Posi trac?
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Elder User
Joined: Nov 2005
Posts: 998
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From: Benton, AR
Posi trac?
I am thinking of adding some horses to my 1979 ford. How do I tell the difference in a 28 or 31 spline rearend? I plan on going from limited slip to posi and don't want to buy the wrong setup.
While I'm at it, is there a cheaper way to go posi, other than ebay?
thanks,
While I'm at it, is there a cheaper way to go posi, other than ebay?
thanks,
Senior User
Joined: May 2007
Posts: 184
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First of all, chevy did posi-trac, and ford/dodge did LSD, both are the same thing just to clarify what we are talking about. If you have a 2wd more than likely you have a 28 spline, 4wd will be 31 spline. If you are still unsure the best way to tell is to take out the axleshafts and count the splines, not any harder than changing the oil in the good ol' 9". There is no real cheap way to get an LSD rear end other than buy a good used one for cheap or getting one for free. The best LSD rearends are the Detroit True-trac and they run about $450, the best place i found to buy one from are completeoffroad.com they are incredibly knowledgable of their products and are very good to deal with with excellent service, I would highly recommend them.
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Super Moderator
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I actually tried to look up all the names for LSD's a while back and did a "know-it-all" post on it on yet another arguement thread. GM's "Positraction" became a default or generic term, just as Kleenex etc. However, in looking these up, I found that there are several different designs of the limited slip. Clutchs/springs, cone/springs, ramps/springs, maybe a couple others. Then there is how effective they are. Fords from a ways back were termed weak, not sure if the current ones are better.
Anyway, pretty pics of several flavors here on this site, so you'll know what to look for ifn's you dasn't already...
Currie Enterprises Racing Rear End Categories
Anyway, pretty pics of several flavors here on this site, so you'll know what to look for ifn's you dasn't already...
Currie Enterprises Racing Rear End Categories
Laughing Gas
Joined: Jun 2007
Posts: 811
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I believe the 31 spline was used on 2 wd starting sometime during 1976. My 76 had 31 spline. Numberdummy passed this tip along to me, and it checked out. Most (not all) 31 splines have to round holes in the end of the axle. Maybee ND can chime in here.
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Elder User
Joined: Nov 2005
Posts: 998
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From: Benton, AR
Thanks for the civil responses. Read that previous post listed above and I would have been slightly pi**ed to get that kind of response. Thankfully I am not in high school. I will be spending some money on this project. It won't be fast enough for the race track but she will be fun as hell to drive.
later
later
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Fleet Mechanic
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From: Middle TN
I like Powertrax lockers for their ease of installation. They make two kinds, hard or soft lockup. The advantage is you don't have to remove and reset the ring and pinion. I believe this is true for all applications. Check out their web site.
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Senior User
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Maybe you got one of the few malfunctioning ones, I have installed over 20 of these in all brands of trucks and all have worked perfectly. Detroit/Eaton is the #1 in diffs, they have been making diffs for a long *** time for damn near everything from logging/highway trucks to quads, they know what they are doing better than anyone else out there. What caused the failure if you dont mind me asking?
