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Well on the way to work this morning my rear axle decided to explode. I haven't gotten into it yet but it felt and acts like the spider gears came apart and locked up the ring and pinion, maybe a broken diff pin too. I don't understand why it broke running a constant unloaded 60MPH instead of during the last 3000 miles of relatively heavy hauling but I guess it was a better time to break. My biggest concern right now is did I hurt the t-case when it locked everything up.

Long intro to my question; the way I'm looking at it I have three options at this point. As a side note that might help your advice I do plan on a NV5600 in the future.

Another Dana 70,
I'm assuming the worst on the R+P and diff case in my truck but nothing came out of the housing. I would put 3.55s with a LSD and run stock brakes if I go this rout.

Go to a DANA 80,
This one will be wider than stock and the most money. Again I would go with 3.55 gears and LSD and disc brakes.

Switch to a GM 10.5 14bolt,
I have one of these left over from my GMC truck days. It would need go through and I don't know what gears it currently has but it would get 3.42 gears and a Detroit Locker. Disc brake conversions are cheap and readily available for these. I haven't measured up for this swap yet but I'm thinking it might be my best option.

Midnite

A Dana 70 from another 1st gen truck will be cheapest and easiest. If you have the time and skills to get another type of rear end to work, then the sky's the limit.

It sounds like you're also considering brake upgrades with this--keep in mind that you can go with bigger wheel cylinders and dramatically increase your rear brake capability with a stock D70.

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Strength and durability are my major concerns. Time is always at a premium but I have the skills needed for this type of work. I'm really starting to talk myself into the 14 bolt but I'd like a little input from someone that has a little more experience.

The 70 would be the easiest but this would be the 4th one in 220,000 miles. Granted numbers 2 and 3 were junk yard pieces but still it just doesn't seem like they last when used heavy. The original made it to 125,000.

As for the brakes the stock ones are okay but why not put on discs if swapping the axle anyway.

simplysmn

Corp 14 bolt the strength of a dana 80 and they will bolt back in fiarly easy .

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got the diff cover off today and took a look at what happened.





My best guess is the center pin's roll pin snapped allowing the center pin to spin which eventually dropped out hitting the case or pinion shearing the pin and locking the rear diff, the immediate stop then busted the spider gears and me messing with it before taking it apart made things worse.

In the end I'm pretty sure the yoke(put a new one on last summer) and brakes/hubs are still good, axle shafts are a maybe and anything else is junk.

After gutting the rear end I gently road tested it in front wheel drive to see if anything else got hurt in the instantaneous stop from 1750RPM. Long story short I no longer have 2nd gear synchro and didn't get fast enough to test 5th.

user name

to and a little insult to injury this was waiting at the house when I got home from work the day it broke.

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on a related note I spent a little time measuring spare parts and this is what I came up with.

corp 14 bolt approx 3" wider wheel mount to wheel mount, spring mounts approx 2" narrower

Axles used for measurements 1978 Dodge W200 dana 60(Should be same mounts and width as a first gen) and 1976 Chevy K20 corp 14bolt.

Transmissions,
NV5600 4x4 bellhousing to transfercase flange approx 31.25" This trans also needs the thicker engine plate figured into the overall length comparison which adds about another 1.5" if memory is right (didn't measure these today).


Getrag 360 4x4 Bellhousing to transfercase flange very approximately 27" (Measured by myself laving on the ground without a light) someone probably has a better measurement.

Overall length addition to swap in an NV5600 approx 5.75" definitely will require new driveshafts. and exhaust modifications.

simplysmn

Well the 1 corp 14 bolt I had in my last crew was like a total of a inch wider on spring perches so I I did was wiggle n push the spring over everything lined up with no troubles .

bryson711

I just put in the modified driveshaft in my truck Friday night after switching from an gut bag 360 to a nv5600 and I had to have 6.5 inches taken from the back and 6.5 inches added to the front. The swap is really labor intensive but I sure hope its worth it

Sent from my DROID4 using Tapatalk 2

u2slow

The Dana 80 is 2" longer in the pinion over the D70. That's gonna mean some driveshaft work, or sliding the axle position as necessary (look into EZ inch or zero-rate). A suspension lift could negate the difference altogether.

I picked up my disc D80 w/3.55 for $400-500 (can't remember exactly). If it is open, I can recycle my D70 Lockright (also 35-spline, pre-92). Later model wheels have more backspace, so that can keep the extra width in check.

14bff is a good choice in some cases. The taller ratios are 3.21, 3.42, 3.73 (no 3.55) so that's a make/break issue for some. There is no ABS tone ring either. Detroit Locker is cheap because it is an insert for the standard open case. Not much for good posi options available. Its a nice axle to setup, because you have screw-adjusters for backlash, and pinion flange shims like a ford 9". You'll need a 1350/1410 conversion u-joint, and the pinion is shorter than a D70. Driveshaft may have to be lengthened depending how much slip-spline engagement you have.

gorms

That's some good info right there....I'm about to swap from a 70 to an 80 and was just gonna hack up the driveshaft and weld the yolk back on. Forgot about those little guys, could use a little boost in height anyhow.

oliver foster

The Zero rate blocks [1 inch lift as well] have two choices, that will move the axle forward or backward 3/4 OR 1 1/2 inches if I remember right.
That might work for that Dana 80 swap Gorms.

BILTIT

3 choices, the two above and dead centre (no offset) as the third.

Mark Nixon

Here's a list of widths on Dana 80s I have laying in the yard:

C&C 2001, 4x2, disc brakes, 69.00 inches.
C&C 2000, 4x2, drum brakes, 68.00 inches.
SRW 1998, 4x4, drum brakes, 69.50 inches.
DRW 1998, 4x2, drum brakes, 72.00 inches.

You can swap on 3/4 ton wheels and run a DRW as a SRW.

I also wouldn't rule out an AAM from 2003-up Dodges, which is really just an updated 14 bolt.

As far as sliding the rear axle on "adjustable" (or multi hole) spring pads, I'd be leery of doing so with anything you plan to haul heavy with, as it also mis-aligns the U-bolts to the axle and can pre-load it to a tipping point.
Then, if the U-bolts relax (and many do) and you get a high load or power event, the axle may walk off the blocks.

Mark.