8hp70 heater bypass

[HEMIMANN]

This mod may be the single best thing I've done for the truck. Especially important because I have the 66RFE. I wouldn't have known about it if not for this Forum - I am quite grateful for the knowledgeable and friendly members here!

I try to repay in kind on subjects I have expertise with.

 

[joesstripclub]

@hawsk99gt I was searching around the internet for insight into our overheating problem, and I found this thread that brought up a potential failure mode I hadn't thought of before:

From Post # 5 on the above thread:

This seems like it could make sense, especially if it's confirmed not to be related to the thermal management unit. Like caulk04 said, it might be internal at this point. I'm afraid my problem might be the same. When that uncontrollable temperature spike hits, it climbs FAST, like 2 degrees every 5-10 seconds. I have to catch it RIGHT when it happens and slow way down, or pull over entirely.

@Wild one , I know you're no stranger to transmission issues. What do you think of a transmission that isn't able to keep the torque converter locked. Would that lead to our overheating issues? Is that an easy fix (programming) or does that need a transmission drop and repair/overhaul? Or is a new transmission best?

Luckily, it only seems to affect me when I'm above 60 mph, so city driving is okay. And the few times it's happened, I've caught the temperature before 230 F. But long trips limited to 60 mph is kind of grueling. I'd want to get this repaired. Are there trustworthy places that work on these transmissions? I can pony up if I know the job will be done right... I've kept good care of the truck since 17,000 miles. She's got a lot of life left in her.

There was a thread recently about torque converter issues on 8 speed trucks. I recall someone logging the converter lockup and it was in and out. I wonder if this is a programming bug or some issue with aging parts.

 

[hawsk99gt]

I was wondering - a separate question regarding the Transfer case. I have 90,000 miles on my truck with a fairly new transmission that was replaced (at 65,000 miles). If I have only used my 4-wheel drive only once in the time I have owned it, do I need to do a T-Case fluid replacement and front Differential fluid replacement? I'm not a mechanic but I do try to do my own servicing if I can.

 

[Daniel Ortiz]

@hawsk99gt , I assume you have the same transfer case the truck came with. I swapped all my gear fluids at 60,000 miles (front & rear differentials & transfer case). If you're like me and are babying your truck, all three components could stand for a fluid change (I kind of whish I had done it at 30,000 miles, but if you don't use 4x4 or tow often, I understand 60,000 miles is still fine). The downside is the Mopar factory fluid is kind of special, and very expensive. That's what I went with, but if you really do your research you can see who in this Forum is using cheaper equivalent fluids with no problems. But if you can only afford to do the minimum, I would at least change the rear differential that is doing all the work constantly, getting hot every time, slowly cooking the lubricant. Do that one at a minimum.

Here is Mopar's 2021 Vehicle Lubricant & Chemical Catalog, use it along with your owner's manual to help guide you as to which lubricants you need for which part and which year truck you have.

 

[joesstripclub]

I was wondering - a separate question regarding the Transfer case. I have 90,000 miles on my truck with a fairly new transmission that was replaced (at 65,000 miles). If I have only used my 4-wheel drive only once in the time I have owned it, do I need to do a T-Case fluid replacement and front Differential fluid replacement? I'm not a mechanic but I do try to do my own servicing if I can.

If you are doing one you may as well do the rest. You will likely be pumping fluid so may as well do them all while you have the equipment out. I'm a crazy person and I changed out all the factory fluids around 10k miles and generally run 30k service intervals. It's probably overkill but its not a ton of fluid so its not that expensive. I also think getting synthetic fluids in makes a big difference and seems to help with gas mileage in my experience.

 

[hawsk99gt]

@hawsk99gt , I assume you have the same transfer case the truck came with. I swapped all my gear fluids at 60,000 miles (front & rear differentials & transfer case). If you're like me and are babying your truck, all three components could stand for a fluid change (I kind of whish I had done it at 30,000 miles, but if you don't use 4x4 or tow often, I understand 60,000 miles is still fine). The downside is the Mopar factory fluid is kind of special, and very expensive. That's what I went with, but if you really do your research you can see who in this Forum is using cheaper equivalent fluids with no problems. But if you can only afford to do the minimum, I would at least change the rear differential that is doing all the work constantly, getting hot every time, slowly cooking the lubricant. Do that one at a minimum.

Here is Mopar's 2021 Vehicle Lubricant & Chemical Catalog, use it along with your owner's manual to help guide you as to which lubricants you need for which part and which year truck you have.

I was thinking of doing Mobile 1 for the fluids

 

[Bigskyroadglide]

7 hour freeway run today. Virginia to Tennessee. 71 degree weather, limited traffic,
Check out these temps

 

[hawsk99gt]

Can someone tell me if I can use this fluid in my RAM's transfer case. It has a Borg Warner 902-A transfer case. I picked up Valvoline Full Synthetic Multi Vehicle Transfer case Fluid. Advanced Auto says that is the only fluid they provide for my RAM. ATF+4 . I would just like a definitive answer.

