2.75 to 3.50 3rd member swop issues


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I’m at my Witt’s end! Did as everyone suggested and everything looks perfect! But still smell gear oil! I pulled the plug and some gear Oil drained out. So I jacked up the car to get a little more out just to make sure enough drained out.
Went for a cruise and still I smell gear oil coming from the back brakes! WTF! Sorry! Just frustrated!
it looks like it is the seals not sealing. Axles look good! No pitting. Nice and shiny. Like I said I never had this issue with the old 3rd member.
Sorry to read this swap is causing such problems. If you take it apart again take pictures of the seals before you remove them and the ends of the axles where the seals ride. This may provide some clues for those trying to help you solve this issue. Pictures can show a lot of things that are difficult to describe with words.
Overfilled fluid will leak past seal, have to check at ride height to be accurate.
It’s hard to pull the plug out at rid height as it is to low for me to get at. Maybe I’ll drive it to a lube shop and get them to pull the plug and see if and how much oil comes out.
If that doesn’t work and I have to pull the axles. I will take pictures
There are multiple axle seals available for the small bearing 9". I'd suggest measuring the seal and the shaft next time you pull the axle shaft. First time I put together my 9" I had the wrong seals in it and it leaked a bunch.
I got my daughter to pull the plug and nothing came out. So the last time I drained some out I took a little too much. But still leaking past the seals. The old seal (Original) never leaked. I did not take a good look at the axles but they looked shiny. Nothing stood out.
I did buy for 28 spline axle. Are there seals made even small for the 28 spline or do I buy an axle shim? If so where would I find them and what’s the best ones to buy
There are multiple axle seals available for the small bearing 9". I'd suggest measuring the seal and the shaft next time you pull the axle shaft. First time I put together my 9" I had the wrong seals in it and it leaked a bunch.
What seal did you end up buying?
Just to make sure I double checked my vent line and the port coming from the differential and all r clear. No blockages
Well I just purchased 2 sleeves that are for a 31 spline. They r supposed to fit a 28 spline. I just have to get seals for a 31 spline axle. Hopefully this is my solution
Perhaps this was asked before and it is not meant to offend you but only to be shure: do you have double checked the seat of the seal on the axle? If it is not 100 percent flat on the flange but in an angle it could leak. First time I put my new seals on I hammered them on in an angle - despite I triple checked it and used a perfect fitted tube and watched every hit. I had to use three seals until it sat perfect flat. But it was only the one side - the other side went on like a charm with the first new seal.

Only for your idea ;)
I checked with a gauge and they look spot on. I’m as confused as all of you. One fella said that they make a seal with a smaller inside diameter. Which would make sense to why it is leaking. I wish I know the type and seal number. I’d rather try that then the sleeves.
And when I press the sleeves on. Do I put silicon on the axle before I press on the sleeve?
I banged them in as far as it seemed to bottom out. When I stuck my finger in to feel. It seemed like there was an 1/8 of an inch. Same on both sides. I’m assuming there in all the way. While I was pounding them in. They just stopped and wouldn’t move anymore. Did it sound and feel like they bottomed out? Hard to tell. But they both stopped at the same place. About an 1/8” from the stop ring. The rubber seal part. So I assuming the metal part of the seal sticks of more and stopped where it is supposed to.
I took out my axles to check for pitting or imperfections. I really don’t see an issue


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I’m sorry I didn’t keep the box with the part number. It was from Napa. They looked like a ford seal green on the out side edge. I will be buying from a different store today. I’m bringing my axles there to see the fitment before I buy them. Thinking I’m not going to install them in all the way so they will be in a better area on the axle
Installed new seals from a different store. They are thicker then the other one which would put the rubber ride on the axle in a different spot. 4th time may be the charm! Let you all know after a nice long cruise