8 speed temp differances

[Wild one]

Going by what the HD 2500 5th Gen guys with the 6.4/8 speed combo are saying ,it sures looks like the 8 speed transmission runs at a alot lower temp in a 2500 then it does in a 1500.The guys are reporting temps right around 160'ish even when towing with the HD 8 speed.I haven't dug into the HD 8 speeds enough to know if they still call for the same ZF 8/9 speed fluid the 1500's call for,if they use the same fluid though,it sure makes you wonder why the big temp differance,and if it might be beneficial to look into one of the aftermarket kits that deletes the heater assembly and thermostat on the 1500's 8 speed

 

[hunterdan]

My guess would be they are using an external cooler and either bypassed the thermostat on the trans, or are using a lower temp one.

 

[Firebird]

Mine is bone stock, I tow 9000 pound camper (loaded) and it holds 168 degrees all day. Definitely much lower temps than my half ton.

 

[AFMoulton]

Mine is bone stock, I tow 9000 pound camper (loaded) and it holds 168 degrees all day. Definitely much lower temps than my half ton.

Can you take a look under your truck and post some pics of around the trans? Looking to see if it’s missing the thermo block like the 1500 8sps have.

I’d go by the dealer and look but the closest 6.4 8sp is 165 miles away.


2018 Ram 2500 6.4L 4x4
Amsoil SS 0W-40

 

[Burla]

Going by what the HD 2500 5th Gen guys with the 6.4/8 speed combo are saying ,it sures looks like the 8 speed transmission runs at a alot lower temp in a 2500 then it does in a 1500.The guys are reporting temps right around 160'ish even when towing with the HD 8 speed.I haven't dug into the HD 8 speeds enough to know if they still call for the same ZF 8/9 speed fluid the 1500's call for,if they use the same fluid though,it sure makes you wonder why the big temp differance,and if it might be beneficial to look into one of the aftermarket kits that deletes the heater assembly and thermostat on the 1500's 8 speed

Let's just call it what it is, fca corn holes guys that buy 1500's with no lube. Longevity or even common sense is taking out of 1500's. I wouldn't trust anything ever built new these days, unless you get the HD distinction, and even then proceed with caution.

The good news, maybe the new 2500 8 speed will be a real truck transmission. Does anyone have some paper out there on the differences between 1500 and 2500 trans?

 

[hunterdan]

Let's just call it what it is, fca corn holes guys that buy 1500's with no lube. Longevity or even common sense is taking out of 1500's. I wouldn't trust anything ever built new these days, unless you get the HD distinction, and even then proceed with caution.

The good news, maybe the new 2500 8 speed will be a real truck transmission. Does anyone have some paper out there on the differences between 1500 and 2500 trans?

The 6.4 in the HD uses the same 8hp75 that the 2019+ 5th gen 1500s use from what I understand.
I really believe it's got something to do with a dedicated trans cooler in front of the radiator. 3/4 and 1 ton trucks are obviously spec'd to tow and haul more, as such, more cooling is required. I bet the internals are exactly the same as the half ton, however they may be missing the heat exchanger and thermostat the half tons use since these trucks don't require mpg ratings. The whole reason we see fluid heaters on half ton trucks is for increased mileage ratings since they count towards the CAFE standards.

 

[Sandevino]

The transmissions in these trucks are completely different animals.

1500’s use the ZF-8HP75 designed for passenger cars and light duty trucks. This one is used in a myriad of vehicles including BMW, Toyota and FCA to name a few. It is light-weight, fuel efficient and sets new standards for economy and fuel efficiency. Read about it here - https://www.zf.com/products/en/cars/products_29289.html

2500’s use the ZF-8HP75-LCV designed for light commercial vehicles. This one is designed for towing, frequent stops and starts and the demands of commercial fleets. This transmission uses a unique vane cell oil pump for maximum efficiency and cooling. Read about it here - https://www.zf.com/products/en/lcv/products_29044.html

 

[Wild one]

Let's just call it what it is, fca corn holes guys that buy 1500's with no lube. Longevity or even common sense is taking out of 1500's. I wouldn't trust anything ever built new these days, unless you get the HD distinction, and even then proceed with caution.

