Bolt-on frame boxing

[The FLU farm]

Here's one for you guys with more CUCV experience.
Checked the vitals under the M1031 today in preparation of finally driving it some day, and noticed these brackets.
I don't recall seeing such brackets before, unless my '91 V3500 had them, and I forgot.

Also found ATF in the transfer case, and not even enough of it. Aargh! Oh well, the rear axle was low, too, so time to stock up on some gear lube.

 

[snowtrac nome]

those are part of an mwo to strengthen frames that were prone to cracking in that area

 

[The FLU farm]

Thanks, that's what I suspected.

 

[cucvrus]

ATF is supposed to be in the transfer case.

 

[The FLU farm]

ATF is supposed to be in the transfer case.

In a 205?

 

[scottladdy]

In a 205?

Yes, according to the -12 Lubricating Order Dexron II at 5.0 qt or 4.7 L.

Also, in the 1986 Chevy Pickup Trucks Service Manual, Page 7D1-6 205 Transfer Case - Dexron II

View attachment 205 Transfer Case.pdf

 

[rustystud]

Yes, according to the -12 Lubricating Order Dexron II at 5.0 qt or 4.7 L.

Also, in the 1986 Chevy Pickup Trucks Service Manual, Page 7D1-6 205 Transfer Case - Dexron II

View attachment 687011

We have hashed this out before. NP205 transfer-cases should have gear oil in them. ATF is not thick enough to lubricate them when they get hot. You wouldn't put ATF in your differential or manual transmission would you ? Same thing here. The gears need a high compression/shear oil. Just look up what "New Process" recommended for them. The military used ATF as insurance since the TH400 uses ATF and if a seal went bad it would containment the transmission. The military didn't care that the life of the transfer-case would be shortened by using ATF as they have plenty of money to replace them. As far as the Chevy Service Manuals goes, all the newer transfer-cases with chains use ATF so they just got lazy and had all the transfer-cases use ATF.
I have almost all the Chevy Service Manuals dating back to the late 1960's. In the older manuals they said to use gear oil in the NP205. So what changed ? Personally I would use what the manufacturer of the transfer-case (New Process) said to use in it.

 

[rustystud]

View attachment Scan0208.pdfView attachment Scan0209.pdf

When the industry recommends 80/90W gear oil I would use that.

 

[scottladdy]

View attachment 687030View attachment 687031

When the industry recommends 80/90W gear oil I would use that.

Hey folks, this is not intended to resurrect "the great debate" relative to people's opinions on what should be run in the NP205. Instead I provided the inquirer with a clear and irrefutable set of facts from the vehicle manufacturer and fleet owner on what they specified for use.

It is true that prior to I believe 1981 GM specified 80W+ Gear Oil for the 205. But after that date it was Dexron II (or better) exclusively.

I know that the vehicle manufacturers typically requested different specs on the products they ordered from their suppliers and therefore cannot state whether or not something was changed in the newer GM TC's that either required or made possible the use of ATF. I also do not know if ATF's were made "good enough" for use in the TC's and that is why the specification changed. I do know what is documented.

Rusty, your documents come from a 3rd party source and the second pre-dates the cut over. They are not from New Process, GM or the military. Just an observation.

People often don't realize that automatic transmissions tend to run a lot hotter than TC's and have similar shear loads in their internal gearing. ATF's MUST meet or exceed specifications for shear resistance, wear resistance, resistance to thermal breakdown, etc. In some instances motor oils have been specified for use in manual transmissions and some esoteric TC's.

I would be interested to see if anyone has access to a formal engineering postmortem on a 205 that clearly indicates the type of lubricant caused a failure.

As with anything, if it is your 205 you should feel free to run whatever lubricant you want to in it. If you feel better about running gear oil then do so. According to the manufacturers and the military ATF is fine for the 205's intended use.

All the best!

 

[The FLU farm]

As with anything, if it is your 205 you should feel free to run whatever lubricant you want to in it. If you feel better about running gear oil then do so. According to the manufacturers and the military ATF is fine for the 205's intended use.

I'll never forget the surprise when checking the fluid levels in my new '91 V3500 after driving it home. I had not expected to see ATF in there. Sure enough, that's what the manual called for.
I put gear oil in there, like in every gear driven transfer case I'd ever owned, suspecting that it was changed to ATF to improve mileage, not for the well being of the gear teeth.
Like with this M1031, I didn't buy that V3500 to chase good mileage, so my first choice is gear oil.

 

[scottladdy]

ATF Thermal Analysis

Some additional "light" reading on the thermal analysis of ATF's in actual use. In case anyone is bored and looking for something to do

https://bobistheoilguy.com/automatic-transmissions-study/

As you can see, ATF's are pretty stout.

 

[The FLU farm]

Gotta read that later, scottladdy, but for now I'm wondering if it was feasible to run an automatic on gear oil, would they?
I suspect that the hydraulic functions got first choice and the gears got to live with ATF as a result.

 

[cucvrus]

Mr Crusty AKA Mad Cow disease is an M1028A1. It has ATF in the NP 205 since the day we bought it at SECO in Augusta Georgia in 1996. It also has the 205 and the controversial transfer case strut/brace/torque rod. And my Son pounded this truck many times. Still going strong. I did replace the engine once about 6 years ago. It had less then 20K on it and has over 50K on it now. Tested time and time again. I like the ATF in the NP 205 because that is what was in all the state/municipal trucks that I serviced back at the GM dealership. It does seem to shift easier in winter weather then the 1979 K30 we had.

