8 speed transmission issues

[Fitz780]

To start off I’m brand new to the forum, I have read quite a few post that are similar to what I’m experiencing but not quite the same.
I have a 2016 Ram Rebel, was my dream truck but have had a lot of issues I’m continuing to deal with today.

I had the first transmission replaced at 900 miles for what the dealership called a leaking front pump seal. ( 1 in 50k trucks). My second one was replaced in February of 21 for ultimately getting stuck in 6th gear. On to my current transmission which has made it 28k miles since my last one and stuck in gear again. I have went to the dealership multiple times for the previous one trying to get them to diagnose a problem with my truck that would cause my transmissions to fail so often. I don’t ride it hard, I don’t tow, I will load the bed up with a few hundred pounds every other month but that’s it. In my discussions with the dealership I have asked them countless times what the safe operating temp of transmission is and I seem like what they are telling me is too hot. They said around town up to 220. And under lots of strain or towing I can see up to 245 degrees. On a 45 min ride from work I often see the transmission temperature at 249. Mind you this is at about 70mph. If I need to accelerate anymore when it’s that hot the transmission just whines when accelerating. I have a Mopar warranty that covers my transmission only because of this ongoing issue. What should I do? I feel like there’s some underlying issues that’s causing my truck to go through transmissions this much. The dealership just wants to throw in another transmission rather then diagnosing what could be the issue. What should I do? Has anyone else had these types of problems.

Thanks,

 

[crash68]

Do you know if the TMU was replaced with the transmission, when the thermal bypass in the TMU screws up you'll see high transmission. For the most part the transmission temp should stay around the coolant temp. The TMU mounted to the side of the transmission, and may not be included with a new transmission.
The dealership would also need to flush the trans cooler out, it's the top couple rows of the AC condenser.

 

[crazykid1994]

Around town driving the transmission should run below 200°. Towing I would expect 230° or less unless you are maxing the truck out. The thermostat for the transmission is 180° and it will generally will run 186°-190° up to 200° on the highway. I would not expect over 200° highway unloaded. The thermostat may have failed. You can get a thermostat bypass for @caulk04 and swap it really easily just to be safe and see if it helps.

 

[Wild one]

As Crash stated get them to flush the lines and cooler,or push to have them replace the A/C condensor/tranny cooler,and put a new thermal management unit on it. The thermal management unit doesn't come with a new transmission,and if the dealer is replacing the transmissions under warrenty,they'll be reusing your original thermal unit.
If they won't replace the thermal unit as part of your warrenty,buy it yourself and have them install it with the replacement transmission.They aren't that bad to buy,and you might be farther ahead buying it yourself,then having to fight them over it.

 

[Fitz780]

As Crash stated get them to flush the lines and cooler,or push to have them replace the A/C condensor/tranny cooler,and put a new thermal management unit on it. The thermal management unit doesn't come with a new transmission,and if the dealer is replacing the transmissions under warrenty,they'll be reusing your original thermal unit.
If they won't replace the thermal unit as part of your warrenty,buy it yourself and have them install it with the replacement transmission.They aren't that bad to buy,and you might be farther ahead buying it yourself,then having to fight them over it.

I went back and looked at the service records for my last transmission and this is what they replaced
Trans with torque converter
Cooler condenser
Trans cooler
Flushed lines and flashed transmission

I hope that helps

 

[Wild one]

I went back and looked at the service records for my last transmission and this is what they replaced
Trans with torque converter
Cooler condenser
Trans cooler
Flushed lines and flashed transmission

I hope that helps

By the looks of that,they re-used your original thermal management unit (TMU) and that's where the transmissions thermostat is located.The 8 speeds thermostat has been known to give issues,and the only way around it,is to replace the whole TMU . I'd hazard a guess alot of the root causes to your transmission issues are the thermal management unit itself.I've never figured out why it's not included with a new transmission,but it's not.

 

[Shawn Burns]

By the looks of that,they re-used your original thermal management unit (TMU) and that's where the transmissions thermostat is located.The 8 speeds thermostat has been known to give issues,and the only way around it,is to replace the whole TMU . I'd hazard a guess alot of the root causes to your transmission issues are the thermal management unit itself.I've never figured out why it's not included with a new transmission,but it's not.

crazy that they will keep throwing transmissions at the problem, rather than diagnosing the source of the problem. I think I would be following WindOne's advise if I was in your shoes.

I have the same truck as you. With Caulk's heater bypass installed in mine, my transmission temp today while towing up some steep grades never reached above 150.

 

[CamperMike]

My stock truck with the 8 speed never sees Trans temps like you are seeing. And I have towed through mountains multiple times. It sure sounds like the TMU is the issue. I rarely remember seeing over 200 on the Trans temp.

 

[CanuckRam1313]

crazy that they will keep throwing transmissions at the problem, rather than diagnosing the source of the problem. I think I would be following WindOne's advise if I was in your shoes.

I have the same truck as you. With Caulk's heater bypass installed in mine, my transmission temp today while towing up some steep grades never reached above 150.

Agreed on all statements!

When there's an issue with the TMU's stock thermostat sticking and wiping out transmissions, for a dealership to just keep tossing transmissions in and not replacing the TMU is silly.

And, with the @caulk04 bypass installed in mine I don't see anything above 150 either. I haul and tow generators periodically and my transmission is so much happier with the new upgraded bypass installed and a full fluid and filter service.

I'd have the dealership install a new transmission, and a new TMU.
Then purchase @caulk04 bypass mod and have it installed at a reputable shop (keep the old one for a swap out...just in case).

