Early vs later dana 18 differences.

Dennis,

I had a question about T90C's and how they differed a while back. There was quite a discussion, mostly concerning gear ratios and crawl speeds. I don't think we mentioned anything about stronger or quieter.

http://thecj2apage.com/forums/t90c-or-not-to-t90c-that-is-the-question_topic36151.html

Stan
48 CJ2A (Grampa's Jeep)
59 Chevy 1/2 ton
Grampa's Jeep Build Thread

Should have proof read. I meant Dana 18. Will edit it.

Dennis
'47 CJ2A 101823
'74 Cherokee

Intermediate shaft size.

'47 CJ2A PU
'48 CJ2A Lefty

"Common sense is not that common"

Also, you may have either a 26 tooth or a 29 tooth gear on the output of the trans., this also means there are two intermediate gears to go with them.

Lee

LEE
44 GPW-The Perfected Willys
49 2A
“If you wait, you only get older”
67 M715
American Made Rolling History

DANA MODEL 18 TRANSFER CASE PROGRESSION

Like all Jeep components the famous Dana model 18 (D18) underwent a continual progression of changes.

The earliest changes occured even before MB / GPW production.

After MB / GPW the intermediate shaft diameter was changed from 3/4" diameter to 1-1/8" for increased strength and durability.

Also the MB / GPW's meager 1.97 to 1 ratio was changed to 2.43 to 1 ratio for the CJ universals.

The 2.43 ratio D18 is a fairly good transfercase and it's plenty strong behind typical early Jeep engines.

The Dana 18 was changed yet again in mid year 1954-1/2.

This progression changed the ratio from 2.43 to a 2.46 to 1 ratio.

Why bother ?

That was Dana Spicer first attempt to quite down the model 18 transfer case.

The gear teeth were re-cut finer and at a slightly different pitch.

The intermediate shaft once again was then increased to 1-1/4" diameter.

The roller bearing count was also increased and the roller cage was eliminated.

The 2.46 to 1 ratio small hole version (3-5/32" index bore) is the time proven standard for the D18.

That implies that this particular small hole 2.46 ratio transfer case assembly was used for the greatest duration of time. (1954-1/2 to 1971)

In 1962 the silent type transfer case was finally perfected and it is commonly known as the Dana model 20. (D20)

All D18's built before 1966 model year have 3-5/32" transmission index bore.

The 2.46 ratio D18 was once again modified in late 1965 for use with the more powerful Dauntless engines.

This last progession of the D18 is commonly called the big hole D18.

The big hole D18 utilizes the stronger and slightly heavier D20 case with it's inherant index bore @ 4".

The big hole D18 gears sets remained the same as the 2.46 ratio small hole D18's.

The big hole D18 front bearing cap was changed to a single stick configuration.

It is the strongest of the D18 transfer cases.

One cannot simply swap the gears between 2.43 ratio and 2.46 ratio D-18's unless all of the gears are swapped.

However one could swap the complete 2.43 gearset into a 2.46 case and in order to utilize the 1-1/4" intermediate shaft.

D-18's were never built as 2.43 ratio with 1-1/4" intermediate shaft from the factory.

Other transfer case parts swap combinations are also practicable.

D20 cases can be used for many drivetrain applications intermixed with 2.43 or 2.46 ratio gearsets.

The ultimate D18 entails the stronger big hole case with 2.46 ratio or aftermarket ratio components plus the use of a twin stick front bearing cap.

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