GM HD Duramax/Allison Owners Maintenance

[wedge88]

Hey Crew!

I recently purchased a 2016 GMC Sierra 3500 HD Denali Duramax and was able to acquire some previous maintenance records, related to oil changes, but nothing on the transmission.  I like to keep maintenance current and detailed records so I'm gonna drain/fill allison transmission fluid and replace spin on filter. (flush is a big no no with Allison)  My manual says filter should be done at 22,500 but it seems most do every other oil change (15k).   There is a lot of information online but nothing definitive about the fluid interval.  Manual only has allison intervals under "Severe" and not "Normal" conditions. I have found some do the fluid drain/fill every other oil change, some do it at 45k and some have never done it.  I get the part of changing the ATF spin on filter every other oil change but is the fluid necessary at this interval as well.  Fluids are $30-$50/gallon and it takes two gallons.  I don't mind the cost but seems excessive and, while I've owned many diesels, this is my first allison combo.   

Also, what fluid are you using for the transmission?  AC Delco Dexron VI, Mobil Delvac Synth ATF or Allison Transynd?  If my research is correct, once you go Transynd, you shouldn't go with anything else but the truck came from factory with AC Delco Dexron VI.  The truck has 70k miles and shifts great.  

Anxious to drop the spin on filter and check the magnet and fluid to see it's condition but want to get all my supplies together beforehand.  

TIA

[MLBurns]

I have always waited until around 100k on every Duramax I've had. Never had an issue and all my trucks pulled heavy loads frequently.

[wedge88]

7 minutes ago, MLBurns said:

I have always waited until around 100k on every Duramax I've had. Never had an issue and all my trucks pulled heavy loads frequently.

I have always done 100k on every one of my other vehicles which is what got me "over-thinking" this one.  What interval do you change the screw on filter?   Thanks 

[MLBurns]

Only at oil change.

[Sparky450]

I don’t run Chevy/Allison. I have a very small  fleet of mainly Gas rigs. Only diesels are an old ford 7.3 and my 18 ram 3500. My transmission guy. Who is a good friend says “run them til they quit, then change the fluid”. The new transmissions all run synthetic that as long as it doesn’t overheat will last the lifetime of the Transmission.  YMMV. 

[MLBurns]

Over time the fluid can break down from heat/moisture so it is a good idea to change it before you "slip" a clutch. Once clutches start slipping it is just a matter of time before you need a rebuild. Dark fluid is usually a sign of slipping and or excessive heat which it is usually too late at that time to change the fluid as the damage is already done.

[MLBurns]

I have had similar results from my trucks. This guy delivers campers for a living, so at least half the miles are under a load.

Edited February 27, 2020 by MLBurns
add on

[RyanB]

So what exactly is "overheat" for a transmission?  I tried to figure that out last year, and I can't find anything that shows what a modern transmission should run.

One of the reasons I sold my Yukon Denali was because I didn't like how hot the transmission would run towing my boat.  Anything going through the mountains it would go to 250*.  Two local dealers and one transmission shop told me that those temps are ok for short periods of time (like climbing a pass), but man that seems hot to me.

[carguy79ta]

My wife drives an 18dmax but it lives in the lap of luxury in my garage.  Has only towed myboat 2x. My 13 Ram CTD has done most of the towing, and lives with a 200hp tune. The rfe68 temps have never been above 175 and is normally at 165 to 168. I changed the fluid at 70k miles, it looked so good, I figure I will go 100k for the next change.

[MLBurns]

[RyanB]

1 hour ago, carguy79ta said:

My wife drives an 18dmax but it lives in the lap of luxury in my garage.  Has only towed myboat 2x. My 13 Ram CTD has done most of the towing, and lives with a 200hp tune. The rfe68 temps have never been above 175 and is normally at 165 to 168. I changed the fluid at 70k miles, it looked so good, I figure I will go 100k for the next change.

My 2012 RAM will run up to about 218 going through the mountains pulling a combined trailer weight of about 15000-16000. 
 

