4r70w to Atlas help!

[71 CA Bronco]

I am getting ready to set motor/trans/atlas II into the chassis and had a few questions. My plan is to go 4R70W to Atlas. I was told its a direct bolt in with the exception of needing to fabricate the crossmember.

Questions:

1. I've read that there is a seal that if not installed will leak trans fluid into the transfer case. Do I need this seal if using a 4x4 transmission? I'm not sure exactly where this seal would go.
   
2. I'm told that you can install with adapter ring and no cutting is required on output/spud shaft. Or, remove adapter ring and cut shaft for less overall length. If this is the case which method do you guys prefer?
   
3. It appears I will be keeping the original 4R70W adapter housing. If this is the case then what type of crossmember and mount should I use or fabricate? Any off the shelf crossmembers that work well? Pictures would be really helpful if possible.

I appreciate any help you guys can offer on this. I just want to do this right. I've come too far to screw it up now.

Rob...

 

[Broncobowsher]

1) not sure. I have not had a factory 4WS 4R70W. What little I have done with an Atlas is there is a seal around the input shaft of the Atlas that keeps fluids separated. Nothing on the transmission side. If you look at the female splines on the input, on the outside of that shaft to the Atlas case (bearing retainer, whatever is stationary just around that shaft) there should be a seal.
2) cut and forward. Always trying to get as much rear driveshaft length as possible
3) Use an Explorer 4WD transmission mount. Make or modify your own crossmember. Not sure if any of the venders having an off the shelf crossmember. The closest I can think of is the ZF adaptor crossmember (BC Broncos?) but have no idea how that will play with the Atlas or 4R70W. It is the only one I can think of that has the late model type of transmission mount.

 

[JSBX]

I am getting ready to do the same thing when my Atlas arrives in a couple more weeks. Has been 6 weeks since I ordered it. I bought a cross member from Bronco Hut for the 4R70W swap.

 

[71 CA Bronco]

1) not sure. I have not had a factory 4WS 4R70W. What little I have done with an Atlas is there is a seal around the input shaft of the Atlas that keeps fluids separated. Nothing on the transmission side. If you look at the female splines on the input, on the outside of that shaft to the Atlas case (bearing retainer, whatever is stationary just around that shaft) there should be a seal.
2) cut and forward. Always trying to get as much rear driveshaft length as possible
3) Use an Explorer 4WD transmission mount. Make or modify your own crossmember. Not sure if any of the venders having an off the shelf crossmember. The closest I can think of is the ZF adaptor crossmember (BC Broncos?) but have no idea how that will play with the Atlas or 4R70W. It is the only one I can think of that has the late model type of transmission mount.

Thank you Bowsher. I appreciate the input.

 

[71 CA Bronco]

I am getting ready to do the same thing when my Atlas arrives in a couple more weeks. Has been 6 weeks since I ordered it. I bought a cross member from Bronco Hut for the 4R70W swap.

You might want to double check that crossmember. I would hate for you to buy it for no reason. The ones I have seen are made for the 4R70W to D20 adapter. Ours will use the Explorer adapter as Bowsher mentioned above and with the Explorer mount.

I believe it to be a completely different crossmember with different mount. Hoping to have someone post a picture of how they did theirs. It would be helpful to see the mount and how they cut shaft and aligned the tcase. Its a bit nerve racking to cut the shaft. I would hate to toast the trans and need to start over.

 

[JSBX]

Got me concerned now. I will call Bronco Hut tomorrow and talk with them about it.

 

[71 CA Bronco]

Got me concerned now. I will call Bronco Hut tomorrow and talk with them about it.

Let us know what you find out.

 

[fordguy]

I am getting ready to do the same thing when my Atlas arrives in a couple more weeks. Has been 6 weeks since I ordered it. I bought a cross member from Bronco Hut for the 4R70W swap.

did not know you decided to go atlas, which bronco?

 

[JSBX]

did not know you decided to go atlas, which bronco?

In my 74. After I figured the cost of low gears, heavy duty output and an adapter the cost for the Dana 20 work was just a little less than an atlas. So I bit the bullet. I had a 351 roller built local using the GT 40 heads that I had. I have all my old stuff out and trying to get this done before OCBR. Going to be tight.

 

[garberz]

I am getting ready to set motor/trans/atlas II into the chassis and had a few questions. My plan is to go 4R70W to Atlas. I was told its a direct bolt in with the exception of needing to fabricate the crossmember.

Questions:

1. I've read that there is a seal that if not installed will leak trans fluid into the transfer case. Do I need this seal if using a 4x4 transmission? I'm not sure exactly where this seal would go.
   
2. I'm told that you can install with adapter ring and no cutting is required on output/spud shaft. Or, remove adapter ring and cut shaft for less overall length. If this is the case which method do you guys prefer?
   
3. It appears I will be keeping the original 4R70W adapter housing. If this is the case then what type of crossmember and mount should I use or fabricate? Any off the shelf crossmembers that work well? Pictures would be really helpful if possible.

I appreciate any help you guys can offer on this. I just want to do this right. I've come too far to screw it up now.

Rob...

1. There’s no seal on the back of the 4r70w, fluid is open to the face of the AtlasII. The AtlasII has its own input seal. You just join them together with a bead of RTV around the adapter hosing.

2. I cut exactly 1” off the output shaft of the AWD 4r70w trans. The only thing critical is you need to make sure the output shaft is short enough, so it doesn’t bottom out inside the input shaft coupler.
You can buy a 1” spacer to avoid cutting, but that’s not a good option with our limited driveshaft length.

