Leaking Differential

[docwilson]

I just discovered my rear differential is dripping gear oil. Unbelievably, some of the bolts were literally finger loose. My original suspension install was botched beyond belief and I suspect the same happened here (Dana Spicer covers installed during a re-gear).

I've since torqued them down and will top off the fluid. Is that sufficient if it doesn't leak further? Or should I take the cover off and put a new gasket or RTV? If I replace the gasket/use RTV, do I need new bolts?

Also, the Dana covers have two fill holes, upper and lower. Which do I use?

 

[WJCO]

I just discovered my rear differential is dripping gear oil. Unbelievably, some of the bolts were literally finger loose. My original suspension install was botched beyond belief and I suspect the same happened here (Dana Spicer covers installed during a re-gear).

I've since torqued them down and will top off the fluid. Is that sufficient if it doesn't leak further? Or should I take the cover off and put a new gasket or RTV? If I replace the gasket/use RTV, do I need new bolts?

Also, the Dana covers have two fill holes, upper and lower. Which do I use?

If it stops leaking, you're good. If it leaks still, put new RTV. No need for new bolts.

The cover has two fill holes? Post a pic.

 

[kevman65]

^^^

What he said. Lower should be a drain, upper a fill. Why they still use a drain hole I don't know. It's easier to drain and clean everything out by pulling the cover.

Reuse bolts if not damaged, they're NOT torque to yield. Yes, use RTV. Much cheaper and more gaskets in the tube.


Afterthought; Isn't Dana the one that uses a magnetic lower plug to pick up loose metal?

 

[docwilson]

If it stops leaking, you're good. If it leaks still, put new RTV. No need for new bolts.

The cover has two fill holes? Post a pic.

Thank you. Here is the differential cover.

 

[docwilson]

^^^

What he said. Lower should be a drain, upper a fill. Why they still use a drain hole I don't know. It's easier to drain and clean everything out by pulling the cover.

Reuse bolts if not damaged, they're NOT yield to torque. Yes, use RTV. Much cheaper and more gaskets in the tube.


Afterthought; Isn't Dana the one that uses a magnetic lower plug to pick up loose metal?

Ok thanks. I wasn't sure, when I looked up torque specs I saw something about not reusing "fasteners" so I assumed it was bolts. I'm hoping just tightening it down does the trick.

As for the fluid, even if too much fluid, worse case scenario is it boils out of the breather line, right?

 

[kevman65]

I would double check the torque ratings for your bolts.

I believe they supply M8 Grade 8.8 bolts and they torque out at 28.4 nM or just under 21 foot pounds.

Since there is no pressure in the diff, snug is good enough.

 

[CalSgt]

I ditched the gaskets when I put my spicer covers on & just used grey gasket maker, mine have never leaked. I think the bottom of the lower hole is about right for stock & just above that for an axle that has been rotated so the pinion points at the TC flange. IIRC I filled mine to the threads on the lower hole, replaced that plug then gave it a few more big squirts of gear oil maybe a quarter of a bottle or less.

ETA: I think I may have just read the specs on the amount of gear oil & did my best guess with the final squirt. I couldn't get the full amount in there with how my axle sits.

 

[docwilson]

I would double check the torque ratings for your bolts.

I believe they supply M8 Grade 8.8 bolts and they torque out at 28.4 nM or just under 21 foot pounds.

Since there is no pressure in the diff, snug is good enough.

Good call. I double checked, they're all 10.9, but the rears are properly stamped and the fronts are poorly stamped. I read about others snapping them when torquing to 30 ft-lbs. I had already torqued the rears to 30 ft-lbs and that felt fine, but on the front they didn't feel right when tightening to that goal, so I ended up keeping it to 20 ft-lbs, which I feel OK about and seems others have too.

 

[docwilson]

I ditched the gaskets when I put my spicer covers on & just used grey gasket maker, mine have never leaked. I think the bottom of the lower hole is about right for stock & just above that for an axle that has been rotated so the pinion points at the TC flange. IIRC I filled mine to the threads on the lower hole, replaced that plug then gave it a few more big squirts of gear oil maybe a quarter of a bottle or less.

ETA: I think I may have just read the specs on the amount of gear oil & did my best guess with the final squirt. I couldn't get the full amount in there with how my axle sits.

Yea, from what I can tell Dana Spicer recommends using top fill hole for first fill and then lower for maintenance/refill. Seems a squirt or two extra in the top would be safe, like you suggested.

 

[wayoflife]

I think the bottom of the lower hole is about right for stock & just above that for an axle that has been rotated so the pinion points at the TC flange.

^^^ THIS is correct. You ONLY want to fill until the fluid oozes out of the LOWER hole. The upper hole exists for axles that have double cardan u-joint style drive shafts installed and have the pinion rotated up to accommodate it.

Over filling a diff will cause the fluid to pump out of the breather tube. Not a big deal but it will make a mess.

 

[docwilson]

^^^ THIS is correct. You ONLY want to fill until the fluid oozes out of the LOWER hole. The upper hole exists for axles that have double cardan u-joint style drive shafts installed and have the pinion rotated up to accommodate it.

Over filling a diff will cause the fluid to pump out of the breather tube. Not a big deal but it will make a mess.

Thanks for the confirmation!