28 Spline Vs 31 Spline

Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by mind84, Dec 26, 2013.

  1. Hey guys, so I saved up a little cash to buy my first high priced items for my 86 project. I figured I would start by rebuilding the rear end. I was going to buy the 3.73 rebuild kit from LRS but then started looking at the 31 spline kits. I'm still not sure what route I will be taking the motor as I keep going back and forth from just a rebuilt 5.0 with some gt4os and explorer manifold to forced induction. Either way it will be kept street worthy with the occasional track run. My question is, does anybody know the safe limits of the 28 spline rear ends? I am a bit of an overkill kind of guy but I really don't want to spend the cash if not necessary. I just want whatever I put in to last. Any advice will help. Thanks
  2. Don't know what the limit is on 28 splines, but a friend that we race with has a Fox Body car with 31 spline 4 lug axles and runs low 9 sec 1/4 mile times with. Every time he runs I am waiting for the lugs to sheer off.
  3. The C clips and the pinion bearing are the two weak points vs. the axles. IMO as long as you are not doing 4000 rpm launches on slicks and are less than 350hp/tq then you should be fine with 28's. With an AOD even better than a Stick. I've run in the 12's on 28 spline axles and guys have gone 11's. You can also upgrade the stock axles to Strange or Moser's and keep the 28 spline differential, but I would run them till you twist them then go with 31 spline axles and carrier.
  4. Low 9s on a four lug! We'll that makes me feel that I can keep my four lugs with my setup as I do not plan on ever pushing that kind of power on this car. I think I'd really like to be around 300hp on good street tires so tit seems the 28 spline should do fine. The LRS kit should come with good quality bearings right? I know it will have royal purple and the friction modifier.
  5. Yep. It has the GT500 better pinion bearings. At 300 hp you'll be fine. Get the kit that has everything- Ford gears, master rebuild kit, oil, friction modifier. It's cheaper than piecing it together yourself. While you are at it, get new axle bearings and seals as these cars are hard on them and you might as well do it all once. LMRS gives stangnet members a discount too.

    PM Jarrod and he'll set you up.
  6. i second upgrading the axles to stronger ones, but keeping the 28 spline diff.
  7. I snapped a 5 lug 28 spline Ranger axle some years back. I upgraded to 31 spline on the cheap (used but new axles, and a truck carrier) and haven't had an axle issue since then. I'm 250 rwhp and was running middle 12s when it broke.
  8. cost wise its not much different if any at all... just go to 31's
    A5literMan likes this.
  9. What all are you wanting to replace? Are you replacing axles too? If so, I would definitely go 31 spline. You can shop around and find a used 31 spline carrier for $100-$150. I robbed one from an Explorer and bought the $107 carbon fiber rebuild kit. No need to do it twice when you decide you want more down the road.

  10. Yep, that is kind of what I said. Run what you have now until you break/twist the axles, then go with the 31 spline setup. That's part of the fun- break parts and then use that as an excuse to tell the wife you need new ones.
  11. Big difference between a stock 28 spline Ranger axle and a Moser 28 spline axle. I honestly don't know how strong the 28 spline axles are. I put Moser 28 spline axles in my car 14 years ago because back then they didn't make 31 spline axles for my car. I probably have 100 track passes on them. Maybe 20 of those are spray passes with something like 550 ftlbs of torque launching between 4000 and 6000 rpms. They haven't broken yet. Just keep in mind that your transmission has one 28 spline output shaft, so with two 28 spline shafts in your axle it's already twice as strong as the connection to the transmission. The 28 spline output shaft coming out of my transmission hasn't given me any trouble yet either. If you care considering to doing a C-clip eliminator, consider pricing out going to an SN axle or doing a disk brake conversion on your stock axle. You might get a bigger bang for your buck that way.

  12. It's not terribly uncommon for guys to break factory Ford 28 spline axles- usually happens when you try to launch hard on sticky tires. I know of a few low HP cars that have managed that.

    Aftermarket 28 spline axles are going to be much stronger, obviously, but at that point you might as well go 31 spline. (Ironically, I have aftermarket 28 spline axles in my car. I'd go 31 if I were to do it over again.)

    I also have to say that I am a proponent of avoiding breaking parts. Breaking parts almost always leads to breaking other parts, and also guarantees an expensive tow truck ride home. If your budget can afford it- build it right the first time.
  13. Your axles are also subjected to the torque multiplier that is your rear end gears, so it's not quite apples and oranges. Plus mo-manly transmissions like the TKO and T-56 use a 31 spline output.
  14. I know there is more load on the axle. Just throwing it out there for comparison sake.

  15. anyone have the lising of what vehicles have the 31 spline carrier that can be robbed?
  16. As far as I know, you can use the differential but the axles won't work fom Ford trucks except the Ranger. I think the 03-04's Cobra had 31 spline trak lock's. Here's a chart for reference. pages 51-52


    Bottom line is you can swap the carrier and then buy new axles.
  17. if you are going to do that, you can just order the good 28 spline aftermarket axles, they are not that expensive, and you dont have to deal with stock axles.
  18. aftermarket 28 spline or 31....hmmmmm
  19. I was at work so didn't have time to reply. First of all thank you guys for all the good advice. Looks like the thread took off and all the other questions I thought of where answered and then some. I never even considered just upgrading the 28 spline axles. I think for what I want the car to be later just upgrading will do the job. I also didn't realize that the LRS kit didn't come with the axle bearings and seals so thanks foe mentioning it Mikestang. Another thing mentioned that I overlooked was the clutches. I will be getting the carbon kit now as well. Thanks again guys, this is exactly why I joined stangnet the day I picked up my 86 ttop. I just had to throw in the ttop part, love that thing:D
  20. If you are happy with your gear ratio, and the gears aren't all torn up, you can rebuild the locker, swap the axles, change the bearings and seals, and not have to reshim the whole damn thing.