Questions about... My rear end?

[Edelbrock]

Hi.

I want to replace the rear axle on my 1977 Blazer. I have a 14 bolt 8 lug FF with an open diff.

I have two axles available that I can install. Both axles are 14 bolt 8 lug FF with limited slip.

Which diff should I go with?

Im GUESSING that one is a G80 out of a 1994 Chevy and the other is a Posi out of a 1968 Chevy?

Not sure what I got or which to use.

Mostly street driving with hard acceleration, occasionally snow and deep mud.

 

[legopnuematic]

Are the pictures of the axles you have? The first one is a Dana, with a Powr-Lok. Not a 14 bolt.

 

[Grit dog]

Both will require shock mount and spring mounts I believe. Assuming both are known good axles.
And Chevy didn’t make 14bolts in 1968 afaik.
Bigger questions are gearing and how your gonna match the front axle so you don’t have an average of a 7 lug truck.

 

[Edelbrock]

The truck currently has 8 lug axles front and rear. 410 gearing on the truck and on both the axles in the pictures. Those pictures that I posted are of the two axles that I have available to install in the truck.

I already had the spring mounts moved to the correct spot to fit the Blazer. Both axles would need the shock mounts moved. The first pic has the shock mounts on the same side of the axle. I have no idea which axle to install, or even really what the diffs (or axles) are really called or what type they are. All I know is that they are both Chevy, both 8x6.5, both full floater, 410, drum brakes. Aside from that, I know they are both limited slip, but which would be the best choice?

 

[legopnuematic]

The 1968 rear is a Dana 60, with a Powr-Lok. The Powr-Lok is generally regarded as a very good limited slip, as it uses two cross pins that ride on ramps, so it is able to apply more force to the clutches on the side with less traction. They are adjustable by playing with the clutches and rebuildable. Good street manners, as slow speed tight turning where others might chirp or bind it’ll slip the clutches and make a smooth turn.

I’ve got one (factory installed) in the Dana 70U in the back of my 2nd gen.

The easiest option if you already have 14b ff under the blazer, is to swap the carrier for a limited slip (g80, clutch type, Detroit locker, whatever) reusing the current ring gear (can’t mix and match those!).

Just need to measure backlash before tear down to set it back up to what it was. Easy on the 14B as it uses those screw type adjusters.

 

[legopnuematic]

I’ve not messed with a 14b FF G80, but I believe they are held in higher regard than the 14b semi float, 12, and 10 bolt G80s that have been known to explode on occasion. Hence the name Gov-Bomb.

 

[Edelbrock]

I have thought about swapping my diff out for a limited slip, but the whole axle is not in good shape - Aside from the diff, I would would have to install new brakes and all of the seals. It leaks gear oil from the pinion seal, and into both brake drums. So I figure if I am doing all the seals, brakes, diff and fluid - I might as well just swap the whole axle. I'm leaning toward the older axle with the Power-Lok.

I'm $125 into the 1968 axle, and $350 into the 1994 axle.

Once I install one of the axles, I plan to sell the remaining LSD and Open diff axles to recoup some $$. Not sure what I will get for them, but I guess I will post them locally and see what happens. Any thoughts on values?

 

[Edelbrock]

I don't know if this is accurate, but here is what Google said:

For off-road performance and durability, a Dana 60 with a posi-traction (limited-slip) differential is generally preferred over a G80 rear end, as the Dana 60 is known for its strength and the posi-traction unit offers better traction control in challenging conditions.

Here's a more detailed comparison:

Dana 60 with Posi-Traction:

• Strength:
  Dana 60 axles are renowned for their robust construction and ability to handle heavy loads and off-road abuse.
  

• Traction:
  Posi-traction differentials, like the Spicer Trac-Lok, provide a limited-slip mechanism, allowing both wheels to receive power even when one loses traction, improving off-road capability.
  
  
• Durability:
  The Dana 60 is a durable option, and the posi-traction unit enhances its ability to handle challenging terrains.
  

G80 Rear End:

• Automatic Locking:
  The G80 is an automatic locking differential, meaning it will lock when a certain wheel speed difference is detected, but it may disengage at higher speeds.
• Reliability (9.5" version):
  The 9.5" version of the G80 is considered more reliable than the 10.5" version.
• Limitations:
  The G80's automatic locking feature may not be as consistent or powerful as a dedicated posi-traction unit in very challenging conditions.

In Summary:

• For off-road use and high-performance applications:
  The Dana 60 with a posi-traction differential is generally the better choice due to its strength, durability, and more consistent traction control.

• For a more budget-friendly option or a vehicle with less demanding off-road needs:
  The G80 can be a viable option, especially the 9.5" version, but it may not offer the same level of performance or reliability as a Dana 60 with a posi-traction unit.
  

 

[legopnuematic]

$125 for just a Powr-Lok as a core is pretty good, to get everything else is even better.

One consideration is the Dana 60 is a 9.75” ring gear, whereas the 14 bolt is a 10.5” ring gear. Strength wise both are plenty strong, but the Dana 60 might offer some more ground clearance compared to a 14b FF. I can’t say for certain though and it may not matter for your use.

On the other hand, the 14b FF has the outboard pinion support bearing, whereas the Dana does not have that support.

There is generally very good support for the Dana equipment, but the 10.5 14B was used in production for a long time as well so it has decent support as well.

 

[DoubleDingo]

Technically you'll have to replace the seals on the axle(s) you install, unless you have already done that to both of them. Since you have to replace seals no matter what, why not just replace seals and install a locker/limited slip of your choice into the current axle? A leaking axle doesn't make the axle a junk axle.

 

[Edelbrock]

Is it always required to replace seals when installing an axle, even if they are not leaking? Or is it just good measure?

 

[Bextreme04]

Is it always required to replace seals when installing an axle, even if they are not leaking? Or is it just good measure?

Depending on where you got the replacements, they likely haven't been rotating in many years... maybe even decades. So the fact you don't see them leaking means nothing. They are almost guaranteed to START leaking as soon as you start driving around on them regularly. Hub seals for a 14BFF are like $10/ea...

 

[Ricko1966]

Why are you so worried about changing seals? They are all easy enough to change,and we can walk you through the do's and don'ts. I can swap a diff and do seals as fast or faster,and way less effort than changing a whole rearend

 

[DoubleDingo]

I will admit to not changing seals on an unknown axle. But I was in my early 20's. Heck, I didn't even check the brakes to make sure they were good, and I didn't even unbolt the cover to change the gear oil. Just swapped it in and ran the piss out of it between 1990 and 2005. It didn't leak, but I got lucky. Would I do that now that I am wiser? No.

For you, if it's just leaking, replace the seals and install the traction device and be done with it.

 

[legopnuematic]

Yeah I wouldn't condemn an axle just because of seals.

First thing though, is the breather/vent tube free and clear? A plugged up vent will cause pressure inside and the pinion and hub seals are not really made for pressure, so they'll leak.

Still need to verify that regardless, if you put new seals in it and it's still plugged they will begin to leak again.

I don't have a part number handy but you can get hub seals for like a 2003+ GM 2500 truck with a 14b ff that should be a better design than the original seal.