9" Third Member Splines
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From: NE Ga
9" Third Member Splines
Gotta '73 f100 w/ 9" 3.00, going to yard tomorrow to get another 9" chunk out of a van that is 2.75. Did ford make a 9" chunk with different axle splines? I would think they should all be the same correct? Just pop out the axle shafts and then just swap out chunks? Anything I should be measuring or taking into consideration?
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From: Williamson, NY
My 77 9" with a 2.75 ratio had 28 spline axles, but I have heard that some may be 31 spline. Why do you want to go to 2.75? I have been considering going to 3.00 or 3.40 ratio for better get up and go off the line.
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From: NE Ga
B/c now i got more than enough power w/ my FE390 and want highway miles and speed. I won't notice enough differnence in the low end for it to bother me. The way I built my 390 can handle it no prob. My dads van has 2.75's in it and it does great on the interstate. I'll always have the 3.00 to put back in though. Easy swap.
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From: Williamson, NY
I bought my 77 F150 in the spring and I got into a unplanned frame off restoration on it, so I really do not know how the trucks going to behave with the 2.75 ratio. I plan on giving it a try before I decide to change any thing. I rebuilt the 302 that cam in it and I bored it 0.030" over, installed an RV cam, Weiand Aluminum dual plane Intake w/ a Holley 650 vac secondary 4bbl carb. For now I think I'm going to stick with the original exhaust manifolds, but add dual exhaust. I also added a set of reconditioned E7TE heads, so I am anxious to see how this truck behaves. The only down side is that I never drove the truck before to know what kind of difference I made with all these upgrades.
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From: NE Ga
after doing some more research, I now find that there is no way of knowing until i'm holding the two center sections in my hand...well looking at them on the ground. Good news is that you can tell a 28 or 31 spline by looking at the end of the axle shafts. All you gotta do is pull the hub cap! Easy enough. By the way, 28 spline= oval hole on the end of the axle shaft 31 spline= two large holes and one counter sunk center hole
Post Fiend
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From: Joppa, Maryland
sorry, but that info on the holes is wrong. I have the two holes and one counter sunk hole and have 28 splines.
"A method to identify 28 spline axle shafts can be by looking at the center brake hub area, a rectangular slot in the center will indicate 28 spline axles.The 31 spline axle shafts will have a different appearance, with one small center chamfer and two outer holes in the center hub, however, 28 spline shafts can also appear like this to, so it does not always indicate 31 spline shafts"
a lot of information can be found on this website including what's above: http://www.kevinstang.com/Ninecase.htm
good luck!
"A method to identify 28 spline axle shafts can be by looking at the center brake hub area, a rectangular slot in the center will indicate 28 spline axles.The 31 spline axle shafts will have a different appearance, with one small center chamfer and two outer holes in the center hub, however, 28 spline shafts can also appear like this to, so it does not always indicate 31 spline shafts"
a lot of information can be found on this website including what's above: http://www.kevinstang.com/Ninecase.htm
good luck!
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From: Williamson, NY
Here's a picture of the end of my 28 spline axle I just installed that shows that the "captain" was right. Nice link captain, a lot of good information!
Jim
Jim
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Post Fiend
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From: Joppa, Maryland
yep, thats exactly how mine looks and i also have the 28spline, a lot of the things are interchangeable, so if you can get the axles also that might be helpful. But if you're going that far you might as well see if you can get the whole thing!
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From: NE Ga
ya i now see that info on the splines is only good for mustangs...at least thats the next sentence after that. Anyways had another great day at the yard!! Got my 2.75's and cleaned 'em up to shiny new. Got the whole chunk for $62 including 30 day warranty which was a little more than i wanted to pay but oh well. I figure i'll more than make it up in fuel cost's.