 

[G-Ride990]

Can someone tell me if I can use this fluid in my RAM's transfer case. It has a Borg Warner 902-A transfer case. I picked up Valvoline Full Synthetic Multi Vehicle Transfer case Fluid. Advanced Auto says that is the only fluid they provide for my RAM. ATF+4 . I would just like a definitive answer.

902-A Tcase? I have never heard of that case by that name. Do you have 4wd auto as a drive mode selection?

 

[hawsk99gt]

902-A Tcase? I have never heard of that case by that name. Do you have 4wd auto as a drive mode selection?

Thats what it has stamped on it. And no auto 4x4 on this one.

 

[hawsk99gt]

BW44-44 is the transfer case. If that helps.

 

[G-Ride990]

Thats what it has stamped on it. And no auto 4x4 on this one.

Thats what it has stamped on it. And no auto 4x4 on this one.

If you don't have the auto selection you have the 44-45, which is a better tcase. Do you have an outdoorsman?

Looks like Mopar specifies this fluid as the correct one for the 44-45 and pre 2016 44-44: Mopar 68089195AA

I have the less desirable 44-44 and I have been running C+ for many years now. Been doing a bit of searching but can't quite nail down a good answer for you on the 44-45 fluid.

 

[hawsk99gt]

OK, I think I am confused. The BW44-44 is the auto 4x4 and the BW44-45 is without auto. So that would be what my transfer case is BW44-45.

 

[G-Ride990]

OK, I think I am confused. The BW44-44 is the auto 4x4 and the BW44-45 is without auto. So that would be what my transfer case is BW44-45.

Exactly. And again, you got the better tcase so that is pretty sweet! Basically us 44-44 guys can't actually lock our tcase into 4wd. Our 44-44 cases only go into 4wd when there is rear tire slip.

Anyways I don't want to get too off-topic with the heater bypass so I will leave it there, if you search the forum for 44-45 transfer case fluid there are tons of posts on the subject. That mopar part number I posted is the correct mopar fluid though for the 44-45, I just think there are better aftermarket options out there.

 

[hawsk99gt]

If you don't have the auto selection you have the 44-45, which is a better tcase. Do you have an outdoorsman?

Looks like Mopar specifies this fluid as the correct one for the 44-45 and pre 2016 44-44: Mopar 68089195AA

I have the less desirable 44-44 and I have been running C+ for many years now. Been doing a bit of searching but can't quite nail down a good answer for you on the 44-45 fluid.

well shoot... I guess I am going to role the dice. Or maybe hold off till next week till I get a definitive answer for the fluid I currently have. So far all my fluids have looked pretty good to me especially my front differential. It was pretty clear for 90k on it. Again I do baby it and it is garage kept.

 

[hawsk99gt]

I really don't want to buy the special Unicorn fluid from the dealership.

 

[hawsk99gt]

OK and thank you for the switch up here

 

[BlownGP]

7 hour freeway run today. Virginia to Tennessee. 71 degree weather, limited traffic,
Check out these temps

That's still crazy how high your oil temp is though.

With a 180 Themro, shutters removed

Trans temp is around 145 on the highway
Oil temp is 190-195. That was a few weeks ago on a 85* day at 75mph

Since the 180 thermo I've never seen much over 200* on the oil unless I was running WOT a few times.

and this Stant 180 T-stat is the most consistent T-stat I've ever had. It will stay at 185* and never move unless I'm sitting in traffic a while.
I've ran several different kinds in my Orange truck including stant they would fluctuate so bad.

 

[BlownGP]

There was a thread recently about torque converter issues on 8 speed trucks. I recall someone logging the converter lockup and it was in and out. I wonder if this is a programming bug or some issue with aging parts.

You got a link to that thread. I'm starting to think that my jerking problem when slowing to a stop.

 

[Daniel Ortiz]

So after reading @hawsk99gt 's report of the persistant overheating problem even after installing one of @caulk04 's bypass plugs, it occurred to me that if there IS an internal problem with my transmission, installing the bypass plug would only mask it by substantially lowering the temperatures, and I might not ever know there was an internal problem, and thus internal WEAR, until much later once much more damage may be done.

So, I decided I wanted to know if it was indeed a faulty thermostat, bit the bullet, and purchased a new one, and unfortunately it comes with an entire thermal exchange unit attached to it.




Now, I own a cheapie pair of retaining ring pliers with adjustable jaws for various angles, but the jaws have a lot of play and for the life of me I can't get enough of a grip on the snap ring to pull it out. I heard someone mention a "good" pair of pliers must be used. Does anyone recall what brand/style those were? I may be looking for a good pair myself. If I can't get this thing undone on my work bench with ease, I don't stand much of a chance wedged up in the underbelly of my truck.