Rear axle questions

[u2slow]

Not a bad idea. Thanks.

Is 80/90 what you all would go with? I've seen some conflicting info on it....

I use plain 80/90W by the bucket.

 

[ROCK HARVEY]

I’m pretty sure synthetic 75w140 is recommended for the rear diff. I run 80w90 dino in the front though.

 

[Nero]

I also used 80w90 in my diff I just assembled, working fine so far.

 

[u2slow]

I’m pretty sure synthetic 75w140 is recommended for the rear diff. I run 80w90 dino in the front though.

The 10.25" diff came out around '85? 80W90 is the original spec.

Fancier oil specs have shown up in order to keep service intervals high as higher torque engines came about.

For me, the moment I entertain some fancy oil, it's a hasty invitation for Murphy's Law to step in with a reason to waste it. There's also differing arguments about break-in with what oil type. Undermining the grip of a trac-lok is not a direction I want to go.

 

[Nero]

So with your expertise, would you still suggest 80w90 in a turboed engine?

 

[u2slow]

So with your expertise, would you still suggest 80w90 in a turboed engine?

Sure. I used 80-90 with my powerstrokes, and continue to with my cummins trucks.

If I was really concerned, I'd get 500-1000km on with 80-90 first. If all looks good, then reload with fancy lube.

 

[Old Goat]

I’m pretty sure synthetic 75w140 is recommended for the rear diff. I run 80w90 dino in the front though.

Why would you not use the same oil front to rear?

Goat

 

[ROCK HARVEY]

Why would you not use the same oil front to rear?

Goat

I figure the front isn’t as critical so I run the cheaper oil there.

Sounds like I could have gotten away with the 80w90 in both based on everybody else’s comments.

 

[IDIBRONCO]

Why would you not use the same oil front to rear?

I figure the front isn’t as critical so I run the cheaper oil there.

Another way to look at this is that the front's only turning when the hubs are engaged so the front's "not as important".

 

[DaveBen]

IDIBRONCO - Another way to look at this is that the front's only turning when the hubs are engaged so the front's "not as important".

Four wheel drive is important! It is most important when you actually NEED IT!! You will NEED IT when it doesn't work!

 

[Stomper4x4]

Yes this is a good point I forgot about. You want a later axle if possible for the more durable long pinion.

Yes this is true. My axle guy was able to convert my 89 axle to alieviate that issue when we rebuilt it.

 

[IDIBRONCO]

IDIBRONCO - Another way to look at this is that the front's only turning when the hubs are engaged so the front's "not as important".

Four wheel drive is important! It is most important when you actually NEED IT!! You will NEED IT when it doesn't work!

That's why that part's in quotes. If you don't need it, then it doesn't matter. For most of the driving that we do, it isn't needed at all.

 

[ROCK HARVEY]

I was thinking more in terms of temperature. I’m not going to be towing heavy for long distances in 4wd, so the front diff fluid is never going to be seeing sustained 200+ degrees. The rear axle might, so I wanted the 140 weight heavy-duty fluid back there.

 

[IDIBRONCO]

I was thinking more in terms of temperature. I’m not going to be towing heavy for long distances in 4wd, so the front diff fluid is never going to be seeing sustained 200+ degrees. The rear axle might, so I wanted the 140 weight heavy-duty fluid back there.

I agree. That's why I'm going to run it in my crew cab, some day.