31 vs 28 spline, do I really need 31?

Kdubslugga · Mar 3, 2007

Ok heres the situation, I need to address my rear end. It has 4.10s and the the blower its too much, I havent driven it yet but i know its to much, I shift way to fast as it is without the SC. My factory traction Lok is Shot, and the rear end is leaking out of the pinion seal. Im debating on whether or not to just rebuild the traction lok or get a Locker rear end. Im looking at the Auburn Posi unit from brothers performance, seeing as it is a resonable price around 375, plus a set of 3.73 gears. My concern is, i dont want to have to get 31 spline axels for 4 lug and then get new axles when i do a 5 lug conversion, dont have that cash right now, I was thinking about getting that Auburn unit with 28 splines and using the stock axles until i do a five lug conversion and then getting some Moser Axles with 28 spline as well. Is it that much more durable. I cant see snapping a new HP Moser Axle with my power level. I dunno need some sugestions

socalracer2007 · Mar 3, 2007

if you are just driving it on the street then the stock 28 axels will be fine. if you are going to put slicks on it and race at the track then go with the hardened 28 or 31's.

tmoss · Mar 5, 2007

I highly suggest you replace your 155lph pump with a 255lph unit with that blower..........

WilwoodFiveO · Mar 5, 2007

if you plan on launching pretty hard at the track like said above you better go to 31 spline, if you don't upgrade you will have a very big problem and will need more than just replacing of a differential. so i say wait a while and buy the 31 spline 5 lugs together. and then just install all at once.

7-UP BILL · Mar 5, 2007

Hardened 31 splines are the way to go. Get a FRPP 31 spline trac-loc (F-150) M-4204-F318 and buy a clutch replacement pack. Repack the clutches and steels w/ 1 steel to 1 clutch disc. Will make it tighter, almost like a locker but retain turning ability. You can get the axles redrilled for 5 lug when you are ready.

86bluecobra · Mar 5, 2007

Personally i would stick with hardened 28 spline axle shafts otherwise the upgrade cost gets out of control. I am going to be installing hardened 28 spline axle shafts in my car.

DocZG · Mar 5, 2007

you could get a 03-04 cobra differential (600hp rated) for about 220 and axles with seals/bearings from summit for 215ish. $450 isnt that bad for a solid rear end.

stangman · Mar 6, 2007

Get the 31's

Here are some pics of my 28's

N8Miller · Mar 6, 2007

for what its worth, the 31 splines are a good way to go. I would couple them with a FMS diff with the extra clutches like stated above (thats my plan... already got it. I got the hookup on them, PM me).

87GTSnake · Mar 6, 2007

Stangman, were those stock or aftermarket axels?

stangman · Mar 6, 2007

87GTSnake said:
Stangman, were those stock or aftermarket axels?

stockers

& in fairness, i got about 40-50 passes out of the stock axles making 450rwhp for about 3/4 of those runs

91notchbk · Mar 7, 2007

I would go with an Eaton Posi over the Auburn. The Auburn uses cone clutches and is not rebuildable. The Eaton is very robust, uses woven carbon discs, 400lb spring pack, and has forged gears. It is also rebuildable. If you have the cash go with an eaton 31 spiline differential and 31 spline axle shafts.

SVT32VDOHC · Mar 7, 2007

I had my stock 28 spline for years until my posi burned out. I then updated to 31 spline axles. I save big money though by using an Explorer 31 spline differential.
The car hooks even harder now....but I would not have updated if my diff if I did not burn out...and plus having my friend at DTS who builds my axles was a plus. I couldn't pass up a beefed up 31 spline Explorer diff for 40 bucks.

stangman · Mar 7, 2007

SVT32VDOHC said:
I had my stock 28 spline for years until my posi burned out. I then updated to 31 spline axles. I save big money though by using an Explorer 31 spline differential.
The car hooks even harder now....but I would not have updated if my diff if I did not burn out...and plus having my friend at DTS who builds my axles was a plus. I couldn't pass up a beefed up 31 spline Explorer diff for 40 bucks.

that's exactly what i did, except i used moser axles & double packed the clutches. if i have to open it back up to put anything else on, like a differential cover, i'm taking it out & putting carbon fiber clutches in it.

$100 for brand new mosers (friend discount)
$50 for an explorer
$20 for fluids

you can't beat a rear build for under $200

86bluecobra · Mar 7, 2007

stangman said:
stockers

& in fairness, i got about 40-50 passes out of the stock axles making 450rwhp for about 3/4 of those runs

those were stock axles and you didn't destroy the splined part of axle at all? why would you need the added strength? The 28 spline axles are just as strong when it comes to construction its just that they don't have the strength going into the spider gears. I also snapped a stock axle but no harm or foul to the splined section. I didn't strip out the spider gears at all. Yes the 31 spline set up probably would be the best but i don't think for you average street and strip car it is nessesary at all.

SVT32VDOHC · Mar 7, 2007

stangman said:
that's exactly what i did, except i used moser axles & double packed the clutches.
you can't beat a rear build for under $200

...Heck yeah, and ours is just as tough as somebody who spent 1000-2000 dollars. I will put any set of tires on my car and run it....and if it breaks fix it for another 200 bucks...I have Mosers too, paid more than 100 though, I think it was around $129.

stangman · Mar 7, 2007

86bluecobra said:
those were stock axles and you didn't destroy the splined part of axle at all? why would you need the added strength? The 28 spline axles are just as strong when it comes to construction its just that they don't have the strength going into the spider gears. I also snapped a stock axle but no harm or foul to the splined section. I didn't strip out the spider gears at all. Yes the 31 spline set up probably would be the best but i don't think for you average street and strip car it is nessesary at all.

it got the under side of the splines also

86bluecobra · Mar 7, 2007

stangman said:
it got the under side of the splines also

It didn't actually strip the 28 spline though right? The axle shaft twisted and broke but a little of the spline busted aswell. 31 spline axles wouldn't help with this problem. 31 spline axles would help if the spline of the axle or the spider gears were being stripped out. they have more surface area grabbing.

stangman · Mar 7, 2007

86bluecobra said:
It didn't actually strip the 28 spline though right? The axle shaft twisted and broke but a little of the spline busted aswell. 31 spline axles wouldn't help with this problem. 31 spline axles would help if the spline of the axle or the spider gears were being stripped out. they have more surface area grabbing.

you mean other than the fact that they're hardened, unlike the stockers

tmoss · Mar 8, 2007

here is an old trick............paint a straight line all the way down the stock axles that get abuse on the track. once a year (or more depending on the abuse level) pull the axles and see if that straight line has started to "curve". If it has, replace it. Sometimes thay just snap, and sometimes they will show signs of stress before that.

31 vs 28 spline, do I really need 31?

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