How to Change Transfer Case Fluid in a Duramax or Full-Size GM Truck

[@mercy4u695]

Thank you Farm Dad for this excellent youtube video! Having not changed my T-Case fluid for quite awhile, and growing tired of blowing so much money at my local GM dealership, where you are never permitted to go near the work bays, and have to wait anxiously for hours in the contemplation room while they do their "magic" behind closed doors. Then you face a huge bill from a pretty female cashier, with a nice apologetic smile, by the way. Their quote was originally over $900. to service my front/back differentials, T-Case, engine oil, and filter on my 6.6 LMM and Allison 100 6 speed trans! This years ago when all fluids were cheaper, so I took on all these jobs myself routinely and regularly. However have never tackled the T-Case fluid. Due to issues many other posters have noted about the upper fill plug's inherent soft aluminum/magnesium casting, limited clearance and tendency to easily round off, I purchased a full set of chrome crowfoot metric wrench heads incl. the 18 ml rachet crow. Unfortunately when I attempted to do what I anticipated was going to be an easy chore this AM, all attempts failed. The normal 18 ml socket head would not fit behind the cross-member, with or without rachet handle. A large open ended wrench did not have enough leverage, my extended length torque wrench was so long and hit the concrete floor. Finally the 18 ml. crowfoot. Sadly the head of the fill plug is just too soft to get even the crow to take a proper torque or bite on. After saying a few Hailmary prayers I finally came across this video. As instructed, with one exception, I gently opened the sensor plug (19 ml) with deep socket. It was barely torqued down and is a tough, plastic plug on top of T-Case housing. So simple! Next I easily removed the 18 ml. drain plug on the base of the T-Case, with factory installed thread sealer on the bolt. Fearing the worst as my truck is at approx. 75,000 miles, with no clear Hx of the T-Case being done, and my 4 low button recently not engaging 4 X4 low. But thankfully all still quiet. I anxiously watched fairly dark, dirty blue Delco fluid drain, but the magnet was not as bad as others I have seen on line forums. From there I refilled with a small funnel with 2.6 litre bottles of TranSynd TES-295 ATF, through the speed sensor hole. Not only does my 4 wheel drive system once again shift easily into 4 low, the whole system is incredibly smooth and responsive. I wish I had found this video sooner, and suspect the dealership uses the same refill method, behind closed doors, charging approximately $300. for the favor. Relief, and thanks again Farm Dad!

[@FarmDad]

You are correct about so much, including the way it is at a dealer and the fact that many gm techs use this method. Best to you!

[@vincerobertson1214]

Do you comply with the advice of adding 1/2 quart extra a.t.f. above recommended fill level also? Sounds like sound advice, I will be doing this on my Allison soon

[@tomkarch9782]

Great video! I just changed the transmission fluid with TES295 spec fluid recommended by Allison. I will also use the same fluid in the transfer case. The reason being is that if the seal between the t-case and transmission fails you will not have motor oil leaking into the transmission and causing big problems. The TES295 has additives that standard ATF doesn't have.

[@jrm163]

Good point!

[@alkalk8938]

A failed seal will not lead to the t-case fluid finding it's way into the transmission, it just cant happen that way for several reasons. If heard this myth several times but the likelyhood of it happening is the same as the likelyhood of transmission fluid getting into the engine if the front seal goes out on the transmission...it just doesn't work that way.

[@therealkilleryo56ss]

This is correct and not to mention he is doing this on a older truck, much more forgiving and newer transfer cases are very sensitive compared to older models. Our new Silverado has power train warranty thru dealership for extended intervals past manufacturers! They perform the services and if the transfer case goes boom they have to replace it!

[@free2chasehappy]

Never thought to fill it through the speed sensor hole, this is so smart! Thank you!

[@FarmDad]

I appreciate you

[@stickybudsgardens6942]

Thanks man, already been doing this for years but the 18short and 19deep mm socket size reminder was perfect!

