Servicing transmission on 2017 2500HD 4WD w/6.0 gas motor

T_ClarkEx39 · July 26, 2023

So, i purchased this truck new in July 2017. Been a fantastic truck other than the crappy fuel economy that is typical of the 6.0 motor and the 6 speed transmission. It had a few hiccups that were covered under warranty including a "service 4wd" code that after 5 trips to the dealer they fixed (and still dont know what they did to fix it). But, here is my "dilemma". The truck has 135K miles. While i have religiously always done oil changes, ect., i have never done a transmission service. Ive had more than one person tell me that these trucks with this transmission that if it hasnt been serviced by now, NOT to service it as it could possibly start faulty shifting. Even the dealer where i bought it said that if i bring it to them to service, they will do it but cannot warrant that it wont start acting up.

Is this true? Fluid is still full and still nice and pink with no burn smell. So should i just "leave it be" from now on and just add transmission fluid if it ever needs it or what?

Snowcamo · July 26, 2023

Leave it be. Use this stuff when it needs some. My work truck leaks.

T_ClarkEx39 · July 26, 2023

interesting. i might jinx myself, but this truck doesnt leak a drop of anything and never has. (knock on wood)

rav3 · July 26, 2023

Heat kills the fluid & that usually kills the torque converters. Your transmission should have been serviced at about 50k, IMO. If it were me, which you aren't, I'd suck out the fluid in the pan, about 4 qts, & replace with Dexron VI. Run it for 100 to 200 miles & do it again. I'd also do the transmission thermostat 'pill flip to lower the transmission running temperature.

I bet you haven't changed transfer case fluid or front & rear differentials.

Too many videos on YouTube on what NOT changing fluid happens.

Do your own research on this & then ask that question

KARNUT · July 26, 2023

I realize I have an older truck things may have changed for the worse with newer ones. And yes I’ve owed plenty of 3/4 and 1 tons. I remember some of my GMs didn’t even call for a transmission fluid change until 150K miles. I wouldn’t hesitate to do a fluid exchange, not a flush. At 165K I gave my avalanche a fluid exchange through the dipstick. I measured the fluid and put the same back in. One week later did it again. Almost 4 years ago.

CamGTP · July 26, 2023

If anything the most I'd do is suck out 2-3 quarts from the dipstick tube and dump the same amount back in. Call it good from there for a long time.

T_ClarkEx39 · July 26, 2023

1 hour ago, rav3 said:

Heat kills the fluid & that usually kills the torque converters. Your transmission should have been serviced at about 50k, IMO. If it were me, which you aren't, I'd suck out the fluid in the pan, about 4 qts, & replace with Dexron VI. Run it for 100 to 200 miles & do it again. I'd also do the transmission thermostat 'pill flip to lower the transmission running temperature.

I bet you haven't changed transfer case fluid or front & rear differentials.

Too many videos on YouTube on what NOT changing fluid happens.

Do your own research on this & then ask that question

I get that. I went thru automotive school in the late 70's (got tired of working on other peoples junk), then became a construction electrician. I built race cars back in the day, and from age 40-55 road raced motorcycles all over the SE U.S. building and maintaining those as well. I'm very aware of what kills transmissions. The rear end was just serviced about a year ago and the 4wd was serviced at 80K. I just screwed up and never did the transmission on this truck (traded in a 2003 D'max i owned since new at 350K for this truck, and because the Allison transmission was so easy and convenient to service, it got a new filter and fluid every 3rd oil change or approx 30K miles).

Having said all that, yes, I'm a dumbass for not servicing the tranny on this truck. At 62 years old i don't feel like climbing under the damn thing anymore (haven't for many years), so I was going to let my dealer do it when they told me about this issue. Since then have spoken to a couple of others that have said the same thing. Hence why I am asking the question here.

Edited July 26, 2023 by T_ClarkEx39

rav3 · July 26, 2023

2 hours ago, T_ClarkEx39 said:

I get that. I went thru automotive school in the late 70's (got tired of working on other peoples junk), then became a construction electrician. I built race cars back in the day, and from age 40-55 road raced motorcycles all over the SE U.S. building and maintaining those as well. I'm very aware of what kills transmissions. The rear end was just serviced about a year ago and the 4wd was serviced at 80K. I just screwed up and never did the transmission on this truck (traded in a 2003 D'max i owned since new at 350K for this truck, and because the Allison transmission was so easy and convenient to service, it got a new filter and fluid every 3rd oil change or approx 30K miles).

Having said all that, yes, I'm a dumbass for not servicing the tranny on this truck. At 62 years old i don't feel like climbing under the damn thing anymore (haven't for many years), so I was going to let my dealer do it when they told me about this issue. Since then have spoken to a couple of others that have said the same thing. Hence why I am asking the question here.

I get it too! I'm 76 & don't like like crawling under cars anymore either. Like I mentioned, suck it out the fill tube & don't bother with the filter. It only stops the big chunks & won't stop/filter the clutch material, which IMO does the most wear. I made a simple vacuum pump from a Harbor Freight $16 A/C venturi pump that runs off my compressor, a little clear PVC tubing from Lowe's & 4 quart jars. Takes about 15 mins to suck the pan out then pour in 4 fresh quarts. I do that about every 10k miles plus I did the pill flip so tyranny never goes over 155F foe most part. We'll see how long it lasts.

T_ClarkEx39 · July 26, 2023

What is this pill flip? Never heard of it

rav3 · July 27, 2023

35 minutes ago, T_ClarkEx39 said:

What is this pill flip? Never heard of it

Here's one video on it. There's several on YouTube.

https://youtu.be/GaG6I-5Ko_A

rav3 · July 27, 2023

3 hours ago, CamGTP said:

If anything the most I'd do is suck out 2-3 quarts from the dipstick tube and dump the same amount back in. Call it good from there for a long time.

Strange, I always get 4+ quarts when I do it. IIRC, the 6L80 holds about 9 quarts, so if you do it 2x close together after driving it a little, you've replaced about 75% of the fluid with new fresh fluid. Add a bottle of Lubegard & transmission shifts good.