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Technical What rear end for 50 mercury ?

Discussion in 'Traditional Customs' started by IRON, May 2, 2020.

  1. IRON
    Joined: Oct 29, 2006
    Posts: 686

    from Florida

    can some one tell me the best rear to put under a 50 merc. No disc brakes, No drag race, just a driver. thank's.
  2. What engine?
  3. 19Fordy
    Joined: May 17, 2003
    Posts: 7,560


    The 1971-73 Mustang 9 inch rear is the same wheel mounting surface distance to wheel mounting surface distance as the 49-51 Merc. 61 1/4 inches. Here's what it looks like in a 51 Merc. I have 4 extra 71-73 Mustang axles if you need them.
    Bolt pattern is 5 x 4 1/2"

    Attached Files:

  4. hennmann
    Joined: Jul 24, 2017
    Posts: 26


    If you are using stock with overdrive there were two options 4.27:1 (mountain diff) which I have in mine or the 3.92:1 (flat land diff) otherwise if you didn't have overdrive the 3.92 was typically used. Other than this 49&50 used the Dana 41 and 1951 used the Dana 44. Yes the 41 is not as heavy built as the 44 but if you drive civilized they last. They can't be that bad because I purchased my 50 in the early 80's and it's still surviving today! My side gears are getting worn and noticed this when I replaced my axle bearings and seals but will do for now. The indication is my axle splines have wear and if they are worn the side gears are worn as well. Parts are harder to find for the 41 but bearings to rebuild are not hard to locate. If your differential gears are worn seems to me the gears interchange with the 44 but I will recheck the book. The carrier assembly and Crown and pinion are slightly smaller in the 41, 5 5/8" bolt circle, as well compared to 6 5/8" bolt circle in the 44. Wondering if yours is a 41? The cover is unique and is kind of shaped like a turtle shell or more rounded instead of the more squared off 44.
    If your not going radical on HP and if your gears are okay I wouldn't be afraid of it and if your bearings are poor replace them. Being a Dana it's as big of a PITA to rebuild as the 44 and by PITA it doesn't have the removable carrier assembly out the front like the Fords but instead you need a spreader to carefully spread the housing to pull the differential assembly out of the housing! In my OEM shop manual they show a special holder to place the entire axle housing on a bench for service work lmao! It's that or pull the rear cover with car on hoist or axles stands and giver there instead of pulling the entire housing and not as easy as pulling the pumpkin out the front leaving the axle housing behind like the Ford diff :-(

    I might add that if a Dana 41 is no big deal for you and if you don't like the ratio you have, there is a seller on eBay who has brand new 3.54:1 for sale but I'm leery of it because with my Borg warner with an OD ratio of .70:1 I'm concerned my 110 HP 255 might labor or be lugging too much in overdrive.
    F-ONE likes this.

  5. hennmann
    Joined: Jul 24, 2017
    Posts: 26


    19fordy is that Mustang diff the good old Ford diff removable from the front of the housing?
  6. 70s era GM intermediate were used a bunch.
    That gives ya the GM small bolt pattern.
    The already mentioned mustang gives ya the small ford bolt pattern.
    I have wondered if the explorer works. It’s can be had in drum brake. Great gearing and posi units are easy to find with these.
    I have also wondered about the late 50s early 60s f100 for mine if I keep the front drums.
  7. I'll note that you can also find that Mustang axle in the 8" flavor as well. If you're running a stock or very mild motor (350" or less) with an automatic, it will be lighter and more efficient compared to the 9". If the motor is 'hot' but at 300" more-or-less, the 8" will still work. The bigger motors have too much torque for the 8".
    Hnstray and anthony myrick like this.
  8. trollst
    Joined: Jan 27, 2012
    Posts: 2,090


    Easy to find, strong, proper width, ford ranger 8.8, with a trac loc, found in every scrap yard. Also mounts to leaf springs in rangers, cut off spring pads, remount them for your application.
  9. woodiewagon46
    Joined: Mar 14, 2013
    Posts: 2,036

    from New York

    You can't beat a 9" Ford. The Mercury is a pretty heavy car so I wouldn't go with the 8". Make sure you get the axle with the large axle bearings.
  10. Before a recommendation.......what bolt pattern are you looking for?
    Been/done, was very easy with what I have.......Same car.........
    Mr48chev likes this.
  11. derbydad276
    Joined: May 29, 2011
    Posts: 1,333


    I used a axle from a 2000 XJ Cherokee 8.25 drum brake .. 3.55 gear ...
    5 on 4.5 .. spicer u-joint ...

    under my 53 coronet
  12. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,308

    from Quincy, IL

    The recommendations above for Explorer and Ranger axles is okay from a strength standpoint, but the overall width is a bit narrow for your application. Ranger 8.8” came in 56.5” and 58.5” width....outside to outside and Explorer are 59.5”.

    In addition, both of those applications have significant pinion offset to the passenger side, which may be okay in your case, but you really should checkout that and driveshaft tunnel width on your Merc before making a decision.

    IMO, the comments above about the adequacy of an 8” Ford unit are correct. The downside of 8” is the very limited stock gear ratios. 2.79/3.00 are most common with 3.25 less common and 3.55, while available in very limited models new, is rare now. Of course their are aftermarket gears available to solve that, but seems to me using an axle that already has what is needed is better choice. That said, 9” came with wide variety of stock ratios and are easily swapped out, but may up the cost.

    All in all, @19Fordy has a really good suggestion, and is in Florida already....may be worth looking into more closely.

