What is viscosity?

What is viscosity?

As we saw in yesterdays’ blog posting we need to be concerned about the viscosity of the lubes we employ in our WW2 jeeps (of course this is true in any vehicle).  More from EM 1110-2-1424 28 Feb 99:

Effect of viscosity on flow of light and heavy oils.

Note–The spout in each container is of the same size, and each grade of oil has flowed for the same time.  Graphic from TM 10-540, December 26, 1940

Viscosity. Technically, the viscosity of an oil is a measure of the oil’s resistance to shear.  Viscosity is more commonly known as resistance to flow. If a lubricating oil is considered as a series of fluid layers superimposed on each other, the viscosity of the oil is a measure of the resistance to flow between the individual layers. A high viscosity implies a high resistance to flow while a low viscosity indicates a low resistance to flow. Viscosity varies inversely with temperature. Viscosity is also affected by pressure; higher pressure causes the viscosity to increase, and subsequently the load-carrying capacity of the oil also increases. This property enables use of thin oils to lubricate heavy machinery. The load-carrying capacity also increases as operating speed of the lubricated machinery is increased. Two methods for measuring viscosity are commonly employed: shear and time.

(1) Shear. When viscosity is determined by directly measuring shear stress and shear rate, it is
expressed in centipoise (cP) and is referred to as the absolute or dynamic viscosity. In the oil industry, it is more common to use kinematic viscosity, which is the absolute viscosity divided by the density of the oil being tested. Kinematic viscosity is expressed in centistokes (cSt). Viscosity in centistokes is conventionally given at two standard temperatures: 40 EC and 100 EC (104 EF and 212 EF ).

(2) Time. Another method used to determine oil viscosity measures the time required for an oil sample to flow through a standard orifice at a standard temperature. Viscosity is then expressed in SUS (Saybolt Universal Seconds). SUS viscosities are also conventionally given at two standard temperatures: 37 EC and 98 EC (100 EF and 210 EF). As previously noted, the units of viscosity can be expressed as centipoise (cP), centistokes (cST), or Saybolt Universal Seconds (SUS), depending on the actual test method used to measure the viscosity.


I just love the WW2 jeep, don't you?

Viscosity?  You may be thinking what the heck is that and why should I care?

Film thickness.  Simplified equations have been developed to provide approximations of film thickness with a considerable degree of precision. Regardless of how film thickness is calculated, it is a function of viscosity, velocity, and load. As viscosity or velocity increases, the film thickness increases. When these two variables decrease, the film thickness also decreases. Film thickness varies inversely with the load; as the load increases, film thickness decreases. Viscosity, velocity, and operating temperature are also interrelated. If the oil viscosity is increased the operating temperature will increase, and this in turn has a tendency to reduce viscosity. Thus, an increase in viscosity tends to neutralize itself somewhat. Velocity increases also cause temperature increases that subsequently result in viscosity reduction. From EM 1110-2-1424 28 Feb 99.

You should care because increased viscosity leads to increased operating temperature which is not good for either your engine or your transmission (or other mechanicals).  That’s why it is best to use the viscosity recommended by the original manufacturers.  For example, the L-134 engine uses 10 weight in the winter and 30 weight during the summer…or using modern oils you might consider using 10w30.  For the transmission, transfer case and differentials use 90 weight during the summer and 80 weight during the winter. Some people swear that you should use 20w50 in a tired engine but the increased viscosity just makes the engine work that much harder and increases the wear.
The tool list is SNL G-23.

The tool list is SNL G-27.

If you have my book “Military Maintenance” (available from lulu.com and most major bookstore chains) it provides a description of what is in Standard Nomenclature List (SNL) G-27.  “Ordnance shops will get most of their information from SNL G-27, including the basis of issue for special tools.  Basis of issue for unit equipment sets of 3rd and 4th-echelon tools is contained in the organization’s T/O&E, but details of the sets are published in G-27.  In addition you can find pictures of special tools in SNL G-175.”

More on the subject?

“Organizational Spare Parts and Equipment (OSPE).  These are individual pamphlets for each make and model vehicle.  They tell what tools the vehicle itself carries (first-echelon tools), and what special tools the second echelon will need to maintain it.  OSPE’s are used as a basis of issue.”

