by the TBV and as the fluid heats the TBV gradually lets cooled fluid flow and mingle with the heated fluid.

 

[chrisbh17]

Looks eerily similar to the "wax pellet" type "valve" on the throttle body of my old Frontier. The coolant passes around the bore where the spring/plunger setup is, the heat is xferred to a wax pellet inside the black plastic piece, which in turn expands or contracts based on temperature which in turn moves the brass/copper plunger and spring up and down. That brass/copper piece is what blocks off the flow in this case.

If thats the case, Im not sure if they make different materials to go inside the black "case", or maybe its just a matter of a thinner or thicker spring?

 

[Podcast]

Very interesting. Basically the TBV is no different than your typical engine thermostat.

Second thought here, unless I'm looking at something wrong, it appears the engine coolant simply flows through a metal block that is inserted into the side of the transmission. If this is the case my thoughts go right to nightmares of customers bringing in their vehicles with a bad radiator in which the coolant is not mixed with the trans fluid. This is another possibility of a similar occurrence depending on how well this block style heater hold up.

 

[chrisbh17]

Very interesting. Basically the TBV is no different than your typical engine thermostat.

Second thought here, unless I'm looking at something wrong, it appears the engine coolant simply flows through a metal block that is inserted into the side of the transmission. If this is the case my thoughts go right to nightmares of customers bringing in their vehicles with a bad radiator in which the coolant is not mixed with the trans fluid. This is another possibility of a similar occurrence depending on how well this block style heater hold up.

I dont think they mix....the trans fluid is routed in a passage separate from the coolant...the coolant comes in to "act" on the TBV somehow but is SURROUNDING it, not going directly through it. This opens/closes the passage for the transmission fluid to flow through the same BLOCK as the coolant, but a different passage. There shouldnt be the possibility of the fluids mixing because they are just going through their own separate passages.

This should be safer than the traditional "send it through the radiator" trans cooler operation, because the passages in the thermostat valve shouldnt ever collapse/break/etc like small cooling passages in a radiator can.

If it is indeed like my Frontier, the issue with the Frontier became the o-ring around the wax pellet container....once the o-ring degraded, it became a common coolant leak point.

 

[tsielski]

I tend to agree that the trans heater is a potential failure point, and should a leak develop internal to it, coolant will mix with ATF potentially destroying the transmission.

There was a member on the Eco Diesel section of the Turbo Diesel Register a few years ago who had posted that he found a way to bypass the TBV. Unfortunately he passed away and never got around to posting what exactly he did. It could simply have been removing it and just replacing the black plastic cap.

Once the weather warms during the spring and summer, I may again look to mess with this, but I don't have a lift and access is tight.

 

[Podcast]

I dont think they mix....the trans fluid is routed in a passage separate from the coolant...the coolant comes in to "act" on the TBV somehow but is SURROUNDING it, not going directly through it. This opens/closes the passage for the transmission fluid to flow through the same BLOCK as the coolant, but a different passage. There shouldnt be the possibility of the fluids mixing because they are just going through their own separate passages.

This should be safer than the traditional "send it through the radiator" trans cooler operation, because the passages in the thermostat valve shouldnt ever collapse/break/etc like small cooling passages in a radiator can.

If it is indeed like my Frontier, the issue with the Frontier became the o-ring around the wax pellet container....once the o-ring degraded, it became a common coolant leak point.

Could be just fine as you indicate. I'm more worried about corrosion whether internal or possibly external but time will tell if this is an issue or not.

 

[tsielski]

Actually heated fluid and cooled fluid do mix. The heater portion of the assembly comes apart from the cast aluminum "manifold" that houses the two o-ringed insertion tubes into the trans itself, and the ports connecting the lines to the trans cooler. I've taken the unit I have apart. Looking at the two, it's clear to see how the two mix.

 

[Podcast]

Actually heated fluid and cooled fluid do mix. The heater portion of the assembly comes apart from the cast aluminum "manifold" that houses the two o-ringed insertion tubes into the trans itself, and the ports connecting the lines to the trans cooler. I've taken the unit I have apart. Looking at the two, it's clear to see how the two mix.

To specify, I'm assuming you're saying heated and cooled fluid do mix but only of the same kind. So heated coolant doesn't mix with cooled tranny fluid for example.

 

[tsielski]

No. Heated fluid does mix with cooled fluid returning from the trans cooler once the TBV opens. It's very clear to see after I separated the heater from the cast aluminum "manifold".