[@FarmDad]

Glad to save you a little time.

[@NDRN88]

Excellent advice, good history/sources, clear, good video, probably my favorite bit I've seen regarding maintenance on a truck. My only criticism is there was no torque specifications mentioned. Last time I torqued down a magnesium transfer case it split and had to be pulled and welded. Thank you!

[@FarmDad]

Good point. Sorry I missed that.

[@vincerobertson1214]

Wow, ugh! Makes me just want to only snug and not torque when replacing drain plug on my t-cases now. Sorry that happened

[@ryanhailey3715]

Thank you for your video sir I ran into a stripped fill plug and was worried I had screwed up by not checking it first haha but this video saved the day man so thanks again!!

[@FarmDad]

Glad this helped you out!

[@Glockito]

Thank you for making it short, simple, and straight forward and also not making it confusing thank you!

[@FarmDad]

That's my goal! Glad to hear it!

[@clydeespinosa6286]

Thanks I added the fluid I went with valvoline syn dex VI. Next time I may use mobile 1 5w30 A previous service shop stripped my fill plug it is permanent on now.

[@brendanhayes2752]

Thanks, my dealer wants 233 to do this! Great video and recommendation.

[@FarmDad]

Glad to help. That's actually not too bad for a dealer price. I've seen worse!

[@Striker50_]

They'll milk you for all you got for these $30 services

[@henryharrison3988]

my 2006 LBZ transfer case calls for Dexron 3 ATF. I can easily add 2.5 quarts with fill factory fill hole

[@johnarnold893]

I'd like to know where the evaporated atf goes to since the transfer case is sealed. I suspect it is more than likely leaking past a seal somewhere.

[@jshock70]

Thank you for the tutorial. I followed your directions but now I am getting a range shift inhibited and abs codes. Also not shifting properly and speedo is not working. Any idea what it could be? I didnt have any issues prior and I cleaned the plug with electrical cleaner thinking maybe that was the issue. Any advise would be appreciated. I'm sure it's something I did but the procedure was so simple I'm not sure what it could be. Thanks

[@FarmDad]

I'd suspect that speed sensor. It could have sent your trans into limp mode if it's not working.

[@jshock70]

@@FarmDad Found the problem. The o-ring got pinched in the threads and stopped the sensor before it was seated all the way. Thanks again!

[@FarmDad]

Glad you figured it out!

[@rigneyte]

Good vid, no fluff, thanks.

[@FarmDad]

Thanks buddy!

[@clydeespinosa6286]

Thanks for this my LMM transfer case fill bold is stuck on. I guess the last shop over tightened or stripped it. This might be the only way now to service. How often do you drain and fill

[@FarmDad]

Every 50k miles is what I aim for.

[@robstanley5083]

I don't think there's an issue with evaporation with the engine oil. Just the ATF. I use the Mobil 1 like you, but just fill it to OEM spec. Have you had any issue with evap. of Mobil 1?? Thanks.

[@FarmDad]

No sir, I have not. You should be good.

[@georgemartinez9414]

Great video, great instructions, great advice, great technician,

[@FarmDad]

Thanks, made my day.

[@deerhunter5305]

Guess AutoTrak 2 doesn't evaporate. I always open the fill port first and fluid always starts coming out.

[@EthanToys218]

Wonderful Tutorial How to Change Transfer Case Fluid, Great Learning video. Thank you so much for sharing, my Friend...2👍😘💞

[@MrAllister9]

if atf evaporates but your using 5 30 instead ... why are you adding the extra half a quart?

[@FarmDad]

Double the insurance. You can choose just to do one or the other.

[@MrAllister9]

@@FarmDad ok and just a question does the 5 30 being thicker cause any type of extra lag in the transfer case? im actually wanting to change my own fluid thats why im asking questions like this ... sorry

[@FarmDad]

@@MrAllister9 no lag. And I don't mind your questions! Keep wrenching!

