8 speed ZF8HP70 transmission overheating fix

[garymtx]

Posting this in the hope that it helps someone else. My 2014 Ram 1500 4x4 with 5.7 and 8 speed transmission has been overheating for the last few months. With no trailer 210-215 F, with ANY kind of trailer 230+ F. Had to stop every 30 miles to let it cool off or it would go into limp mode (4th gear). After much research, I found out that the "transmission fluid heater" also has a "thermatic valve" built in to it. This combined unit is unique to the 1500 models, the 2500 and 3500 have a completely separate "thermatic valve". I have installed a new one and also opted for a PPE deep aluminum pan that holds an extra 2 quarts of trans fluid (buy the ZF8 for $19 a quart online, NOT the $40 a quart dealer stuff). It will take about 4.5 to 6 quarts depending on pan depth. The temperature hasn't been above 180 F since the switch. I'll be adding an additional trans cooler next. Seems overheating transmissions are a common problem with Rams in general. The "heater" supposedly improves transmission efficiency 1% "until the transmission comes to operating temperature" and is then supposed to cut itself out. Sure doesn't seem that 1% is worth the major PITA it is.

 

[Tim Garceau]

Just replaced my pan/fluid for <$100 total. Took around 5 full quarts leveling the pan and using the proper temps/procedure.

Never has cooled or shifted better after 90k miles, combined with a TCM tune this is what was intended from ZF engineers. Lubelife is overpriced hype, after 10 k I’ll probably do another gallon of Maxlife to clean the rest of the green $hit out.

OEM pan magnets were caked with crud, I recommend everyone follow ZF’s intervals and not FCAs “lifetime fill”. Just like lifters/cam, their marketing designs large dollar failure modes Out of warranty so you purchase new.

 

[stenerson]

Just replaced my pan/fluid for <$100 total. Took around 5 full quarts leveling the pan and using the proper temps/procedure.


View attachment 211016

100 bucks total? What pan did you buy?

 

[Tim Garceau]

100 bucks total? What pan did you buy?

I outsourced but it was a quality Asian produced item with perfect fit. Injection molded parts aren’t labor intensive so I have no problem leaving the states and saving money due to more efficient designers. All ZF8 trans use the same pan regardless of what your dealership or Mopar cross references.

If you only used Maxlife ATF, it can be done under $80. I’m preferred Amsoil so you pay a little more but still no where near lubelife pricing which was $25+/Liter.

 

[stenerson]

Thanks!

 

[stenerson]

"Seems overheating transmissions are a common problem with Rams in general. The "heater" supposedly improves transmission efficiency 1% "until the transmission comes to operating temperature" and is then supposed to cut itself out. Sure doesn't seem that 1% is worth the major PITA it is

When mine comes to temp it usually doesn't vary much even in mid-summer....Did you figure out what was causing the overheating?

 

[Longhorn1500]

Posting this in the hope that it helps someone else. My 2014 Ram 1500 4x4 with 5.7 and 8 speed transmission has been overheating for the last few months. With no trailer 210-215 F, with ANY kind of trailer 230+ F. Had to stop every 30 miles to let it cool off or it would go into limp mode (4th gear). After much research, I found out that the "transmission fluid heater" also has a "thermatic valve" built in to it. This combined unit is unique to the 1500 models, the 2500 and 3500 have a completely separate "thermatic valve". I have installed a new one and also opted for a PPE deep aluminum pan that holds an extra 2 quarts of trans fluid (buy the ZF8 for $19 a quart online, NOT the $40 a quart dealer stuff). It will take about 4.5 to 6 quarts depending on pan depth. The temperature hasn't been above 180 F since the switch. I'll be adding an additional trans cooler next. Seems overheating transmissions are a common problem with Rams in general. The "heater" supposedly improves transmission efficiency 1% "until the transmission comes to operating temperature" and is then supposed to cut itself out. Sure doesn't seem that 1% is worth the major PITA it is.

Welcome to this GREAT forum and thank you for sharing your experience!!

 

[crash68]

Did you figure out what was causing the overheating?

When these 8HP transmissions start to overheat it is usually the thermostatic bypass valve in the Thermal Management Unit on the side of the transmission which is what the OP replaced.

 

[stenerson]

When these 8HP transmissions start to overheat it is usually the thermostatic bypass valve in the Thermal Management Unit on the side of the transmission which is what the OP replaced.

Oops, just reread it thanks. The valve is built into it so I assume the entire unit needs replacement?

 

[crash68]

The valve is built into it so I assume the entire unit needs replacement?

That's correct.
There is Paramount Performance transmissions that offers a lower temperature bypass valves for these transmissions but you have to buy one of their transmissions to buy one.

