Ford 9" Differentials
 

I know this issue has been beat to death but since I can't find an answer anywhere I have to ask. I know that the 57 through 72 Ford pickup differentials are basically a bolt in swap for the 48 to 56 Ford trucks. My question is what is different about the 73 to 79 Ford pickup differentials that won't allow them to be a bolt in swap, or will they? This last weekend I saw several 74-78 Ford F-100 trucks at the wrecking yard that still had the differentials underneath them and thought about getting one for my 52 F-1 gasser project.

The difference: The axle housing is longer than the 1957/72's used, so while it may work, the rear wheels will stick out past the fenders.

The rear springs are also 1/4" wider after 1972 = 2 1/2" vs 2 1/4"

The shackles, spring mounting pads, etc are also different to accomodate the wider springs.

My cyberspace guess (because I’m not sure) would be; differential housing width (too wide) and spring pad location. Are you sure the ones in the graveyard are 9 inch? Easy way to tell is if the bottom two bolts have to be taken off with a wrench; as they are not accessible with a socket? Those wacky 8.8 sometimes pretend to be 9 inchers. Nothing wrong with the 8 inch Ford, had one in a 37 coupe with a big block, worked fine.
:)
“But being wrong keeps me humble”

Number dummy is correct and even gave you the measurement! Nice!... Maybe number dummy or someone can help me here. Ford made a Big bearing rearend, which I have in my 56. Anyone know what years those rearends were. I need to replace the axle seal on one side and want to make sure I have the right seal to go in.

can you measure the vertical distance between the backing plate bolts (center to center)? And the wheel bolt pattern size?

For you Havi, I'll measure it. LOL..... Looks like I got 2.375 inches bolt to bolt on backing plate bolts and the wheel is 5 on 5.5". If this helps, I know the bolts that go into the backing plates are 1/2" bolts and not the normal 3/8" .
Ed

My guess is that you have the early style big bearing rear end. 2.375" center to center vertically, and 3.5" center to center horizontally (backing plate bolts). Galaxies and Early broncos had these. The new style is 2" vert by 3.562" horiz. I don't know what mods were done to fit such a rear end under your truck but the Bronco was a narrow rear end as my '66 rear was awfully close to rubbing the bedsides on my '48. Should be a sealed ball bearing type.

I was told (friend) that my rearend was more likely to have come from a 60 Ford F100 truck? When I did the disc brake conversion on the rear, I ordered the early style big bearing brackets which fit. This is the interesting part. The brackets and spacers were 1/8" off, causing the calipers not to fit correctly? I was told by the manufacturer that I had a Jeep Scout axles in the 9 inch which are 1/8" shorter from the backing plate to the lug bolts flange than regular 9 inch axles???? (I was told this is a popular change for people who needed to tuck their wheels in by 1/8" in addition to offset of the wheels. I had to put 1/8 spacers in on the backing plates for the brackets to work. So, now that I'm trying to replace a leaking seal, I'm not sure what seal it is? LOL... I guess I'll have to pull it and match it up at the auto parts.

# RW207CCRA bearing part number. I guess it is possible as the Jeep/Scout had the same 5x5.5" pattern. However, they never had a 9", so the axles would have had to have been from a Dana. Which might be a different bearing altogether, thus maybe causing some leakage?

I thank everyone for answering my question it is appreciated! My friend told me he has a 9" out of a late 50's Ford truck that I can have just come and get it. You can bet I'm all over that! I just wonder why Ford made that change in 73? Maybe they finally ran out of those particular axle housings and suddenly had to make more so they made them wider to better fit the trucks? I suppose only the designers at Ford would know the answer to that one!

It never leaked before, so I'm sure the seal is defective. It's actually not that bad, but if I drive on the highway for a about 25 miles or so, I'll notice a slight film of oil on the inner rim, whereas the other side is dry. I could let it go, but I'm anal about having oil on the rim and having to crawl underneath and wipe the oil off. I've changed the rearend gears twice now from 3.5 to 2.75 and back to 3.5 again without changing the seals. I'm surprised they aren't leaking more than they are. I'll pull the seal and take it with me to match one. Thanks for the help. Sorry to hijack the thread....
Ed

It may have something to do with traction and handling. I believe during that time, the auto makers discovered that wide track handled better than narrow. Although the difference is not much and may not make a difference, that may be one reason for the slightly wider rear end.

9" rear axle introduced in 1957 cars & F100's.

F100: The axleshafts are the same 1957/67. 1968/72 F100's have wider rear brakes (2 1/4" vs 1 3/4"), so the axle shafts are 1/4" longer.

1973: The F100's (and F250/350's) are all new, the 9" rear axle changed along with them.

Poseur 8.8 introduced 1983.

Large axle bearing 9's = 1957/87 F100's, 1961/72 Police Cruisers & Station Wagons, some 1969/72 Galaxie/LTD's, 1961/71 T-Birds, 1966/77 Bronco's.

Axle (BALL) bearing was originally: C1SZ1225A that was later replaced by C9AZ1225A: 1 17/32" I.D. / 3.5/32" O.D. / Marked with Industry bearing number: 88128; FPP, F208AKK; USA.

Rear axle seal for this rear end: Original # of B7A1177A replaced by C9AZ1177A, this seal was later replaced by EOTZ1177C.

Despite having a larger wheel bearing, this is the same axle seal the other 9's used = 1 1/2" I.D / 2 1/2" O.D.

NOTE: In 1966, Ford introduced another 9" but the ring gear is actually 9 3/8" This rear end came standard in Birds & Galaxie/LTD's with 428's initially, later was used with 429/460's thru 1972.

This rear end was ALSO standard equipment on 1968/72 F100 Camper Specials, optional on other 360/390 F100's, and has 31 splined axle shafts.

Thank you Number Dummy, you're a wealth of information for all of us. Plus, you give me flashbacks of my days as a Ford parts runner for Saunder's Ford. LOL...

Bill, I would like to send you a PM about radiators, but you probably get a zillion of them everyday, let me know if it's ok. Heck, I think I have yer email, don't I?