Help Me Decide AOD or 4R70W

[englewoodcowboy]

The AOD internals are fine. In fact some of the early AOD parts are sought after by good builders because they are machined cast vs thin stamped. The weak links of an AOD are easily remedied when you rebuild it with upgraded clutches and new servos if your unit does not have the A servo. Second the 4R70W gears are so slightly different they are not very noticeable if you properly gear your axles which you will need to do regardless due to the steep OD that the AOD or 4R70W have. They both have the same OD ratio and the AOD 1,2,3 is so close to the C4 most will never honestly be able to tell you the difference. Where the gear change comes in handy is in the off road crowd that are wheeling in the lower gears all day long but for a DD it is an excellent transmission. The other weak link in the AOD is the lock up shaft if you are dumping a lot more torque to it you will need to replace it with a billet one but for stock or slightly warmed up 5.0 HO it will hold fine. Just remember the 4R70W and AOD are virtually the same transmission with a few changes, most notably is the electronic control, a slightly wider gear set and an electronic lock up converter.

 

[englewoodcowboy]

To me that is even more of a reason for a 4R70W. The selectable lockup convertor is why. When cruising the freeway and need a little more power than available in overdrive you can get the convertor unlocked and get a little more, without the scream of a full on downshift. Unlocking the convertor is a half gear between 3rd and 4th gears. You just can't do that with an AOD no matter what parts you put into it.

You have a slight point however the AOD does the same function though it is mechanically decided by way of the governor vs computer however I have driven many AOD cars over the years and never really noticed a difference until you pointed it out so for most, again I think this is really a non issue...

I am not saying other info is wrong, it is all accurate but the OP asked if the AOD is OK assuming he already had one and it is unless he wants to spend more money because the 4R70W does cost more to outfit into an EB. I built my AOD to handle over 400# torque and built it for easily $500 less than a 4R and all my internals are rebuilt. Build a 4R you still have electronics that could need replacing to achieve the same level of rebuild so again it all comes down to end use preference and how much you want to spend. They are both really good transmissions.

 

[Broncobowsher]

The AOD does have a locked up convertor, sort of. It isn't decided, its built that way. The direct clutch shaft (that long skinny one) is a torque convertor bypass. The long part of it splines into the front of the convertor, bypassing the slip. 60% in 3rd and 100% in overdrive. It can't be turned on and off. The lockup is based strictly on what gear it is in.

This engineering was abandoned in favor of a selectable lockup convertor, just like every other manufacturer currently uses. I have a magazine article from the 80s that talked about putting a bypass on the convertor lockup wire to allow the driver to unlock the convertor on grades for a little better performance. Back when the lockup was based on speed and not tied into the computer well enough to cycle it based on load. Remember the 80s automotive computing was rather simple. Especially outside of the fuel injection.

 

[englewoodcowboy]

The AOD does have a locked up convertor, sort of. It isn't decided, its built that way. The direct clutch shaft (that long skinny one) is a torque convertor bypass. The long part of it splines into the front of the convertor, bypassing the slip. 60% in 3rd and 100% in overdrive. It can't be turned on and off. The lockup is based strictly on what gear it is in.

This engineering was abandoned in favor of a selectable lockup convertor, just like every other manufacturer currently uses. I have a magazine article from the 80s that talked about putting a bypass on the convertor lockup wire to allow the driver to unlock the convertor on grades for a little better performance. Back when the lockup was based on speed and not tied into the computer well enough to cycle it based on load. Remember the 80s automotive computing was rather simple. Especially outside of the fuel injection.

You are correct. The little shaft is the weak link when adding a lot more power which I am doing so I have to get a billet one. The way the valve body is programmed now vs the original OEM workings is it does shift to OD then it applies the lock up. One major difference is the AOD lockup clutches are in the transmission vs the electronic lock up clutches being in the TQ Converter. The nice thing in the AOD to me is you are right, you do get 100% lock up in OD when it engages and it only hits a 60% lock up in drive to allow slippage for the TQ converter to build its TQ in a pull. I honestly have ever needed to turn off the OD in any of my vehicles equipped with that feature however that is daily driving, not off road and when I do venture off road I never am in a high enough gear to have that function kick in. I know you are supposed to turn the OD if towing but I have never had the need to.