“Tool Sets, Motor Transport (SNL N-19).  This one has a tool-by-tool listing, with pictures, of everything in the second-echelon unit equipment sets (including the Armored Command sets), plus the hand-tool kits of general automotive mechanics and automotive specialists.  It’s good only for identifying the tools in the sets; the basis for requisitioning sets is company’s T/O&E.”


By Robert Notman

Paperback, 170 pages

Price: $24.95 plus shipping

Ships in 3–5 business days

The 1/4-ton, 4×4, truck of World War Two started out in the hands of the Infantry and a little company called American Bantam Car Company. Bantam worked with the Army’s Quartermaster Corps to produce the pilot model that was accepted and then fulfilled their initial contract for 70 trucks. During testing of the pilot both Ford and Willys-Overland were invited to check out this new vehicle. The vehicles were studied in great detail. Soon, at their own expense, Ford and Willys-Overland submitted pilots for testing too. This book covers the production prototypes–Bantam BRC-40, Ford GP and the Willys MA.
This book is available through major book sellers and Lulu.com.
Army Jill on a picnic during WW2 - Large Poster
Size: 34.0″ x 23.0″
Questions? Order by Phone! 877 809-1659
Army Jill on a picnic during WW2 – Large Poster looks great in your garage, office or den!  Get the inspiration to keep working on your jeep (or other military vehicle).

Beautiful blonde Jill in a scene from a picnic during WW2.

$19.99 plus shipping. Price subject to change.
AVAILABILITY: In Stock, will ship in 2-3 business days (shipped separately)

Product Number: 79695471 Order on-line by clicking the link or TOLL FREE (US) and give the operator the product number.

Product Information
Perfect for dressing up any wall, this is the perfect size for maximum visual impact, or instantly creating a theme for a room. Images look great on this high-quality poster, printed on heavyweight 7 mil semi-gloss paper using superior dye inks. Image size 25” X 35”. Treat yourself or give as a gift.
In order for Jill to go on the picnic she needed to have her jeep in order.  Don’t forgot to service your transmission when needed and remember that you really can rebuild your transmission.  There’s only about 57 different parts–take it one step at a time!
Trouble Shooting And Rebuilding The T-84J

Trouble Shooting And Rebuilding The T-84J

by Robert Notman

Price is subject to change.Availability: In Stock.Product Number: 030-13014504

Genre: Automobiles
Paperback: 158 pages
Description: Rebuild the T-84J WW2 jeep Transmission Yourself! 42FordGPW
Trouble Shooting and Rebuilding The T-84J Transmission is an aide designed to help the novice to decide whether or not to rebuild the T-84J themselves. It covers all sorts of “tricks” and “how-to’s” for tearing down, cleaning, inpecting and then assembling the rebuilt transmission. You will learn trouble shooting tips. Why is your transmission jumping out of gear? Is the T-84J really supposed to be noisy? And much, much more! You also might be interested in the CD version–to see a live action version of what is going on in the book. 42FordGPW
Product Details:
· Paperback: 158 pages
· Binding: Wire-O
· Publisher: Robert Notman (August 2004)
· Product Number: 030-13014504
Where did the jeep name came from?

Where did the jeep name came from?

In the book, “Jeep – Its Development and Procurement Under the Quartermaster Corps 1940-1942“, Rifkind briefly explores where the name “jeep” came from and how it came to be applied to the jeep.  He said:

The origin and meaning of the word “jeep” are not too certain.  Writing in reply to a query on this subject from the Editor of the Winston Dictionaries, Philadelphia, Pa., the QMC Motor Transport Division on October 30, 1941, stated:  ”The word ‘jeep’ has no official military status, but over a long period of years has come to mean to Army men a new type of military motor vehicle.”  The editor was informed that until the advent of the 1/4-ton truck the word had been generally applied to the 1/2-ton, 4×4, used for command reconnaissance and general cargo purposes.  When 1/4-ton made its debut, it was variously dubbed “jeep,” “baby jeep,” and “peep.”  During the 1941 maneuvers, it was said that the Army mechanics and others generally came to refer to it as the “peep,” to distinguish it from the 1/2-ton “jeep.” QM 095 M-A (Winston, John C.,  Co.), Major G. H. Vogel to Thomas K. Brown, Jr., Editor, The Winston Dictionaries, October 30, 1941.  Other names attached to the 1/4-ton about this time were “jeepie,” “son-of-a-jeep,” “blitz-buggy,” “bantam,” “puddle jumper,” etc.

