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Gear issue in 8.8 with heavy duty rear cover

Discussion in 'Offroad Drivelines' started by N2FORD, February 10, 2019 at 9:54 PM.

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    1. N2FORD

      N2FORD Elite Explorer

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      Sorry in advance for the long story. I have a 01 Sport Trac with a 8.8 4.10 trac loc. The pinion bearing had gone bad, lots of noise and movement. I decided to try and find a good used one. Found one at the pull a part near me and it seemed really good and tight with no leaks. I put it in about six months ago and added a heavy duty rear end cover. I added the proper fluid and filled to the fill plug on the rear cover. That plug is a little higher than the front plug. The rear end started to blow fluid out of the vent tube if driven on the interstate. I thought at first it was just a little over full and would settle. It did seem to get better. A couple of weeks ago it got warm enough to roll the back window down. Wow what I heard scared me, the rear end is howling pretty bad. Changes as I roll on and off the gas. Checked the fluid and it was still full by the front plug. Took the cover off and the gears seemed shiny and the fluid seemed frothy. So I have now gone to pull a part and picked up another rear end. My question is did the overfilling of the rear end cause my problem or the extra capacity with the larger cover cause the frothy fluid to cause the overflow issue? Just wanted advice before I decide if I want to use that cover again or not. IMG_20180727_151546055.jpg
       
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    3. swshawaii

      swshawaii Explorer Addict

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      Factory fill plug level should always be used regardless of any aftermarket covers increased capacity. If you filled it to the "Solid" 8.8 covers fill plug, it was definitely overfilled. That was the reason for the vent tube overflow and likely the foaming. Surprised you didn't blow out axle seals.

      leaky rear differential vent tube
       
    4. BKennedy

      BKennedy Elite Loser Staff Member Moderator Elite Explorer

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      I have a Solid cover on the front axle (Dana 44) and the first time I filled it, I filled it until fluid started coming out the fill hole. Fluid started seeping out the plug welds on the first trip. Realized it was nearly a quart overfilled and I just fill it with the recommended amount now. I use a zip tie as a dip stick to check the level. The Solid cover doesn't add any capacity, they just put the plug hole up higher.

      With the 8.8, you could remove the OEM plug, then fill it from the cover as it would be easier and stop when it starts running out the OEM plug hole. Fluid capacity should be 3 quarts.
       
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    5. CDW6212R

      CDW6212R Hauls the mail. Elite Explorer

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      Ditto, always use the stock fill hole as the proper level to fill it to. If an aftermarket cover is used, it's handy to be able to fill it with the larger or higher fill hole.

      The fluid hand pumps are about the best way to fill through the stock hole. But if there's room at the back with a fill hole, that should be faster by squeezing the bottles above the diff. Amsoil just started to sell gear oil in quarts in flexible "bags" instead of bottles. I haven't tried any of those yet since I still have the stock covers on mine.
       
    6. N2FORD

      N2FORD Elite Explorer

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      Thanks for the replies. I guess the excessive frothing of the excess fluid thinned the gear lube that caused the gear wear and noise? I plan on using BG fluid in the next one. We are a BG dealer at my work and seems like good stuff. It looks like the replacement rear ends is going to need spider gears, that should be fun. IMG_20190208_055028614.jpg
       
    7. CDW6212R

      CDW6212R Hauls the mail. Elite Explorer

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      The spider gears are easy compared to the ring and pinion. Try to work with a good R/P already in place. Use the best gear oil you can, what is BG brand? I prefer Amsoil, which is now about $14 a quart plus taxes.
       
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    8. N2FORD

      N2FORD Elite Explorer

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      www.bgprod.com They are a automotive chemical supplier. Their BG44k is a well know fuel additive, they seem to make a quality product.
       

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