transmission temp vs. reliability

[LRutigliano]

Anyone have experience with their 48RE taking a dump?



If all I do is tow exclusively (no racing or hard launches), with my mods (80hp injectors, CAI, intake manifold, exhaust and Smarty on Level 1 with stock RP and stock TM), will the transmission fluid temp predict failure?



My temps are always relatively low (145F towing on the flats, maybe up to 170F towing up BIG hills at 30-35mph, up to 165F towing up BIG hills at 55-60mph in 3rd gear) Sensor is in the pan.



I've had no TCC shudder or any other issues (knock on wood).



I'm saving for a complete trans build up (triple disk TCC, billet input, laminated flex plate, modified VB, new clutches, bands and steels and maybe billet output) all rated for 600hp, but I can't get myself to pull the trigger... because its over $5k.



However, when I'm towing, I'm always wondering if I'm going to get stranded with the trailer.



I have 17,000 miles and stock size (265/70-17) tires with 3. 73 gears.



Any comments or suggestions are welcome, hopefully swaying me one way or the other.



Thanks,

Louis

 

[AllianceDiesel]

#1 killer of trannies is temp. I have a chart floating around somewhere that I will get you the temps and when and what starts to fail

 

[cerberusiam]

How heavy are your loads? Up to the rated loads the trans is pretty tough. However, if you start getting up over 25k its a crap shoot.



Your posted temps are quite good for longevity, even if they are in the pan. If you tow and do much slow speed stop and go driving the hot line would be a better place for the sensor. Will give you an idea what the max temps are instead of the constants.



Answer to your question, I toasted my trans at 105k by running the Smarty mostly on #3 and towing my trailers. After seeing what happened to the trans, ANY power mods or heavy towing is going to reduce the life expectancy unless you make some mods.



If you want to spend $5k for some peace of mind that is fine, but, for half that you can pretty well bullet proof the trans for your use. You just don't need that type of build unless you are gonna thrash the truck.

 

[amsoilman]

As MOPARTECH said, Heat is the KILLER of ATF.

GM made a study several years ago on Automatic Transmission Fluid, and determined that a fluid operating temperature of 175 Deg. F. would equate to a 100,000 mile service life for an Automatic transmission. The Study also found that fluid life would be reduced by 50 percent for every 20 Deg. F increase in fluid operating temperature above that optimal temperature.

At 212 Deg F. Varnishes start to form. At 235 Deg F. Seals harden. At 255 Deg F. plates slip, and at 295 Deg. F. Oil Forms Carbon. Above 300 Deg F. Severe Component Distortion occurs.





Wayne



The best line of defence is to reduce the operating temperature of the transmission. One way is to use a full Synthetic ATF, which has proven 20-30 Deg F. reduction.

 

[AH64ID]

Since the ATF will be damaged by heat prior to the guts of the transmission I would move your temp sender to the output line, where the fluid is the hottest.

 

[cerberusiam]

GM made a study several years ago on Automatic Transmission Fluid, and determined that a fluid operating temperature of 175 Deg. F. would equate to a 100,000 mile service life for an Automatic transmission. The Study also found that fluid life would be reduced by 50 percent for every 20 Deg. F increase in fluid operating temperature above that optimal temperature.

At 212 Deg F. Varnishes start to form. At 235 Deg F. Seals harden. At 255 Deg F. plates slip, and at 295 Deg. F. Oil Forms Carbon. Above 300 Deg F. Severe Component Distortion occurs.

The key here being SEVERAL YEARS ago (about 15), well before the development of the newer synthetic fluids.



One has to compare apples to apples here or the numbers are meaningless. The quoted numbers do not apply to ATF+4 or any comparable fluid.

 

[JimB1]

Send oil sample to the lab.



Cheapest, most reliable indicator of where your transmission & TC are right now and a great answer to how well its handled 17k miles of your type workload.

 

[amsoilman]

The key here being SEVERAL YEARS ago (about 15), well before the development of the newer synthetic fluids.



One has to compare apples to apples here or the numbers are meaningless. The quoted numbers do not apply to ATF+4 or any comparable fluid.

It is true there have been advances in the ATF world, but GM still adheres to these numbers, regardless of the fluid used. Just make sure the ATF+4 is used on the Chrysler Automatics beyond 1997.

 

[AH64ID]

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[cerberusiam]

but GM still adheres to these numbers, regardless of the fluid used.

I find that hard to believe when the Dexron VI considerably exceeds those performance specs. Is it really believeable that a major vehicle vendor would adhere to an obsolete specification like that?



Consider this, Dexron VI passed the tests conducted using a 4L60 trans with temps at 325 degrees for 450 hours.



ATF+4 passed ISO tests for wear, fluid shear, and acidity after 1500 hrs at 325 degrees.



Both fluids are rated as a fill-for-life at 100k in normal service. Dexron at 50k and ATF+4 at 30k in severe duty.



Given the testing extremes, is 210 or even 230 degrees for 30 minutes even cause for a blink? :-laf



Much ado about nothing with all the doom and gloom over fluid temps. The bigger problem is all the NVH directives that give us a slippity sloppity shifting trans that tends to eat itself up slipping the clutches all the time. All the components inside the trans have been upgraded and developed to take the higher heat and extended fluid fills and extremes.



The 48RE and Ally both suffer from the same problems, lousy programming to keep things smooth and silky while they self destruct.



Fix the source of the problems and all the symptoms (aka high trans temps, burned clutches, etc) don't even factor in. Lock the TC sooner and firmer, make a shift a SHIFT instead a slip and you won't see temps get anywhere near being a problem.



Shift kit + better TC = happy transmission.

