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Author
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Topic: Converting a 31 spline Locker to 28 Spline?
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skips69
Gearhead Posts: 287
From: Catlin, IL USA
Registered: Mar 2001
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posted 01-29-2003 09:17 AM
   
Someone just told me that I could take the locking unit out of a 31 spline 9" rear, drop it in a 28 spline 9" rear with no other modifications. Has anyone heard of this before, or something similiar along these lines? If this is the case, there are plenty of 31 spline 9" rear ends in this area in local junkyards, mainly in eary to late 70's Ford trucks. Some our surely lockers. Anyone know of this and can shed some light? Just following up on another tip, or hearsay. Thanks!
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V8 Thumper
Gearhead Posts: 3603
From: Orange, Ca. United States of America
Registered: Dec 2001
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posted 01-29-2003 09:32 AM
Provided that the bearings are of correct size (31 splined carriers will have 3.062" bearings, as do some 28's) yes; it is a bolt-in. Swapping ring gears to another carrier will require you to reset the gear lash. You will of course need 31 spline axles of identical length to your 28's to duplicate the spline engagement.Outter axle (wheel) bearings will be something else to keep in mind. If your housing is small-ended, big axles will have little bearings at the hub resulting in shorter service life. ------------------
1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9" All Blue Oval, no blue bottle
http://mustangsandmore.50megs.com/V8Thumper.html
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Moneymaker
Administrator Posts: 19964
From: Lyons, IL, USA
Registered: May 99
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posted 01-29-2003 03:05 PM
Yup.  ------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
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www.moneymakerracing.com
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n2oMike
Gearhead Posts: 1641
From: Spencer, WV
Registered: Jan 2001
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posted 01-29-2003 03:41 PM
quote:
Originally posted by V8 Thumper:
Provided that the bearings are of correct size (31 splined carriers will have 3.062" bearings, as do some 28's)
Not all housings used for 31 spline applications had 3.062" housing bores. Most I've come across had the standard 2.89" bearings. To convert the 28 spline 'pumpkin' to the 31 spline, all you've gotta' do is CLEAN the 28 spline housing with gasoline. (or something that will clean ALL the grease off so a good backlash measurement can be taken) Then measure the backlash of the old setup. After you've done that, remove the differential unit, and knock the ring gear off with a brass or lead hammer, and re-install it onto the 31 spline diff. Reset the 31 spline unit and gear into the case and set it to the original backlash, and you're done with it. Since the pinion was never removed, and the differential unit is all that was changed the backlash is all you've got to worry about. Reinstall the pumpkin into the housing, and install a set of 31 spline axles that are the same length as the original 28's, and you're done. As for the housing bearings... You can install whatever size bearings you want onto the new differential unit. If the housing measures 2.89", and the 31 spline diff has the larger bearings installed, you can simply install new 2.89" bearings. Good Luck! ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220
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skips69
Gearhead Posts: 287
From: Catlin, IL USA
Registered: Mar 2001
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posted 01-30-2003 07:48 AM
I never wanted to go to 31 spline axles, due to the cost. That was why I was intrigued to hear that this could be such an easy swap. I can find 9" lockers for the 31 spline axles pretty easily around here, but my car is equipped with a 28 spline, 9" rear, those are pretty scarce and much more expensive when I do come across one. I have thought of going to an aftermarket locking unit for the same 28 spline differential, but by the time I am done buying the components to make mine into one, and the better 3.50:1 gears for the upgrade, buying a used one that is already a locker seems cheaper. Still too costly for me either way, so will keep looking for a deal, or hope someone moves into this area that is more knowlegeable concerning rebuilding rear-ends and setting the back lash. It still imtimidates me too much to try it myself. My only experience has been swapping pumpkins and taking my current diff apart, cleaning it and reassembling it with all the correct shims - just as it came apart. Thanks for the replies though, it disspells the myth about it being an easy drop in type swap.
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rm302 boss
Moderator Posts: 649
From: Austin Texas
Registered: Dec 2002
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posted 02-01-2003 12:10 PM
Ford Galaxie's are a good sorce of 31 spline stuff.. Fairlane's as well. Thats where my 31 spline set up came from. I think it was a 65 Galaxie with a trac lock...
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1970 Boss 302
1990 Taurus SHO
1985 Mustang GT 351W
1995 Land rover Disco
1980 Triumph Spitfire (auto-X car)
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