How did this truck come to be called the “jeep”


Another explanation of the word “jeep” is that it originated from the slurring of the initial letters of the War Department’s vehicle classification, “general purpose” (G.P.), under which the 1/4-ton was listed, into a single monosyllable.  Credence is lent this theory by the fact that an early spelling variation of the word was “geep.”  Regardless of how the name originated, after a 3/4-ton model was developed late in 1941 to replace the 1/2-ton truck, the title of “jeep” was settled permanently on the 1/4-ton, apparently by common consent.  On February 19, 1942, Lt. Col. Edwin S. Van Deusen, MT Chief of Procurement and Engineering, speaking before the Metropolitan Chapter, Society of Automotive Engineers, New York City, said that the 1/4-ton was “affectionately know to millions now as the “jeep”.

WW2 Jill Cartoon Mug
front / back: front image back image
Questions? Order by Phone! 877 809-1659
WW2 Jill Cartoon Mug

Blonde WW2 Jill, wearing a red bathing suit and riding in a jeep.

$12.99 plus shipping. Price subject to change.
AVAILABILITY: In Stock, will ship in 2 business days

Product Number: 97144798 Order TOLL FREE (US) by calling the number at left and giving the operator the production number OR just click the link to order on-line!

Product Information
The perfect size for your favorite morning beverage or late night brew. Large, easy-grip handle. Treat yourself or give as a gift to someone special.
  • Measures 3.75″ tall, 3″ diameter
  • Dishwasher and microwave safe

You might also be interested in finding out more about WW2 jeeps:

The early history of the jeep!

The early history of the jeep!

Jeep – Its development and procurement under the Quartermaster Corps, 1940-1942

Authored by Herbert R Rifkind
Introduction by Robert V Notman

If you are interested in the history of the development of the jeep there is little substitute for the effort undertaken by Herbert R. Rifkind while World War II was still raging. This book was written from the Quartermaster Corps’ perspective but draws on numerous resources and documentation to put together a pretty good picture of what happened. The other thing in its favor is that Rifkind’s work was written in 1943. But even by that time the jeep story was clouded over who did what and when.

Rifkind covers Bantam’s involvement, Willys-Overland and Ford companies developments, the contracts and other details important to the student of the WW2 jeep!

What makes it even more valuable is that Rifkind actually lists the sources he used. So if you can figure out the record system used by the government back then and determine where to find them, you will find a gold mine of information to research.

This book includes a reproduction of the original manuscript created by Rifkind. You will even find some pen and ink changes.

Publication Date:

Aug 02 2011
ISBN/EAN13: 146370917X / 9781463709174
Page Count: 228
Binding Type: US Trade Paper
Trim Size: 8.5″ x 11″
Language: English
Color: Black and White
Related Categories: History / Military / World War II
You can find Rifkind’s book here.
I just love that "Go-Devil" Engine!  But what I really love is all the little details about the jeep--check out this book!

If your WW2 jeep transmission is noisy then maybe it needs some tender lovin’ care! Sure that transmission is not going to be as quiet as a modern Caddie tranny but it shouldn’t be a screamer.

Many times on this website we have had questions asked about “is it normal for the jeep (T-84J) transmission to be “noisy”. I have asked this question myself. It had been too long since I “rebuilt” my transmission…about 15 or so years, so I couldn’t remember what it sounded like when it was “new”.

Some claim that the jeep transmission is normally noisy…or it’s cousin the transfer case. So according to them it’s no big deal. Perhaps it is all a matter of degree. One man’s noise is another’s music?

