New auto and Atlas for my build, opinions?

[ngsd]

Looking for suggestions. I am considering replacing my off road rig transmission and t case. It currently has a 351 FI, with a NP435, dana 20 and Klune V. I love the gearing but it is getting tired. I also want to go auto this time around. The question is what would be the optimal set up for this. I would like to make it at least drivable on the street to get to the trails so not just totally off road. I had thought about every combo and to get the gearing I wanted was thinking of a 6R80 with an Atlas 2 3.8. Am I over thinking it?
Has anyone done this or what are your experiences?

 

[Spaggyroe]

I have a 6R80 / atlas 2 combo in my 69. It's an awesome combination. My atlas is 3:1. If I were doing more rock crawling, I would've gone with a lower gearset.
It's a VERY versatile way to go I.M.O. My atlas 2 shifts significantly better than my D20. I also personally think that the 6R80 is the best auto trans you can put in a Bronco.

My only advise is, to ensure that your differential gearing is well suited for your tire size. I had 4:11's and the 6R80 would not hold 6th on the freeway. I had to drop down to 4:88's and that worked perfectly. I'm running 35" tires.

My 66 had a NP435 / dana 20 in it. It never gave me any issues and the NP435's first gear is amazing, BUT it shifts like... well. a truck. lol.

 

[ngsd]

I have a 6R80 / atlas 2 combo in my 69. It's an awesome combination. My atlas is 3:1. If I were doing more rock crawling, I would've gone with a lower gearset.
It's a VERY versatile way to go I.M.O. My atlas 2 shifts significantly better than my D20. I also personally think that the 6R80 is the best auto trans you can put in a Bronco.

My only advise is, to ensure that your differential gearing is well suited for your tire size. I had 4:11's and the 6R80 would not hold 6th on the freeway. I had to drop down to 4:88's and that worked perfectly. I'm running 35" tires.

My 66 had a NP435 / dana 20 in it. It never gave me any issues and the NP435's first gear is amazing, BUT it shifts like... well. a truck. lol.

Thanks, I am just exploring the options and that helps. Do you have a build list of things I would need to consider or think about? I have a Dana 60 rear axle (stock EB width), 37" tires with 4:56 gears and ARB Lockers so I would like to retain that. I will be doing a 4 link on it too.

 

[Spaggyroe]

In your case, you'd need a trans controller. https://www.usshift.com/usq6.shtml
You'll need a way to connect the cooler lines. https://www.summitracing.com/parts/pma-pa68505
A trans cooler. I used this and mounted it under my passenger seat area. https://www.summitracing.com/parts/der-13870
I used this in-line thermostat to turn the cooling fan on and off. https://www.summitracing.com/parts/der-13021
Lines to connect the two. I used a local hose shop.
A shifter. There are a number of options here. I used a column shift kit from BC Broncos https://bcbroncos.com/shop/steering.../21-57021-column-shift-rod-6r80-transmission/ People have adapted an F150 shifter, and also used other floor mounted aftermarket shifters.
Crossmember. You may need to fabricate something here. I used this one https://bcbroncos.com/shop/engine/engine-small-block/21-57043-6-speed-crossmember/
That's all I can think of for now but I'll add to this post if I think of anything else.

Remember that the 6R80 has two overdrive gears. You may want to consider re-gearing your axles down to about 5:13 or so. I know that's an added expense that you probably don't want to deal with, but I think you'd be much happier in the end.

Somewhere on this site is an excellent write up about putting a 6R80 in an EB.

Good luck with the build. It sounds like it's a BEAST of a Bronco.

 

[ngsd]

In your case, you'd need a trans controller. https://www.usshift.com/usq6.shtml
You'll need a way to connect the cooler lines. https://www.summitracing.com/parts/pma-pa68505
A trans cooler. I used this and mounted it under my passenger seat area. https://www.summitracing.com/parts/der-13870
I used this in-line thermostat to turn the cooling fan on and off. https://www.summitracing.com/parts/der-13021
Lines to connect the two. I used a local hose shop.
A shifter. There are a number of options here. I used a column shift kit from BC Broncos https://bcbroncos.com/shop/steering.../21-57021-column-shift-rod-6r80-transmission/ People have adapted an F150 shifter, and also used other floor mounted aftermarket shifters.
Crossmember. You may need to fabricate something here. I used this one https://bcbroncos.com/shop/engine/engine-small-block/21-57043-6-speed-crossmember/
That's all I can think of for now but I'll add to this post if I think of anything else.

Remember that the 6R80 has two overdrive gears. You may want to consider re-gearing your axles down to about 5:13 or so. I know that's an added expense that you probably don't want to deal with, but I think you'd be much happier in the end.

Somewhere on this site is an excellent write up about putting a 6R80 in an EB.

