Diff leaking from vent

IllCobra

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So, I can't figure this out. I traded my stock irs to someone with a "beefed" up irs - Ford diff cover, MM Rear Race Grip Package (similar to what Full Tilt Boogie offers), G-Force axles, etc. And since I installed the new irs it has been leaking. There is some hard shaking/vibration from the rear end at high speeds, 120+, that I now believe to be the drive shaft ( I didn't get it balanced with the different irs) and needing to upgrade the front irs bolts to the 14mm ones.
I am not 100% sure if this is the cause of the shaking, but would the vibration from this cause the differential to expel the diff fluid from the vent tube?
diff leak.jpg
 

01yellercobra

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How much fluid did you put in? Usually when it's leaking like that it's from being overfilled.
 

01yellercobra

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That's too much. Especially with the FRPP cover. Max fill is 1.25 quarts. I did 1.15 last time to make sure it would blow out. So your choices are either to let it keep blowing out, draining it, or trying to suck some out.
 

olympic

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Yep, 1.25 quarts including the friction modifier. It should be around 3/4" below the fill hole. My Ford Racing cover did the same thing when I filled it up to the hole. After putting the proper amount in it was fine.

The driveshaft shouldn't need rebalancing when swapping the IRS but wouldn't hurt to get it checked. With all the suspension mods maybe check the driveline (U-joint) angles as well. Tremec makes a handy app for measuring these angles,
 

IllCobra

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That's too much. Especially with the FRPP cover. Max fill is 1.25 quarts. I did 1.15 last time to make sure it would blow out. So your choices are either to let it keep blowing out, draining it, or trying to suck some out.
Yep, 1.25 quarts including the friction modifier. It should be around 3/4" below the fill hole. My Ford Racing cover did the same thing when I filled it up to the hole. After putting the proper amount in it was fine.

The driveshaft shouldn't need rebalancing when swapping the IRS but wouldn't hurt to get it checked. With all the suspension mods maybe check the driveline (U-joint) angles as well. Tremec makes a handy app for measuring these angles,
Son of a B! Thanks for the tip guys. I'll let some out and also check the U-joint cause that's something else that has been bothering me
 

dazwelding

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I had a similar issue. I installed the Full Tilt Boogie expansion tank and that allowed the excess fluid to move to the tank. At the time I thought the fill was to the bottom of the fill hole, which I now know is not correct, but the expansion tank caught the excess fluid.
 

IllCobra

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I had a similar issue. I installed the Full Tilt Boogie expansion tank and that allowed the excess fluid to move to the tank. At the time I thought the fill was to the bottom of the fill hole, which I now know is not correct, but the expansion tank caught the excess fluid.
You mean you thought the fill hole was the hole at the bottom of the diff? How were you able to keep all the fluid in without it immediately leaking out? How much was the expansion tank if you don't mind me asking?
 

dazwelding

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You mean you thought the fill hole was the hole at the bottom of the diff? How were you able to keep all the fluid in without it immediately leaking out? How much was the expansion tank if you don't mind me asking?
No, I thought the fill level was to the bottom of the fill hole, I did not realize that the fill level was below the fill hole. That’s just what I was taught when I started working on cars when I was a teenager.
I filled it from a hole in the trunk with a clear tube and just watched until it was full. Still made a mess though.
I don’t remember the price on their tank, I purchased it years ago, and I also purchased there whole rear end kit at the same time.
I would not recommend intentionally doing it this way, it just worked out for me that I overfilled it and I had the expansion tank, so the tank caught the overflow. I got the tank because I am building the Cobra to track it.
 

PC03GT

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You mean you thought the fill hole was the hole at the bottom of the diff? How were you able to keep all the fluid in without it immediately leaking out? How much was the expansion tank if you don't mind me asking?
I have one too from FTBR, it's 30 bucks on their website
 

IllCobra

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Where did you guys mount the catch can? In the trunk like FTBR says? Does any diff fluid leak out the blue vent tube? I figured it would if it's just vented to atmosphere, right?
 

dazwelding

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Where did you guys mount the catch can? In the trunk like FTBR says? Does any diff fluid leak out the blue vent tube? I figured it would if it's just vented to atmosphere, right?
If fluid blows out the vent tube, that would mean the overflow completely filled and is overflowing. It would have to be a very bad day for that to happen. There is a sight glass on the side, so it is easy to monitor the level of fluid in the can. It’s a really nice piece. I mounted mine to the side of my battery box in the trunk, it was too easy to mount there!!
 

IllCobra

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If fluid blows out the vent tube, that would mean the overflow completely filled and is overflowing. It would have to be a very bad day for that to happen. There is a sight glass on the side, so it is easy to monitor the level of fluid in the can. It’s a really nice piece. I mounted mine to the side of my battery box in the trunk, it was too easy to mount there!!
I am going to order one, that way I don't have to worry about it spraying out the vent again cause that ruined my polished exhaust.
 

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