Nice. Did ya ever consider a floater rear axle?

My builds usually follow a dream then whatever I can afford and or finding a good deal.  Like the axle shafts were $200 for brand new 31 splines.  But no I never considered a floating rear axle but have see a few for sale in my area.  Even the 9 inch housing I have was bought at a great price.

Yes, I have all tools to narrow a big or small bearing 9 inch housing.  When I checked my housing I found one side was not straight, it is now.  Lol

RPM, aka Bearing Bob wrote:

Nice. Did ya ever consider a floater rear axle?

A full floating rear is primarily used in applications where the rear has to carry a ton of weight (3/4 ton and above trucks).  Such rears are by their nature absurdly heavy.  My F250 has a 10.5" Sterling that's a full floater (axle shafts bolt to the hub flanges, vehicle weight is supported by the hub bearings).  The benefit is that the vehicle's weight is born by two big tapered roller bearings on each side instead of one ball bearing and the axle shaft.  If the axle shaft breaks you can't loose a wheel, and can still flat tow the vehicle (heck you might be able to still drive it on the front axle in a 4x4).  The ring gear and carrier in that rear weighs about 90lbs.  The rear hub to hub weighs like 350lbs.  Brutally strong?  Oh heck yeah.  I never broke mine with 1,000lbs/ft of torque in a vehicle weighing 8,000 lbs.  I've also had 3 tons of weight in the bed (per the dump scale) and towed some heavy trailers.  Nothing is indestructible, but its as close as it gets. 

In a car weighing 3,000 lbs, even making insane power a rear like that is still overkill to a level of insanity.  Now, the aftermarket may have full float kits for rears not originally sold as full floaters (I actually have one in my K5 Blazer built by Warn for the 10.5" 10-bolt), but the best use for these is for off roading (big tires, ridiculous torque via gear multiplication in low range, etc.) where you may need to extricate a broken vehicle in some backwater and even just being able to tow it with all 4 wheels still on the truck is hugely important.  A street car is probably never going to break an axle (especially a 31 spline one).  If you have rear discs you aren't going to lose a wheel even if it does.  A 31 spline 9" is going to be plenty for any street car application, and even a lot of race car applications.

Last edited by TKOPerformance (4/14/2024 11:30 AM)

The standard bearing on early Mustangs ain't the best for side loads when cornering. I've never seen a floater on a drag car.

Well I don’t plan on road racing my mustang and it will only see the drag strip maybe once or twice a year.   The only thing I would like to have done differently is use the BB early 9 inch housing I had.  Sadly I acquired it after I bought the disk brake brackets for the SB axle.   The car will see 99% street use.

Today’s progress wasn’t much but again it’s progress.  Painted the housing is the same Satin black as the engine bay and all the links for the axle were sprayed in gloss black. I also sprayed the dash trim and speaker grill in satin black. 

BobE wrote:

RTM - progress looks great, as the saying goes; "How do you eat an elephant?  One bite at a time".
A word of caution regarding painting the dash top gloss black, the sun's reflection can cause issues ... just saying. 

 
The dash trim and speaker cover are satin black like the engine bay, doors and dash.  The roll bar is the same satin black.   Only the SoT rear links are gloss black.

Got the rear axle bolted in and rechecked for the back spacing I’ll need for the 17x11 rim.  Looks like 6.5 BS will be a perfect fit.   I may go with 6.75 BS just to give myself some extra room and if needed I could use a 1/4 spacer. 

The fronts look like 4.5 will be good but the tire does hit the inner frame at full turn.  It does so with either 4 or 4.5 BS.  The rims I want don’t come with more than 3.5 for a 17x7.  If I go to 17x8 then I can get the 4.5.  I’ll look at this a few more times before I commit to a size. Just want to make sure I order right the first time.

You're making great progress, when is it planned to be on the road? 

RPM, aka Bearing Bob wrote:

RTM wrote:

Got the rear axle bolted in and rechecked for the back spacing I’ll need for the 17x11 rim.  Looks like 6.5 BS will be a perfect fit.   I may go with 6.75 BS just to give myself some extra room and if needed I could use a 1/4 spacer. 

The fronts look like 4.5 will be good but the tire does hit the inner frame at full turn.  It does so with either 4 or 4.5 BS.  The rims I want don’t come with more than 3.5 for a 17x7.  If I go to 17x8 then I can get the 4.5.  I’ll look at this a few more times before I commit to a size. Just want to make sure I order right the first time.

 
Have you moved the axle thru its travel limits to see if it clears the wheel opening lips?

 
Not yet but I’m pretty sure it’ll be fine.  The one picture makes it look closer than it is.

MS wrote:

Rear axle doesn’t just move straight up and down, so be sure your travel verification process includes the axle in a drastic “leaning” condition with one side down and one side up. Thet is where I developed a rub condition on the inner wheel housing.  BFH fixed it.

 
Good point MS.  I’ll need to verify that as well as the front travel. With the room I have to tuck the 315 inboard, I shouldn’t hit anything.   I’ll get pictures of the travel testing and post them for future reference.

Looks really nice Bob. Can not that rear trim piece be straightened? I knocked several dents and dings out of my hood and headlight trim pieces.