9 inch ford

D

denny

Greasemonkey
Feb 4, 2017
181
63
28
#1
looking for some opinions here on my 9 inch swap. got a kit with 35 spline axles that came with the housing kit from e-bay. this is a Quick Performance kit. i have never messed with the 9 incher before and always had gm 12 bolts and 10 bolts. this will go into my 81 malibu. i kinda get my projects lined up in the winter here (midwest) so i can start them in the spring and have everything ready. also have a Right Stuff rear disc kit ready. what i found out is when you have the 35 spline axles that puts you in another category for posi's and cases. seems like i can locate a million 31 and 28 posi's but 35 spline are in a different price range along with the 2.250 cases. i use my malibu as a street car only with street type rubber. it is equipped with a 375hp blue print crate engine with turbo 350 trans and current 3.70 open stock rear. i really don't think i need 35 spline axles and i think 31 would do just fine for my type of crusing. one of my options is to sell the 35 spline and buy the 31 spline axles and smaller carrier bearing case which seem to be everywhere around here. i really don't think this crate engine is going to bust up a 31 spline 9 inch with street tires. my career mechanic friends say go with the 35 spline and suck up the extra cost and quit whining about the extra cost (lol). spool is totally out of the question. i'll not get the hell scared out of me again with one. ok so all opinions are welcome. btw those 35 axles look like tree stumps. thanks.
 
fleming442

fleming442

Geezer
Dec 26, 2013
5,095
5,433
113
#2
I was told that 28 spline are good to mid-10s. I'm putting about 650ft/lb through 28's on drag radials in a stick car- probably 20k miles over the past 10 years.

So, yeah, sell the 35s; you don't need them.
 
565bbchevy

565bbchevy

Geezer
Aug 8, 2011
5,916
4,922
113
Michigan
#3
I personally would go with 31 splines since it opens up plenty more options for carriers and is overkill for your power level anyways but always plan for the future when building your rear end (adding more power).
35 splines would obviously be way stronger but the added weight will just cost you power.
 
Northernregal

Northernregal

G-Body Guru
Oct 24, 2017
583
1,647
93
Red Deer AB
#4
A local guy here was running 35 splines in his sub 9 second turbo 3rd gen Fbody. He was upgrading this year to 40 splines as he was going from 1400hp to +1600. He could carry the front end 160ft with the 35 splines.

Food for thought.
 
D

denny

Greasemonkey
Feb 4, 2017
181
63
28
#5
I was told that 28 spline are good to mid-10s. I'm putting about 650ft/lb through 28's on drag radials in a stick car- probably 20k miles over the past 10 years.

So, yeah, sell the 35s; you don't need them.
thanks for the reply. thats the way i'm leaning right now. got such a good buy on the housing kit and thats what came with it. ran 33 spline on my 70 chevelle 12 bolt about 15 years ago and ran low 10's. never a problem. i'll have to see what never used 35's complete go for. maybe will cover some of the cost of 31's.
 
D

denny

Greasemonkey
Feb 4, 2017
181
63
28
#6
I personally would go with 31 splines since it opens up plenty more options for carriers and is overkill for your power level anyways but always plan for the future when building your rear end (adding more power).
35 splines would obviously be way stronger but the added weight will just cost you power.
thanks for the reply. just wanted to get some opinions. leaning the 31 spline way.
 
D

denny

Greasemonkey
Feb 4, 2017
181
63
28
#7
A local guy here was running 35 splines in his sub 9 second turbo 3rd gen Fbody. He was upgrading this year to 40 splines as he was going from 1400hp to +1600. He could carry the front end 160ft with the 35 splines.

Food for thought.
good running f-body. sounds like he might need the 40's.
 
B

bracketchev1221

Master Mechanic
Jan 18, 2018
344
297
43
#8
31’s are fine. I ran 8.80’s with a 33 spline 12 bolt with 15 year old axles.
 
MC96

MC96

Master Mechanic
Dec 7, 2015
309
257
43
#9
You will be fine with 31
 
lilbowtie

lilbowtie

Royal Smart Person
Jan 7, 2006
2,440
2,192
113
Canton Mi
#10
Another thing to consider in your decision the 35 spline axles are more than likely drilled for 5/8 studs - probably need new wheels to accept them.
 

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