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From: NE Ga
Wouldn't ya know it
well I pulled an axle out of my truck yesterday and found I have 31 splines which won't work with the 28 chunk i aquired. I now have a new question. I'm wanting to put the 2.75 ring and pinion onto my 31 chunk. I know very well how to set backlash but my question has to do with marking the ring where it meets the pinion so that it goes back in the same tooth. Why is this necessary? I could understand if you had the same amount of teeth on the pinion as the ring so that it would run on the same teeth all the time but here we have alot more ring teeth than pinion so it would have to go around a good 10-20 times i would think before it would ever end up on the same tooth that you marked it at...right? The reason I ask is b/c i dissasembled the 2.75 gears I had and didn't mark them. I'm going to mark my 3.00 set when I take them down but am I screwed for having a good setup b/c of this? Would it even matter even with the proper shims and backlash? Thanks
Butt-Head
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From: Reed Point, MT
Originally Posted by 73F100*8Mile
I know very well how to set backlash but my question has to do with marking the ring where it meets the pinion so that it goes back in the same tooth. Why is this necessary? I could understand if you had the same amount of teeth on the pinion as the ring so that it would run on the same teeth all the time but here we have alot more ring teeth than pinion so it would have to go around a good 10-20 times i would think before it would ever end up on the same tooth that you marked it at...right? The reason I ask is b/c i dissasembled the 2.75 gears I had and didn't mark them. I'm going to mark my 3.00 set when I take them down but am I screwed for having a good setup b/c of this? Would it even matter even with the proper shims and backlash? Thanks
Hunting vs. non hunting gears:
Your 3.0:1 is an example of a non-hunting ratio. Meaning that each tooth always meshes with the SAME teeth on the other gear every revolution. All integer gear ratios are non-hunters, i.e., 30 teeth on the ring gear and 10 on the pinion. Hunting gears are the goal of mixing non-multiple tooth numbers. Each revolution a given tooth meshes with a DIFFERENT set of teeth on the other gear. This generally improves break in properties and tolerance of imperfections and damage sometimes resulting in a less damaging failure mode due to decreased harmonic vibration. Contrary to some belief mixing non-multiple tooth count does not always result in a non hunting gear set, however your 2.75 is a "hunting" gearset.
As far as marking them goes.....
Hunting gear sets do not need to be marked as no matter which teeth are set in mesh, they will always mesh with different teeth as the gearset works. On the other hand, a non-hunting set will HAVE to be timed properly if they have been previously run in a vehicle because of the "set" the gears have taken and the wear pattern on the teeth....very similar to a used roller bearing in that you don't mix and match used inner and outer races or cups and cones.
Cody
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From: NE Ga
ok thats good news to me. Now, what are the chances that i can use the same shim thats in the 3.00 set when i install the 2.75 in the 3.00 case? My boss said he had to buy a $35 shim kit one time. I don't really want to do that.
Butt-Head
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From: Reed Point, MT
Well, I don't want to give out bad advise or WRONG advice, but I have set up countless rear differentials for customers and tons of 9" ones too for myself over the years. I would TRY to use the original pinion shim first and see where that gets you. Yes, it's a pain and time consuming taking out the 5 bolts that hold the pinion support on, adding/subtracting thickness, and setting the backlash again, but get yourself a good baseline to start from because you're going to need a shim anyway you look at it....might as well start with what you have. At least you don't have to press the inner bearing off of the pinion a million times with a 9"!!
As far as a pattern goes, getting a "perfect" pattern is not going to be attainable, especially since you're putting in a used gearset. All you're looking for is a scrub in the center of the gear face...heel or toe biased contact is really not that critical (as long as it's not right on the toe or heel). I like to give the 9" a little bit more (about .002") backlash than specs due to the extreme pinion drop (rides very low on the ring gear) to help get a little more oil in there and allow for expansion since a lot of heat is generated by the excessive wiping between the two gears.
As far as a pattern goes, getting a "perfect" pattern is not going to be attainable, especially since you're putting in a used gearset. All you're looking for is a scrub in the center of the gear face...heel or toe biased contact is really not that critical (as long as it's not right on the toe or heel). I like to give the 9" a little bit more (about .002") backlash than specs due to the extreme pinion drop (rides very low on the ring gear) to help get a little more oil in there and allow for expansion since a lot of heat is generated by the excessive wiping between the two gears.