 

[nvrstuk]

Which is the better tranny, 4r70W IMO. I spent a lot of time researching and talked to several high performance tranny builders and the 4r70w has been improved upon in many areas over the AOD. I run a lot of torque and HP and my choice was a no-brainer, but even for a 90% DD, go 4r70w.

I'm guessing the shop didn't want to do any wiring...ask almost anybody and their ultimate fear is not welding or fabwork or whatever...it's W I R I N G.... : ) Most shops would much rather stay away from something custom like wiring, programming, and then dialing in custom programs and stick with a standard build of an older model tranny...

 

[englewoodcowboy]

I'm guessing the shop didn't want to do any wiring...ask almost anybody and their ultimate fear is not welding or fabwork or whatever...it's W I R I N G.... : ) Most shops would much rather stay away from something custom like wiring, programming, and then dialing in custom programs and stick with a standard build of an older model tranny...

I am my shop and wiring is my forte but I did not want to spend the extra money to buy another trans and controller etc. I had the AOD, I did the research and the advantages to me were very minute at best so I opted to build my AOD to handle what I am doing with it. I personally prefer simplicity and the AOD to me is exactly that of a C4 with an OD.

 

[Lon L]

I am my shop and wiring is my forte but I did not want to spend the extra money to buy another trans and controller etc. I had the AOD, I did the research and the advantages to me were very minute at best so I opted to build my AOD to handle what I am doing with it. I personally prefer simplicity and the AOD to me is exactly that of a C4 with an OD.

How do you like your gearing with the AOD? I am planning 4:56 with mine, my tires are a true 34" tall.

 

[nvrstuk]

I am my shop and wiring is my forte but I did not want to spend the extra money to buy another trans and controller etc. I had the AOD, I did the research and the advantages to me were very minute at best so I opted to build my AOD to handle what I am doing with it. I personally prefer simplicity and the AOD to me is exactly that of a C4 with an OD.

Lon L started this thread asking about differences between an AOD or a 4r70w. I responded to his questions about the two transmissions and the recommendation of a SHOP that suggested an AOD, hence my comment. I was not insinuating or suggesting anything about any of your comments about your choice of an AOD as I was responding to the gentleman that started this post.

 

[englewoodcowboy]

I am going with 4:88 for 35" tires which are only 34. Something. The 4:88 will have the engine in OD running at around 2200 rpms @ 70mph which is suited well to the small block fords. I have spoke with a few that are running the AOD and they all say cruise rpm gearing is crucial, it would be the same for the 4r70w as they share the same OD gear.

 

[Broncobowsher]

I am going with 4:88 for 35" tires which are only 34. Something. The 4:88 will have the engine in OD running at around 2200 rpms @ 70mph which is suited well to the small block fords. I have spoke with a few that are running the AOD and they all say cruise rpm gearing is crucial, it would be the same for the 4r70w as they share the same OD gear.

OD is close, but slightly different. AOD (with the 2.4 first gear set) has a 2/3 OD, .667 ratio. The 4R70W (with the 2.8 first gear) has a slightly different .70 OD ratio.

 

[Germd]

Spent some time reviewing this thread as my tranny is in getting rebuilt. Mine is an AOD behind a fairly stock mustang 5.0L EFI. I opted to rebuild the AOD with fresh internals rather than replace it with a 4R70 for several reasons.
Like Duffy, mine is 80% street, 20%off road. The AOD is already here and modded for the truck - so I don't have to buy another trans. I never had any issues with it before it developed a fluid leak. The idea of adding additional wiring and computer programming just to go with a different trans makes me nauseous. I'm old school and would rather modify a brick to do a job than try to figure out more electronics. I'm running 34" tires & have stock gears in mine now, but plan to soon add 4.10 or 4.88's
There is some really good discussion in this thread from guys with far more technical knowledge than me - but I just thought I'd throw my "average guy" thoughts in the ring.

