4 Lug vs 5 Lug Axle Bearings

Discussion in 'Technical' started by Acornridgeman, Jan 6, 2006.

  1. Acornridgeman

    Acornridgeman MCCI Wisconsin State Rep Moderator Supporting Member

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    This thread is about the bearing sizes found in Ford 8" 4 lug and 5 lug rear axles.

    I had a rather bad expirience on ebay the other day. I was selling a Maverick 5 lug rear end. A buyer wanted to know how much it would cost to ship just the axles so they could do the 4 lug to 5 lug swap. I told him it would not work because the bearings are a different size and that he needed to buy the rear housing as well as the axles. He told me that the 5 lugs would swap right in and called me basically a liar that wanted to make more money off him for doing the shipping on the larger housing. He told me that they swap just fine and I was full of it.

    So I would like to get this debate solved once and for all with the facts. There are some very good long time people here that swear both ways on this. Also, auto parts stores only list the one bearing for both axles. Yet again, we have some people here that have said they are quite obviously a smaller bearing in the 4 lug rears. It is quite possible that Ford may have made 4 lug rear ends with 2 different bearing sizes, just like they did with the 9" rears. Since the bigger bearing in the 8" is the smaller bearing in the 9", that would mean that Ford would have used an even smaller bearing in the 4 lug rears, which would mean that Ford had 3 different bearings used between the 8" and 9". :huh:

    Maybe they started out with a smaller bearing in early production, but later changed to a bigger bearing in all cars before the change over to all 5 lug axles regardless of engine size? This is the only thing that would explain such a divide in opinion on this swap between the board members.

    Rock auto lists the bearings for both a 4 and 5 lug axle as a RW207 with a 2.8346 diameter and a .8444 width. I threw a calipers on a 5 lug set I have out right now and they were 2.835 dia and .845 width, so that is correct.

    Calling all 4 lug owners:
    Does anyone have a 4 lug axle sitting around their garage they can measure? What I would like to know, is the year and engine size of the car they came from. If you don't know that, just measure it anyway so we can get a sampling of cars. If we can get a good sampling of bearings from 4 lug cars, we might be able to decide this swap question for good. I think there are 2 different bearing sizes that have been used with the 8" 4 lug rears. That is the only possible explanation for the difference in opinion about swapping axles. Lets prove it one way or the other! Post your bearing measurements!

    thank you,
    Eric J






    .
     
    Last edited: Jan 6, 2006
  2. stmanser

    stmanser Looking for a Maverick

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    this is very intersting... reason... i have a 4 lug on my car right now and a 5 l;ug in the backyard that i am interested in putting in.... if the bearings are the same then i will save myself a lot of time and money by just putting my 5 lug axles in the 4 lug housing and be done


    please.. tell me what you find out.. this could help me GREATLY.
     
  3. Grabber5.0

    Grabber5.0 Gear-head wannabe

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    No, you tell him what you find out. :bouncy:
     
  4. Jamie Miles

    Jamie Miles the road warrior

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    Great... the only reason I am still running 4 lug rear wheels is because I was told I can't swap just the axels. Guess I'll have to try it now.

    I've got a '72 2 door that originally had a 200 in it. I'm going to try axels from a '76 2 door that originally had a 250 in it. I'll try it next weekend. I'll let you guys know how it goes...
     
  5. mike75mav

    mike75mav Member

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    If the bearings are the same the axles are not. I just look it up and the 5 lug axle is not the same length as the 4 lug.
     
  6. Jamie Miles

    Jamie Miles the road warrior

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    If the rearends are the same length, why would the axels be any diffrent? I'm trying this and finding out once and for all. I'll also pull a axel out of my '74 Grabber and my '73 4 door, both of which had 250's and try those axels to.
     
  7. mike75mav

    mike75mav Member

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    OK You had to make me get the book again didn't you. A 4 lug axle length is right 29 1/2 and left is 25 9/16, 28 spline.

    A 5 lug axle length is right 29 5/8 and left is 25 5/16, 24-28 spline.

    This is way a 5 lug will not work in a 4 lug housing. I still don't know about bearing couldn't find anything.
     
  8. Jamie Miles

    Jamie Miles the road warrior

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    I'm still trying it... :D
     
  9. Dan Starnes

    Dan Starnes Original owner

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    Just wonderin,, is the difference in the center section?
    Dan
    very good post
     
  10. Acornridgeman

    Acornridgeman MCCI Wisconsin State Rep Moderator Supporting Member

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    Mike - I do believe the differences in length are because of the flange thickness and wheel lug studs being longer for the 5 lug. The shaft that is inside the housing would be the same, but the part that sticks out is a little beefier. Something else we need to measure I guess.

    Dan, every 8" pumpkin is a 28 spline and are all interchangeable with each other. I've never seen anything different for an 8"

    Jamie, if you do pull anything apart, measure the 4 lug bearings to see if they match the sizes posted above. You would only need to pull it a little way out to measure them with a calipers.

    This has been driving me crazy lately. It will be nice if we can decide this once and for all! Thanks all for the input to this thread (y)

    Eric J
     
  11. Jamie Miles

    Jamie Miles the road warrior

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    I'll measure the bearings in all my cars, 72, 73, 74 and 76. (y) I want to know once and for all. It seems every time this topic comes up there are just as many saying it will work as saying it wont.
     
  12. Acornridgeman

    Acornridgeman MCCI Wisconsin State Rep Moderator Supporting Member

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    Rick, if you have a little time, pull out one side of the 4 lug and measure that bearing. If it is the larger 2.835 x .845 it will be the same as the 5 lugs. If it is different we need to know the size, year car and engine.

    Thanks
     
  13. Dan Starnes

    Dan Starnes Original owner

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    Yeah, Eric,, I returned to this post because my mind lead me to the possibility of flange difference. That being different than a 5 bolt, with mass production and bean counters finding a way to keep the bearing the same in some of these housings. Up to us to figure it out. Nothing worth while is easy.
    Dan
     
  14. stmanser

    stmanser Looking for a Maverick

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    i will try and pull out the axle on my 4 lug...

    but my name is Simon... not rick... :)

    does it matter which side i take out.. i suppose the passenger side would be easier.. since i have more room on that side of the car..


    could i just remove the 4 lug axle... slide in the same side 5 lug axle and bolt it in place... what would i be looking for if it wont work.. obviously sliding into the center section will be fine.. but will there be slop in the axle.?
     
  15. M.A.V.

    M.A.V. Yep,my real initials.

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    My step son bought a 1971 Grabber a few years ago that was a 4 lug 6 cyl car with a 3.00 gear in it. We wanted to swap it to 5 lug so we did the front disc swap up front then I told him we would just pull the axles out of a 1972 Parts car I had and which had a 2.78 gear ,and stick them in the `71 housing...They will not fit :tsk: due to the axle bearing on the 5 lug axle shafts are too big.

    I took a closer look and found that the HOUSINGs on the 4 lug cars taper down at the very end to accept the smaller bearing.:huh:

    So we swapped the entire housings out. Then we took the 3.00 center section from the 4 lug axle and swapped it into the 5 lug axle.(just to get the extra ratio.:) )

    Nothing is different but the housing ends and the bearing sizes.:tiphat:
     

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