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18 6L80 Fluid Change


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Posted (edited)
45 minutes ago, Black02Silverado said:

75w-90 will be fine.  You got a good start on both trucks.

I used 80w90 in my rear differential because I had about 2.5 quarts lying around.  Got 75w90 for the front differential myself - I thought that is what it called for?  Actually, Amsoil calls for 75w90 and this was the reference I was using.  https://www.amsoil.com/lookup/auto-and-light-truck/2019/gmc-trucks/yukon/5-3l-8-cyl-engine-code-c-l83-c-flex/?volume=us-volume

 

80w90 is thicker but not substantially so.  Remember not all that long ago 80w90 was the recommended viscosity for average use and 75w140 was the recommended viscosity for towing!

Edited by BlaineBug
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11 hours ago, dieselfan1 said:

I'm in the process of getting all my fluids changed on both of my 18's.

I priced out Amsoil transmission fluid and by the time I buy the fluid and filter I'm over $150. I can have the dealer do it while I wait for $219. 

I'm going to have them do the Transmission fluid and filters on both trucks. I'll do the rest myself. I ordered the 75w90 gear lube for the diffs on Amazon.

The rear calls for 75w85 but I can't see the difference.  Anyone? Grumpy?

I'm putting a new rear differential cover on my lifted truck at the same time. 

I'll pickup a gallon of Delco dexron6 for the transfer cases at the dealer. 

So around $275 total for each truck.

 

BTW I also got some Mobil1 0w20 in the 5 qt jugs for $22.37 on Amazon too. 

Ac delco PF63E filters on eBay for around 4 bucks each.

For that I'll keep changing oil every 3000 miles

Your good. 75W90 is what I use too. That 75W85 stuff is another fuel saver. I never noticed a difference and the gears don't know what year diff it's in! :rolleyes: 

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12 hours ago, BlaineBug said:

I used 80w90 in my rear differential because I had about 2.5 quarts lying around.  Got 75w90 for the front differential myself - I thought that is what it called for?  Actually, Amsoil calls for 75w90 and this was the reference I was using.  https://www.amsoil.com/lookup/auto-and-light-truck/2019/gmc-trucks/yukon/5-3l-8-cyl-engine-code-c-l83-c-flex/?volume=us-volume

 

80w90 is thicker but not substantially so.  Remember not all that long ago 80w90 was the recommended viscosity for average use and 75w140 was the recommended viscosity for towing!

Yes, and some move up to the 75w-110 because they haul and tow a lot.  I didn't see the need to do so.  The Severe Gear 75w-90 served well in my 2002 with all the towing it did.

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  • 3 weeks later...

Well, back from my trip towing our camper for a total of about 11 hours through some pretty good hills in northern MI and a pretty stiff wind on the way back home (thank goodness for the new WDH with sway I put on)

 

the trip up to camp the trans got to 161 with ambient right around 70 degrees.

the trip home with more traffic, 85 degree outside and a stiff headwind it got up to 189 in town traffic with lights but went back down to 170s once I got moving.

 

Needless to say I am very pleased with the pill flip and changing the fluid.

 

 

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I did the pill flip today.

Dramatic difference in the the amount of time it takes to get warm.

I took a 25 mile drive mostly County roads 45 - 55 mph.

Sat at a couple stop lights that were backed up a bit 4-5 minutes each.

Outside temp was 92° when I pulled back in my driveway the fluid was 164°.

Same drive a couple days ago 96° outside  and my fluid hit 198°

Remember I'm rolling on 38s with 10.5" lift with stock 3.42 gears so I run it in tow haul a lot because it helps big time.

I just changed my fluid so this was a no Brainer

BTW mine was really easy. No clips to hold the lines in , just a bolt on a metal tab. Took me 20 minutes. 

16234511117416135004201990290820.jpg

Edited by dieselfan1
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When I did mine fluid temps on a day like today, mid 90 F, I could hit 225-230 F. Told it was a bad thermostat so I bought a new one. No different. Hum... Did the flip and BOOM!! 163 F when it's 100 F out motoring down the Interstate. It will go higher in town or construction/accident traffic. But cools right back down once moving again. 

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Alright ... I gotta ask, I've read a lot about "flipping the pill" but I have yet to read good instructions on how to do so.
Is there a vid or something? Really, I can do a body lift and a level kit but this kinda stuff is foreign to me.
Sorry ... O_o

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1 hour ago, MikeBMW said:

Alright ... I gotta ask, I've read a lot about "flipping the pill" but I have yet to read good instructions on how to do so.
Is there a vid or something? Really, I can do a body lift and a level kit but this kinda stuff is foreign to me.
Sorry ... O_o

I'll send ya a PM tomorrow. To late tonight. 

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Driving around town and some hwy yesterday Temps in the upper 80s . I went about 75 miles and my trans temp never went above 158°. 

I wish I would have done this day 1.

Anyone on the fence doing this mod should do it . It's easy and it really works. Save your trans.

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I towed my cargo trailer yesterday for around 100 miles. 6x12 6'6" inside height. It's lifted 4.5" also so it's around 8' tall , truck is around 90" tall.

It was full so around 3000 lbs total.

Outside temp was 70°. Trans never got above 170°.

More proof it works guys.

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So many people talk about flushing the trans fluid.

 

ever since I joined here, not one person has told me how this is possible. How do you flush the trans fluid when there is a thermostat that doesn’t open until 190 degrees?

 

i asked my dealer this, and they said they don’t do flushes. This is not some small town dealer either. The only thing they do to change trans fluid is drop the pan and change the filter and then refill it.

 

There are so many people, even in this thread, that mention the dealer “flushed” their trans. How the hell did they do this?

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57 minutes ago, truckguy82 said:

So many people talk about flushing the trans fluid.

 

ever since I joined here, not one person has told me how this is possible. How do you flush the trans fluid when there is a thermostat that doesn’t open until 190 degrees?

 

i asked my dealer this, and they said they don’t do flushes. This is not some small town dealer either. The only thing they do to change trans fluid is drop the pan and change the filter and then refill it.

 

There are so many people, even in this thread, that mention the dealer “flushed” their trans. How the hell did they do this?

 

With the pill flipped or block plugged this is straight forward. That said it would take a test block or thermostat removal I'd think unless there is a test port that can be tapped. Just thinking out loud. I put on a PML pan with a drain plug after the first filter change drop and fill. After that I drop 8 and refill with 8 about every 25K. 

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Posted (edited)
On 6/27/2021 at 7:44 PM, Grumpy Bear said:

 

With the pill flipped or block plugged this is straight forward. That said it would take a test block or thermostat removal I'd think unless there is a test port that can be tapped. Just thinking out loud. I put on a PML pan with a drain plug after the first filter change drop and fill. After that I drop 8 and refill with 8 about every 25K. 

Yeah and I seriously doubt the dealer is doing either of those things. I’ve been wondering this and asking this question for 5 years now lol.

Edited by truckguy82
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Posted (edited)

STL010_web.jpg

Has anyone tried this instead of flipping the thermostat? I know flipping the thermostat is free, but they are saying 40-45 deg. difference in temp. from OEM. If you live in a cold climate during winter and it gets to -10 plus would this do damage to the transmission due to lack of heat?  

Edited by 14LTZ-1LZ
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