Your transmission issues should be remedied after that (fingers crossed for you!).

 

[BuschLatte420]

249 normal that doesn’t sound normal, no matter how long of a drive how hot of a day and how Hard I beat on my truck I never saw 200 yet.

 

[EdGs]

249 normal that doesn’t sound normal, no matter how long of a drive how hot of a day and how Hard I beat on my truck I never saw 200 yet.

^^^^^^ 1000% agree.^^^^^^

The highest I've ever seen mine is 195°.

2015 SLT QC 5.7L 2WD, 169,000 miles.

 

[huntergreen]

Can you try a different dealer ?

 

[FraserBoy3]

Was having a similar issue, and my investigation found the Coolant By-pass valve was stuck, pushing HOT Engine Coolant to the Trans Cooler. Had already removed (replaced with brass slug) the Trans Heater 'T'-stat during first service.
So I just removed the coolant lines going to the Trans Heater.
Live in Fla, so not required, and none of the Charger/Challengers with same Engine/Trans have it. I believe it was RAM squeezing a little more MPG.
My Trans temp went from constant 220F and higher to Oil Temp (or less).

 

[KyJack]

I have a 2020 Ram 2500 2020 Hemi 6.4
I've had on 4 or 5 occasions my trañny lock up saying not in park on the display. It will start to roll then come to an abrupt stop. I'm worried it's going to snap the drive shaft.
The dealer says nothing they can do because they can't replicate the issue.

 

[Dusty]

First, what one individual may see for transmission temperatures does not necessarily represent "normal."

My typical around town temps average between 148 and 190, but this is dependent on how much stopping and acceleration the vehicle realizes, and how long the drive. I just dragged a 3500 pound Belmont construction trailer (empty) from Harrisburg, PA, and tranny temps reach a high of 225 on a very hot day of 90+ degrees. When I drag my 6900 pound trailer and tractor to the Southerntier I will see tranny temps as high as 235 on hills in hot weather.

Never had a transmission issue.

Transmission temps vary too much from vehicle-to-vehicle. It's highly unlikely no two people have the same identical driving cycle.

With respect to the dealer replacing transmissions under warranty, the transmission order is not fulfilled by just a simple request. Warranty replacements, especially transmissions, must be authorized, and a technician must submit a print out of a number of checks performed before the authorization is approved. Part of that includes a PCM & TCM trouble code dump. Cheating can cause the dealership to eat the entire cost of a transmission!

At the moment I have no reasonable explanation why two transmissions in a row suffered the same failure mode, but maybe we don't have the full story.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, factory dual exhaust, 18” wheels. Build Date: 3 June 2018. Now at 93319 miles.

 

[Wild one]

First, what one individual may see for transmission temperatures does not necessarily represent "normal."

My typical around town temps average between 148 and 190, but this is dependent on how much stopping and acceleration the vehicle realizes, and how long the drive. I just dragged a 3500 pound Belmont construction trailer (empty) from Harrisburg, PA, and tranny temps reach a high of 225 on a very hot day of 90+ degrees. When I drag my 6900 pound trailer and tractor to the Southerntier I will see tranny temps as high as 235 on hills in hot weather.

Never had a transmission issue.

Transmission temps vary too much from vehicle-to-vehicle. It's highly unlikely no two people have the same identical driving cycle.

With respect to the dealer replacing transmissions under warranty, the transmission order is not fulfilled by just a simple request. Warranty replacements, especially transmissions, must be authorized, and a technician must submit a print out of a number of checks performed before the authorization is approved. Part of that includes a PCM & TCM trouble code dump. Cheating can cause the dealership to eat the entire cost of a transmission!

At the moment I have no reasonable explanation why two transmissions in a row suffered the same failure mode, but maybe we don't have the full story.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, factory dual exhaust, 18” wheels. Build Date: 3 June 2018. Now at 93319 miles.

The common denometer is his TMU, it's not replaced when they warrenty a transmission,so that's where i'd start.

 

[16MaxSteelOutdoorsman]

I tow a travel trailer, about 5k lbs, on a 90 F day, trans temp never went above 194 F.

 

[hawsk99gt]

You know that is the one thing that I haven't replaced, and that is the TMU. I have the same story as you. Had my transmission go at 61K miles (now I am at 99K) and then I noticed after driving a long trip from North GA to Central FLA I got a warning from the truck that the trans was overheating. 275* if I remember right. I did opt to get CAULK04 thermostat by pass. And for the most part it works. But just recently on another post I did upload a pic of my dashboard and my trans temps was around 235* from doing a trip around Atlanta. It didn't happen till I was returning back home after stopping at a Home Depot. Stayed at that temp for most of the ride home on the express way. I was running about 75 mph. When I got down to 55mph in the mountains it dropped to like 195*. I have been given quite a bit of suggestions here, and I appreciate the input. But I am wondering if that is what I need to do and get a new TMU replacement and have the dealer swap it out and give me back the old one so I can get the thermal by pass back for possible installation in the future.

 

[redvetram]

Those seem like pretty high tranny temps. I had a 2014 V6 that would hit 240 on a really long uphill mountain climb towing a horse trailer. I bought a 2019 V8 and have never seen it go over 200, even towing 7000# in the mountains.

 

[hawsk99gt]

Those seem like pretty high tranny temps. I had a 2014 V6 that would hit 240 on a really long uphill mountain climb towing a horse trailer. I bought a 2019 V8 and have never seen it go over 200, even towing 7000# in the mountains.

Yes it is. The only thing I am towing is me, myself & I. Some times the wife too.