4r70w to atlas transfer case

[captgriz]

i was hoping to get some information about swapping the atlas 2 speed transfer case for the dana 20, i have an explorer efi with 4r70w tranny, the bronco has a 1" body lift. has anyone done this swap and how hard or easy is it. also i have been told the atlas does not leak fluid like the dana 20 that i have replaced all the seals multiple times. thank you for any input.

captgriz

 

[BanditBronco]

We have gone over this a bunch lately with just about every parts combo available. I would try using the search function and typing in the keyword "atlas" and/or "4r70w" to see what you can come up with. A lot of those threads started from trying to figure out what crossmembers work with what and what is available.

Based on the amount of variables involved I would not consider this a "bolt in" mod. Can it be done by just removing items, ordering items, and bolting in new items, definitely, but not likely.

If what you are searching for is a transfer case that doesn't leak, my suggestion would be to use a drivetrain shop in your area to reseal the dana20 with the expectation that if it leaks, you will bring it back till it doesn't leak. There are Dana20's out there that don't leak, mine was not one of them. My atlas weeps but doesn't drip.

If you can't seem to find the answers you are looking for, let us know and someone will take the time to dive more into it for you.

 

[JSBX]

Some times it easier to google what you are looking for with the words Classic Broncos on the end such as [ 4R70W to atlas Classic Broncos ] It will bring up lots of post on the subject. I did this swap it was very involved with a lot of research but there are plenty of post on it that should help you.

 

[captgriz]

thank you all for your input. i guess i need to figure out how involved i want to get. thanks

 

[nvrstuk]

What everyone else said about search methods but my question is my D20's (like 6 of them) never leaked. I mean didn't even weep oil.

Where is yours' leaking?

Is it popping out of gear?

What kind of shape is it in. I mean there's two output shafts which are the same principle as your frt/rear pinion yokes and then a couple flat gaskets...

Let's seal the 20 up so you don't have a $3,000 parts swap to keep your driveway clean.

 

[captgriz]

nvrstuk, it is leaking on both front and rear yoke seals. i had the case all rebuilt, leaked rite from start. so i replaced both yoke seals and the little O ring seal and they still leak. everyone i talked to say the dana 20s always leak. so frustrated was going go atlas, but would prefer to keep the dana20. i will take any info you have on how to keep it from leaking.
thank you nvrstuk.

 

[stretch]

The 4x4 4r70w will bolt up directly to the Atlas or NP205. If you have a D20 already on the 4r, you probably have the AA kit installed. I’m not sure if you can get the Atlas with the correct spline that will also mount to their adapter housing. Keep us informed as I’m sure this could help someone else.

 

[nvrstuk]

Same people that say Dana 20's always leak are the carb haters too! LOL Not really but I am a leak hater... seriously, I've pulled a D20 when it was doubled up to my 203 because it was weeping between them. lol

So, it sounds like you need the felt or whatever the original OE gasket was that was behind the output shaft nut. This sealed the weep/leak between the splines and the seal.

I don't know what the part # is but somebody here does. Check it out on some exploded D20 diagram. It will show up!

I can guarantee you 100% that you can seal that baby up tight!! Guaranteed.

 

[nvrstuk]

Check this thread out.

https://classicbroncos.com/forums/showthread.php?t=207537

Here ya go:
Front output shaft to front output yoke:

"Apparently the fluids will seep out along the splines of the yoke. Cleaning the surfaces and applying a thin film of sealant on the face of the washer behind the nut can stop this leak point.

Viperwolf1 has also found what I beleive to be the correct size o-ring to install in this location if you want to try it the OEM way: Yoke o-ring-1-1/4"OD x 1-1/8"ID x 1/16". Danco happened to be the brand at the hardware store and it is their #29

From what I have found the dimensions that Viperwolf1 supplied is for a AS568A Dash No. 024 o-ring.

Thanks for the input from Lilthom in post #23 & Viperwolf in post #24"

 

[captgriz]

nvrstuk. thank you for that info, i will give it a try. cant stand the leaks.

 

[Broncobowsher]

It took a few tries, but I got my leaky D20 to dry up. It was as dry as the 4R70W. The 351 was pretty good as well. Just a random drop from the rear main once in a blue moon. And that was an old fashion split seal.

As mentioned, weeping through the splines is pretty common for a yoke leak. RTV under the washer (after everything is clean) works pretty good. Hylomar on the front output shim back was the fix there. The PTO fought me a couple times until I tried some anaerobic sealer. Fill and drain were done with Teflon paste. Wasn't overnight, but I did get it to dry up and hold synthetic gear lube.

 

[nvrstuk]

Yeah, some of us were extra lucky having doublers and PTO take offs and of course the oil in the PTO gear box... lol