9" Rear Questions

Joe Grippo · 12-02-2013, 01:05 PM

Apologies if this is in the wrong forum...

First off, some info on my car….1970 Mustang bracket car, 3400lbs., small block 351 Windsor, automatic leaving off a footbrake, Caltracs & 29.5x9” slicks. It runs 10.50’s with average 60’ times in the low 1.40’s with nice wheelstands.

So I am upgrading my 9” rear to 35 or possibly 40 spline axles and I need to buy a new larger bore case.
First question, is a Mark Williams Aluminum Thru-Bolt 9” center section a good idea? The rear end is braced and straight and I will be using a light weight steel spool and Pro Gears.
Concerned about deflection and longevity, mostly. And how much weight is really saved?
Stick with a nodular iron case?

Secondly, regarding 35 vs. 40 spline axles, obviously the price difference is significant, would 35’s be sufficient or are 40’s overkill for my application? I must say I like the peace of mind overkill can provide sometimes!
Are there any details I am overlooking or is this a straight swap into my housing? Housing ends, bearings, seals etc.?

12-02-2013, 01:05 PM	#1
Joe Grippo Member Join Date: Apr 2002 Location: Elverson, Pa Posts: 158 Likes: 125 Liked 41 Times in 4 Posts	9" Rear Questions Apologies if this is in the wrong forum... First off, some info on my car….1970 Mustang bracket car, 3400lbs., small block 351 Windsor, automatic leaving off a footbrake, Caltracs & 29.5x9” slicks. It runs 10.50’s with average 60’ times in the low 1.40’s with nice wheelstands. So I am upgrading my 9” rear to 35 or possibly 40 spline axles and I need to buy a new larger bore case. First question, is a Mark Williams Aluminum Thru-Bolt 9” center section a good idea? The rear end is braced and straight and I will be using a light weight steel spool and Pro Gears. Concerned about deflection and longevity, mostly. And how much weight is really saved? Stick with a nodular iron case? Secondly, regarding 35 vs. 40 spline axles, obviously the price difference is significant, would 35’s be sufficient or are 40’s overkill for my application? I must say I like the peace of mind overkill can provide sometimes! Are there any details I am overlooking or is this a straight swap into my housing? Housing ends, bearings, seals etc.? __________________ Time Wasters....http://www.flickr.com/photos/joe_grippo/sets/ http://www.youtube.com/user/JoeGrippo?feature=mhum Last edited by Joe Grippo; 12-02-2013 at 02:54 PM. Reason: fat fingers