2008 Denali Transmission Fluid and Filter Change

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Mr T

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Folks:

Took my Yukon Denali to my bro's shop for a DIY transmission fluid and filter change, as well as changing oil in both axles.

I suppose I could do a detailed write-up, although I doubt many would find that very effective.

I do, however, think a few of my lessons learned might be reasonable to share with members of this good board.

1) Note there is no drain plug on the 6L80, so draining and removing the pan WILL BE messy. I managed to splash a significant amount on my head and ht shoulder. At least transmission fluid it doesn't have the vomit-inducing odor that axle grease does.

2) To get the pan out, I needed a cheater bar to slightly lower the left side exhaust pipe 1/2 inch. This facilitated a side rotation of the pan and then it came out with some soft movements back and forth. It does NOT come off easy; don't damage your transmission using force.

3) My gasket has 50K miles and 3 years on it. It was in excellent condition and did NOT need replacing. The OEM gasket is of very high quality.

4) Now that it is out, clean it up dinner-plate clean. I used a solvent to clean it out and then used a degreaser after that. I of course rinsed it a great deal to ensure all that was left was just the pan. While cleaning it, make sure you clean both the pan and tranny surfaces (mounting edges) before you put your cleaned, used gasket, back in place. Some may suggest to always replace this gasket; however, like I said mine only had 50K and was in excellent condition. It didn't leak an ounce.

5) Removing the filter takes a constant down pressure and a side-to-side rocking motion. If the existing filter gasket isn't damaged, I didn't see a logical reason to replace it. I was able to literally "snap" the new filter into the old gasket with a sharp snap sound.

6) When putting the tranny pan mounting screws back in place, don't forget to tighten them in a rotating pattern (going back and forth across the tranny). This helps avoid binding or smashing the gasket too much on any one side. Do all of them by hand first and only tighten by hand till step 7.

7) Make sure you have a torque ratchet to reduce the risk of stripping your transmission's soft aluminum. I read somewhere that 8lb/feet is what the Chevy Sierra's transmission required. I'd like someone--if they have such documents--to confirm what the torque setting should be for the 6L80 transmission that is on the Denali (6.2L). Again, I used 8 which isn't very much force. So I tried to be soft.

8) A full change took 6 quarts; you must use Synthetic Dextron VI. Once you've put at least 5, use the warm/hot instructions to closely monitor how much you are adding. Keep in mind if you over fill, without a drain plug, removing any will be very difficult. Thus, take your time and don't automatically assume you'll need 6 quarts, since your tranny might not have drained out as much. It all depends on how long you leave the pan off. They continue to drip for quite a while.

I hope this helped a bit and I'd love someone to tell me if they have a manual, or similar, that says what the "real" torque setting should be on the mounting bolts.
 

Zed 71

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For others, keep in mind that changing the transmission fluid by dropping the pan, only 60% of the fluid is changed. Around 4 or more quarts are still left in the transmission, lines, and cooler (as applicable).

Hmm, actually 8 ft-lb of torque (96 in-lb) is quite a bit (just from memory) for those aluminum bolts. For my sports coupe it was 35 in-lb (~3 ft-lb) for the aluminum parts. I will confirm when I get home although I have torque specs for the 4L60E.
 
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Zed 71

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Per Chilton guide:

4L60E transmission fluid pan bolts 97 in-lbs (8.08 ft-lbs).
6L80 is 80 in-lbs (6.66 ft-lbs)

Are you sure you have the6L80? I thought those came out in 2009.
 
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Mr T

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Zed:

How would I confirm which I have?

Per wiki:

http://en.wikipedia.org/wiki/GM_6L80_transmission

But wiki has been wrong before and will continue to have issues :)

---------- Post added at 11:46 AM ---------- Previous post was at 11:42 AM ----------

Wait, I don't know why I'm asking. I'm sure I have the 6L80. When I go into Manual mode I get 6 speeds, not 4.
 

Zed 71

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^ yep if you have the manual mode then you have the 6-speed. Brain fart on my part, the Denalis had the 6 speed before the Tahoes.
 

