31 Spline Halfshaft Upgrade

vatdevil · #1 (**permalink**) 02-26-2014, 05:06 PM

Changing out the existing T Bird 28 spline halfshafts to 30-04 Mustang Cobra halfshafts. These are brand new from Ford. I will reuse the existing 36 spline center bars. I'll post more here as I get free time. Carrier will be a TrueTrac and bushings will be solid aluminum (front and rear).

blown871 · #2 (**permalink**) 02-26-2014, 05:54 PM

Thanks for starting this thread. Ahead of me will be my first full summer with my SPF... and I am mentally checking off things .....that 'may be' coming my way.

LMH · #3 (**permalink**) 02-26-2014, 09:20 PM

I have the same thing except I used the 04 aluminum differential and opted for 300M center shafts. Really strong!
Larry

vatdevil · #4 (**permalink**) 02-27-2014, 01:58 AM

Quote:

Originally Posted by LMH

I have the same thing except I used the 04 aluminum differential and opted for 300M center shafts. Really strong!
Larry

I considered using 4340 center bars, but has anyone broken the stock ones? The 4340 center bars are $460 from driveshaft shop.

LMH · #5 (**permalink**) 02-27-2014, 07:07 AM

I did read of a couple FFR guys shearing the axle off at the CV joint but I don't recall what the circumstances were. Could have been drag racing with slicks for all I know.
I just went ahead and had them installed since I had already shipped my CV joints to the DSS. It was expensive though!
Larry

LMH · #6 (**permalink**) 02-27-2014, 07:11 AM

I'm not exactly sure how SPF mounts their differential but if it uses the cast mount on the aluminum diff cover, you might want to consider a stronger cover. The OEM Ford cover on their differential is a weak point.
Larry

GTBill · #7 (**permalink**) 02-27-2014, 03:36 PM

I broke the right axel at the Hub, after the CV.
For once I was not beating the Hell out of the Beast, just moving in 40MPH traffic. I went for slight acceleration and nothing but an increase in RPM.
Replaced it with an Olthoff HD replacement and the beatings continue.

vatdevil · #8 (**permalink**) 02-28-2014, 05:01 AM

Quote:

Originally Posted by vatdevil

Changing out the existing T Bird 28 spline halfshafts to 30-04 Mustang Cobra halfshafts. These are brand new from Ford. I will reuse the existing 36 spline center bars. I'll post more here as I get free time. Carrier will be a TrueTrac and bushings will be solid aluminum (front and rear).

Ford part number is 2R3Z4K138AA and cost is around $650 pair. Ford recently put these back into production. Generally good up to 550 RWHP on a much heavier Mustang.

vatdevil · #9 (**permalink**) 03-29-2014, 04:38 AM

Eaton Ford 8.8 31 spline Truetrac (913A561)
Ford Cobra IRS differential girdle (M-4033-G3)
Ford IRS bearings and seals (M-4413-A)

buddyg · #10 (**permalink**) 03-29-2014, 04:50 AM

So I'm guessing a lot of people are having the stock ones fail?

vatdevil · #11 (**permalink**) 03-29-2014, 04:56 AM

Solid mounts from Craigs Cobras

vatdevil · #12 (**permalink**) 03-29-2014, 05:02 AM

Quote:

Originally Posted by buddyg

So I'm guessing a lot of people are having the stock ones fail?

Some yes. But thats not the main reason for my upgrading. I want the performace gain of the Truetrac and to eliminate wheel hop (solid mounts). Upgrading the halfshafts just seemed logical to do with other changes.

I will also convert the back mount to solid. Pic to follow when complete.

madmaxx · #13 (**permalink**) 03-29-2014, 06:27 AM

I have beaten the living sheet out of all my SPF with more than 500hp never had any issues. I average 2k miles on a set of rear tires. The SPF suspension is max proof!

eschaider · #14 (**permalink**) 03-29-2014, 01:04 PM

If you search around you might be able to find one of these 8.8 covers. They are machined from billet and are about as close to indestructible as you can get. There are provisions for an oil cooler and all kinds of other nice to have stuff.

Ed

blown871 · #15 (**permalink**) 03-29-2014, 02:12 PM

Good groceries that is pretty.
Besides being tapped for coolers. Does the covers on these rears stand to have the reinforcement beef to it? Is this a week point?

vatdevil · #16 (**permalink**) 03-29-2014, 03:21 PM

Quote:

Originally Posted by blown871

Good groceries that is pretty.
Besides being tapped for coolers. Does the covers on these rears stand to have the reinforcement beef to it? Is this a week point?

Yes ....I've seen a number of them break to pieces on Mustangs. The Ford Racing upgrade is cast aluminum and quite a bit stronger than the original crap. It has load bolts for the bearing caps and built in full/drain plugs. Thickness is 1/2 to 3/4 inch.

LMH · #17 (**permalink**) 03-29-2014, 04:27 PM

The production Ford cover on the 8.8" IRS differential is very thin. Combine that with rubber or other non-solid front mounts and solidly mounted rear, it's a recipe for disaster. The aftermarket covers or the FMS covers are much stronger. LPW makes a nice cover.
Larry

blown871 · #18 (**permalink**) 03-29-2014, 04:34 PM

Wow; thanks for the schooling. I have had my head into Chevys my whole life and now... the light has shined down upon me.

eschaider · #19 (**permalink**) 03-29-2014, 06:00 PM

Quote:

Originally Posted by blown871

Good groceries that is pretty.
Besides being tapped for coolers. Does the covers on these rears stand to have the reinforcement beef to it? Is this a week point?

This is a weak point as several have already mentioned. This is what the broken version of the OEM cover looks like;

The cover on the left is an early billet replacement that the original provider has stopped producing. If you like the billet cover in post #14 above it could probably be made again however, the setup headache puts the minimum order quantity around a dozen pieces to get a shop interested.

Ed

buddyg · #20 (**permalink**) 03-30-2014, 02:38 PM

Quote:

Originally Posted by eschaider

If you search around you might be able to find one of these 8.8 covers. They are machined from billet and are about as close to indestructible as you can get. There are provisions for an oil cooler and all kinds of other nice to have stuff.

Ed

Dang that is purdy!