4r70 to np205. What's needed?

[buckenbronco]

Just wondering if a adaptor is needed for the 4r70 to np205. Other then moving the cross member is there anything else I should know.

 

[bronconut73]

Nope. It will bolt right up but I hear there is a "boss" that needs to ground down.
Also a custom mount will be needed for the 205. I think BC or one of the other vendors sell a mount. I want to go this route too.
You'll need new drive shafts too.

 

[buckenbronco]

Thanks. When you say boss what do you mean. Alignment plug?

 

[sykanr0ng]

You will need to cut a notch in the round mounting flange on the rear of the ZF5 or 4R70W or M5OD to clear one of the NP205 shift rails.

You will need to make a crossmember.

 

[pcf_mark]

You can use the gasket as a guide to see where u need to grind. Just make sure u have it clocked right and it will be obvious. Trim the gasket first then use it as a template.

 

[Broncobowsher]

If you are starting with a 4WD/AWD version of a 4R70W, no big deal.
If starting with a 2WD/RWD version of the 4R70W, you need an output shaft, tailhousing, and a rebuild to install them.

So you have a the correct transmission. You will find the shift rail on the 205 does not clear the tailshaft on the transmission. Carve away. Be sure to leave a little sealing surface when done. That will get you a 205 bolted to a 4R70W.

Crossmember? More work. The mounting is completely different from the stock Bronco. The Bronco has two angled bolts trough rubber doughnuts spaced wide apart. The 4R70W has the more 2WD like single rubber mount in the center. So some fabbing and adapting will be needed. That should get you everything bolted up between the frame rails once you get that done.

Driveshaft, what flanges do you have on the NP205? Expect there to be some flange swapping, driveshaft building going on. I recall the only factory NP205 with both 1310 CV flanges is the '78 Bronco (one year only). Everything else has at least one or more U-joint flange and/or sized for 1330 joints.

You will have to adapt/build a shifter.

But I think the speedometer cable will plug right in.

 

[buckenbronco]

What's the difference between married and divorced transfer case

 

[sykanr0ng]

What's the difference between married and divorced transfer case

Married means the transfer case is bolted to the transmission.

Divorced means there is a driveshaft between the transmission and the transfer case.

 

[sanndmann3]

Here is my experience, your mileage may vary...
I replaced my C4/D20 combo with the 4R/205 due to continued breakage of transfer case. Apparently the low range doesn't like to be spun at 5k+ all day long...
I was under the impression that the original crossmember could be modified but I found out that is not the case. The shift rails pass too close to the front output. The 20 has more room and threads the needle, so to speak. going thru pics and will throw them up in no particular order...

pic 1: the tail housing from 4R with the scallop cut (at bottom)for shift rail.
pic 2 & 3 shows how the original crossmember interferes with output/shift rails
pic 4: shows the crossmember I made with a harbor freight pipe bender. had to dive under the output to clear everything...
pic 5: the finish cross member.
pic 6 & 7: the crossmember in the truck and passenger side support that is welded to the inspection cover.

thats all the pics I can find right now...

 

[sanndmann3]

Also, it is possible to twin stick the 205. I found info on the required mods to the shift rails on pirate.

JB Fab sells a twin stick set up but I just sourced a 2nd 205 that was complete with shifter and adapter housing. blasted and painted the adapter and sold it on ebay for more than the set up cost me...

 

[buckenbronco]

Thanks sandmann for the info and pics. What's the advantage to twin stick. And also why the extra support in the last picture

 

[sanndmann3]

2 sticks are better than 1...

It just gives you the ability to have the front axle engaged (hi or low) while the back is in neutral. can come in handy in tight spots off road...

The 205 is a heavy beast. you don't want to just hang it off the aluminum tail housing as the bolts are relatively small. I also have a mount on the drivers side that isn't pictured.