 

[AH64ID]

One thing I noticed in my toyota tacoma was that the transmission fluid was fill-for-life, with a check at 100K... I put a gauge in the hot line, it would get to 230* easily towing 1. 5K on a dirt road, 5K below the 6. 5K limit. At 75mph on a 90* day it never went below 200*... . obviously they aren't concerned about the heat as much as I was..... I am sure the same it true with the Dodge auto... . but then again I would say most folks here suffer from a SEVERE case of TMI... .

If it bothers you then change it... if it doesn't then you will spend less money than others.

 

[LRutigliano]

How heavy are your loads? Up to the rated loads the trans is pretty tough. However, if you start getting up over 25k its a crap shoot.



Your posted temps are quite good for longevity, even if they are in the pan. If you tow and do much slow speed stop and go driving the hot line would be a better place for the sensor. Will give you an idea what the max temps are instead of the constants.



Answer to your question, I toasted my trans at 105k by running the Smarty mostly on #3 and towing my trailers. After seeing what happened to the trans, ANY power mods or heavy towing is going to reduce the life expectancy unless you make some mods.

If you want to spend $5k for some peace of mind that is fine, but, for half that you can pretty well bullet proof the trans for your use. You just don't need that type of build unless you are gonna thrash the truck.

Ceberusium, when you "toasted" your transmission at 105k, did you get any early warning or where you left stranded?



What failed in your transmission?



Thanks,

Louis

 

[cerberusiam]

Ceberusium, when you "toasted" your transmission at 105k, did you get any early warning or where you left stranded?



What failed in your transmission?



Thanks,

Louis

I got really, really, REALLY lucky. It failed at home immediately after I ran from Seattle to Wilmington NC and back with a loaded truck and trailer both ways in every kind of nasty weather possible. I am lucky it didn't quit me in Alliance NE in January, that would be SCARY. :-laf



I had 10k on the shift kit and other pieces and it was working like a charm even with the stock TC. Temps NEVER went over 210 and that was only on a hard loaded acceleration before the shift kit. After the kit it would not break 200 degrees and was always a positive shift. What finally got it was over extending the direct clutch apply piston and cutting the seal. We tore it down and were amazed it even moved and worked as well as it did. All the seals, hard parts, and clutches with the exception of the directs were in perfect shape.



I tow mostly on Smarty #2 or #3. Had very few miles running on #5 and then only empty. I use my truck but don't abuse it, and, drive pretty conservatively when towing. Firmly convinced the first thing that needs to be done is a shift kit even stock.



We are pretty sure it looked like below when we put the shift kit in as we saw quite a bit of clutch dust in the pan and on top of the VB. Putting 10k towing on it looking the pics below has given me a whole new appreciation for how tough the 48RE is and how much help a shift kit and few billet pieces are. Somebody tries to tell ya how bad the 48RE is, here's some pretty solid proof it will take some abuse and keep going.



Direct clutch pack

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Input shaft is toast also

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Here is what finally precipitated the rebuild, it was the 5th or 6th bite out of the seal that did it

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[TMax]

I toasted my transmission about 5,000 miles after upgrading it with a billet triple disk TC and a reworked valvebody. I was towing my 5er (about 10,000lbs) up a long grade and it felt like someone pushed in the clutch... . of course on an AT that's not a positive thing. After tearing into it, it was apparent that the TC had failed to achieve lockup and it just got it too hot. The crazy thing is that my digital guage never showed over 215 deg. but the sensor was put into the test port on the side of the transmission where the instructions said to put it. Bad idea there as I think it is nowhere near accurrate. We have since rebuilt the trans, and installed a lockup switch where we can at least try to electronically force the TC into lockup. I am confident that this was a flukish event as the builder has an excellent reputation. You just never know. All you can do is make sure you are in lockup where possible. The switch was easy by the way. I do not know why Dodge does not install a transmission temp sensor knowing that these trucks are going to pull. For that matter, why no EGT guage either?

 

[ACerf]

I tow a 12,400 lb trailer on a regular bases. I have added a Mag-Hytec transmission pan that adds another 4 qts of fluid. I also change the fluid at somewhere between 25-30K. So far I have had no problems with 100,000 on the truck. I continue to use the Mopar ATF+4 fluid in the transmission, as this is what is recommended by Dodge. I am going to change the fluid in the Power Steering unit. I did not realize that the power steering can directly effect the braking of the truck. This also uses ATF+4.

Thats my two cents, for what it is worth :-laf

 

[cerberusiam]

I do not know why Dodge does not install a transmission temp sensor knowing that these trucks are going to pull.

Trans temp sensor is on the VB and will activate a little light on the dash, kick the trans out of OD and unlock the TC when it reads above 260 degrees for a period of time, if it reads the temp correctly.



'Course by that time the trans is probably toasted anyway so when the light comes just drop it off at the nearest dealer. :-laf



Real gauges so we can see what is actually going on? You think they really want to answer the questions about THAT? :-laf:-laf

 

[TMax]

'Course by that time the trans is probably toasted anyway so when the light comes just drop it off at the nearest dealer. "

Yes, some us learn little life lessons the hard way. We have since put the probe into the DD pan. I am sure that location is less than optimal but I guess there's another lesson somewhere I get to learn.

 

[Yo Hoot]

Trans temp sensor is on the VB and will activate a little light on the dash, kick the trans out of OD and unlock the TC when it reads above 260 degrees for a period of time, if it reads the temp correctly.

Does anybody know what would cause the trans to begin UPshifting and locking into 3rd and then fourth starting at around 28-30mph? I get no Tow/Haul light like the manual states. It does this intermittently.

I hit the pan with an IR gun when it was in this mode and am getting no more than 205F at the hottest spot.