[@Toolaholic7]

Kodiak Truck whom does reman those transfer cases use the 5w30 synthetic engine oil in their reman transfer cases,has a sticker on them saying it

[@FarmDad]

Good to know

[@robcurley4415]

Is it ok to run Castrol Transynd 668 in my t case? 19 L5P

[@tinaspanke965]

When we ordered our transfer case, they told us to put 5W-30 motor oil in it synthetic and why don’t he just popped that rubber plug out on the top of the transfer case and just poured in there it pump shit he’s got

[@beowulf885]

if i use 5w-30 instead of transmission fluid, will the slip yoke clunk go away????

[@FarmDad]

I wouldn't count on it.

[@beowulf885]

@Farm Dad well I already greased it, hopefully after the grease wears away the motor oil will be more slippery than ATF

[@OrionsKelt]

Many overfill by 1 quart. Good video.

[@FarmDad]

Thank you!

[@chrisnielsen3562]

What’s the best fluid for a 2006 261 LD manual transfer case ? So many wrongs and rights here 😂

[@Ghost-xi6js]

Why not just park on a downhill slope or jack the rear of the truck up and then add 2.5 quarts through the fill port?

[@danieljones8587]

Good comment. I've been tilting cars & trucks to fill the transfer case and rear differentials for years.

[@jeffscott3160]

ATF is fine for the manual transfer case, but not if you have the auto transfer case. GM specific fluid, autotrak II, should be used for that gear box.

[@jimclifford1241]

This is true and so very important.

[@Toolaholic7]

No it is not,ATF foams up which the chain aerates the fluid.Kodiak Truck's reman transfer cases use the 5w30 synthetic engine oil

[@rocketsurgeon1746]

Great video. Thanks

[@FarmDad]

Welcome!

[@twogunsforme1]

Just jack your vehicle to the side and then fill the transfer case and you will for sure get a little more in than what you would normally get in through the fill port alone.

[@kfelix2934]

I have rhino ramps so if you back on them and get the rear end a little higher you can get more ATF/oil in the transfer box

[@throttle_down_beers_up]

Motor oil doesn’t go in the transfer case suppose to use auto trak 2 fluid.

[@FarmDad]

Go buy a rebuilt transfer case and you'll see that it'll recommend 5w30.

[@lelenbates3367]

I am going to give this a go and give the sensor blast of brake cleaner before I remove it to clear the dirt.

[@FarmDad]

Good plan 👍

[@tankhorton70]

Any leaks from adding three quarts over two?

[@FarmDad]

No sir.

[@jrm163]

How do you think of Tom Larch’s comments below please? Thanks!

[@FarmDad]

I don't know much about the properties of TES 295, but seal failure is a valid risk.

[@jrm163]

@@FarmDad I was thinking of using 5w-30 for TC, but considering of the failure of the seal in between TC and Transmission, using the same fluid (for TC) as Transmission makes more sense! Thank you for your information though!

[@FarmDad]

@@jrm163 welcome. I would overfill for sure though.

[@jrm163]

@@FarmDad But you mentioned somewhere below that ATF would create foam (while 5W-30 wouldn’t).

[@FarmDad]

@@jrm163 atf is what is normally in transfer case. I have had good results substituting 5w30, but if concerned about seal failure, ATF is a safe choice.

[@seymourbutz6951]

Supposed to use auto trak 2 in the duramax tcase

[@bnorby213]

False only half tons with auto 4wd

[@220kingo]

Is Mobil 5-30 better than ATF oil?

[@jimclifford1241]

No, it is not

[@cdsmit27]

Yes it is. I just bought a t-case from kodiak truck and that's what Mark recommends. He's built thousands of these with no issues. I'd believe him over anyone.

[@MultiNachito123]

Good video bud!

[@FarmDad]

Thanks!

[@GrnXnham]

OR you could just use the fill port, put in the correct amount, and then ACTUALLY check your level occasionally. Every 30K is recommended in my manual.