2007tahoe

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3) My gasket has 50K miles and 3 years on it. It was in excellent condition and did NOT need replacing. The OEM gasket is of very high quality.

Thats funny b/c I use alldatadiy most of the time and it stated that the 4l60e trans pan gasket and rearend cover gasket are reusable on my 07. Yea that was not the case. Both of the gaskets were paper gaskets and not rubber. They tore into about 20 pieces.
 

JPB07Denali

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Mr.T
Thanks for the write up.
I made a vacuum tank out of 6 inch PVC drain pipe to collect the tranny fluid. I use my shop vac for the vacuum source. (It has about 48 inches of lift)
I Inserted a 1/4 inch ID rigid PVC tubing into the fill tube and I suck the fluid into the vacuum tank. That part works well. 6 quarts came out - clean and easy. Takes about 20 minutes with warm tranny fluid.
Now - I am struggling to remove my pan from under the vehicle now that it is all unbolted.
You did something to the left exhaust pipe.
What do you call a cheater bar ? Do you deflect or dent the exhaust pipe itself ? Can you please explain that part a bit more?
I am contemplateing unbolting the rear tranny bolts on the rear rubber mount and raise the whole tranny up to get some clearance. Has anyone tried this?
Any further advise will be appreciated.
Thanks
 

dcorcino

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I was doing this by myself on the ground so a cheater bar was not useful to remove the pan. So what I did was loosen (not remove) my exhaust bolts from the cat back, used a large C clamp and I slowly and carefully clamped down on the exhaust and lower cross member just before the connection point. This will lower the exhaust enough to remove and reinstall the pan quite easily by yourself. Having the use of both hands is nice as well.
 

Toster

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The 6L80 with the Y pipe.... OMG what a PITA! I never did get it!! I spent several HOURS prying and trying. Finally I said F'it and I got the filter out the new one in and buttoned it back up. (yes with the old gasket) I know the pan did not get clean but by this point I was willing to accept 85% as good enough.

Just a couple of notes: unbolting the trany at the cross brase and jacking it up DOES NOT HELP (don't waste your time!). After I thought about it it made sense why it doesn't increase the gap in-between the trans pan and Y pipe. The manifold is bolted to the block, Y pipe to manifold (duh) but when jacking up the trans you're really tilting the engine forward and so the space does not increase. I tried loosing the Y to manifold bolts.. lol.. I stopped in fear of breaking them off.

This is a very good thread I find on this topic: http://www.gmfullsize.com/threads/how-to-4l60e-transmission-flush-filter-change.179148/
There was some confusion on the thread which brass adapter to use. The Hayden 397, works great. When I first unscrewed the aluminium fitting I like many others on the thread, I was greeted with antifreeze fluid!! YIES!! Don't Unscrew the fitting from the radiator. Use the Hayden 397 mentioned on page 8. It will fit right in to the quick connector and Trans fluid will be easily pumped out in to a bucket. I removed my Cold air box, and had plenty of room to get to the line on the top passenger side.

I ended up using just shy of 15 qts of fluid. I pumped out all fluid that the truck could, (~5qts) then I used a small hand pump from Harbor Freight to empty the remaining fluid in the pan after trying and trying to get it out. (~2+qts) I only did this after dumping some on me of course! Then after fighting and fighting to get the pan out I was able to just get the filter out and new one in. I put it all back together and added 5 qts, and started the truck, it pumped out the dirty fluid. I added 5 more and it kept pumping out dirty fluid. I might have ran it just a little long after it turned "clean". I added 4 qts, checked it and then started it and let it get up to temp. It showed low, so added about another .5 qts.

What should have been a very easy thing Chevy made a huge pain


2011 Tahoe Z-71 with trans cooler
 

mattluttrell

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FYI, it takes about 15 minutes to change the fluid on the 6L80e if you make an adapter hose and come in by the breather. Here is my how to video


Sent from my SM-G920T using Tapatalk
 

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