Swapping A Dana 18 For A Dana 20.

Can I take a later cj5 dana 20 and my dana 18 from behind my t14 and make a dana 20 that will fit the t14 with the 10 spline vs 6 spline variations?

 

You need to know what input gear the 20 had on it. They either had 20 degrees or 17.5 degree pitch on a 26 tooth gear. The 18-8-49 gear is the only 26 tooth gear that fits on a T-14 with it's 10 splines. It has a 17.5 degree pitch. So the 20 transfer case that you use must also be one that uses a 17.5 degree input gear.

 

'72-'75 CJ's with inline 6 and T-14 transmission used a 10 spline input model 20. Be aware your 18 with 10 spline input has 2.46-1 low range and the 20 uses a 2.03-1 low range.

 

Novak has a table of transfer case gears that will tell you the Jeep and Dana numbers for the gears. The Novak Guide to Dana 18 & 20 Gears Interchange 1941-1979

 

I've looked for this gear/number info before, but never found more than one application at a time. The page you linked is a great reference to all the variations in one place. Thanks Tim!
-Donny

 

Woot! Glad I could help!

Likely worth cutting and pasting into your notebook. Stuff comes and goes from the internet.

 

Yes, but..

Silly question: Why? Dual offset yokes have significant advantages. Also the D44 is a great rear axle for a vehicle of our weight.

 

A flanged 44 for a centered output is cheaper and more available than an offset flanged 44. JMO - if I had a Jeep with an 18 I'd spend what's needed to get the offset axle, but I have the means. I'm not so enamored to earlys though, and would probably start with a '72 or newer.

And! I'm not so convinced that you need the flanged axle. If you feel the need, a full-floating conversion may be the sensible option.

 

Yeah, if I’m digging into the rear “cuz I need it”, I leaving with a full floating D44, which case the offset or not is rather irrelevant. A FF44 is well strong enough for most any set of tires we’d run at this wheel base.

 

I highly doubt many on this board need more strength than the stock offset 44 provides. Some do, but I bet it isn’t common.

 

Actually lots of differences between the D18 and D20 applications.

Factory Jeep D20 has lousy reduction ratio compared to factory Jeep D18.
D20 runs much more quitely and is the more efficient design.
D18 keeps the differential carriers inline allowing one to better straddle trail obstacles.
D18 allows for higher lifts than D20 due to rear propeller shaft angles.
D18 is easy to "twin stick" if not already equipped that way..
D20 never had a factory twin stick shifter, so its aftermarket or ho-made....
D20 is big hole only (4" index bore)
D18 a can be small hole (3-5/32" index bore) or large.

I tend to consider the D20 as the better choice on the hi-way but see the D18 as a better choice for off-road use.

 

Semi-related. Can I machine out a small hole 18 to 4” without serious impending hassles?

 

Sure you can.... but it has to be precise.
That said you may be better off to use a "big hole" which is a stronger case design.

 

Thanks guys. My debate right now is to use wagoneer width axles or a short wheel spacer. I don't wheel much in it and it is my daily driver. I am running with 33s when turning tight. I think I am around 2.5" lift with some stupid stiff 11 leaf packs front and rear.

My 27 front is in need of a rebuild and I have a 44 front I plan to make fit in its place. Building the front axle has caused me to debate if I want to go wider with the rear or just shorten the front a bit more. The front is a hp44 from a 78 f150 that will need shortened in either case as well as swapped driver to passenger side.

The 20 would be the simplest swap vs something that may need a transmission swap and or adapters.

 

Also the 18 gives you the ability to use an overdrive which is a huge upgrade in an early CJ

 

Almost any 20 case will work with the 18 guts.

 

I may end up at this route.

 

If you are speaking strictly Jeep this is true. IH Scout 800 for about 3 years used a twinstick 20. Can be hard to find but will be a bolt on for Jeep 20. Consists of front output housing, shift rails, shifters, and assorted small parts like pivot pin, etc. the pivot pin is different from the 18. Diameter is the same but the groove for the set screw is on the opposite end of the pin. I want to say they were used in the 1968-1970 range.

 

Interesting stuff.
I sure would like to find a set up like that.

 

Herm has a few as I have sold him several of them in the last couple of years.