Building a super 18 transfercase

I know this has been covered many times, but I am trying to convert my cj to a an offset t-case so I can run a Warn OD. I did a diesel swap and need the extra gear options that will give me. This isn't going to be anything fancy. I'm no pro, but I just thought I would post my progress. I started today....I felt like Dexter. I layed down some plastic and put on my apron...and set up my "kill room" haha. I have tons of transfer cases laying around but no large hole 18's that will fit my t18 tranny output so I am putting my 18 guts in a 20 case. The 18's I have are from willys pickup and have 1.250 intermediate shafts but have the small hole and bearing. Like I said nothing to exciting just new seals cleaned painted and installed. I put 18 gears in a 20 case but kept it center output, but that was a long time ago. Here are some pictures of my progress. Thanks for looking.

 

I will be watching this, I picked up a dana 20 that is mated to a t18 that I need to convert at some point.

 

Well Here is what is left of my d18. It came apart pretty well. I do need a new "good" pair of external snap ring pliers but I got it apart without damaging anything. The intermediate shaft shows some wear and/or pitting. I will see how the d20 shat looks. They seem to be in good shape most of the time....but I guess they aren't spinning all the time like an 18. I may end up ordering a new shaft and bearing set. Everything else in the t-case look really good. Tights bearings and no signs of heat, wear or neglect.

 

I got the 20 tore apart tonight and started cleaning parts. Man the dana 18 is much nicer to work with..... I had a heck of a time getting the bearing off the shaft to remove all the parts. I won in the end but it was not the most enjoyably evening. Everything was a mess so I started soaking parts and scraping 30 years of grease. Fun FUN!!

 

oven cleaner, a wire brush and a hose takes care of the grime before you take it apart fairly well. enjoy.

 

Yeah I will probably have everything dipped before paint/re-as sembly. I have several 20's I tried to pick the cleanest one...lol Now i'm trying to decide If I should assemble it before or after I paint it. I usually paint all the pieces individually but then I usually mess it up when I put everything together. Any thoughts?

 

Also...one other question.... The yokes from the 18 look a lot more wimpy than the ones on the 20. Would you recommend using the heavier yokes? They look slightly longer so I didn't know if the sealing surface would be In the right spot. My jeep is not overly blessed with power but its a no brainer if the beefy ones will fit. Thanks!!

 

Not sure if anyone Is looking at this or not but My t-case is about finished. I finished cleaning everything and painted some parts, then I started assembly. I put the shift rails in the lathe and polished them. It took forever to degrease everything, but I feel good about it now. If you are building A "BIG hole" spicer 18 a few things to watch out for......fill plug location. depending whether or not you are running a t case e brake or not you may need to move your fill plug....intermediate shafts size can be an issue. Both my 18 and 20 had 1.250 shaft so I didnt have any problems. Other than that it is a pretty easy swap. I drilled and tapped a new fill hole.....I turned down an extra drain plug to plug the original fill hole.... I used new paper gaskets and Black high temp RTV on both sides as well. Al seals and gaskets are brand new....I hope this thing stays dry.

 

Looks great, thanks for documenting!


I understand the process much better, I rebuilt a dana 18 before just not converted a dana 20

 

I did mine years ago (pre ecj5.com) and it went well.. Good pics man and very cool ol skool lathe in the back..

Bubba

 

Looks good.
2 things about leak sources that you probably already know, 1 is put some RTV on the yoke splines or they will leak through the splines, 2 is the speedo cable adapter is a common leak source. I have tried with some success to make a little paper gasket to fit between the cable housing and the adapter, and I have thought about using the lathe to turn a little O-ring recess on the cable adapter.

Don

 

looks good, I also have a bunch of extra cases laying around, and was planning on moving stuff over from an 18 to a 20. I like how you moved the fill plug, I'd like to see more details on that process.

 

Thanks Jonny! Sure the fill plug move as pretty easy.... I just made a flat plug to fill the old hole just make sure its tight and sealed up good because you will have to take of the rear bearing cap to get to it. Then I just drilled it out to 45/64ths and use a 1/2" pipe tap and Boom you have a new fill hole. You will just need a 1/2" pipe plug. There is a big beefy flat spot on the side of the dana 20 case where the stock spicer 18 plug was.

 

I also forgot to mention....I left out the interlock pill. I love being able to grab 2low quickly. My buddies make fun of me but I use low range all the time....backing out of the garage, backing up my camper, etc etc....but I also never have clutch problems. The t-18 reverse makes it really nice and low too. So long story short I like being able to use 2 low. Right now my jeep has a 2 stick dana 20 that controls the front and rear axles independently so you can have front drive only or H front and L rear if you really want to break stuff or low front and high rear if you want to do really dramatic rolling burnouts....haha just kidding.

 

does the original dana 20 fill plug need to be machined in order to use d-18 internals in it? now that I think of it, that rear-facing plug might interfere with the parking brake. Thanks for the tips! Interesting use of your twin sticks, I like using 2-low as well, the Jeep doesn't rev too well until it gets warmed up. And if I let it warm up in the garage, it smokes me out!

 

I used and extra d18 oild pan plug because they are flat.....but I still had to turn it down on the lathe because there is only a tiny bit of clearance between the rear bearing cap and the face of the case. It you could also run a tap in farther so It cuts the threads at the fatter end of the pipe tap.. then your plug would thread in farther... I suppose you could weld It shut also.

As you can see from the pictures there isn't much room even after facing off my plug. It is just enough to let the speedo cable thread on.

 

ahhhh, now I get it thanks for the pics, good luck with your build!

 

Silly question here, but when you put the 18 guts into the 20 case, is the shift pattern the same as the 18? Or do you now use the shift pattern as if it were a 20?

 

It's the Same as the 18. Nothing changes other than the case. No parts from the 20 are used other than the box it's self.

 

Thank you, when my 18 went in for a rebuild, we found that the case had been broken and re welded, so my builder stuffed all my parts into a 20 case, same part number as yours. I guess I need to update my signature to say super 18!