Good luck with the build. It sounds like it's a BEAST of a Bronco.

Thanks that is very helpful.

 

[bigmuddy]

Alot of people have been happy with the 4r70w. I am getting ready to do this if my rig ever comes back from paint..

Although not as slick as the 6r80, it may not require a regear for the final drive/overdrive.

 

[Spaggyroe]

The overdrive ratio in the 4R70W is 0.70:1
The higest of the two overdrives in the 6R80 is 0.69:1

So, essentially the same either way in top gear.

 

[BanditBronco]

To take advantage of either 4 or 6r you would want to regear to at least 5.13, I would go one deeper than that if it was me. You are more than welcome to take a ride in mine if I end up at the Stampede. 351w, 4r, atlas 2 3.0, 37's with 5.38's. The only difference in mine would be that it actually shifts nice since it doesn't have an aftermarket controller.

 

[bigmuddy]

351w, 4r, atlas 2 3.0, 37's with 5.38's. The only difference in mine would be that it actually shifts nice since it doesn't have an aftermarket controller.

what does that mean> it shifts nice because it doesn't have an aftermarket controller? Are you using the stock EFI computer to control it?

 

[BanditBronco]

what does that mean> it shifts nice because it doesn't have an aftermarket controller? Are you using the stock EFI computer to control it?

Correct, I have run it both ways and much prefer how to acts with the stock computer compared to the aftermarket.

Another note,

That is probably the only reason I would lean towards the 4r instead of the 6r is this discussion. I haven't done any research, but I would assume the 6r uses its own TCM in stock form. Would be awesome if it wasn't integrated into the ecm at all and could be modified to work as a stand-alone TCM and Harness. Are the coyote swaps with 6r's using an aftermarket computer or OEM?

 

[nvrstuk]

You have a 351W not a 170 ci 6cyl. You will be fine with the 6r with 35"s and 4.56. You will need a US Shift controller and you can program that so your trans isn't hunting for gears, you can program it so it will NEVER hunt for a gear because you shift it manually, you can make it work easily for what you have.

I have run a 351W with 4r70 with KluneV, with D20 for almost dozen years. I ran a ZF 203/D20 before that for 11yrs. I ran a 4r70 with a KluneV and Atlas and then a 205 and loved it. GREAT combo for off and on road. I ran 35's and 37's with 4.56 gears and never lacked for a lower crawl gear with an auto (or my ZF).
I ran a 418/4r/KluneV/205 for years with 37"s and 4.56 gearing. Loved it -great combination. Never once did I want lower gearing off road. You have a torque converter.
Not trying to piss anyone off but a buddy of mine is currently regearing (not cheap) because he thought he needed 5.13 gears with his 289, ZF, 35"s, Titan and 205, literally HATES it on the highway. SCREAMS down the highway. I tried to convince him 4 yrs ago he wouldn't need 5.13"s but everything he read....
Just giving you real feedback cause if you drive the highway at all, a 351W doesn't like to be wound out all the time like a 289 or 302.

I really disagree that you need deeper gears- strongly disagree unless you do nothing but off road. I ran 50,000 miles with 4.56 gears with either 35" or 37" tires. So what if it shifts down on a long hill... that's what drivetrains are supposed to do. If you can NEVER drive it on the freeway in OD then you have some gearing issues.

I currently run 40" tires with 5.13s and have no need to gear to anything lower. Why would you need 5.13's with 35"s is beyond me, especially with a 6r that has a 4.17 first gear. If you like 3,000 rpm down the highway then yes. I have NO idea how much highway driving you do.

I do rocks as often as possible. Till Covid we were going 3x/year to Moab. and playing locally. I ran my 4r70 with 4.56 gears and 37's for 16 or more years. Never needed lower axle gears. You have a torque converter for that- it essentially doubles your crawl ratio and with a 50% lower first gear with the 6r it's unneeded..
It's so effective that I quit using my doubler box and ran 2.7:1 exclusively instead of doubling up with my 4r. Then when I installed the 6r 2 1/2 yrs ago with a 50% lower first gear the need for lower gears is gone.

If you really felt the need you could go 4.88 and not be winding out on the freeway but you'll be happy with the 4.56's.

I wrote an in-depth article on 6r installations in a Bronco here on CB. Here's the link.- hope it helps. https://classicbroncos.com/forums/a...-trans-into-a-bronco-behind-any-sbf-engine.2/


If you want more info on gearing choices and why with a 6r that has a 4.17:1 first gear you don't need super low axle gears because first gear in it is almost 50% lower than a 4r. here is some more info. That 4.17 is HUGE and you can feel it when wheeling and around town it is an amazing difference.