Before I rebuilt my transmission last year I was deeply concerned over the noise coming out of the transmission. To be fair to those who responded, it is difficult if not impossible to diagnose sounds that have been translated into the written word. I had right to be concerned as it turned out, the cluster gear was about 1/3 gone! And still Frankenjeep(tm) lived! It clung to life even as I pushed it to 55mph (with an evil non-sacrosanct or is that synchrosanct? over-drive) for a final round trip of about 138 miles before the rebuild. The tranny never let me down.

When I disassembled the T-84J that when I discovered the damage. Not knowing what other damaged might have been caused by bits of metal “floating” around in the case, I elected to buy all new gears and shafts. For this project I purchased most of the parts from three vendors. I repurchased some parts because the brand new synchro from one vendor turned out to be brand new junk…could not get it to slip. Some parts I purchased from Europe through Ebay.

While many of my parts were likely re-usable I felt it best to use all new gears and shafts. I did re-use the shift forks, the case and the tower. Pretty much everything else was new. I figured that if their were any problems with the tower, it’s an easy to replace item while the transmission is still installed in the jeep.

Assembling the T-84J is really not difficult. There are about 58 parts, so it isn’t brain surgery, just following the steps and asking for clarification when the steps aren’t as clear as they could be. (That’s why I am writing/editing/filming a how-to rebuild the T-84J) So anyone with basic tools can do the job.

After assembly and installation in the jeep, I have now driven it for over a year…not as many miles as I would have liked…but I can tell you that the transmission is NOT noisy at all. Sure it’s no coup de’ville caddy quiet. But there are not loud whines or any grinding noise…., except when I misshift.

Why would anyone think that the T-84J is a noisy transmission. After all, you purchased a rebuilt transmission for respected dealers. Perhaps all of you know this but I didn’t. Rebuilt can be a misleading term. I was told by a dealer that I respect that basically a dealer rebuild consists of new bearings, synchro, new shafts, gaskets, seals and small parts kit as I remember it. The gears aren’t replaced. This doesn’t mean they wouldn’t replace a broken tooth gear but also means that the parts could be just inside of their wear tolerances (like the bushings).

Of course this all could be my imagination. I distinctly recall that my transmission was very loud prior to the rebuild. I even tried synthetics (okay) and higher viscosity lubes (don’t do it!). I drove it this morning without the top and I couldn’t hear it, perhaps just a quiet hmmmm but nothing more.

So if you don’t know the condition of your transmission and it is noisy perhaps it isn’t “normal” and is begging for a rebuilt. My latest T-84J rebuild included about $600 worth of new parts from Richard Grace. Very reasonable. Sure the fellow I rebuilt this for could have purchased a “new” rebuilt transmission for that but it would have had all new guts for that price. I put it together for him and that might have been worth about $400 of my time, if I had been charging. So for about grand you could have basically a new transmission. It took me several weekends to take the transmission apart, order the parts I needed and to assemble the transmission. I discovered other parts (shift rails) that failed to clean up, that needed to be replaced. Also, I was filming the rebuild. All of this added up to delays. It more than likely wouldn’t take a shadetree mechanic, more than a weekend to rebuild the transmission, assuming you pre-ordered all the parts up front.

If you assemble it yourself instead of having someone do it; you would save a lot and learn a lot.
While I enjoy driving my jeep much more than working on it…sometimes working on it can be fun as well.

Trouble Shooting And Rebuilding The T-84J

Trouble Shooting And Rebuilding The T-84J

by Robert Notman
Availability: In Stock.

Product Number: 030-13014504

Genre: Automobiles
Paperback: 158 pagesDescription: Rebuild the T-84J WW2 jeep Transmission Yourself! 42FordGPW

Trouble Shooting and Rebuilding The T-84J Transmission is an aide designed to help the novice to decide whether or not to rebuild the T-84J themselves. It covers all sorts of “tricks” and “how-to’s” for tearing down, cleaning, inpecting and then assembling the rebuilt transmission. You will learn trouble shooting tips. Why is your transmission jumping out of gear? Is the T-84J really supposed to be noisy? And much, much more! You also might be interested in the CD version–to see a live action version of what is going on in the book. 42FordGPWProduct Details:

· Paperback: 158 pages
· Binding: Wire-O
· Publisher: Robert Notman (August 2004)
· Product Number: 030-13014504

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