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Transfer Case Progression

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 64CJ5 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Aug. 2018 at 2:51am
Thanks for the information.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bob W Quote  Post ReplyReply Direct Link To This Post Posted: 30 Aug. 2018 at 1:46am
Thanks for taking the time to compile and post this great information!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 30 Aug. 2018 at 1:38am
DANA MODEL 20 TRANSFER CASE PROGRESSION

Although the D18  was improved; Dana Spicers 1954 attempt to silence the transfer case was a failure.
Just prior to the1962 model year the "silent type transfer case" was finally perfected.
It is commonly known as the Dana model 20. (D20).

This unit was an absolute ingenious re-design of the D18.
The new D20 was basically a re-configured D18.
And so It utilizes many of the very same parts as the ever famous D18.

The main difference between them being the very similar yet improved case casting.
This 4" index bore casting allows for additional transmissions having larger rear main shaft  bearings.
For clarity I refer to the basic case castings as either big hole or small hole and  certainly not as D20 nor D18 cases.
As an added benefit, the big hole also allows one to separate the transmission from the transfer case without removal of the mainshaft gear.

The mainshaft gear::


For ease of identification; "all" big hole cases have the addition of a second shift rail pocket exiting out the rear of the casting. 

Here we see the shift rail pocket on small hole vs the big hole case:

This additional shift rail pocket is required for use with D20 transfer case assemblies.
These big hole cases are a bit more stout than the small hole cases with no increase of overall space.
As a bonus the internal area specifically surrounding the intermediate gear was slightly increased.

The D20  was initially placed into the newly developed Gladiator and Wagoneer models.
At the time it evidently was deemed impractical to install the D20 into CJ models.
Willys Motors reasoning was likely influenced by the short wheel base and offset of the CJ's rear axle.
 
In 1972 AMC Jeep Corporation  lengthened the CJ to 84" and the D20 became the new standard for CJ's.
Jeep's Dana 20's Circa 1962-1979 were always geared with  the meager 2.03 ratio gear sets..

A few different designs for D20 front bearing caps were used on the various Jeep models..

The D20 front bearing cap shown here is designed to accept the "J" shifter assembly:


Several different shift lever assemblies were designed for various Jeep models.
Sadly all Jeep models used single stick control on the D20 transfer case.
This "J" shifter is most often considered to be the best of the single stick controls.


All early lube fill plug were on the LH end but that practice changed around 1972

Big hole cases without a LH fill plug vs  case with the LH fill plug:


Later big hole with the rear fill plug:

Beginning in 1970 mechanical type of "lever and tube" clutch control assemblies changed on CJ's to a cable control system
So many of the post 1970 big hole cases are no longer tapped to accept a clutch control pivot stud..

Pre 1970 -1972 big hole that is untapped for clutch control.



That said we still see some big hole cases being tapped to accept clutch control pivot studs way into the late 1970's 
Here we see a post 1976 case with a bolt plug in the pivot stud tap:


Beginning in 1980 the D 20 gave way to the D 300.


STAY TUNED.........



Edited by oldtime - 10 Oct. 2018 at 4:09pm
Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963)
Zero aftermarket parts

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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 29 Aug. 2018 at 2:23am
DANA  MODEL 18 TRANSFER CASE PROGRESSION

Like all Jeep components the famous Dana model 18 (D18) underwent a continous progression of changes. 
The very first transfer case changes occurred before mass production of the MB/GPW.
Bantam was concerned with where to place the transfer case outputs in relation to the axle carriers..
The early Bantam BRC transfer cases had LH outputs and LH differential carriers

In 1945 the intermediate shaft diameter was changed from 3/4"  to 1-1/8" for increased strength and durability.
Also the early military ratio of 1.97 to 1 was changed to 2.43 to 1 for all 1945 and later Jeeps.

The 2.43 ratio D18 was used from 1945-1954-1/2.
It is a very good transfer case and it's plenty strong behind  any Willys engine.
These Brown / Lipe units remained basically unchanged through CJ2A and CJ3A production.

In 1953 both front and rear output shafts and their associated nuts were changed.
A "Hug Lock" nut replaced the previous "Castlelated" nut. 
The Hug Lock nuts have less thread pitch and they also interchange with those on the axle pinions..

Shaft changes and A-980 vs 801367 nuts:

As the 1953 3B came into production the safety wiring of bearing cap bolts was done away with.

The D18 was changed yet again in mid year 1954-1/2.
This progression changed the ratio from 2.43 to the 2.46 to 1 ratio.
So why did they bother ? 
This was actually Dana Spicer's first attempt to quiet down the model 18 transfer case.
The gear teeth were re-cut finer and at a slightly increased pitch.
The intermediate shaft  was once again increased in size to 1-1/4" diameter.
The roller cage was eliminated and the needle count was increased to 48.

Here we see the  1-1/4" intermediate shaft and associated parts:


With this 2.46 ratio transfer case the rear output companion flange yoke was upgraded.
This upgrade from part # A 950 to # 807784  provides slightly increased propeller shaft angles without yoke binding.
The 2.46 ratio transfer case became the "time proven standard" concerning Jeep transfer cases.
That implies that  this transfer case was produced for the greatest duration of time. (1954-1/2 to 1971) 

Here we see the early shorter companion flange yoke next to the improved longer yoke:


The slightly longer #116714 flange was used on all CJ's prior to November 1962.
The slightly shorter #912105 flange was used on all CJ's after November 1962.
The slightly longer #116714 flange was used with the shorter 4 tooth drive gear Jeep # A-1511 / SW # 477021.
The slightly shorter #912105 flange was used with all other speedometer drive gears.
Here in this pic you see both early and later CJ yokes mentioned above.


In 1956 the CJ park brake operating lever was changed from the A-17254 to 915892. 
It went from 5-3/8" OAL to 7-11/32 OAL in order to accomidate the T98-A transmissions.

Here we see the longer park lever that was now required with CJ-5 and T98-A applications:


In 1963 the D18 received a small change concerning shift fork set screws. 
They went from # A 963 set screw having safety wire to the Allen head set screws.

Old type vs updated shift fork set screws:


"All"  D18 transfer cases built before 1966 model year have a 3-5/32" transmission index bore.
The 3-5/32" index bore indexes direct to the T90 mainshaft bearing (Fafnir 307 K)
There were no more 3-5/32 index bore cases built after the 1971 CJ's with  F-134 engines..

The D18 received a divergent factory change in late 1965. 
These D18's were specific  to CJ's with Dauntless 225 engines.
This case was upgraded to the 4" index bore casting that was previously developed by Dana Spicer.
This larger index bore allows for transmissions having larger mainshaft bearings than a T90 uses.

Here we see the Small hole vs the big hole indexing bores:

For clarity I will refer to the 2 case castings as either "big hole" or "small hole" and  certainly not as  D20 cases.. 
This last factory progression of the D18 is commonly called the "Big Hole D18".
This big hole D18 utilizes the stronger and slightly heavier casting with it's inherent 4" index bore. 
The big hole D18 gears sets remained the same as the previous 2.46 ratio small hole D18's.
However the factory big hole D18 front bearing cap was changed over to a single stick configuration.
The big hole D18 is certainly the strongest of the factory D18 transfer cases.

Stay tuned .....more to come.



Edited by oldtime - 19 Jan. 2019 at 5:40pm
Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963)
Zero aftermarket parts

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