How to know what size axles I have 28 or 31

shelbygt · Dec 10, 2007

I just bought a 98 Cobra and the previous owner put in axles that have no provision for the ABS tone ring. I am trying to get it all working again, so I need to figure out if it has 28 or 31 spine axles, so I can locate the correct axles or possibly an adapter for the tone rings.

Thanks,
Dave

RandyStinchcomb · Dec 10, 2007

stock is 28 spline but tobe 100% sure, you'll have to remove one of the axles and count the splines

Mustang5L5 · Dec 10, 2007

ABS rings can be bought and pressed on. They are not really axle specific.

http://www.bobsfords.com/Merchant2/...e_Code=BF&Product_Code=7956&Category_Code=SPD

Smokeurhonda · Dec 10, 2007

What brand axles did he buy? Some come with provisions for toner rings and others don't. But really the only way to know is to pull an axle and count em.

laserstang21 · Dec 10, 2007

where can a find 31 spline axles

Smokeurhonda · Dec 10, 2007

anywhere, what brand do you want? try summitracing.com buyfordracing.com

Mustang5L5 · Dec 10, 2007

Smokeurhonda said:
What brand axles did he buy? Some come with provisions for toner rings and others don't. But really the only way to know is to pull an axle and count em.

you can just pull a rotor off and look

Smokeurhonda · Dec 10, 2007

how? there isn't enough clearance to really get a good look at the diameter of the axle. and even if you can different axles have different thicknesses towards the hub. So the only way I see it to count the splines?

chuck943 · Dec 10, 2007

Smokeurhonda said:
how? there isn't enough clearance to really get a good look at the diameter of the axle. and even if you can different axles have different thicknesses towards the hub. So the only way I see it to count the splines?

Yeah he can't tell by looking at the hub,the big difference is in the taper at the spline end of the axle. The 28 spline has a larger taper in the spline end of the axle where the axle is machined at the splines, where on the other hand the 31 spline has very little taper at the spline end of the axle. If you where to set the 2 side by side you can see the difference from clear across the room.

Mustang5L5 · Dec 10, 2007

Smokeurhonda said:
how? there isn't enough clearance to really get a good look at the diameter of the axle. and even if you can different axles have different thicknesses towards the hub. So the only way I see it to count the splines?

If the axle is capable of taking ABS rings, there will be a raised flat about 3" off the hub. There is pleny of room to look and measure with some calipers with the ABS ring not present.

Why buy new axles why you can just press the rings on and call it a day.

Mustang5L5 · Dec 10, 2007

chuck943 said:
Yeah he can't tell by looking at the hub,the big difference is in the taper at the spline end of the axle. The 28 spline has a larger taper in the spline end of the axle where the axle is machined at the splines, where on the other hand the 31 spline has very little taper at the spline end of the axle. If you where to set the 2 side by side you can see the difference from clear across the room.

Why do we care how many splines the axles have? I'm confused.

I know the original poster wanted to know how to tell spline count but he doesn't need to change axles if he can just pressed two ABS rings on for $18 each.

All he needs to do is pull a rotor off and measure the diameter of the flat at the end. I'm sure someone has a stock axle kicking around. I know I do, but i can't measure it right this second. If his measurement matched the stock diameter, then he can order two ABS rings, and only have to pull his axles out once. Pulling axles is messy, so why do it twice.

For all we know, the previous owner blew the stock axle, and replaced it with a GT 8.8 that did not have ABS (yes, the do exist) and just swapped the cobra brakes over. He could have stock Sn95 axles and just easily press them on for $40 rather than $200 axles.

But if he wants aftermarket axles anyway, then yes he will have to pull and count

Smokeurhonda · Dec 10, 2007

OK that's where the confusion came in. I thought you were talking about looking at the hub to know the spline count. And yes you are absolutely right about looking at it to know if it will accept toner rings.

shelbygt · Dec 10, 2007

tone rings

I contacted DTS (simply because the car has a DTS rear cover on it) and they said they had an axle w/ABS there and it has a "stepped up" area on the axle for where the ring presses on and my axles do not have this. If you look at the axle picture, it looks as if there was never any rings installed. I just can not imagine why anyone would replace axles with 28's and not put the ABS rings back on. That leads me to believe they might be 31's. I have seen they do make the ring adapters for 31's, but then I have to figure out who made the axles, if they are aftermarket. I would love to only take the axles out 1 time, but I think I may have no choice but to pull them and count the spline.

Stan Weiss · Dec 10, 2007

What did the original owner have done? You can not just replace 28 spline axles with 31 spline axles. Who did the work?

Mustang5L5 · Dec 11, 2007

Yup, changing to 31 requires changing the diff as well.

I think you have no choice but to pull an axle and count

chuck943 · Dec 12, 2007

View attachment 342611

Maybe this will help. This is a pic of a 28 and 31 spline axle from a 8.8 Crown Vic. The one on the left is the 28 spline and the one on the right is the 31 spline. I have circled in red the difference (besides the spline number) of the two. You can see the large taper in the 28 spline as opposed to the 31 spline. I measured both axles at the hub base and they are identical in size there and all the way up the axle until you get to the taper. Of course these are factory axles, I am not sure if an aftermarket would be different. But based on this it appears the ring should work on either one.

Smokeurhonda · Dec 12, 2007

I've got moser 31's. The taper actually is farther up the axle towards the hub. I also know that when I ordered them I had to specifically request the provisions for the ABS toner rings.

shelbygt · Dec 13, 2007

I am thinking these axles are definitely not designed to use the ABS tone rings. I will take them out this weekend and see if I need to get 28 or 30's w/abs axles. I also suspect the gears are 4.56s, so I will hopefully have a stamp on the gear I can read. If not, I will be counting the rotation prior to removal. I'm just curious as to what they are.
Thanks all for your help,
Dave

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