 

[Longhorn1500]

That's correct.
There is Paramount Performance transmissions that offers a lower temperature bypass valves for these transmissions but you have to buy one of their transmissions to buy one.

That would be one expensive bypass valve!!

 

[stenerson]

That would be one expensive bypass valve!!

It's a good deal. It comes with a transmission.

 

[kad]

OEM pan magnets were caked with crud, I recommend everyone follow ZF’s intervals and not FCAs “lifetime fill”.

Do you have a reference for ZF's intervals?

-K

 

[Tim Garceau]

Do you have a reference for ZF's intervals?

-K

Here you are, 80-120km (50-75k miles) on page one.

https://aftermarket.zf.com/remoteme...38411/si-zf-si-oelwechselkit-8hp-50130-en.pdf

Most service video I came by aren’t filling the torque converter correctly by revving to 2000 RPM for 30 seconds. Will it matter? most likely not if you’re following the rest of the procedure.

 

[garymtx]

That's correct.
There is Paramount Performance transmissions that offers a lower temperature bypass valves for these transmissions but you have to buy one of their transmissions to buy one.

Thank god I didn't need a new transmission..yet. Fluid that came out was discolored but not black and didn't smell burnt, no debris or metal on magnets just some slime. Just fyi for everyone, here are the parts used.

Pan in raw aluminum w/drain plug and heat sinks, filter included in price.. https://www.xtremediesel.com/ppe-zf-8hp70-heavy-duty-aluminum-transmission-pan?variant_id=116906

Fluid, ZF Lifeguard 8 (this is what ZF recommends). https://www.fcpeuro.com/products/lifeguard-8-automatic-transmission-fluid-1-liter-s67109031201

Factory fluid heater..https://www.moparpartsgiant.com/parts/mopar-transmission~68463479aa.html

New factory gasket..https://www.amazon.com/Genuine-Chrysler-68172556AA-Oil-Gasket/dp/B00FZFO2U4

 

[Mas647]

Did you have any problems with the bigger PPE pan clearing the exhaust?

 

[Wild one]

It's only the trucks that have the thermal heater on the transmission,the cars don't heat the tranny fluid like the trucks do.But to remove the heater assembly would entail drilling and tapping the trucks tranny case,as they aren't drilled for cooler lines like the cars are. The biggest change I've found was dropping way down to a 160 high flow Milodon thermostat,the engine still runs at 185F ,but my tranny runs in the neighbourhood of 169 to 173 with the 160 T-stat.But you have to be tuned for the 160 otherwise it'll turn on a check engine light for being outside the warm-up parameters,and it's only a summertime thermostat,you'd want to throw at least a 180 back in if you live where it snows,as the interior of the truck won't get warm enough for the snot to quit dripping from your nose.I speak from s'perience,the first time it went to -10C up here,i had to run the seat and steering wheel warmers just to have the truck livable,lol

 

[Kap1]

Here you are, 80-120km (50-75k miles) on page one.

https://aftermarket.zf.com/remoteme...38411/si-zf-si-oelwechselkit-8hp-50130-en.pdf

Most service video I came by aren’t filling the torque converter correctly by revving to 2000 RPM for 30 seconds. Will it matter? most likely not if you’re following the rest of the procedure.

Hi, thank you for posting this guide.

Couple questions:

1. Everywhere else on this forum, the "official" instructions (green screenshot from Wildone) are to jack up the end of the truck to make sure transmission is LEVEL. However, in this guide, they do not specify anything about leveling the transmission or jacking up end of the truck. SO... do we have to jack it up or not?

2. Another difference is that the other "green screenshot" instructions specify to jack up truck so that wheels can spin freely, and call for accelerating to 2nd gear. However, these instructions simply say to hold brake firm and shift between the gears slowly and manually shift up to D2 gear.

These instructions are easier to follow than the "green screenshot" instructions...

So which instructions are correct and should be followed on my 2013 Ram with 8hp70?

Thanks in advance!

 

[Tim Garceau]

Definitely level the rail to insert the intended amount of fluid back in, you’ll need to jack the rear axle up a good 10-12 inches(depending on your stance lift/level/drop). This will make the trans level as the output shaft is at a much lower angle than the ZF cars(which my link is in reference for).

All ZF videos I’ve seen have the truck/car on level ground/lift, which is incorrect for the Ram. Measure what comes out and you’ll agree.

 

[jjjefferson]

Anyone try one of these? It bypases the heater and removes the t-stat.

https://revmaxconverters.com/produc...-8hp75-transmission-cooler-thermostat-bypass/