Rear Axle Comparison

[3 on the tree]

I've got a D70 under my ambulance. It has 4.10 gears and some type of posi, this is a dually. Is this unit as strong as a 14 bolt FF. I am thinking about parting out the rig and keeping the rearend for future projects. Is the 14 bolt easier to get parts for? I read about alot of folks switching over to the 14, but hardly ever anything about the D70-whats up? Also, what's a good D70 going for out on the market?

 

[Hogback Fabrication]

The pros for running a 70 are pretty much only that you can run deeper gearing (more than 7:1 I think) while 5.13 is the lowest you can run in a FF14 bolt. The housings, wheel bearing, axle shafts, etc. are all very comparable. The ring and pinion on the FF14 bolt is a better design with a third pinion bearing to keep it stable and keep it from eating ring gears and better tooth contact. Basically what it comes down to is that almost all GM one ton's came with FF14 bolts and the spring pad width is the same. Dana 70's usually have a different spring pad width. Also, Detroit lockers are very cheap for a FF14 bolt while lockers for the 70 are pretty expensive (because the 14 bolt has a very strong 2 part carrier design which can support a carrier in place of the spider gears).

 

[atho]

The pros for running a 70 are pretty much only that you can run deeper gearing (more than 7:1 I think) while 5.13 is the lowest you can run in a FF14 bolt. The housings, wheel bearing, axle shafts, etc. are all very comparable. The ring and pinion on the FF14 bolt is a better design with a third pinion bearing to keep it stable and keep it from eating ring gears and better tooth contact. Basically what it comes down to is that almost all GM one ton's came with FF14 bolts and the spring pad width is the same. Dana 70's usually have a different spring pad width. Also, Detroit lockers are very cheap for a FF14 bolt while lockers for the 70 are pretty expensive (because the 14 bolt has a very strong 2 part carrier design which can support a carrier in place of the spider gears).

The Dana 70 can go down to 7.17 gears. The dana axles are all designed to use 2 pinion bearings spaced farther apart, rather than 3 close together like the 14 bolt, which accomplishes teh same thing. I have never seen nor heard of a dana axle chewing up gears because it didnt have enough pinion bearings. The D70HD that came under dually pickups has the same perch width. 35 splines at the centersection vs 30 for the 14 bolt (negligible). Some detroit lockers are cheap for the '70 because some of them have 2 piece carriers. Which brings me to my next point...

there are 2 reasons I see that the 14 bolt is more universally accepted. #1, the 14 bolt came under way more trucks than the '70. The '70 came under trucks from every one of the big 3 as well as International, but just arent as common. #2, the dana 70's that are out there came in 6 or 7 versions, not all of which are good. 14 bolts stayed basically the same except for some small changes over their production.

Chevy dually pickups and some Ford E350 ambulance conversions used the 70HD, which uses D80 carrier bearings and has massive 4" axletubes. Dodge pickups and perhaps some Fords used the 70B, which is the "normal" 70. The plain D70 has a strange pinion offset. Ford used the 70U (smooth centersection) before they made the transition to the 10.25. Those are just 4 types, there are more out there...and thats only in rear apps.

fwiw, I was going to run a D70 (4.88 locked), but I decided to stick with my Eaton H072.

 

[3 on the tree]

My axle is under a 81 E350 Ambulance. Are there any specific codes on the axle tag or the centersection to identify it as a HD?

 

[mofugly13]

Pull an axle and count the splines. If there are 35, then you probably have a D70U, or an HD. Measure the axle TUBE diameter, my D70 is 3 1/2", I believe the HD has 4" tubes. Also on my D70U, the tubes neck down at the end where they meet the backing plate mounting bracket. I got mine off an '85 F250 diesel. There was a metal tag on it under two of the cover bolts, I plugged the numbers into Dana's website and it came back as a 70U

 

[rjfguitar]

I have a 14BFF under my K5 and a D70 under my dodge cummins. The D70 looks physically larger to me but the internals look basically the same size(probably because they are). If I had to bet, I would say the 70 is slightly stronger. I just pulled 79,100lbs behind my dodge cummins tonight and didn't blow up the rear end.

The cummins guys are blowing up D70's but only under huge power numbers like 700+ RWHP and 1500+ ft lbs. The 14BFF has never really been in an application where it's strength could really be put to the extreme test, unlike the D70.

 

[Hogback Fabrication]

Dodge has started putting the FF14bolt under its trucks since GM has sold the rights to a company called American Axle Manufacturing (the rear end is called an AAM 14 bolt). Now, I have heard that that Dodge and Chevy have started putting dana 80's under their 1 tons with diesels but I think most 3/4 and 1 tons have the AAM 14 bolt. I may be wrong so start the debate . Also, you are right about never hearing about people breaking a dana 70 because of a ring and pinion failure. Really, you don't hear about anyone having failures with either. But the design of the 14 bolt is better. It doesn't allow the pinion gear to climb the ring gear because of its third bearing (like the F*rd 9"). Also, as aformentioned the ring gear contact is better. Does any of this matter? Probably not, the shafts as strong as they are are probably the least strong link. Both a 14 bolt and a dana 70 are very comperable, I would vote for the 14 bolt unless you want lower than 5.13 gearing.

 

[84_Chevy_K10]

New Dodge trucks have AAM 9.5" front axles, 10.5" AAM rears in 3/4 tons, and 11.5" AAM rears in the 1 tons. Nothing is shared between them and GM corporate axles. A magazine did an article that seemed to allude to the fact that they were similar, and while they might be, no parts interchange.

 

[atho]

My axle is under a 81 E350 Ambulance. Are there any specific codes on the axle tag or the centersection to identify it as a HD?

when you run the bill of material number through the decoder at www.drivetrainsuperstores.com , it will tell you what kind of '70 it is. your BOM should be a 6 digit number starting with 6. bom should be stamped into the passenger side axletube, facing the same direction as the diff cover.

 

[POWERMAD]

D70 axles... they make good weight.
I helped my buddy load 5 at one time. 4.10's and 4.56 gears.
For some reason he sets aside 14FF axles

The only reason I can see on using a D70 is if ya have need of more than 5.13 gears.
Or that's what ya have to work with.

Realisticly I can get a 4.10 14ff for $100, For another $325 it is locked, or for a small amount of time weld the sucker up tight.

$425 for a 14ff locked, price what a Detroit is for a D70.

 

[3 on the tree]

well I ran the numbers and it is a 70B. The tag is also marked LS, which I think means limited slip. Does anyone know what type of limited slip was used in these axles and their life expectancy? Thanks for everyone's info and opinions.

 

[mofugly13]

They come with either a trac lok, which is Dana's posi, or a power lok which is their limited slip. I have heard really good things about the power lok.

 

[Poohbair]

I am running the D70HD Dually rearend in my K5. I put it in because I wanted to run dually axles and Hummer rims. It does have the 4" axle tubes. It looks cool under the back of the K5 because it just looks different than the 14bolt that you normally see!

I have heard people argue that a D70 gives you more clearance than a 14bolt... I have no idea if this is true or not. The 14 bolt I took out was shaved and stuff, the D70 isn't (YET...) and I never measured my clearance w/ either one. I just figure it is what it is. I may go to 7.17's if I get a trailer just because it is cheaper to do that than to buy a doubler!!