6l80/90 Filter/Fluid change

[16LT4]

I'm sure there's a few threads around, but here's my experience.

 

My '16 (purchased 2 weeks ago, has 73k on the original fluid, which was quite brown.  They run the trans very hot in these things and the fluid just cooks.  I refuse flushes as they usually do more harm than good, but in a case like this with such high mileage on original fluid, I like to do a drain/fill every few hundred miles until the fluid comes out red.  Unfortunately, as many of you know, the exhaust routing and lack of drain plug turns a simple drain/fill into an exercise in creative rigging.  I'll do a filter every 30-50k depending on use, but I'm not dealing with dropping the pan for drain/fills.  So, I purchased a new pan and put in a drain plug.  I got a new pan because I didn't want to destroy the original and possibly be left without a pan.  As you see, I used a jack under the tailshaft of the transfer case, and a ratchet strap from the exhaust under a block of wood with a bottle jack on the cross member to anchor the block.  When taking off the pan bolts, I loosened the front, removed the sides, removed all but 1 of the rear, and then slowly loosened that last one on the rear.  The pan drained nicely into a catch container this way, and I didn't have to wear any ATF, nor did any make it to the many cardboards I'd spread under the truck (other than splatter/splash from the drain pan).

 

I picked up an M12x1.75 GM drain plug with gasket from the local parts store, and also a nut of the same pitch.  I put it in the vice and "castlated" it with a cut-off wheel, making sure to cut from the inside out to not burr the threads.  I then eyeballed a spot for the drain plug, and chose a spot just forward of the magnet.  (This proved to be a bad spot as the drain plug contacted the filter and wouldn't let the pan seat, so I ended up having to cut the drain plug down 3-4 threads from the end and then clean the threads with a file so it still threaded easily.  It took a few test fits until I was satisfied I'd cut enough off to not interfere with the filter.)  The drain plug measured ~0.46" so I used a step drill bit and drilled out to 0.5", inserted the drain plug (with the rubber gasket removed so I wouldn't melt it) into the hole, and threaded the castle nut (castle to pan) down tight by hand.  This is why I castled it, so that a half-pint or so wouldn't remain in the pan when draining it, as the fluid will flow through the notches.  Quick tacked it with the MIG with the heat turned way up to get  quick, but penetrated, weld on 2 opposite angles of the hex (so as to not fill in the notches), removed the drain bolt, and then sent it with the MIG on the other 4 angles.  I then cleaned up the weld splatter with a sanding wheel, ground off the heat bubbles on the opposite side of the pan, and done.  Reused the original gasket, torqued the bolts to 89 in-lbs in clockwise circular fashion starting from the middle and working out (after snugging with my speed driver) and filled.  I used up the rest of my Dex 6 ATF on the shelf (I've still got a useless quart of Mercon V.... grrrr... hisssss.....), so 2 quarts of Redline D6 (leftover from my X3's last fluid change), 4 quarts of Castrol Dex 6 (from both the X3 and the Olds) and a pint of Autozone Dex 6 went in (found under the hood of the Olds from years ago when the TC was leaking from a cracked neck, to avoid another trip to the parts store).  I plan on draining the fluid again on my next oil change (at 4k on this oil, 4k on the next, to get me to my preferred 5k OCI at 80k, then at 85k, etc), at which time I'll use all Castrold Dex6 with a bottle of Lubeguard Red (I love the stuff for older, especially high-heat and poorly maintained, transmissions, and I consider 70k on ATF poorly maintained).  I put a bottle in the original trans of my 442 a few years ago when I replaced the TC and all seals and installed a cooler, and that trans is flawless despite over 30 years of abuse.  

 

Hopefully at least one person finds use of this thread.  Total time took about 2.5 hours due to the metal working, but future drain/fills will go even quicker than an oil change.

[16LT4]

The truck didn't have any of the common late model GM trans issues and I thought it drove fine, but it definitely drives and shifts even smoother now.  It's on par with the 6L45 in the X and even smoother than the 2004-r in the Olds.

[Black02Silverado]

Nice.

I was considering doing the same thing.  Only that I have a friend that can Tig weld the nut in place.  GM some times just doesn't make sense to remove the drain plug but then they want you to take it to them to have the service done. 

[16LT4]

15 minutes ago, Black02Silverado said:

Nice.

I was considering doing the same thing.  Only that I have a friend that can Tig weld the nut in place.  GM some times just doesn't make sense to remove the drain plug but then they want you to take it to them to have the service done. 

Agreed.  I will say, though, the number of transmissions I've worked on that didn't have drain plugs outnumber those that do  probably 4-1.  My X3 has basically the Colorado's transmission in it, and that does have a drain plug, so GM just wanted to give us Silverado owners the finger (between no drain AND the exhaust).