Here's my installation and gearing changes and why on my build thread. Hope this helps. Starts in on 6r info around post 329?? Long and some chit chat in there but lots of pics.

https://classicbroncos.com/forums/t...5-wb-stretch-2-floor-lower-p-s.278607/page-17

Hoping nobody hates but gearing too low is pretty common because people go on line and figure some chart can be substituted instead of experience, type of wheeling, weight of vehicle, tire diameter, type of wheeling, etc, etc. . With a stock OE torque converter (low stall) you can cruise & wheel all over Moab or Sand Hollow with a 6r and 3.0:1 Atlas and never have a need for anything lower and so what if you're cruising along in your 1st OD, (5th gear) up a slight grade instead of your 2nd OD (6th).
I'm heading back to Sand Hollow this weekend.

 

[ngsd]

You have a 351W not a 170 ci 6cyl. You will be fine with the 6r with 35"s and 4.56. You will need a US Shift controller and you can program that so your trans isn't hunting for gears, you can program it so it will NEVER hunt for a gear because you shift it manually, you can make it work easily for what you have.

I have run a 351W with 4r70 with KluneV, with D20 for almost dozen years. I ran a ZF 203/D20 before that for 11yrs. I ran a 4r70 with a KluneV and Atlas and then a 205 and loved it. GREAT combo for off and on road. I ran 35's and 37's with 4.56 gears and never lacked for a lower crawl gear with an auto (or my ZF).
I ran a 418/4r/KluneV/205 for years with 37"s and 4.56 gearing. Loved it -great combination. Never once did I want lower gearing off road. You have a torque converter.
Not trying to piss anyone off but a buddy of mine is currently regearing (not cheap) because he thought he needed 5.13 gears with his 289, 35"s, Titan and 205, literally HATES it on the highway. SCREAMS down the highway. I tried to convince him 4 yrs ago he wouldn't need 5.13"s but everything he read....
Just giving you real feedback cause if you drive the highway at all, a 351W doesn't like to be wound out all the time like a 289 or 302.

I really disagree that you need deeper gears- strongly disagree unless you do nothing but off road. I ran 50,000 miles with 4.56 gears with either 35" or 37" tires. So what if it shifts down on a long hill... that's what drivetrains are supposed to do. If you can NEVER drive it on the freeway in OD then you have some gearing issues.

I currently run 40" tires with 5.13s and have no need to gear to anything lower. Why would you need 5.13's with 35"s is beyond me, especially with a 6r that has a 4.17 first gear. If you like 3,000 rpm down the highway then yes. I have NO idea how much highway driving you do.

I do rocks as often as possible. Till Covid we were going 3x/year to Moab. and playing locally. I ran my 4r70 with 4.56 gears and 37's for 16 or more years. Never needed lower axle gears. You have a torque converter for that- it essentially doubles your crawl ratio. It's so effective that I quick using my doubler box and ran 2.7:1 exclusively instead of doubling up.

If you really felt the need you could go 4.88 and not be winding out on the freeway but you'll be happy with the 4.56's.

I wrote an in-depth article on 6r installations in a Bronco here on CB. Here's the link.- hope it helps. https://classicbroncos.com/forums/a...-trans-into-a-bronco-behind-any-sbf-engine.2/


If you want more info on gearing choices and why with a 6r that has a 4.17:1 first gear you don't need super low axle gears because first gear in it is almost 50% lower than a 4r. here is some more info. That 4.17 is HUGE and you can feel it when wheeling and around town it is an amazing difference. About Post #330
https://classicbroncos.com/forums/t...5-wb-stretch-2-floor-lower-p-s.278607/page-17

Here's my installation and gearing changes and why on my build thread. Hope this helps. Starts in on 6r info around post 329?? Long and some chit chat in there but lots of pics.

https://classicbroncos.com/forums/t...5-wb-stretch-2-floor-lower-p-s.278607/page-17

Hoping nobody hates but gearing too low is common with a stock OE torque converter (low stall). You can cruise all over Moab or Sand Hollow with a 6r and 3.0:1 Atlas and never have a need for anything lower. I'm heading back to Sand Hollow this weekend.

That was helpful, thanks for the link to your post I was searching for that and that made it easy.

 

[Yeller]

Couldn’t agree more with nvrstuk. I run 4.55 and 37’s. With 35’s I feel it’s perfect. The only time I feel it’s not enough with 37’s is trying to run faster than 70, the wind resistance gets high enough the engine needs a little more spin but how often do I really need to drive faster than 70….. with 35’s it didn’t matter. And off road with an auto once you get to 40:1 in 1st gear your returns diminish rapidly, past 50:1 is in my opinion a waste of effort. A 6r with a 205 and 4.56 is 40:1, perfect in my opinion. A4r70 with a 3.0 atlas is 38:1, close enough.

