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 Post subject: 9 inch pinion offset?
PostPosted: Tue Nov 25, 2008 10:14 am 
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Can anybody tell me what the pinion offset is on a 9 inch ford axle, I want to center the pinion and am trying to figure the differance in axle tube lengths, hope that makes sense :? :?
Thanks.


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PostPosted: Tue Nov 25, 2008 10:36 am 
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THE DIFFERENCE IN AXEL LENGTH SHOULD GIVE YOU THAT MEASUREMENT.
MICK


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PostPosted: Tue Nov 25, 2008 10:48 am 
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Location: Edmonton Alberta Canada
The offset on a Ford 9 is 2 1/2" If you are chopping the diff yourself you should really get a pinion center guage.

Corey


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PostPosted: Tue Nov 25, 2008 5:44 pm 
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The wording here is critical. To answer your question...We all have to be thinking the same. The pinion is 15/16" to the Right if you figure from the center portion of the housing (weld to weld or Right case bolts across to the Left case bolts). What I'm saying is if you find the cenerline of the center portion of the housing & go from there (which is the way it should be done). This is the only measurement that is the same on ALL 9" rears.
With that being said....I have a question. What type of vehicle are you working on? Dragster, chassis car, regular manufactured production car (of what make & model)?
I'm assuming that your starting with a housing that doesn't fit your chassis & your going to cut, weld, ect. from there & get axles made, correct?
I don't like the figuring done from the stock width 9" & subtracting (this is how you end up with guys talking numbers like the 2 1/2", which may where it is in Corey's car or someone elses, but doesn't make it correct as a starting point). Post up the answers & I'll be glad to help. Lorne


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PostPosted: Tue Nov 25, 2008 6:02 pm 
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Location: Edmonton Alberta Canada
Actually Lorne you are exactly right about the 15/16" offest. I got lazy and measured a old pair of axels I had sitting around and just blurted out the answer :smt018 . It didn't dawn on me until you made your post. I've done enough of them, you would think I should know that.


Cheers


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PostPosted: Wed Nov 26, 2008 8:36 am 
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Thanks so far guys :D What I have is a funny car/altered type chassis and I want to swap out the 59 olds axle that's in it and go for a 9 inch Ford type, so far I've got (I'm starting from scratch here) some big Ford ends and an old third member for mocking up, I've machined up a jig to align the ends and third member on a common shaft (like the Mark Williams one) and that's as far as I've got.

I need a solid mount axle which is 26 inches from housing end to housing end, so if the pinion offset is 15/16" and I want a centered pinion would the right hand side be (from pinion centreline) 12 and 1/16" and the left hand side be 13 and 15/16" ? :scratch:

Thanks.


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PostPosted: Wed Nov 26, 2008 11:55 am 
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Ok, Here is the way I would go about it since you want the pinion centered...Get the housing you want to use, either buy a pinion centering gauge, make one or my preferred method for centered pinions...Get a Third member that has at least pinion & yoke in it, put it in housing. With some scraps you can make a pointer set-up that rotates on the pinion bearings for accurate measuring that can be made in an hour that will be well worth it, I can explain it in more detail if you would like .
Total from wheel flange to wheel flange is what measurement we are interested in. Forget about the measurement from housing end to housing end at this point. What is important is axle flange to axle flange (total between your wheels) & then subtract from there. There are different thickness housing ends & axle set-out (distance from backing plate to axle flange) to add to the mix of things to foul you up.
Give that measurement & we will continue from there, no rushing here, we don't want to end up with a too short of axle or Two. By the way... No your axle lengths are not correct. ;) Lorne


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PostPosted: Thu Nov 27, 2008 11:16 am 
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The flange to flange measurement I want is 30", I have a dummy pinion shaft and pointer to determine pinion center. I guess I got the measurements the wrong way round? :oops:


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PostPosted: Thu Nov 27, 2008 10:15 pm 
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Ok, Let's go some more. Is the engine/trans. assembly centered in the frame for sure? Being an altered, you have a little "wiggle room" for slight thickness stack-up (axle set-out or drum/disc thickness), but let's try to get you real close. Do you have a plan for brakes yet? Stock Ford, GM - Drum, Disc, or any certain A/M company? This can effect the housing width you need to end up at the predetermined total you want.
What do you have for an axle plan? Number of splines? Cut & re-spine stockers, custom made A/M ones or maybe some left over, short ones from some other narrowed rearend?
Do you have the center section you are going to use, using a Spool? A stock one (even the wrong spline will do) that is completely assembled or at least a carrier in the pig will do for the mock-up. Do you have any 9" axles of the same spline or smaller? This isn't completely nessesary, but will make it less likely you will end up wrong & I suggest trying to borrow some parts or buy a cheap rear if you don't have them. Post up some answers & we can continue.
As to "Getting the measurements the wrong way round." I'm not sure if you ment...The Right & Left measurements switched or "Going about it wrong"...To give you the short answer, niether of your axles will be the the numbers your thinking & the Left axle is NEVER longer in a 9", unless the pinion is to the Left of center for some reason. I have your axle lengths figured (assuming your using stock Ford brakes & a standard posi/spool), but I want you to work through this so you understand how we got there. Talk to you later, Lorne


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PostPosted: Fri Nov 28, 2008 1:58 pm 
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The engine/trans are centered in the rails and I run a solid coupler, I'll probably go for Strange disc brakes and 35 spline axles/spool from Strange also with 4.11 gears, the housing ends are Strange big Ford. I don't have any axles etc.. at the moment just a used third member (empty) this won't be used in the final build. I can probably get some used stock 9 inch parts if they're any use.

Thanks!

(I did a search on the net for "Ford 9 inch pinion offset" and got measurments from 1/2" upto 2 3/4" , no wonder folks get confused)


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PostPosted: Fri Nov 28, 2008 4:43 pm 
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Joined: Sun Dec 30, 2007 10:29 pm
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Here's the kicker, the trucks (& some vans) from back in the '60's up until '84 had a 4" pinion offset. Years ago (before I did rears) my friend had a guy do a 9" for his Chevelle. He started with a truck rear, measured the same amount off of each side & had the axles cut & re-splined. The upper control arm brackets were something to see, one was way down on the shoulder & the other was almost up on the top & yes, the pinion was 4" to the Right (3" more than GM had it), the driveshaft was very near to rubbing the tunnel toward to back (I believe there was some hammering involved for clearance there).
Back to your project, I'm not aware of any oddities with the Strange spool (Mark Williams has a different spline location inside) but I would like to see you have it or at least check with them (maybe someone on here can tell us they swapped one in at a later date) to confirm that it is a direct replacement for a stock carrier in respect to the spline placement.
What I suggest you do is put complete center on a bench & install stock axles without a housing (make sure they are fully engaged). Now measure out from the pinion (in your case 15") with a square & make a mark on each axle. Now if you pull the axles out & measure from the line you made to the spline end & you have the total length for each axle. Of coarse there are other ways to do this, but this is the easiest, no figuring, way to do it. Post up the lengths you get! If
you don't want to get the spare junk, we can do it another way. From this point, since your using big Ford/Strange brakes, your axle set-out will be 2 1/2", so you would subtract this from each axle from the line you made. This will leave you 25" right? This is your HOUSING width. Put your dummy pig in your housing & measure 12 1/2" each way from the pinion, mark the axle tube. Now put your bearing end on the line & mark off the thickness of it...this is where you will cut the tubes, make sense? If not speak up now. I hope this all makes sense, I'm not a teacher or a writer. Talk to you later, Lorne


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PostPosted: Mon Dec 01, 2008 2:39 pm 
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Lorne, it makes perfect sense, thanks!
I'll get some old axles and other bits so as I can measure.


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