OK, this isn't something i know about so I'm asking. I have the opportunity to buy a 9" rear, 3.73, 31 spline, auburn posi. Axles too. I do know its a car rearend, but thats it. My question is whats the likelyhood that it will fit w/o modification? If it does have to be modified what would have to be done? thanks in advance Jonathan
9in rear If I remember right, the only 9in bolt in rear would be out of a57-59 Ford car or a 66-77 Bronco. The Mav's and Comet's with 8in rears are 57in from flange to flange. To use any other housing you will have to get it shortened to that dimension and move the spring perch pads. Custom axles will have to be made also. I shortened a truck housing and used the small bearing ends so I could retain the 8in axles. Worked very well for the past several years in our drag Mav. When more cubic inches were added(393) I did another 9in truck housing that had larger axle bearings. Bought Strange axle ends, and Moser 31spline axles with bearings, the cost was around 600.00 and I did the cutting and welding here on the housing. You can purchase the complete assy. from either one or have them cut one to your specs. The 8in is pretty tough unless your are running high HP and cubes. Gear selection is limited to 4.62 max and posi units are a bit hard to acquire and cost mucho denaro. The decision is not an easy one on which way to go, as is the cost factor. Good luck either way, the results are a lot better than spinning that one wheel on the launch pad. HE HE HE.
good deal actually I had looked at just buying a new posi pumpkin for my 8", but this looks to be a good deal, i.e. cheap! So depending on the cost of it and having the tubes cut and rewelded, the axles cut and resplined it might be a good way to get a 9" before I need it but at a good deal to prepare me if i step up the hp. i really don't know, it all depends on how much its all going to cost. 1974CometGT said he had his cut and rewelded for like 175, not sure if that included resplining the axles though. I do assume that included moving the spring perchs. thanks for the info, Jonathan
I have seen higher gear ratios for the 8", I can't remember where off hand but I remember seeing something like a 5.11 for an 8".
The gears and posi are getting hard to locate at a low price. At a website www.perogie.com. you can see the 9 ratios they offer along with center section etc. but cost is high.
rearend for you What is your intended purpose for the car? Answer that first. If just a little more for playing on the street, get the posi for the 8" and put in 3.55s at the same time. 9"er is nice if you want to run high HP at the races. Think about this, your 8" fits, your brakes are easy to get parts for. You don't have to play with brake lines and cables. You can use your current axles, bearings, and the 8" is lighter. Now what was it you needed a 9" for, besides bragging rights. actually it's funner bragging about how you can beat their butts and you didn't need a 9" setup.
just to much trouble I'm pretty much decided its not worth the effort and cost to get the 9. If in the future i break this 8, then it'll be time for a 9. Now I have to look for a posi center w/ 3.73-3.93ish gearing. Not gonna be using it til i get a trans, but its one step at a time.
ok so i went out and measured my 9" out from under a 79 granada flange to flange it is 1" total wider than the 8" under my mav........spiring perch location is the same it is a DIRECT BOLT IN i though this was so (there is an article on Charlie Pings web sight) he used a lincoln versails rear (disc brake) but i wanted to measure mine to be certain.
Rear ends from early 70's Cougars and Mustangs have the same perch width, but are wider. So you can get one of those, have the ends moved inboard to match the stock width, then use your 28 spline axles from your 8" in your new 9". 28 spline axles will stand up in an 11 second automatic car for a looong time.
