I have a pair of Rockcrusher Dana 60s with ARBs and 4.88 gears. Stock rear D60 takes about 6 pints but with the bigger gears, ARB and who knows what else with the housing itself, I'm not sure where to start. Does anyone have a similar setup and remember how much oil they put in them? Is there a point on the inside of the housing that I should be using as a marker? Last time I guessed wrong and had oil blowing out all over things.

Thanks,
Whit

Have you tried contacting Rockcrusher and what asking them the fill capacity is?

Rockcrusher stopped building axles.

sounds a little strange to me. all the axles i have filled have a fill plug that i stick my little finger in to check the level. if finger touches oil then full enough. now a little different story if the pinion angle is extreme (non-stock configuration). but even then, some aftermarket diff covers like the ones i had on my HP44 and 60 were BTF covers that had extra high positioned fill hole to compensate for an extreme pinion angle.

bottom line here, why do you need to know the exact fill capacity? why not just start filling until you can feel oil with little finger or even until oil begins to pour out of hole? if you overfilled before i assume the oil came out the diff breather hose?

As I recall from when I had an ARB and a Rockcrusher diff cover in my D44 you just need to put in the correct amount called for and dont forget that the RC covers have a higher fill plug height than over stock. I do like the person above me posted.

To the bottom of the emblem on the cover. I actually overfill my front and no issues, if I do the rear to the fill hole it will blow oil out the breather. My front was built by Rockcrusher, my rear is a Solid , whats the difference, who knows. I'm actually thinking my rear gears are installed a little "tight", and therefore generate more heat.

Don't need exact but it seems rather strange that there is no diffinitive answer to this. Rockcrusher should have had this nailed down to a science and sent out a recomendation with the axle.

If you fill it to the hole the oil seeps out the rear seal, at least it did on my front. Something a little less blew out the breather tube. The rule of thumb (or pinky) seems to be the reasonable next step. Especially since that will be slightly less than last time I filled them. I just don't want to go too low.


bottom line here, why do you need to know the exact fill capacity? why not just start filling until you can feel oil with little finger or even until oil begins to pour out of hole? if you overfilled before i assume the oil came out the diff breather hose?

One diff guy explained to me this way:

Fill your differential until the oil just breaks the plane of the bottom of the axle tube(Oil is sitting in the bottom of the tubes).
This allows the outer bearings to get lubricated at all times.
The natural movement of the diff fluid will circulate oil to the ends of the axle tube too. This method insures lubrication of the wheel bearings, even on level driving surfaces. Not to mention cold weather, when oil is stiffer.

Make a dipstick so you can get it right every time.



Another mechanic told me if I overfilled the diff, extra oil will be pushed out the breather vent and it would be fine. Put plenty in......let the excess blow out.......there's you ideal fluid level. It's really messy though.

I'd also like to know the proper scientific method for determining fluid level with so many rear axle variables.

Currently using the first method.