3. I made a crossmember from 1 1/2” square tubing. Very simple, I was able to keep it straight, no cuts or bends. I clocked the Atlas all the way up to where it sets 1/4” away from the drivers side frame rail. The straight crossmember runs just under the front driveshaft. The issue I had with this setup is, the front drive shaft runs at about 20* angle at ride height with 3 1/2” lift. I needed a higher angle driveshaft to make it work. $! Watch your front driveshaft angle when mocking it up. The CV joint is only good for 26*.

Mark

 

[BanditBronco]

I am getting ready to do the same thing when my Atlas arrives in a couple more weeks. Has been 6 weeks since I ordered it. I bought a cross member from Bronco Hut for the 4R70W swap.

unless you are running an adapter housing like the zf one or the other one everyone uses, cant remember exactly which one that is, the cross member won't work. I ordered one thinking it would be bolt in just like you, and realized to was made for the adapter housing and stock style dana 20 mounts. If you are mounting an atlas directly to a 4x4 4r70w that cross member will not work.

 

[BanditBronco]

Here are some photos of how I made my crossmember. Just like garberz I clocked the atlas as far towards the drivers side as I could so it is about a 1/4 from the frame. To make this work with a 1" body lift I had to trim out the body stiffener crossmember and I also pushed the entire drivetrain forward 1/2-3/4 of an inch so that the atlas would sit inside of the trans tunnel and not half in and half out. I used the stock style mounting ends of the stock crossmember so I didn't have to modify the frame at all.

 

[71 CA Bronco]

1. There’s no seal on the back of the 4r70w, fluid is open to the face of the AtlasII. The AtlasII has its own input seal. You just join them together with a bead of RTV around the adapter hosing.

2. I cut exactly 1” off the output shaft of the AWD 4r70w trans. The only thing critical is you need to make sure the output shaft is short enough, so it doesn’t bottom out inside the input shaft coupler.
You can buy a 1” spacer to avoid cutting, but that’s not a good option with our limited driveshaft length.

3. I made a crossmember from 1 1/2” square tubing. Very simple, I was able to keep it straight, no cuts or bends. I clocked the Atlas all the way up to where it sets 1/4” away from the drivers side frame rail. The straight crossmember runs just under the front driveshaft. The issue I had with this setup is, the front drive shaft runs at about 20* angle at ride height with 3 1/2” lift. I needed a higher angle driveshaft to make it work. $! Watch your front driveshaft angle when mocking it up. The CV joint is only good for 26*.

Mark

Thanks Mark. Kinda what I thought but needed confirmation before getting into this phase. I guess I'll need a lession for measuring driveshaft angle. Is there a tool that makes this easy?

 

[71 CA Bronco]

unless you are running an adapter housing like the zf one or the other one everyone uses, cant remember exactly which one that is, the cross member won't work. I ordered one thinking it would be bolt in just like you, and realized to was made for the adapter housing and stock style dana 20 mounts. If you are mounting an atlas directly to a 4x4 4r70w that cross member will not work.

Yep, same issue for me but fortunately I figured it out before buying the cross member.

 

[71 CA Bronco]

Here are some photos of how I made my crossmember. Just like garberz I clocked the atlas as far towards the drivers side as I could so it is about a 1/4 from the frame. To make this work with a 1" body lift I had to trim out the body stiffener crossmember and I also pushed the entire drivetrain forward 1/2-3/4 of an inch so that the atlas would sit inside of the trans tunnel and not half in and half out. I used the stock style mounting ends of the stock crossmember so I didn't have to modify the frame at all.

Wholly smokes. That is some fine craftsmanship. Looks like it was cut on a CNC. Any chance you kept the dimensions, or had it drawn up? I'm sure there are other members that could use the info. Thanks brother...

 

[71 CA Bronco]

Cross Member

Found this thread.

https://classicbroncos.com/forums/showthread.php?t=183817

A was thinking this was the answer until I read the last post by Chuck from BC. He was thinking it would have a strength issue by levering the mount.

 

[JSBX]

Cross member

For the ones that are following this thread. BC Broncos has a cross member that will work with a 6R80 or 4R70W. Dana 20 or atlas. This is per Jason at BC. Since I am not much of a fabricator or welder I ordered one today. Thanks to all the ones that responded to this thread.
James.

 

[71 CA Bronco]

For the ones that are following this thread. BC Broncos has a cross member that will work with a 6R80 or 4R70W. Dana 20 or atlas. This is per Jason at BC. Since I am not much of a fabricator or welder I ordered one today. Thanks to all the ones that responded to this thread.
James.

To clarify its for 6R80 to Dana 20, or 4r70W to Atlas. There are two different mounting holes on the cross member. You would still go with the modified stock mount for 4R70W to Dana 20. I ordered one today also. BC part number 21-57043, if anyone needs it.

Thanks Guys.....

 

[71 CA Bronco]

Well scratch that. The BC crossmember listed above does NOT work with 4R70W to Atlas. A few members ordered one and its off quite a bit. Back to the drawing board.

 

[1buckeyefan1]

For the ones that are following this thread. BC Broncos has a cross member that will work with a 6R80 or 4R70W. Dana 20 or atlas. This is per Jason at BC. Since I am not much of a fabricator or welder I ordered one today. Thanks to all the ones that responded to this thread.
James.

Sorry to dig up an old thread.. but how did this work out for you? I'm looking at fabricating vs using the BC mount using the stock 4R70W 4WD/ZF adapter and Dana20.. but don't want to purchase one only to be unable to use it (which looks like what happened to folks using an Atlas)