 

[needabronco]

I'm very happy with my AOD 99.9% of time. With a valve body you can manually select first gear and it will stay there. A lot of guys trash the AOD and several of them have never ran one. I've never ran a 4R70W although I have one sitting on the side of my house. I will agree the ability to electronically lock and unlock OD would be a nice feature to have...

With either trans, you do have to go rather deep with your gearing in order for OD to be usable. I run 4.88's with 35" tires and really wish I had 5.13's. 2200 RPM's isn't enough to push a barn door down the highway at 70. If I bump up to 75-80 MPH I'm in the 2500-2800 RPM range and the power is fine, but with the short wheel base, soft shocks, and soft springs 80 MPH can be a handful on the freeway, especially on worn out roads with huge expansion joints over bridges.

 

[bax]

An AOD is no where near as good as the 4r. I have completely destroyed 2 AOD's Im talking internal hard part breakage. First one I shattered the sun gear on the back of the drive drum. this destroyed the planetary set ( many pieces) and put a huge gouge in the top of the case. #2 was close to the same failure. The main drum broke on it. the fact is the aod internals are crap. if you must go AOD put the 4r internal parts into it. better yet go with a 700r. Im running a c6 gave up on the overdrive.

 

[needabronco]

To be fair Roger tell everyone what you had bolted to those AOD's.... 99% of those that ask this question run stock (ish) 302's and maybe 351's.

 

[bax]

Yeah ok but a bad choice is just that. The fact is regardless of power the internals of the aod are not as good as the 4r. I get not wanting the computer for the 4r. this is also why i went the AOD route. I should of put the internals of the 4r into the aod and tried that. Yes to much power killed mine. The hard shift into second at wot is bad for them. if I ever try it again it will be a 700r

 

[399strokerEB]

I ran an AOD behind a stroked 351 and a heavy foot for 6 years, never broke anything but u-joints. My only complaint is I don't have enough gearing now that i swapped to a mild EFI 351, currently running 4.56 and thinking about 5.13. Offroad it does fine but its a little fast in first(gearing) and its a little lacking in power in OD(again gearing). I'm not sure what all has been done to the trans but it is built. I do like the idea of being able to take it out of lockup in OD but honestly it doesn't see enough highway time to warrant a trans swap.

 

[Lon L]

It has been nice having the Bronco back and drivable , however I am excited to move on to the next stage. The Adapter will be ordered Monday, The 4R70w has been built, the Computer and harness all worked out; AND I will never be able to say this enough "Thanks Garry". His tune was great, his recommendations spot on. Now that I have good fuel pressure the Bronco is running really well. I also ordered some Stainless Cooler lines that are for a C4, I hope they are close enough to massage into place. Monday I will order a Dana 20 Reseal kit for a fresh transfer case , and new 31 spline axles. The trans shop is going to handle obtaining the carrier and gears( he said he gets a great price).

Anyway I just want to post an update and to say thanks to all of you who provided input. This is a great community of people with a wealth of Knowledge and you all deserve a Thank You .

PS There have been a couple of folks express interest in my NV3550 setup. It will be available in a couple of weeks and will include everything from a Steering Column Manual) to Shifter . The folks who have contacted me thus far are first inline, if they pass I will let you know. The Price for the Entire set is $1200.00

 

[chuck]

Just adding a little info here. The PSC stand alone controller for the 4r70w has knobs to adjust the shift points= no laptop needed. We have been using the 4r70w for several years now behind the 420 hp Coyote without failures... other then the atlas output shaft that failed,,, and a few U-joints. Just info.

 

[Lon L]

Today I took my Bronco to the Trans Shop and dropped it off along with about 3k in parts. Should be done in a week or so. I am excited to get this stage handled so I can get it to the Restoration Shop.