I don’t understand those low temps. My Grand Cherokee, our Expedition MAX, and all the rental cars I drive see 200* in normal non towing conditions. 

7 minutes ago, MLBurns said:

Do you know how recent this chart is?

[carguy79ta]

9 hours ago, RyanB said:

My 2012 RAM will run up to about 218 going through the mountains pulling a combined trailer weight of about 15000-16000. 
 

I don’t understand those low temps. My Grand Cherokee, our Expedition MAX, and all the rental cars I drive see 200* in normal non towing conditions. 

I've pulled 15k  but it was thru the mole hills of MO.. I have to watch the water temps with the 200hp tune and pulling. I obviously dont hammer down when pulling like that, but you can tell when the turbo is working and putting out more heat. There are a couple good hills by LOTO but nothing like what you have to deal with.

[jjackkrash]

I have never seen any of my D-Max trucks hit 200 degree transmission fluid temps.  The hottest I ever remember it getting under a heavy load over a pass mid summer was barely cracking 180 and that stood out to me.   

[jjackkrash]

That video was a good watch.   Keep the truck stock, change the fluids when the book tells you to, drive like the accelerator is an egg, get a million miles out of your truck and over 100k on a set of tires and 12 mpg towing a fifth wheel.   Well, at least I change my fluids on time.  

[spikew919]

On 2/27/2020 at 10:44 PM, carguy79ta said:

I've pulled 15k  but it was thru the mole hills of MO.. I have to watch the water temps with the 200hp tune and pulling. I obviously dont hammer down when pulling like that, but you can tell when the turbo is working and putting out more heat. There are a couple good hills by LOTO but nothing like what you have to deal with.

It’s actually not the turbo causing heat. It’s all the fuel the 200hp box tuner tune is throwing at the engine. The turbo is actually cooling the egts with more air. If you don’t have an exhaust temp probe, you may want to invest in one. A lot of those tuners are pushing egts over 1350 degrees which is right at the limit to serious piston damage. And with pulling that weight they are prolly going over 1500 on that tune. 
 

just a heads up. On diesels, more air is better. 

Edited March 1, 2020 by spikew919

[carguy79ta]

12 hours ago, spikew919 said:

It’s actually not the turbo causing heat. It’s all the fuel the 200hp box tuner tune is throwing at the engine. The turbo is actually cooling the egts with more air. If you don’t have an exhaust temp probe, you may want to invest in one. A lot of those tuners are pushing egts over 1350 degrees which is right at the limit to serious piston damage. And with pulling that weight they are prolly going over 1500 on that tune. 
 

just a heads up. On diesels, more air is better. 

I'm going to get an egt probe, just havent yet. when you are pulling, you can tell when the temps are rising. I.e. Pulling a hill, torque convertor locked. Glance at boost pressure, up over 30, ease off the throttle. I basically feather the throttle when I tow. When I towed my boat with lead and all about 11k, with the (L5p)duramax, since there is no tune on it I just would hammer down on hills. As much as I love my Cummins, the whole duramax package performed flawlessly.

[MLBurns]

17 hours ago, spikew919 said:

It’s actually not the turbo causing heat. It’s all the fuel the 200hp box tuner tune is throwing at the engine. The turbo is actually cooling the egts with more air. If you don’t have an exhaust temp probe, you may want to invest in one. A lot of those tuners are pushing egts over 1350 degrees which is right at the limit to serious piston damage. And with pulling that weight they are prolly going over 1500 on that tune. 
 

just a heads up. On diesels, more air is better. 

Exactly why you should be very cautious if your truck has and air-to-water intercooler. Once you get the water/ coolant hot under heavy loads or have a hot tune, everything becomes heat soaked and can't cool down as fast as an air-to-air intercooler. The extra heat makes everything else run hotter. My trans temps have always been around 175-180 on my Duramax's, I think I got close to 200 pulling my toy hauler up big hills.