Dana20 transfercase-Rebuild myself?

How hard is it to do? Mine is leaking oil out the front and rear outputs. Also by the shifters. It seems to work fine, but I have only driven it very little. Shifts good. Is there a place that has rebuilt ones? thanks for any info.

 

If it's just leaking, I'd replace the output seals first. The Dana 20 is easy to take apart, and if not noisy, I'd just take it apart, clean it, and put it back together with new seals and gaskets. The gear-driven Dana transfer cases always seem to leak a little, so you might just want to feed its habit. JMO - no noise, and it's full of oil -> no worries.

 

I was able to do it myself and while I have rebuilt several motors I had never done a transmission or transfer case. There is a good writeup in the technical service manual and a pretty good set of instructions at the Novak web site. Really the hardest thing was depressing the poppet balls-springs while inserting the shift rails. Get a digital camera and take some pictures while dissembling.
Good luck !

 

I like the just seals idea.

Take off the pan and look for metal.
Like you said it sounds ok.

Mine was full of metal but it was from the tranny.

On the seals...
thin film of rtv on outside of seals.
And look at the yoaks where the seal touchs,
make sure not to big of groove worn in,
or just really rough surface.
thin film of rtv on splines before yoak goes back on.

They make a double seal you can get too.

 

Sorry guys I should have posted that the output shafts seem to wooble around when you push on them. I think the bearings are loose. I drained it and all the fluid was milky, must have got water in at some point. But it does seem to work fine. I found a local guy who has a couple for $60. each. One with a t14 the other a T15. I think I have the t14, is the t15 better. price with the trannys is $140. What do you think- Go take a look and hope all is well or rebuild mine? The only problem I see in rebuilding mine is the shims on the bearing and ajusting the output shafts. Thanks Dan

 

why even consider someone else's junk ?
fix what you have.
you already have stated it works fine.
drop the pan, inspect, fix what needs fixing and be happy.

 

Rebuilding the Dana 20 is not that difficult, If you have ever been inside of a manuel transmission or built a differential you shouldn't have any problem. Some of the bearings have to be pressed off and on and you have to set the preload on them with shims. If the transfer case has had water in it for awhile then I would want to have a look at the bearings in the transmission also. If you are going to do this yourself you should find a service manuel because it will list dissassembly and assembly procedures step by step.
Good luck.

 

Thats what I do... buy someone else junk and spend alot of money on it and then sell it. Just ask the wife. Yea Ill probably try to rebuild it if a deal doesn't pop up!

 

Hmm. Dana 20s are plentiful and cheap. If you want a replacement, check your local 4x4 club forum. Lots of them out there.

You'll need a dial indicator to check the preload if you rebuild your own. Doesn't have to be fancy - Harbor Freight has one for $8 on sale now, and a magnetic base for $13.

If you originally had the 304, it came with a T-15. The T-14 was used with the 6 cylinder engines and is not as strong as the T-15.

 

Thanks all. Maybe I should look into the t15 d20 combo as an upgrade. Ido have a 360...and a manual...

 

Okay the d20 is out and on the garage floor! It looks like the rear yoke has a wobble but not the shaft. the front has a slight movement in the shaft. the gears look fine. No metal in oil. One good thing about the leak is the bolts weren't rusty. Got it out in 30 minutes. The tranny seems nice and tight. I might go look at the one that is local if he calls me back. Anything else to look at on a used one? Thanks again for all the help

Dan

 

i had my dana300 rebuilt by a shop a couple years ago, before i had my garage to do all my work in now, i was in a time and space crunch so i just bit the bullet and had them handle it for me. i've helped a friend with his t-case since, really not that tough. anyways, even after the rebuild, i have tiny leaks, seemed solid for a bit, but after that 1 year warranty was up, it sprang the tiniest leaks, not really enough to concern me yet. i think most all old stuff (like 70's and earlier jeeps that take abuse) just leak a little here and there.

as far as swapping for another d20 tcase, if your going to invest in a swap, i would reccomend a d300. i'm sure if you look you will find one inexpensive, and it is one hell of a unit. mine has yet to give me any grief, besides that minor leak. i just needed my tranny rebuilt and told them to overhaul my tcase so i could be worry free about the two of them. d300 is the way to go, in my opinion, even if i had the $$$$ to invest in an atlas, i'd keep my d300 and put that money elsewhere in the jeep.

