31 spline axle upgrade- What is necessary

[Jim Vander Wal]

This is from memory, did it back in 2005.

Disconnect the drive shaft.

Pull the top bolts on the spindles. Pivot these outward. During this process you'll need to pry the inner CV axles out of the diff case. Big screwdrivers seemed to work well. Just get them out of the way.

Don't stretch out the boots too much, they are the only thing holding the CV assemblies together.

Unbolt the 4 (?) bolts holding the diff case in place. They are obvious and not hidden. It will start to drop during this process. Support it somehow while you're unbolting and lowering it. Weighs 80-100 pounds.

You're done. It's easy on the Ford 8.8 IRS units. The newer Dana units are problem.

FYI, in 55,000 miles I never broke a 28 spline axle. Tore boots, trashed CVs, wore out tires and brakes, sucked up a lot of gas, got real wet many times, went fast, went quick but never broke an axle. About the only ones I know of that broke were drag racers running slicks. The 31 spline system is a good upgrade, I just don't know if it's necessary.

Jim

[Ace23]

Originally Posted by LMH

Best have an SPF expert answer the specifics of that one. I've never taken an SPF differential out. Mine just unbolts, two in the front and two in the rear. That's after pulling the axles out of course.
Might look at a high strength cover for the back of the differential while it's out. The production cover is very weak, so easy to change while it's apart.
Larry

Great idea on the cover. At this point what's another $200.

Originally Posted by Jim Vander Wal

This is from memory, did it back in 2005.

Disconnect the drive shaft.

Pull the top bolts on the spindles. Pivot these outward. During this process you'll need to pry the inner CV axles out of the diff case. Big screwdrivers seemed to work well. Just get them out of the way.

Don't stretch out the boots too much, they are the only thing holding the CV assemblies together.

Unbolt the 4 (?) bolts holding the diff case in place. They are obvious and not hidden. It will start to drop during this process. Support it somehow while you're unbolting and lowering it. Weighs 80-100 pounds.

You're done. It's easy on the Ford 8.8 IRS units. The newer Dana units are problem.

FYI, in 55,000 miles I never broke a 28 spline axle. Tore boots, trashed CVs, wore out tires and brakes, sucked up a lot of gas, got real wet many times, went fast, went quick but never broke an axle. About the only ones I know of that broke were drag racers running slicks. The 31 spline system is a good upgrade, I just don't know if it's necessary.

Jim

Jim thanks for the details. We considered not doing the 31 spline upgrade but with going to a more aggressive rear gear and running drag radials I thought it was good insurance.... I don't drag the car at all but it will be good to know it's not a weak point in the car.

[Inertia]

Originally Posted by Jim Vander Wal

Tore boots, trashed CVs, wore out tires and brakes, sucked up a lot of gas, got real wet many times, went fast, went quick but never broke an axle.
Jim

Hi Jim, did you upgrade the CVs when they failed and if so what to?
Cheers
Steve