  13. The f100 9 inch up tp 72ish should be very close to the stock width. Except for the 57 version.
    Same bolt pattern as the mercury.
  14. Mr48chev
    Joined: Dec 28, 2007
    Posts: 31,296


    49/51 Merc stock rear axle is 61 inches wms to wms. Lug pattern is 5 on 5-1/2
    57/72 F100 rears are 61-1/4 wide nine inch rears. Meaning once you have the housing and axles swapping gear ratios is just pull the third member and put another one in and bolt it back together.

    That is if you need to match the front drum bolt pattern so you only have to carry one spare.
    I ran a 65 Chevelle rear under my 51 for a lot of miles and the only issue was that I didn't cut the ears for the control arms off the center section and they beat up the hump over the rear axle. Car had a nova subframe though
    This is one of the easier and more accurate rear axle width charts around.
    All measurements are wheel mount surface to wheel mount surface as backing plate to backing plate doesn't mean squat even though some guys are wrapped up in it.
    51 mercules and Hnstray like this.
  15. F-ONE
    Joined: Mar 27, 2008
    Posts: 3,092

    from Alabama

    I thought the same too, about the spreader as that’s what the manuals show.
    Squirrel; whom I trust his experience, said it’s possible to service/remove the gears of the Dana 41 without the spreader.

    As far as the original question, the only reason I would change out the rear axle in a Mercury, is that it was broken.
    I have found the Dana 41 to do well even behind an warmed up OHV V8.
  16. IRON
    Joined: Oct 29, 2006
    Posts: 686

    from Florida

    OK guys, thank's so much for the help, got to find a donor car then we can use Eng, trans & rear from that car. like to keep FORD in a ford. thank's IRON.
  17. 19Fordy
    Joined: May 17, 2003
    Posts: 7,560


    Here's what the 71-73 Mustang 9 in. center section looks like. Removes from the back.
    This one has Traction-Lok.
    DSC00255.JPG car #13.jpg

    Attached Files:

    Hnstray likes this.
  18. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,308

    from Quincy, IL

    @19Fordy I understand what you mean about 'removes from the back', but that would more commonly be referred to as 'removes from the front'.......the reference is to the third member assembly being removed from the housing.
  19. 19Fordy
    Joined: May 17, 2003
    Posts: 7,560


    OK, Thanks. I didn't realize the terminology is not literal in relation to the front of the car as I assumed.
    In this 3rd member, the ratio was changed from 3:73 to 3:55. The car has overdrive.
  20. TinWolf
    Joined: Sep 12, 2006
    Posts: 190

    from Sweden

    I got the stock -51 Merc Dana 44 3.3-1 rear axle in my -51 Merc that had the overdrive rear axle 4.27-1, hard to find a original , have no idea if the other -51 Merc Dana 44 rear axles can be converted with later 3.3-1 ring / pinion , Ive seen new the ring / pinions for Dana 44:s are available but never tried to convert or heard anyone attempted to do so ?? The upside is ofcause getting the stock -49-51 Merc boltpattern and stock track width !
  21. 1957 Ford Ranchero is in my 51 Merc, hard to find now.
  22. Bounder
    Joined: Oct 31, 2011
    Posts: 251


    I put a 8.8 out of a 2001 Explorer in my 50 Merc. Now I have disc brakes and limited slip. But it has a 3.73 gear ratio and turns a few more rpms than I would like. My leaf springs were shot so I had to buy new ones and had to have a new driveshaft made. But I'm running a 79 351 and a C-6 transmission.
  23. Marty Strode
    Joined: Apr 28, 2011
    Posts: 6,933

    Marty Strode

    The problem with the F100 9" rears is, the pinion is offset 4-3/8" to the passenger side, and both axles are the same length.
  24. Squablow
    Joined: Apr 26, 2005
    Posts: 16,047


    '51 Merc rearend is a regular Dana 44 so there's tons of gear ratios and parts available for them. I've got one from a Merc-O-Matic car for mine for the (numerically) lower gears.
  25. banditomerc
    Joined: Dec 18, 2005
    Posts: 2,372


    When i built my 51 merc (1981), it had the flathead & merc o matic trans..when i swapped out to a 350/350 auto ,the rear end performed great..i drove it all over,it never let me down..
  26. Dangerousdan
    Joined: Apr 12, 2018
    Posts: 292

    from Arizona

    If I were to look for the rear gear ratio would it be indicated on the rear housing or maybe some where else? Thanks
  27. 1pickup
    Joined: Feb 20, 2011
    Posts: 1,194


    61.00 1964-1971 Ford Full Size
    61.00 1949-1951 Mercury
    61.25 1957-1972 Ford F-100 Pickup
    61.25 1960-1964 Ford Full Size
    61.25 1971-1973 Mustang
    61.25 1967-1973 Torino, Ranchero, Fairlane
  28. Dixie Rambler
    Joined: May 8, 2020
    Posts: 32

    Dixie Rambler

    I have a 53 Chrysler and am wondering...Does anyone know the best front end suspension to upgrade my stock front end too?

    I put a Ford 9 inch rear end in a s the rear is good. I just want to upgrade my suspension now.
  29. Beanscoot
    Joined: May 14, 2008
    Posts: 2,402


    Summit sells ring and pinion gear sets for the 8" in 2.80, 3.00, 3.25, 3.40, 3.55, 3.80, 4.11 and 4.62 ratios.
    I'm not sure why it's often stated that there is a limited gear ratio selection available. I guess people are thinking of common stock ratios.
    They also are available with limited slip.
  30. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,556


    Unless you just want to change to change the Dana will do the job

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