The good news, maybe the new 2500 8 speed will be a real truck transmission. Does anyone have some paper out there on the differences between 1500 and 2500 trans?

Mike have you dug into what fluid they spec for the HD's 8 speed.If they spec the same fluid as the 1500's 8 speed,it might be worth while deleting the heater and thermostat using one of the aftermarket kits available now,especially the guys that tow alot with their 1500.
I know the wifes 6.4 Challenger with the 8HP70 runs alot cooler then my trucks 8 speed does,and the cars don't have the heater assembly.If your just touring around at speeds under 70 mph,and not beating on the car,the 8 speed in her car runs right around 160/165

 

[Wild one]

This is how ZF 8 Speed Automatic Gearbox Works - YouTube

 

[Sandevino]

Here’s a tear down and rebuild video of the ZF-8HP -

 

[Wild one]

Here’s a tear down and rebuild video of the ZF-8HP -

LOL i just posted that video the other day,it's in the thread about enabling 2nd prime,lol.

 

[Sandevino]

LOL i just posted that video the other day,it's in the thread about enabling 2nd prime,lol.

Great video... I enjoy watching his videos as they’re obscenely thorough

 

[Wild one]

ZF8HP70 Teardown - YouTube

ZF8HP75 Teardown - YouTube

ZF8HP90 Teardown - YouTube

Ray's Garage- ZF8HP70 Unit Disassembly (Portuguese Subtitles) - YouTube

 

[Wild one]

Great video... I enjoy watching his videos as they’re obscenely thorough

This video does leave a few questions about the power path/flow through the tranny though. ZF had a video a few years back of how they got 8 gears out of the 4 gear sets,but i'll be damned if i can find it now.It actually showed the fluid path and how they engaged the differant gears and clutches,and was good at showing the internal workings,but i can't find it anymore

 

[Sandevino]

This video does leave a few questions about the power path/flow through the tranny though. ZF had a video a few years back of how they got 8 gears out of the 4 gear sets,but i'll be damned if i can find it now.It actually showed the fluid path and how they engaged the differant gears and clutches,and was good at showing the internal workings,but i can't find it anymore

Give this a watch...

 

[crash68]

@Wild one I found the explanation of how the 8 spd shifts in text form, might make make your head hurt reading it though..
https://www.thetruthaboutcars.com/2014/03/saturation-dive-zf-8-speed-automatic/

 

[Burla]

Mike have you dug into what fluid they spec for the HD's 8 speed.If they spec the same fluid as the 1500's 8 speed,it might be worth while deleting the heater and thermostat using one of the aftermarket kits available now,especially the guys that tow alot with their 1500.
I know the wifes 6.4 Challenger with the 8HP70 runs alot cooler then my trucks 8 speed does,and the cars don't have the heater assembly.If your just touring around at speeds under 70 mph,and not beating on the car,the 8 speed in her car runs right around 160/165

I didnt even know the 2500 had the 8 speed yet

If it is a different fluid, it may take some time before we even see the spec. Best bet is catch off lifegard sheet.

 

[Burla]

The transmissions in these trucks are completely different animals.

1500’s use the ZF-8HP75 designed for passenger cars and light duty trucks. This one is used in a myriad of vehicles including BMW, Toyota and FCA to name a few. It is light-weight, fuel efficient and sets new standards for economy and fuel efficiency. Read about it here - https://www.zf.com/products/en/cars/products_29289.html

2500’s use the ZF-8HP75-LCV designed for light commercial vehicles. This one is designed for towing, frequent stops and starts and the demands of commercial fleets. This transmission uses a unique vane cell oil pump for maximum efficiency and cooling. Read about it here - https://www.zf.com/products/en/lcv/products_29044.html

thank you

 

[Wild one]

@Wild one I found the explanation of how the 8 spd shifts in text form, might make make your head hurt reading it though..
https://www.thetruthaboutcars.com/2014/03/saturation-dive-zf-8-speed-automatic/

I've read that before,but thanks for digging it up Crash,it's worth reading again.I remember him saying how the 1 calculation had taken him roughly 6 hours to calculate,lol

 

[Wild one]

ZF8HP Rebuild - YouTube