Lightweight Axles

FED 387 · 10-18-2010, 11:33 PM

Many of the problems with both aluminum spools and 9 inch Ford aluminum differential cases has to do with deflection of the parts under hard accleration(hole shots)---If you think about how you install either a Dana/12 bolt or Ford 8.8 ring gear you are actually spreading the housing a few "thou" to do it. and if you have an alum spool instead of a steel one the aluminum will deflect more than the steel will---Vehicle weight ,engine HP,type of trans (stick/auto) trans brake or not and rear end gear ratios all come into play here and actually have everything to do with if the parts will live in your application---If you have ANY doubts call the spool manufacturer tech line and get their recommendations---What works in my car may or may not work in yours----Ask the tech people they will not lie to you--asking around on forums like this one can confuse some people---Go right to the source ask em they are more than happy to help--Comp 387

Adger Smith · 10-19-2010, 01:55 AM

Strength also has to do with the ratio you are using. A 6.50 gear with a very small tooth count pinion is more prone to fail due to deflection than a 4.56 with a bigger pinion. Yes, the alum will deflect more than steel, but the ratio is the deciding factor. Think about what is happening when the ring gear moves away from the pinion. The contact area gets smaller and moves to the thinner/weaker part of the gear. As I said in my previous post the Alum deflects too much for the gear ratio I'm using. It might not for the gear you are using.

Rod Greene · 10-19-2010, 11:55 AM

I ran the MW aluminum spool and 40 spline rifle drilled axles in my Demon for over 15 years leaving the line at 7000 plus in a car the weighed 3300 + most of the time. Never broke anything. Never even cracked a tooth. I ran 5:57 or 38's. Nothing better than MW.

Jim Caughlin · 10-19-2010, 11:59 AM

FED387, I don't agree with you about 'Ask the tech guys, they won't lie to you'. Maybe not lie but they will error on the way too heavy duty side. Virtually all of my drivetrain components were opposite the advise of their manaufacturers who assured me they would either break outright or wear prematuely. Weight and friction loss are too big of an issue in Stock and SS to take their conservative 'don't want our brandname badmouthed if I'm wrong' attitude. I've learned a lot over the years by looking at cars that have been in my shop and their undersized light duty 'mistakes' which seem to have held up for years without breaking. None of us want to break parts at an inoppertune time but look at the fastest cars and you will see some pretty flimsy parts, I don't think it's by accident. The smart and fast guys are more than happy to tell you that 1350 ujoints, power robbing 9" Ford rearends and all of those cool looking heavy duty parts are the hot setup.

Jim Caughlin
SS 6019

10-18-2010, 11:33 PM	#1
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,425 Likes: 550 Liked 334 Times in 181 Posts	Re: Lightweight Axles Many of the problems with both aluminum spools and 9 inch Ford aluminum differential cases has to do with deflection of the parts under hard accleration(hole shots)---If you think about how you install either a Dana/12 bolt or Ford 8.8 ring gear you are actually spreading the housing a few "thou" to do it. and if you have an alum spool instead of a steel one the aluminum will deflect more than the steel will---Vehicle weight ,engine HP,type of trans (stick/auto) trans brake or not and rear end gear ratios all come into play here and actually have everything to do with if the parts will live in your application---If you have ANY doubts call the spool manufacturer tech line and get their recommendations---What works in my car may or may not work in yours----Ask the tech people they will not lie to you--asking around on forums like this one can confuse some people---Go right to the source ask em they are more than happy to help--Comp 387

10-19-2010, 01:55 AM	#2
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Lightweight Axles Strength also has to do with the ratio you are using. A 6.50 gear with a very small tooth count pinion is more prone to fail due to deflection than a 4.56 with a bigger pinion. Yes, the alum will deflect more than steel, but the ratio is the deciding factor. Think about what is happening when the ring gear moves away from the pinion. The contact area gets smaller and moves to the thinner/weaker part of the gear. As I said in my previous post the Alum deflects too much for the gear ratio I'm using. It might not for the gear you are using. __________________ Adger Smith (Former SS)

10-19-2010, 11:55 AM	#3
Rod Greene Senior Member Join Date: Mar 2002 Location: TN Posts: 530 Likes: 433 Liked 242 Times in 81 Posts	Re: Lightweight Axles I ran the MW aluminum spool and 40 spline rifle drilled axles in my Demon for over 15 years leaving the line at 7000 plus in a car the weighed 3300 + most of the time. Never broke anything. Never even cracked a tooth. I ran 5:57 or 38's. Nothing better than MW. __________________ Rod Greene Real men shift for them selves. Slowly working on TA Challenger for D,E/S and a 72 Challenger for SS/K, L as if I don't have enough other projects.

10-19-2010, 11:59 AM	#4
Jim Caughlin Senior Member Join Date: Mar 2002 Location: Woodburn, Or Posts: 685 Likes: 84 Liked 805 Times in 245 Posts	Re: Lightweight Axles FED387, I don't agree with you about 'Ask the tech guys, they won't lie to you'. Maybe not lie but they will error on the way too heavy duty side. Virtually all of my drivetrain components were opposite the advise of their manaufacturers who assured me they would either break outright or wear prematuely. Weight and friction loss are too big of an issue in Stock and SS to take their conservative 'don't want our brandname badmouthed if I'm wrong' attitude. I've learned a lot over the years by looking at cars that have been in my shop and their undersized light duty 'mistakes' which seem to have held up for years without breaking. None of us want to break parts at an inoppertune time but look at the fastest cars and you will see some pretty flimsy parts, I don't think it's by accident. The smart and fast guys are more than happy to tell you that 1350 ujoints, power robbing 9" Ford rearends and all of those cool looking heavy duty parts are the hot setup. Jim Caughlin SS 6019