GM Transfer Case Fluid Loss

[bsmith0404]

Read about a problem with fluid loss on GM transfer cases on the duramax forum. Quite a few having problems with low fluid levels in the transfer case. A couple different theories on the cause, most feel it's the Dexron VI fluid evaporating/burning off. A few people have experimented with other types of fluid/oil with good success. I'm not going to advocate those here as they are not recommended by GM.

I'll admit that the transfer case is one of the few neglected areas when I do my maintenance, I guess it's seldom used, out of sight, out of mind. Well today I finally crawled up underneath and checked it out. Low and behold, I was 3/4 quart low...that wouldn't sound too bad if it wasn't for the fact that total capacity is only 1.5 quarts. I toped it off and have now added it to my list of things to check at every oil change.

Some believe this is related to the problem of the internal shaft wearing a hole in the case as well.

[Desert185]

1.5 qt capacity! That's all?

Duntov and Earl are rolling over in their graves.

[bsmith0404]

yep, I was surprised too.

[rnkburg]

Are you talking about the pump rub where it rubs a whole in case and leaks it out or is this a new issue on the newer trucks


Sent from my iPhone using Tapatalk

[bsmith0404]

Originally Posted by rnkburg

Are you talking about the pump rub where it rubs a whole in case and leaks it out or is this a new issue on the newer trucks


Sent from my iPhone using Tapatalk

Based on what I read, it sounds like a similar rub. Not sure if it's the same as the older GM transfer case had or different to the newer ones. The people who had the problem just said the lack of lubrication on the shaft wore a hole in the case. I know the old cases had a mod kit you could do, but I thought GM had fixed that issue.

[T3/T4 Hybrid]

Can you go up to a high quality of Synthetic which could have a higher boiling point so evaporation is less likely to happen? You could also look at an external cooler for the transfer case also.

[bsmith0404]

Originally Posted by T3/T4 Hybrid

Can you go up to a high quality of Synthetic which could have a higher boiling point so evaporation is less likely to happen? You could also look at an external cooler for the transfer case also.

I added synthetic to mine this time. I'm going to do a complete change in 20k miles, just checking to see if the synthetic makes a difference. Obviously with some standard fluid still in the case I will see some loss, but it should be reduced with the synthetic. I will continue to monitor and see how it goes. One thing I'm still researching and trying to understand is the use of Transynd. The Allison also uses Dexron VI fluid, and Transynd is the best known (based on test done by Allison) fluid for the Allison, yet I read you should NOT use Transynd in the transfer case. Not sure what the deal is with that. As for an external cooler, for me anyway, it's too easy to just pull the lug and add a few ounces, no need for the expense of a cooler.

[T3/T4 Hybrid]

Originally Posted by bsmith0404

I added synthetic to mine this time. I'm going to do a complete change in 20k miles, just checking to see if the synthetic makes a difference. Obviously with some standard fluid still in the case I will see some loss, but it should be reduced with the synthetic. I will continue to monitor and see how it goes. One thing I'm still researching and trying to understand is the use of Transynd. The Allison also uses Dexron VI fluid, and Transynd is the best known (based on test done by Allison) fluid for the Allison, yet I read you should NOT use Transynd in the transfer case. Not sure what the deal is with that. As for an external cooler, for me anyway, it's too easy to just pull the lug and add a few ounces, no need for the expense of a cooler.

I don't blame you for not wanting the added expense of the cooler. But I would check the fluid level in that transfer case religiously! Plus with it only having a 1.5 qt capacity I would change it all out to full synthetic for the added insurance.

[christopherglenn]

External coolers rely on pressurized oil, I don't know if that is available in the Tcase..

[T3/T4 Hybrid]

Originally Posted by christopherglenn

External coolers rely on pressurized oil, I don't know if that is available in the Tcase..

You have to add a pump to the system for it to work. The pump can be run with a temp activation switch or with a manual switch in the cab of the TV.

[{tpc}]

Are we discussing diesel fuel type vehicles that may be different from regular gasoline ones? I'm just confused because in my GM, the transfer case fluid is different from the transmission fluid which I know is dexron VI. But maybe there is a "dexron VI" branded fluid for the transfer case as well?

[bsmith0404]

The transfer case is the same in the diesel and gas trucks. Yours is a bit older and used different fluid. Not sure which year GM started using Dex VI in the transfer case. The evaporation problem seems to be more associated with the Dex VI fluids, but I can't say for sure if that is the only ones with the issue.

[Quad]

Lots of people including myself that are on the diesel place and other diesel forums have gone away from DEX III and VI. In its place I have went to a good 5w30 synthetic oil in transfer cases. I use Mobil myself. Some over fill by one qt also, I however don't. The manufacturer of the transfer cases released a story write up a few years ago stating to use motor oil and not ATF. However for warranty purposes if your truck is new, you have to use what the vehicle manufacturer states to use in order to claim warranty.


Sent from my iPhone using Tapatalk

[Quad]

Using Motor oil will also solve your problem of evaporation of ATF.


Sent from my iPhone using Tapatalk

[bsmith0404]

The 5W30 cure was what I was referring to in the original post that I decided not to post details on since I didn't want to start a debate about if this was a good idea or not. My post was more a heads up to make people aware and let them do their own research. But, since it's been brought up now, I have considered making the change, but since I'm still under warranty I haven't. I think I'm going to watch the levels closely for a while and see if I can figure out if there is a consistent pattern related to miles, or if the amount of fluid loss varies with temps and use.

Still haven't figured out why 5W30 is okay, but Transynd isn't.

[Quad]

Ah ok, sorry for being that guy lol. You know, I haven't heard that Transynd wasn't ok for transfer cases. But it's been awhile since I did my research also. I was looking for the article I read a few years back from the manufacturer of the transfer cases. But couldn't find it. Transynd from what I remember is a really really good ATF. Exceeds the same standard as DEX III. I think it was a TES 295???? And Transynd meets standard TES 395. I don't remember the exact standards. Going off of memory.


Sent from my iPhone using Tapatalk

[{tpc}]

Originally Posted by bsmith0404

The transfer case is the same in the diesel and gas trucks. Yours is a bit older and used different fluid. Not sure which year GM started using Dex VI in the transfer case. The evaporation problem seems to be more associated with the Dex VI fluids, but I can't say for sure if that is the only ones with the issue.

Ah ok, thank you for the info. Yes mine and my wifes even older envoy I believe use some sort of blue colored transfer case fluid, that on other forums, they say to only use the stuff direct from the dealer. Its a little on the pricey side but I think you need less than 2 quarts, so it isn't really bad.

Does make sense not to have multiple fluids though if one can do the job.

[Quad]

The blue fluid is called Auto Trak if I remember right. And not that your asking or anything. But I don't believe you can interchange it with motor oil because of the additional addictive package in Auto Trak fluid.


Sent from my iPhone using Tapatalk

[bsmith0404]

Not sure about the TS395, I looked at the jug of Transcend I have and only see the 295 standard required by Allison. I saw one post on the Duramax forum that someone said not to use Transynd in the transfer case, but from what I remember, he didn't explain why.

[Quad]

Yeah I'm trying to go by memory on the standard numbers. Don't remember those exactly. I was planning around lunch time today looking around and seeing what I could find about Transynd in T cases.


Sent from my iPhone using Tapatalk