D18 rebuild with Twin Stick conversion

So, yesterday I tore in my D18 after retrieving my parts from my neighbor (Herm shipped FedEx, I wasn't home so they left them over there, they went camping... there's a post in off topic), ANYWAY.

Wow, this was a lot of work. Or I made this a lot of work
I took it out to the shop i work at, and while i did have the day off i still had work interfering here and there.
I can see getting this done in 2-4 hours NEXT time. But NEXT time i think I will ship to Herm as his rate seems very reasonable ($110) after what I just experienced. Also i got lucky in that I didn't need much in extra parts i.e. gears, case, nuts and bolts, etc...
As it was I was at my shop with just a few distractions from 11am until 3:30am (<<not a typo).

I did Herm's 1-1/4" rebuild kit with the 1-1/4" intermediate shaft kit as well. Then I threw in the Twin stick conversion just because extra levers are always nice.

First things first! I would strongly recommend pressure washing before you begin THEN taking all your disassembled parts to a machine shop for a hot tank ($20-$30 I think?) before you begin inspecting and replacing things.

MOST of my time was spent at the parts washer or with BrakeKleen and wire brush working on the greasy pile I had in front of me.
Pre teardown:

This might be why my E-brake wasn't working?

The Pieces:

The old parts:

Fortunately the gears all looked really good:


Anyway, it took me from 11am to about 7:30pm to get torn down and clean. There were a lot of rusted bits that didn't move where the case wasn't oily. Good argument for having a massive rear main seal leak would be the total ease all bolts under the JEEP would turn (once you chip the goo off).

seems like I lost a few pictures or forgot to take them.

Here is the clean case:



Going back together:


All done (sorry about the photo gaps):







Plus the addition of me not having exactly the right tools.

I set the end play according to the Novak instructions. I got .003 which is nice and tight but in spec. NOTE; set this with output yolks OFF! the felt seals makes it difficult to check the end play by sucking up slack and adding tension in this direction.

I used 3 different sets of instructions to get through this.
Thanks to WillysTech, Novak and JeepsUnlimited sites.
It is pretty straight forward when all is said and done, but there are a few vagaries in everyone's sets of data that i had to problem solve.
Add to this my lack of a few of the right tools. And you get a greasy marathon.
Like i wrote above, NEXT time it would be an afternoon's work if I had good parts like i did here.

I'll be painting it up today and putting it back on my T86. Should be all back together by Thursday.

 

It took me longer than that.... while it works great... It still leaks really bad!

Congrats!

 

+1

 

Well I'll see about leaks in a couple of days. Mine actually looked to have been serviced not to many miles ago. But the rear output seal was badly hammered (literally) in place. I would bet it never sealed after that installation. It wasn't leaking badly anywhere else. It was plenty oily from a mainseal issue that is now gone.

I used grey RTV very sparingly but i used it everywhere. I made sure to get around the bolt holes and both sides of gaskets. I also did the threads on most non blind holes. As I type it occurs to me that I didn't do the output splines. I have read that some do this.

I think I'll wait to see if it is an issue.

PS, I wanted to mention that I think I will be putting my stock E-brake back on after I source some parts. Unless there is a fairly easy disc setup instead. I suspect later on I will have floating rear axles with locking hubs and will want to go to 11" drum with e-brake but the stocker should suffice for now.

I also opted to leave the interlock pill in and just run with hubs unlocked if I want 2wd low. I chickened out about taking it out while reading about the consequences of mis-shifting without the pill. JUST the thing I would do on my first trail test!

 

Not sure you have to worry about "mis-shifting" with the d18 t-case when the pill is removed. You do have to be carefull to not overload the rear drivetrain whan in 2-Lo.

 

I believe it because that does not look like a stock Dana 18 case to me. That looks like a Dana 20 case that someone modified with Dana 18 gears.
The give away are the two caps for the shifter rails pressed into the back of the case. A Dana 18 has a single bulge cast into the rear of the case for the Hi/Lo range shifter rail.

I’ve been running mine without the interlock pill for several years without any issues.
If you feel the shifter is a little sloppy and may pop out of gear, change the detent ball and spring for the shifter.

 

Wouldn't a Dana 20 case have a centered output?

 

Yes, it would. That’s why it would have to be modified with the Dana 18 gears to have the offset rear output.
This isn’t an uncommon mod., I’ve actually looked into it myself.

“There were some conversions that changed the centered rear output to a Dana 18-style offset rear output so that the stronger 20 could be used in place of the 18 on older vehicles. Jeep, IH, GM, and Ford all used versions of the Dana 20.”

http://www.fourwheeler.com/techarti...rbox_anatomy_dana_20_transfer_case/index.html

 

Interesting. Thanks for the information.

 

It was my understanding that the Dana 18 gears from the big-hole/big-shaft Dana 18 go right into a bare Dana 20 case. The 20 has a cover where the 18 has a rear output, and vice-versa. The 20 is a common source for a replacement 18 case, and is reputed to be somewhat stronger than the 18 case.

Just what I gather from reading and listening...

 

NO modifications must be done to put the 29 tooth 18 gears in a 20 case. You just have to use all the output shafts, output housings, etc.
It's a great way to get a bit stronger case with the 1 1/4" intermediate pin, and a large hole case.
Make sure you get one with the filler on the side and not the back if you are using a transfer case mounted park brake or you won't be able to fill it. Also make sure it has the boss or is already machined for the clutch linkage pivot on the driver's side. Not all of them are machined for that, some don't even have the boss, and many have the fill on the back although the side of the case can be drilled and tapped for the fill.
I just did one last week and a ton of them over the last 15 years.

Now, if you want to put the 18 gears in the 20 case and keep it a 20 but get the 2.46-1 low range, there is some grinding on the case to do.

Edit post:
There are a very few 20 cases that you must grind a touch off the pan rail to get the idler gear in if you install it last and I ran into one a couple weeks ago that had excess casting material on the inside of the pan rail on the front output end of the case that had to be clearance some. These were not "usual" however.

 

WHen you installed the output shaft and shimmed the rear housing did you put a light layer of RTV on all shims to prevent leaks there also? Those shims are a known source of leaks on many jeeps.

 

Actually that’s a bit confusing.
I’ve got three Dana/Spicer 18 cases also, of various vintage, and all have the single cast bulge. But what would the second cap for? The Dana 18 case doesn’t need it for the 2WD/4WD shift rail because the rail doesn’t go all the way through the case since it’s coupling the front output to the rear output right in the front output housing.

http://www.novak-adapt.com/catalog/dana_18_parts.htm

 

Crazy. Thanks for the info Patrick, I will certainly keep that in mind in the future.

 

The Big Hole 18 (4" index bore) was specific to Dauntless 225. It was never used with a Hurricane.
Jeep obviously implemented the D 20 case that was already in use since 1962 for the fullsize Jeeps.

I agree with Patrick I have an original "big hole 18 case" from a very early 1966 (built in 1965) It has dual shift rail caps.
Also like Nickmil said the early big hole 18 cases (pre 1972) have the fill plug in the traditional side location while all late Dana 20 CJ's (post 1975) have the fill plug in the rear location.
Perhaps Tim can verify fill plug location during the intermediate years ?

The model 20 case is no stronger than the big hole 18 case of the same era.
They are one and the same.