 

[Podcast]

No. Heated fluid does mix with cooled fluid returning from the trans cooler once the TBV opens. It's very clear to see after I separated the heater from the cast aluminum "manifold".

OK, so how do they "un-mix" after the fluids have mixed? In other words, what mechanism separates the coolant from the trans fluid after they are mixed together? Coolant cannot run through the clutches of the transmission.

 

[tsielski]

Not saying that COOLANT (antifreeze & water) mixes with ATF. Saying that heated ATF mixes with "cooled" ATF when the TBV finally opens

 

[Podcast]

Not saying that COOLANT (antifreeze & water) mixes with ATF. Saying that heated ATF mixes with "cooled" ATF when the TBV finally opens

That's what I tried to explain but failed lol, thanks!

 

[blackbetty14]

I think the easiest option is to get a replacement valve that still allows the tranny to heat up but is fully open by 160/180 vs just starting to open at 180. That one tranny company made a new 160 version but he will only sell u the $200 part if you buy one of his tranny’s.

 

[crash68]

Hey all. Just got my new Ecodiesel. Put about 30p miles on it now between the first 2 days. The temp here has been between 0 and 20 degrees Fahrenheit. My old truck with the Hemi trans in this weather was only 110 degrees. In my new truck it's between 150 and 160. Is this normal for an Ecodiesel? Seems high but not sure. A guy would think it would he the same. I can only imagine it's gonna get 180 during the summer. That's really hot for a trans.

Don't be surprised if your transmission temps run between 185°-192°F in the summer time. There have been a lot of EcoDs already over the 100K mark running trans temps like that and higher while towing with no issues. Critical temp per ZF is upwards of 240°F.

 

[Dusty]

I couldn't find anything regarding the fluid used in the 8HP70/8HP90 (ZF) transmissions, but I found this interesting statement in the Chrysler spec sheet for ATF+4:

"Through the use of its patented additive package ATF+4 will maintain the original shift quality of all Chrysler designed automatic transmissions. It contains superior properties for low temperature operation to -55 degrees F, and maintains a high viscosity index above 350 F. ATF+4 produces superior wear and rust prevention qualities especially when compared to Dexron-Mercon or aftermarket synthetic fluids. ATF+4 controls oxidation to a much higher degree than Dexron-Mercon series fluids and is a notable improvement over ATF+3. "

While it's true conventional ATFs degrade at increasingly higher temperature, keep in mind that the temperature range specifications for non-synthetic Dexron-Mercon no longer apply. ATF+4 and the ZF fluids are full synthetic and have a much wider heat range. In the summer time I have seen tranny temps (indicated) over 200 F on my 8HP70 (203 was the max while towing on a 90+ degree day). Others, I've been told, have also. There's an Over Temp message for the transmission available in the computer algorithm, so if you haven't seen it pop up I'm betting your fine.

 

[Dusty]

Should of thought of this earlier. According to the 2010 Ram service manual, the 545RFE's normal fluid operating temperature is between 80 F and 240 F. Of course, this spec corresponds to Chrysler's ATF+4. Since the temperature sensor is in the sump on RFEs, we can assume the spec is for sump temperature, noting that the fluid in the torque converter is likely higher at times.

I don’t have access to Ram service literature for any year that uses the 8HP70/8HP90 transmissions at the moment. Nor have I found any fluid specs for the ZF LifeGuard 8 fluid or the Chrysler MS-ATF 8/9 equivalent (68218925AA), other than the auto-ignition point is 608 F and the stuff isn’t dyed red.

Opinions gleaned from the web are all over the place. People selling auxiliary tranny coolers say never over 200F, or never over the engine coolant temp. I did find reference to a “GM in-house towing team expert” that said, ”…we design vehicles so that in all but the most extreme conditions, the fluid temperature in the transmission sump stays below 270 degrees F.”

Based on my experience, RV motor homes quite often find themselves with tranny temps hitting 270 in hilly terrain. I’ve towed 9600+ pounds with mine and the 8HP70 got just a little over 200F. Unless you get a transmission over temp message, I wouldn't worry about seeing temps over 200 at times.

 

[kad]

I wish my 8-speed ran that low. Even in these cold temperatures, once all warmed up on the high way, my 8-speed temp varies between 183 and 188. Aggressive driving can get it into the 190's easily.

I see the same temps on my '14 with the 5.7 and the 8 speed.

-K