[@FarmDad]

True, problem is hardly anyone ever checks it.

[@mikef6706]

I still do NOT understand how using the fill port it will NOT be filled properly?

[@FarmDad]

It ends up being underfilled and if fluid evaporates you end up killing your transfer case.

[@greasemonkeybd]

would 5-20 be ok? because I have a gallon of that

[@FarmDad]

I think it would be a little too thin when hot and would stick to 5w30 if overfilling.

[@greasemonkeybd]

@@FarmDad thanks

[@lilgerber875]

What about 10-30w full synthetic?

[@liampoirier]

I’m looking for the pump you used for this

[@FarmDad]

Here you go: amzn.to/33R6NmT

[@liampoirier]

Thanks for the quick reply apreciate it!

[@RobPGamerVaper]

Ahhhhh I think this is why when I checked mine today it gushed out of the fill/check it must have been over filled this way

[@FarmDad]

Better than opening one that's almost empty, right!

[@ramonatrujillo155]

Is this the same for a 1999 Chevy Tahoe 5.7

[@FarmDad]

That uses a different transfer case.

[@twogunsforme1]

Of you overfill that transfer case you can cause cavitation which is not good for the gears adhere to the recommendation of the professionals who designed the vehicle components they know what’s best

[@FarmDad]

This is why you switch to 5w30 rather than Atf, which foams when overfilled. This is the new recommendation of professionals.

[@ronaldbabbitt6318]

2009 6.6 ok?

[@raulrodriguez7655]

What is if awd

[@FarmDad]

That uses a different transfer case.

[@ronaldbabbitt6318]

2009 2500 hd Duramax T Case OK?

[@FarmDad]

Should be the same t-case with only a few revisions and different electrical connectors. May still suffer from these issues, but I suggest you research it more.

[@shane462]

this guy put motor oil in his transfer case...

[@sagesalem6174]

It burns off atf in those transfer cases, and you can only add 2 quarts without it foaming

[@cody6.6max]

Damn right we do

[@xvii5799]

Hhmmmm spec is 1.6 quarts

[@randylee2549]

do not overfill! correct!

[@gueroburban4989]

Book says 1.6 auto trak 2 fluid and dexron 6 for awd transfer cases! You are correct

[@randylee2549]

@@gueroburban4989 yup

[@BryceAWD]

Overfilling causes fluid foaming, and a lubricant with air bubbles provides poor lubrication. More fluid is not better.

[@FarmDad]

Well, 5w30 is a lot less likely to foam than atf, plus there's still a lot of room in this t-case. I've been running mine for years like this and have seen no evidence of foaming.

[@tyler1671]

My built t case with oil exploded in 2kmiles. My next one run the stuff it calls for no issue 50k later

[@FarmDad]

Most replacement t-cases call for 5w30. I will almost guarantee you that your original failed due to pump rub, not oil.

[@tyler1671]

@FarmDad wel.i can promise it didnt... it was BUILT (few better internal materials etc) no pump rub with a pump rub kit

[@cody6.6max]

@@tyler1671oil didn’t cause that man

[@cody6.6max]

Mines been built five years Kodiak truck says 5w30 on the case and the man hisself tells u on truck master KZbin channel

[@tyler1671]

@cody6.6max anyone who's posted videos related to tuning egr stuff etc is a absolute fuclkng tool bag... why's everyone geting million dollar fines no one will tune efi for turning stuff on off up down etc but let's to have s*** tuning, it does nothing but blow a bunch of black smoke. Or you know?Let's just blow it in traffic.You know, right next to an eighty year old woman that has her husband in the passenger seat.That's ninety years old and has emphysema, and can't breathe, and there we go doing that.And let's just keep on being a******* .. at the end of the day everyone keep doing what you doing but stock the fuck up on parts the epa can fine us all

[@inthegarage8944]

Over filling it causes foaming which actually does harm it 🫠