F150 9” question....

greasemonkey

Well-Known Member
Joined
Nov 16, 2010
Location
Statesville, NC
Good morning, ladies & gents. I’ve got a question for y’all that I know will be stupid, but I’ve done a lot of searching and haven’t found much info on the subject....

I’ve got a CJ7 with a full width 44 and an EB 9”. I bought it like this and the previous owner did not build it, so I have very little info on the donors for all of the parts... anyhow what I’d like is to put an F150 9” under there and swap my chunk into it. I’ve been reading that the pinion is off center - have any of y’all had any driveline vibes or issues with this setup?

I’d prefer to keep it full width to match the front end, otherwise cutting it down would leave me where I’m already at.

thanks for any info y’all got!
 
If you don't have vibes now, I don't see how you would by adding a housing with some offset. If you're running high lift the offset may contribute to some vibes.
How much lift and what type rear driveshaft?
 
It’s set up SOA with 2” springs and a CV driveshaft. Also, it’s got a D300 mated to a TF727 so the driveline isn’t terribly long.

the 9” that’s in it now has the pinion pretty well centered up.
 
It would be ok. Ford did this on some stuff to ensure enough angle on the two yokes to get the needles in the caps to turn over.

Turns out that some of the trucks they built had very little pinion angle. So offset combats this problem. Otherwise the needle bearings would stay static and wear quickly.

If it worked for Ford factory it'll be ok. As long as the offset creates two equal and opposite angles at the rear end and transfercase your good. (Two joint design). Also looking top down not just a side plane.

Now if you have a CV axle you should run as little angle between the drive shaft and rear yoke as possible. This design cancels vibes at the CV where two angles constantly offset one another. This design does not account for the rear placement to basicly side step center on every rotation. (Offset rear end) This would cause vibration. Again looking from the top down this plane would created an angle the CV could not cancel.
Throughout I used "CV" I really should edit it to read Double Cardigan. Since a lot of newer stuff runs a true CV design...my fault.
 
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It would be ok. Ford did this on some stuff to ensure enough angle on the two yokes to get the needles in the caps to turn over.

Turns out that some of the trucks they built had very little pinion angle. So offset combats this problem. Otherwise the needle bearings would stay static and wear quickly.

If it worked for Ford factory it'll be ok. As long as the offset creates two equal and opposite angles at the rear end and transfercase your good. (Two joint design). Also looking top down not just a side plane.

Now if you have a CV axle you should run as little angle between the drive shaft and rear yoke as possible. This design cancels vibes at the CV where two angles constantly offset one another. This design does not account for the rear placement to basicly side step center on every rotation. (Offset rear end) This would cause vibration. Again looking from the top down this plane would created an angle the CV could not cancel.
Throughout I used "CV" I really should edit it to read Double Cardigan. Since a lot of newer stuff runs a true CV design...my fault.

From my understanding- which isn’t saying much -the angle should be the same at both ends of the shaft. Since I’m running a CV shaft, then I should have the u-joint end at the diff at pretty much zero since there’s no angle to match because of the CV?

I don’t have the drive shaft length handy, but I can’t imagine it being more than 40”, so the lateral offset of the pinion would be around 2 degrees. With that only being felt at one end, I wouldn’t get any vibes or chew up the u-joint?


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Just a guess here, but....

With a cv driveshaft used on a leef spring setup, the rear pinion should be pointed slightly up in comparison to a straight line to the yoke of the t.c. to account for some axle wrap in the springs that will point the axle yoke down under acceleration. Around 2-5 degrees IIRC
 
CV point axle end directly at the transfercase for zero angle between drive pole and yoke.
Off set side to side skews this by introducing and angle.....but a 2 degrees I don't think you'll be hurting much.
Give Oliver's a call in Winston. He could confirm or deny anything I'm spewing.

After my initial post I read a whole lot of contradictory innerweb key board engineering. This is the principles I have always built with. 3 degrees is the max I would live with. Per another fella I lean on quite regularly whose automotive education and experience far exceeds mine. He's a Master Ford cert guy and my guru when I get stumped.
 
Just a guess here, but....

With a cv driveshaft used on a leef spring setup, the rear pinion should be pointed slightly up in comparison to a straight line to the yoke of the t.c. to account for some axle wrap in the springs that will point the axle yoke down under acceleration. Around 2-5 degrees IIRC

Actually, you have that backwards.
Under acceleration on a leaf sprung rig, the pinion will rotate up a few degrees. So in that case you set the pinion about 2-3* low so under throttle it will line up.
 
I mean I know if I just shorten one side a couple inches, the overall width would be 63” and still very close to the same as the front - but I do not have the provisions to shorten an axle. Also I liked the idea of both shafts being the same length.

I’ll get under it and measure the driveshaft today. I’ve read that the pinion on the axle in question is 2 & 1/8” off center. I’ll try to come up with that angle lol I suck at math.

Internet searches are sometimes good but in this instance I’ve found very little. I had figured it may have been a common swap without modifying the F150 9”. Y’all have given me 1,000% more info than anything I’ve found on the web!
 
Not to be a hack...but for the sake of conversation.
Run a 2" wheekl spacer on the appropriate axle end and weld on the perches accordingly so the offset is basically taken out of the equation.

I mean, I've done worse.

If it were me, Id run the pickup axle, offset and all, and rock out.
 
Not to be a hack...but for the sake of conversation.
Run a 2" wheekl spacer on the appropriate axle end and weld on the perches accordingly so the offset is basically taken out of the equation.

I mean, I've done worse.

If it were me, Id run the pickup axle, offset and all, and rock out.


I’m just about to pull the trigger on it, to tell you the truth. As far as the spacer idea - I’m trying to get away from them. Right now I’ve got 2.5” spacers on the EB 9” that’s under there at the moment. I wish I had the tools to shorten that side on the truck axle because it would still be plenty wide enough at 63”. I’m pretty sure the offset wouldn’t be too much of a problem on the trail, but I just want my kids to be able to drive it around town without any driveline problems.


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The pinion offset on the 9" ain't going to hurt anything unless your driveshaft is 12" long. Hell I've seen guys run LC offset diffs in Tacoma's with no vibes till 65+. Quit over thinking it and just build the thing.
 
The pinion offset on the 9" ain't going to hurt anything unless your driveshaft is 12" long. Hell I've seen guys run LC offset diffs in Tacoma's with no vibes till 65+. Quit over thinking it and just build the thing.


I’ve been continuing with researching this and from what I can tell, the 8.8 is similar in offset and I know that it’s a common swap for the YJ & TJ and has been for years. I can’t find where there’s been any issue with it.

so that, along with all y’all’s expertise has helped a ton. I’ll get that truck axle in soon!

thank all y’all so much!
 
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