Factory Five Racing Forum banner
1 - 9 of 9 Posts

·
Registered
Joined
·
603 Posts
Discussion Starter · #1 ·
Question. I am going through my manual and looking for parts that I am wanting to put on my new FFR. I have a question (Might be a little stupid but i am stuck) about "SPLINE" differences. I think it is the amount of teeth. if this is the case. I would think that 31 would be more tough, because you have more teeth engaged. if that is the case, do I stay the same amount (31) from the Transmission all the way back through the rear end. direction please.
 

·
just another builder
Joined
·
8,238 Posts
This is dictated by the parts...for example a t5 has a 10 spline input shaft a tko has 28 spline. The output of the TKO is 31 spline...I'm not sure what it is for the T5...In short, It's not something you select as much as something dictated to you by the combo of parts used...IHTH
 

·
Junior Charter Member
Joined
·
89 Posts
G3, there are different spline counts on different components as you go back so you need to match your inputs and outputs on the tranny. Also the rear end has different axles you need to be aware of if you are upgrading to 5 lug. If you go from 28 to 31 spline axles then you need to change the differential. Easy right? Isn't research fun?
scot
 

·
Senior Member
Joined
·
1,595 Posts
31 spline axles are stronger than 28 spline ones.

Bill G
 

·
section 8
Joined
·
5,136 Posts
What bill said all 87-93 mustangs have 28 spline axles . If you have plans for big power or sticky tires upgrade the rear end first .Only because your going to change to fox widdth and 5 lug anyway the only cost addition is the posi unit about 250 FRom Ford Racing. Then when you blow up the t5 you can get the tremec tko and the matching yoke from several forum vendors.
 

·
Premium Member
Joined
·
2,513 Posts
Originally posted by quicksand:
This is dictated by the parts...for example a t5 has a 10 spline input shaft a tko has 28 spline.
TKO600 has a 26 spline input shaft doesn't it?.
 

·
Blue Oval Scribe
Joined
·
9,177 Posts
Yes, TKOs have always been 26 spline, which is a standard GM clutch disc hub...

To get more to the point G3, the more splines you have, the more surface or contact area you have, so the contact point is stronger. This is why the TKO has 26 splines instead of the usual 10 or 11. The same for rear axles. 28 spline is the standard with aftermarket axles going up to 31, 35, and even 40 spline!

This is why a serpentine belt can grab so much better, as those six ribs equal 12 seperate surface areas between the grooves for more contact area.

So you see, you can't just pick "31-spline" all the way back from the clutch. If you want to upgrade to stronger components they come with their own spline count and you have to match the connecting peripheral accordingly (clutch disc, driveshaft yoke, axle shaft).

HTH...
Mark
 

·
FFCobra Fanatic
Joined
·
12,975 Posts
Pretty sure the manual is refering to the rear axles. Depending on rear used it could have 28 or 31 splined axles. You can upgrade a 28 splined rear with 31 splined axles but you will also need to change out the spider gears in the rear since they are what the axles slide into.
Spider gears used, 28 or 31,determine the axles used.
 

·
Junior Charter Member
Joined
·
11 Posts
I have been researching IRS parts to fill in the gaps from my 2003 Mustang Cobra donor.

The 03-04 Mustang Cobras have Independent Rear Suspension. If you are not going with IRS, you can stop thinking about the 31-spline thing here.

The stock differential has 31 splines on the outputs to the half-shafts. Earlier Cobras, T-birds, and Mark VIII's all use 28-spline output shafts.

There is a huge cost difference in buying the half-shafts with 31-spline inner CV's. The stock axles are too long. FortesParts.com will sell you stock replacements milled down for about $1200, but he must shorten all the way to the narrower pin-drive width. The DriveShaftShop.com only has a full chromoly halfshaft with the 31-spline inner CV and charges $1400 for it. These options are rated for about 550hp and 900hp, respectively.

If you have donor halfshafts with undamaged inner CV's, the driveshaftshop will sell the axle and outerCV for $1000 that plug right into your inners.

If you go 28-spline, donors are much easier to find and a full new set of halfshafts are no more than $700.
 
1 - 9 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top