9" rear axle sizes
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5th Wheeling
Joined: Apr 2021
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9" rear axle sizes
Im starting to look for parts to rebuild/upgrade to a true trac in the rear end in my 78 f150. Looking around, I've seen carrier bearing sizes differ. Is there a way to tell OD of carrier bearings etc without pulling the 3rd member and actually measuring. I was going to order the parts before winter while I'm still driving it but if there is no definite way, I may just have to wait till its parked for the winter to take my measurements.
Lead Driver
Joined: Jul 2017
Posts: 9,600
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From: San Jose, CA
Not sure how to tell from the outside. Maybe the casting number is indicative, but not sure what the numbers would be.
Three bearing sizes, but I think the biggest ones were aftermarket only. Or maybe found on something exotic, such as a Boss 429 Mustang!
So that leaves two bearing sizes and two spline counts. I wonder if they were intimately related?
In the Broncos before’78 only 28-spline axles were available. But I think someone has found that some Broncos had the small version of the carrier bearings, while some had the bigger (middle overall) size. Thanks Ford!
I think I’ll inquire of a friend/customer/forum member on another forum, as to what he knows.
He usually knows far too much about such things. 😉😁
Three bearing sizes, but I think the biggest ones were aftermarket only. Or maybe found on something exotic, such as a Boss 429 Mustang!
So that leaves two bearing sizes and two spline counts. I wonder if they were intimately related?
In the Broncos before’78 only 28-spline axles were available. But I think someone has found that some Broncos had the small version of the carrier bearings, while some had the bigger (middle overall) size. Thanks Ford!
I think I’ll inquire of a friend/customer/forum member on another forum, as to what he knows.
He usually knows far too much about such things. 😉😁
Cross-Country
Joined: Jun 2016
Posts: 81
Likes: 31
stock 9 inch center section for your 1978 F150 will have the 2.891 O.D. carrier bearing LM 102949 cone and LM 102910 race and the axles should be 31 spline using Timken set 20 tapered bearing ,, starting with the 1970 model year Ford did not make any center sections with the 3.062 carrier bearing they went to the what they called the slim line bearing with 2.891 O.D. ,,, the aftermarket cases usually all come with either the 3.062 carrier bearing or the larger 3.25 carrier bearing
Lead Driver
Joined: Jul 2017
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From: San Jose, CA
Thanks for the info John. So the part about "starting in '70" means that, before 1970, Ford might have put either the 2.891 OR the 3.062 bearings in various vehicles? Any way to tell what's inside based on an outside number or other identifier? Or do you still have to pull it apart to find out what you have?
Of course, the other thing you need to worry about amork, is whether or not the 9" assembly in your truck is all original or not. After 46 years, it might have been swapped out once or twice.
Of course, the other thing you need to worry about amork, is whether or not the 9" assembly in your truck is all original or not. After 46 years, it might have been swapped out once or twice.
Cross-Country
Joined: Jun 2016
Posts: 81
Likes: 31
no way to tell from the outside you have to pull it , 3.062 carrier bearing was more predominant in the early 60's era cars/trucks and then it was hit and miss between the 2 sizes ,, i doubt your diff has ever been changed out in that time frame.
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5th Wheeling
Joined: Apr 2021
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Thanks for the info! Looks like I’ll be pulling it and ordering parts after. No big deal, I was just hoping there was an easy button for finding it. The new engine isn’t making a tired factory limited slip very happy.
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Lead Driver
Joined: Jul 2017
Posts: 9,600
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From: San Jose, CA
The "easy" button is buying all the parts you might need, then returning (or hoarding!) the ones you don't use.
We have to do that all the time with the steering columns on Early Broncos. In '73, '74 and '75, and especially '74 and '75, if you don't already have the column taken apart, you might as well just buy all the parts, early and late, that are available.
Because you literally never know what Ford put in it during those years.
Paul
We have to do that all the time with the steering columns on Early Broncos. In '73, '74 and '75, and especially '74 and '75, if you don't already have the column taken apart, you might as well just buy all the parts, early and late, that are available.
Because you literally never know what Ford put in it during those years.
Paul
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