 

[Skinny]

It's a set of gears and bearings...pretty sure it will be happy with any lubricant in it. The 205 will accept either one and be happy with no ill affects.

So I'll throw a bone into your explanation. The T5 Tremec 5 speed came off the line with gear lube just like every other manual trans in its day. After having firm shift reports the fix was to put ATF in it. That was by the car manufacturer with vehicles still under warranty. Sure there are bronze synchros that have fluid compatibility issues which can cause problems but the 205 has none of that. Fill it with whatever you have and keep on trucking. Why does it seem like lately things on SS have been turning mountains out of mole hills? Just today I passed a dozen square nose Chevy's with broken tcases because they didn't have torque rods...

 

[cucvrus]

Yea I seen the same thing and they were all Dante's Peak wanna be vehicles. HA
https://youtu.be/2e7sr7Zvv7Q

 

[scottladdy]

Shear resistance of Newtonian vs Non-Newtonian fluids

... if it was feasible to run an automatic on gear oil, would they?

Well, I'm just going to go out on a really shaky limb here and say, if it was feasible then the answer would be yes. You pretty much answered your own question.

It is commonly misunderstood that the shear strength of a fluid is directly related to that fluids viscosity, commonly misstated as a fluids "thickness". Viscosity is more properly defined as a fluids resistance to flow.

Newtonian fluids do have a general behavior that roughly correlates shear resistance to that fluids viscosity. For all Newtonian fluids in laminar flow the shear stress is proportional to the strain rate in the fluid where the viscosity is the constant of proportionality. However, for non-Newtonian fluids, this is no longer the case as for these fluids the viscosity is not constant. The shear stress is imparted onto the boundary as a result of this loss of velocity.

Gear oil is Newtonian. ATF is non-Newtonian. I will save you from all of the math that goes with this unless you really really want to see the formulas involved. But the short answer is that equating the suitability of either of these fluids as a gear lubricant based on how closely they resemble honey flowing out of a jar is based entirely on ignorance and tribal knowledge. It is not based on science, engineering or empirical testing.

Some additional light reading: Low and High Temperature Non-Newtonian Behavior of Automatic Transmission Fluids

Mountains? Molehills? I never get insulted or upset by someone else's ignorance. I provide science and engineering to back up my statements and where I do provide opinion I try to clearly state that. I just try to help out those who are willing to learn. Those that are not, well it is a free country.

And guys, let's try to be fair to Dante's peak. It scored a whopping 27% rotten tomatoes.
https://www.rottentomatoes.com/m/dantes_peak

 

[The FLU farm]

Well, since ATF was invented long ago, I suppose that it wasn't developed enough to be used in early transfer cases.
Or nobody had thought of using it in such applications yet. Or its use was based on mileage gains. Or all of the above.

 

[scottladdy]

Well, since ATF was invented long ago, I suppose that it wasn't developed enough to be used in early transfer cases.

Pretty much this is the correct answer:

"In the 1950s, 1960s, and 1970s, ATF contained whale oil as a friction modifier. But since whale oil would break down at higher temperatures, cars produced in the 1970s and later would not be able to use whale oil because of the higher engine coolant temperatures employed to reduce emissions and save fuel."

"Automatic transmission fluids[edit]

The original Dexron transmission fluid was introduced in 1968. Over the years, the original Dexron was supplanted by Dexron-II, Dexron-IIE, Dexron-III, and Dexron-VI, which is the current fluid. GM has upgraded the Dexron specifications over the years; newer fluids are generally but not always backward compatible with previous fluids. Because there are still applications for which Dexron-VI either has not been proved suitable or deemed to be not necessary, there remains a market for fluids that claim to meet the earlier specifications.
DEXRON[edit]

The original Dexron fluid, like its predecessor Type-A/Suffix-A, used sperm whale oil as a friction modifier. The U.S. Endangered Species Act banned the import of sperm whale oil, so the fluid had to be reformulated.[SUP][1][/SUP]
DEXRON-II, IID and IIE[edit]

Dexron-II was introduced in 1972 with alternative friction modifiers such as Jojoba oil. However, it caused problems with corrosion-prone solder in GM's transmission fluid coolers;[SUP][2][/SUP] accordingly, corrosion inhibitors were added to the product. The resultant fluid, released in 1975, was called Dexron-IID. However, the corrosion inhibitor made the new fluid hygroscopic, which while it was not a major problem in automatic transmissions, made Dexron IID unsuitable for other hydraulic systems in which it was commonly used.[SUP][2][/SUP] A further reformulation, to address excessive hygroscopicity[SUP][citation needed][/SUP], but primarily to improve low temperature performance (20,000cP @ -40C vs 50,000cP@-40C for Dexron-IID) was named Dexron-IIE (GM Spec GM6137M)."

 

[cucvrus]

Please continue with the lesson master. You have our full attention. The Sea Shepard is docked and awaiting your next command. Seriously that is all good information. Thank you.

 

[ken]

Back to the frame braces. They were installed because the frames were bending there, while being lifted with a crane at GVWR to be loaded on ship/trains.