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did a complete change (12 qts and gm filter, used gm dexron vi ) at 50k miles. as i have previously installed a trans cooler and lokar dipstick this greatly simplified adding removing the fluid. i tow a small travel trailer i figure about 5k towing miles, fluid was darker than i expected, but no burned smell and trans pan was still clean with no debris or metal in it.
 

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Hi guys
Thanks in advance.
I'm wanting to do a fluid and filter change on my transmission 2015 z71 what do I need to refill the transmission and where do I fill from?
 

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Hi guys
Thanks in advance.
I'm wanting to do a fluid and filter change on my transmission 2015 z71 what do I need to refill the transmission and where do I fill from?
Read through this post: https://www.coloradodiesel.org/threads/is-it-possible-to-do-a-diy-transmission-service.67325/

I explained it here and someone else (Duken4ever I think) adds a picture of the inside of the trans pan for reference.

I think the 2015’s have the same 6 speed 6L50 transmission as our diesel trucks (since all 2015 trucks were gas engines...) the procedure should be exactly the same.
 

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I just looked into the owners manual this evening for my '16 (both the normal manual and the Duramax Diesel manual), as it has been a while since I've looked at the maintenance schedule. I noticed that under the normal service, there is no recommended interval and for the severe service schedule it states 45,000 miles. I normally just do all the recommended services at the severe intervals, but just haven't gotten to the trans yet. I am a technician for another brand, but work across the street from a Chevrolet dealer. I spoke with their "transmission guy", who is GM World Class Certified. He initially told me that 60,000 miles was the interval recommended for this transmission. I told him I could only find 45,000 miles in the maintenance schedule which he thought that was odd as its the same transmission as the Silverado/Sierra 1500's and their interval is 60k miles. I asked if there was access to or if the the torque converter has a drain at all, as the brand I work on, those vehicles do. He said they do not. The reason for doing the transmission flush is to clear the fluid out of the torque converter as well as the transmission cooling system. If you only drop the pan and change the filter, you're leaving about 1/3 of the fluid still in the system. I would agree, as the brand I work on, if the pan is dropped and filter changed, you get 6 quarts out. When draining the torque converter as well, there's another 3 to 3.5 quarts drained. I was hoping to find a more "official" normal condition scheduled mileage in this thread, but I'll just plan to be taking mine to the dealer soon to drop the pan/change the filter and perform a flush as the tech and I discussed. Sitting at 56k now, kinda wish I had done it at the 45k mark like I had initially planned, but just didn't get to it. For those commenting on the differential services, the '16 schedule doesn't state anything about the differentials, but the transfer case is 97,500 miles under normal conditions and 45,000 miles under severe conditions.
 

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I just looked into the owners manual this evening for my '16 (both the normal manual and the Duramax Diesel manual), as it has been a while since I've looked at the maintenance schedule. I noticed that under the normal service, there is no recommended interval and for the severe service schedule it states 45,000 miles. I normally just do all the recommended services at the severe intervals, but just haven't gotten to the trans yet. I am a technician for another brand, but work across the street from a Chevrolet dealer. I spoke with their "transmission guy", who is GM World Class Certified. He initially told me that 60,000 miles was the interval recommended for this transmission. I told him I could only find 45,000 miles in the maintenance schedule which he thought that was odd as its the same transmission as the Silverado/Sierra 1500's and their interval is 60k miles. I asked if there was access to or if the the torque converter has a drain at all, as the brand I work on, those vehicles do. He said they do not. The reason for doing the transmission flush is to clear the fluid out of the torque converter as well as the transmission cooling system. If you only drop the pan and change the filter, you're leaving about 1/3 of the fluid still in the system. I would agree, as the brand I work on, if the pan is dropped and filter changed, you get 6 quarts out. When draining the torque converter as well, there's another 3 to 3.5 quarts drained. I was hoping to find a more "official" normal condition scheduled mileage in this thread, but I'll just plan to be taking mine to the dealer soon to drop the pan/change the filter and perform a flush as the tech and I discussed. Sitting at 56k now, kinda wish I had done it at the 45k mark like I had initially planned, but just didn't get to it. For those commenting on the differential services, the '16 schedule doesn't state anything about the differentials, but the transfer case is 97,500 miles under normal conditions and 45,000 miles under severe conditions.
I did a pan drop and filter change at 45k. Also did the rear diff but just never got around to the front or the transfer case. I plan to do those here soon as I just ordered the stuff for them. I'm at 85k now. I will change the transmission fluid again at 90k or so. I haven't had any problems since I removed the old oil and added new, even though I only got 6 of 11 qts. or whatever "full" is out. I'm not sure if the receommended change is every 45k or the initial 45k and then again say...60-80k miles after that. I don't have a manual with me so I don't know.
 

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I changed the diff's and transfer case at 7,700 mi to clear any mfg debris and had an ASE shop flush the transmission. All replaced fluids were synthetics. I don't tow so I plan to sample the trans every 3-4 oil changes to better determine when a fluid change is in order. At that time, probably 75,000 mi, a flush and filter change will probably be indicated. I don't know about the diff's and transfer case, but maybe a change at 100,000 mi would be indicated.
 

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Just hit 43k on my 2016 Colorado diesel and looking to do my first trans fluid change. Has anyone done this yet? Is there a filter? Thoughts on having it flushed?
i drained( not flushed) my oil at first engine oil change(5,000) i will do it again at 30,000 figuring 25,000 for each trans change
 

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i drained( not flushed) my oil at first engine oil change(5,000) i will do it again at 30,000 figuring 25,000 for each trans change
i have been led to believe that there is not the usual transmission drain plugs in these twins. instead the shop knows how to do it but they were not designed to be changed by a do it yourselfer .i think they said not even a dip stick on them. i am close friends with a service manage at a gm store he said the best advice is to service the transmission regularly,and swap out the converter at 100,000 miles and it will save you an expensive trans overhaul one day. so i will probably do that when the time comes
 

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i have been led to believe that there is not the usual transmission drain plugs in these twins. instead the shop knows how to do it but they were not designed to be changed by a do it yourselfer .i think they said not even a dip stick on them. i am close friends with a service manage at a gm store he said the best advice is to service the transmission regularly,and swap out the converter at 100,000 miles and it will save you an expensive trans overhaul one day. so i will probably do that when the time comes
You are correct there is not a dipstick or a drain plug. It seems such a dumb thing that GM sells these trucks and lists all the towing information yet omits these two items. The best thing one could do if you're going to be towing is properly maintain the transmission oil. Because I purchased my truck to tow a travel trailer with, I ended up replacing the trans pan for a PML pan which adds about 2.5 quarts more oil in the sump, has a drain plug and I also added a Lokar dipstick.

With all the hygroscopic issues with the trans fluid and living in the humid state I live in this concerned me. Even a handful of 6L50 owners had converters changed out from slipping/chattering. When GM finally diagnosed that situation and resolved the 8 speed converter problems with a fluid swap to the Mobile LV blue label I followed suit. I change out the stock pan with the PML pan and while under there I changed the filter at 10K. I pulled the supply line from the cooler and dumped it into a 5 gallon white mud bucket and replace the fluid quart for quart. Once the new fluid made it's way through the converter and trans and finally reached the bucket you could easily see the change in color and transparency from old to new. The transmission up-shifts and down-shifts noticeably smother, to me this is just cheap insurance.

I also change out the oil in both diffs, the GM synthetic gear oil is dirt cheap. The factory rear diff oil had the consistency of mayonnaise (glad I changed it) the front looked pretty normal.
 
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