 

I would definitely recommend notching the nut, unless you can find an M12x1.75 castle.  I couldn't.

 

I will say that the magnet was quite clean, just a slight film of break-in clutch particulate.  The magnet in my F150 when I first drained the fluid at 142k (I bought it at 140k) was a literal mountain, I couldn't even make out the shape or size of the magnet.

[Grumpy Bear]

While I installed a PLM pan with a drain the result and reasons were the same. My first fluid change was over $200. Now it cost me the price of the fluid and a twenty dollar bill. Same as my oil change. I like this modification. Well done! 

[16LT4]

8 hours ago, Grumpy Bear said:

While I installed a PLM pan with a drain the result and reasons were the same. My first fluid change was over $200. Now it cost me the price of the fluid and a twenty dollar bill. Same as my oil change. I like this modification. Well done! 

What is this PLM pan of which you speak, I suspect one with a built-in drain plug?  I friend mentioned some aftermarket pan with a deeper sump and cooling fins, is this it?

 

On my F150, one pan drop was enough and I was able to source an aftermarket pan with a drain plug.  I would have prefered to go that route with this one, as I had to buy a pan anyway (didn't want to drill the hole in a wrong spot, which I nearly did anyway, and be left without truck for a few days), but couldn't find one from me [albeit brief] search.  They also make a drain plug kit that just requires punching a hole in the pan, but I didn't go that route because it would leave 1/4-3/8" fluid in the pan (with of the inner retaining nut).  I wish I'd done this to the Olds when I had the trans out a few years ago.  

[aero10]

That's a lot of work compared to getting essentially the same effect out of a pump like this:

https://www.amazon.com/YaeTek-Excellent-Extractor-Scavenge-Transfer/dp/B01MZAE56R/ref=mp_s_a_1_3?keywords=12v+oil+pump&qid=1560177274&s=gateway&sr=8-3

 

Is there a reason you went with adding a drain plug versus just pumping the fluid out?

[diyer2]

I understand the process of draining fluid as compared  to pumping out or sucking out fluid.

I would never do this to my motor oil.

A trans is different to me.

Yes, drain and fill should be better.

But I have never seen a trans filter that was plugged up unless the trans was already shot .

The y pipe is a pain to deal with.

I use this, works great. https://www.amazon.com/gp/product/B0002AJR8E/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

Do the pan drop and filter at 40 - 50 K miles.

Then suck out 6 quarts every 15 K miles and replace with new fluid.

Drop pan and filter at 100 K miles.

My 2 cents.

 

[16LT4]

32 minutes ago, aero10 said:

That's a lot of work compared to getting essentially the same effect out of a pump like this:

https://www.amazon.com/YaeTek-Excellent-Extractor-Scavenge-Transfer/dp/B01MZAE56R/ref=mp_s_a_1_3?keywords=12v+oil+pump&qid=1560177274&s=gateway&sr=8-3

 

Is there a reason you went with adding a drain plug versus just pumping the fluid out?

1) I've never found pumps to be as great an extraction as a full gravity drain, especially when pouring an additional cup of ATF down to further move out particulate (if any).  Now that the job is done, a gravity drain is far easier and less messy than dealing with a pump and hoses.

 

2) I had to drop the pan anyway to swap filters, and was in the mood for a fun project.

 

3) If I didn't want to get a second pan, the job would have cost me under $10 in materials.

[aero10]

23 minutes ago, dukedkt442 said:

1) I've never found pumps to be as great an extraction as a full gravity drain, especially when pouring an additional cup of ATF down to further move out particulate (if any).  Now that the job is done, a gravity drain is far easier and less messy than dealing with a pump and hoses.

 

2) I had to drop the pan anyway to swap filters, and was in the mood for a fun project.

 

3) If I didn't want to get a second pan, the job would have cost me under $10 in materials.

Fair enough. I hadn't thought about trying to rinse out the last bit of particulate.

[dbunke]

I just did the same thing with my 2015 2500hd 6L90 trans.

 

With the 2500 you don't have to worry about the exhaust pipe though. I welded a bung to the out side of the pan and used a short drain plug so it does not protrude into the pan at all.

 

I also used a new GM pan bought at Rock Auto for $13.....   I will now change fluid every year.....

 

Another bonus of the 2500 is there is no Trans cooler thermostat. Even in summer temps pulling a 10,000 lb trailer I have never seen over 180 degree fluid. Mostly 150 - 160 out on the highway.  At 40,000 miles my fluid was still red and smelled ok.