What's really stopping me? T-case Question.

[porkchop]

I was out in the garage looking at my D18 and D20 t-cases. I noticed that they are almost identical except for the side that the rear output is on and the shift tower. What is stopping me from making the D20 into a D18 using the D18 shift tower. This way I would be able to use the factory t-case adapter for the D20. Here are some pics of both of them to see what I am saying.

http://members.fortunecity.com/porkchopsredfsj/id53.htm

http://members.fortunecity.com/porkchopsredfsj/id58.htm

http://members.fortunecity.com/porkchopsredfsj/id56.htm

http://members.fortunecity.com/porkchopsredfsj/id60.htm

So tell me can this work?

[yorkdork]

Bryant, I thought you were setting that up for a overdrive? Does't that mount on the transmission output side? Not over stepping your knowledge, just wondering.

Ralph [img]tongue.gif[/img]

[porkchop]

Yes it does bolt to the tranny output side. I am still getting the OD but I am just curious as to why you can't make a D20 into an D18 (Minus the gear ratio). I never noticed how close the t-cases are until I got them side by side.

[miked]

<homer simpson> ummmm, twin stick </homer>

[porkchop]

anyone?

[scotty]

sorry,pc,i havent been online for awhile(computer prollems). i am alittle confused in what you at trying to do.

you cannot swap the 18 shift tower onto the 20. the 18 shift tower is different because of the way it creates 4wd. inside the shift tower a coupler is lidd onto the shaft that the rear output and gears are on. the 18 is basically 1/2 of a 20(internally) that connects the front to the rear to make 4wd. the 20 has a set of gears(high,neutral,and low) for each output-ons set for front,one set for rear. therefore you must swap all the guts.

from the pic i can see that your 18 is a 3inch index hole,and the intermediate shaft looks real small. what diamter is it? in order to swap the 18 guts into your 20 housing,you need to have an 18 with a 1.25 inch dimeter intermediate shaft.

also what adapter are you using? if its a factory adapter you will not be able to swap the 18-in-a-20-housing onto your factory 20 adapter cause the 18 input gear is not swappable.

it has been awhile since ive had it apart,you may be able to construct a 2.03 low range 18-in-a-20 housing using the intermediate and rear output gears for the 20,but the output shaft,and all other internal parts from the 18. then you could swap the 2.03-low-range-18-in-a-20-housing onto a factory d20 adapter. a pto will still work,as the 20 and 18 input gears both have the little teeth on the rear that the unit engages,but i do not think that an overdrive will,as it replaces the input gear,and your back to square 1 with it not being swappable. if it were swappable,it would prolly not work,cause the overdrive input gear is designed for a 2.46 low range.

hope this helps. again,sorry have been offline for a week or so now...

[porkchop]

The last thing you had said is what I am thinking about doing, if it is possible. I am still confused about the shift tower. I haven't taken it apart yet but it looks like it will bolt right on.

The diameter of the intermediate shaft on the 18 is the 1" That is why I am thinking of trying this "creation". I would use the 18 as is but aren't the 1" shaft real weak and won't hold up to the 360, TH400 combo?

These cases are the same except for the fact that the 20 case is a little beefer.

I don't have an adapter yet, I am still looking for one. Do you know where one is?

[porkchop]

After tearing into it, I am almost positive I can make this work. I just need diagrams for both.

[Bob Barry]

<BLOCKQUOTE>quote:</font><HR>Originally posted by porkchop:
After tearing into it, I am almost positive I can make this work. I just need diagrams for both.<HR></BLOCKQUOTE>

Well, here's one for the D18:

http://www.jimsoffroadwarehouse.com/show_plate.asp?PlateNo=70

Can't find a D20 diagram, though.

[scotty]

pc,the shift tower will bolt on.all of my 18 parts are in a 20 housing.however, the shift rails are different,so you must use matching components. you cannot swap the 18 tower onto the 20 because they control tings differently. in the 18,4wd is created in the tower as a coupler is slid from the yoke onto a splined part of the rear output shaft. the d18 and d20 output shafts are diffrent. well,on the 20 it would be the front output shaft,since the rear output is on the other side. in a d20 the other rail moves a very long sliding fork that moves the gears into high/neutral/low positions on the rear output side of the case.

in order to use the d18 shift tower,you must use all the matching shafts and forks.i think it is possible to use the 2.03 gears in the 18,less the ones for the rear output,of course. you will need to use the intermediate gear from the 20 and assemble the d20 front output gears on the d18 rear output shaft.since you will be using a 20 housing,the 20s 1.25 intermediate shaft will work. last and not least,you will need to fab a cover for behind the input gear,since the rear output is now on the other side,and you will have a big hole there otherwise

i would still highly recomend using an aftermarket kit that uses a 6 spline output shaft. you are then left with the option of using 2.46 gears,which im pretty sure that you will have to use in order to use an over drive.

[porkchop]

OK Scotty I know what you are saying, but the front out put shafts of the D20 and the D18 are the same width and have the same sline count. The large sliding gear and the small sliding gears on the 20 and the 18 have different sline counts on the outside (this is becuase of the ratio). So there is no reason why the gears from the 20 won't fit onto the shaft from the 18. This way I am retaining the 2.03 low but have the twin stick right/right drop.

Also on the plate for the back I can buy from www.willysjeepparts.com for $12.

If this is still confusing call me at the house and we can figure it out.

[scotty]

pc,sounds like we are on the same page.i just wasnt sure if you were trying to swap just the shift tower.

but you are correct bout the shafts and splines,let me know how it goes,or drop me a line if ya got any questions while you got them both apart.