...just my opinions. good luck

 

Will the dana 300 fit w/o driveshaft mods? If not then no, trying to keep it simple.

 

The only Dana 300 that will fit comes from a 1980 (right year? only one year for sure) Scout II with a manual transmission, and has what's called the "texas" bolt pattern (because it looks like the state). These are scarce, highly sought after and command a high price. Your driveshafts would probably be ok with this unit, but maybe not. However, if you can afford the texas D300, you should be able to afford new driveshafts.

The Jeep D300 is much more common, but still costs a lot more than the Dana 20 unless the seller doesn't know what he's got. Plus, the transmission-to-transfer case pattern changed, so it won't bolt up to your transmission unless you install an expensive adapter kit or change to a different transmission or both.

The 300 is clearly superior to the 20, but not a simple swap-in.

 

ya, my cj had the t5 and d300 in it when i got it. i didn't know it was a hassle, apparantly someone already did that part for me. i have been nothing but happy and proud to have that d300 in there though, treated me real well.

i guess if you come across a tranny/d300 combo for a good deal, jump on it, otherwise, sorry for the misleading advice.

 

Just to chime in.
The Dana 20 is a good case.
For along time.

There are better ones,
but that doent mean yours is bad,
or that you have to up grade,
fix it keep it.

IMHO

 

Apparently Novak agrees about the Dana 20

"The Dana 20 is found in 1962-1979 Jeep vehicles. It is also found in IH Scout trucks. It's design was outstanding and remains one of the strongest and most refined of all the popular transfer cases."

 

You can break the output housing of a D20 if abused in a heavy vehicle with big tires and some power. The D300 has the same problem, but maybe a little stronger ... not sure.

In a CJ, the main attraction of the D300 is the better low range gearing: 2.03:1 v. 2.62:1 for the D20 and D300 resp. You can match the low range gearing of the D300 in the D20 with special gears (early Bronco or Tera), but a D300 can have a 4:1 reduction with Tera gears. Check the article on Pirate4x4 named Uber20.

Wicked4x4, no need to apologize - we are interested in your experiences - I just filled in a few details.

 

Again, thanks everyone. I'm going to try to clean up my d20 today and open it up this weekend.

 

Not trying to step on toes here Tim so if I am I want to apologize up front, but would like to clarify a few things and add a little.
Doing the Bronco/18 gear set will net a 2.46-1 low range whereas as you noted the low range of the 300 at 2.62-1.
Tera and some others make a 3.15 gear set for the 20. O'Brien's was making even lower gear sets but some required cutting a "window" in the case to clear the gears and welding a kind of doghouse on it. I know Tera is making applications for other than just Jeep and had one that would work with a stock Jeep TH 400 trans.
Several manufacturers including Tera and JB Conversions make a 4-1 gear set for the 300 that is readily available.
STAK 4x4 is making new 300 cases that is supposed to be stronger than the stock unit and will even allow a left hand front output.
I don't think anyone is making 20 cases any more. Tri-County Gear I think in Pomona, CA was making case girdles for the 18 and possibly the 20.

The 300 had two rear output shafts. A short version used in '80-'83 CJ-5's and '7's equipped with the 258 and automatic trans only. The longer version was used in all other CJ-7's as far as I have been able to determine. The short shaft is approximately 3/4" shorter and uses a new output housing. Easily identifiable as the speedo driven gear housing threads into the housing. All 300 rear output housings including the rare Scout "Texas" pattern were aluminum despite some books and mags that say otherwise. The short shaft is stronger than the long shaft. The short shaft uses a slip fit speedo drive gear like the 20 and 18 transfer cases. The long shaft have the speedo gear cut into the shaft which makes a weak point. The long shaft also has a step down at the yoke splines that frequently makes a weak point as well. The long shaft has a slip in speedo driven gear housing with a retainer that holds it in like a 231, 241, etc. transfer case so is easily identifiable.
There are all kinds of kits to upgrade the 300 to larger output shafts from various manufacturers. Not sure if anyone is making one for the 20.

The disadvantage to the 300 is they are getting harder to come by as they are popular and were only used from '80-'86 in CJ's only and '80 IH Scout 2 (Texas Pattern). The 20 is very available in various forms and parts are easy to find.

I'd rebuild what you have and be happy. If you want to upgrade later you always can. Nickmil