 

[Broncobowsher]

Instead of yelling about what ratio, I'll throw my advise this way. 60 MPH = 2000 RPM. Gear as needed for the overdrive and tire size. It is a touch on the low side, but at highway speeds the drag of a Bronco (more so one that is lifted on bigger tires) is a touch on the high side, so they cancel each other out. If you scale that up, 90 MPH = 3000 RPM which is about where you need to be in the torque band to push the brick through the wind that fast. Not counting the direct inject motors (they tend to make some serious low RPM grunt) most modern trucks were geared about the same way. My 2010 runs at maybe 1900 RPM at 60 MPH, but has better aero.

As for an engine screaming down the highway, most of the time that can be traced back to the cooling fan. Explorer front drive with a clutched fan to fix that.

 

[BanditBronco]

The good news is, either way if your highway ratio doesn't end up where you want it, you don't have to undo any of the hard work you just put in. If you are headed down hill to Florence, I think you will be good, if you are headed up the hill to table mesa you might not see overdrive.

 

[bigmuddy]

You have a 351W not a 170 ci 6cyl. You will be fine with the 6r with 35"s and 4.56. You will need a US Shift controller and you can program that so your trans isn't hunting for gears, you can program it so it will NEVER hunt for a gear because you shift it manually, you can make it work easily for what you have.

I have run a 351W with 4r70 with KluneV, with D20 for almost dozen years. I ran a ZF 203/D20 before that for 11yrs. I ran a 4r70 with a KluneV and Atlas and then a 205 and loved it. GREAT combo for off and on road. I ran 35's and 37's with 4.56 gears and never lacked for a lower crawl gear with an auto (or my ZF).
I ran a 418/4r/KluneV/205 for years with 37"s and 4.56 gearing. Loved it -great combination. Never once did I want lower gearing off road. You have a torque converter.
Not trying to piss anyone off but a buddy of mine is currently regearing (not cheap) because he thought he needed 5.13 gears with his 289, ZF, 35"s, Titan and 205, literally HATES it on the highway. SCREAMS down the highway. I tried to convince him 4 yrs ago he wouldn't need 5.13"s but everything he read....
Just giving you real feedback cause if you drive the highway at all, a 351W doesn't like to be wound out all the time like a 289 or 302.

I really disagree that you need deeper gears- strongly disagree unless you do nothing but off road. I ran 50,000 miles with 4.56 gears with either 35" or 37" tires. So what if it shifts down on a long hill... that's what drivetrains are supposed to do. If you can NEVER drive it on the freeway in OD then you have some gearing issues.

I currently run 40" tires with 5.13s and have no need to gear to anything lower. Why would you need 5.13's with 35"s is beyond me, especially with a 6r that has a 4.17 first gear. If you like 3,000 rpm down the highway then yes. I have NO idea how much highway driving you do.

I do rocks as often as possible. Till Covid we were going 3x/year to Moab. and playing locally. I ran my 4r70 with 4.56 gears and 37's for 16 or more years. Never needed lower axle gears. You have a torque converter for that- it essentially doubles your crawl ratio and with a 50% lower first gear with the 6r it's unneeded..
It's so effective that I quit using my doubler box and ran 2.7:1 exclusively instead of doubling up with my 4r. Then when I installed the 6r 2 1/2 yrs ago with a 50% lower first gear the need for lower gears is gone.

If you really felt the need you could go 4.88 and not be winding out on the freeway but you'll be happy with the 4.56's.

I wrote an in-depth article on 6r installations in a Bronco here on CB. Here's the link.- hope it helps. https://classicbroncos.com/forums/a...-trans-into-a-bronco-behind-any-sbf-engine.2/


If you want more info on gearing choices and why with a 6r that has a 4.17:1 first gear you don't need super low axle gears because first gear in it is almost 50% lower than a 4r. here is some more info. That 4.17 is HUGE and you can feel it when wheeling and around town it is an amazing difference.

Here's my installation and gearing changes and why on my build thread. Hope this helps. Starts in on 6r info around post 329?? Long and some chit chat in there but lots of pics.

https://classicbroncos.com/forums/t...5-wb-stretch-2-floor-lower-p-s.278607/page-17

Hoping nobody hates but gearing too low is pretty common because people go on line and figure some chart can be substituted instead of experience, type of wheeling, weight of vehicle, tire diameter, type of wheeling, etc, etc. . With a stock OE torque converter (low stall) you can cruise & wheel all over Moab or Sand Hollow with a 6r and 3.0:1 Atlas and never have a need for anything lower and so what if you're cruising along in your 1st OD, (5th gear) up a slight grade instead of your 2nd OD (6th).
I'm heading back to Sand Hollow this weekend.

Good real world intel! This is the reason I like CB.com over the Facebook forums...