Rear End help
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Rear End help
Ok, so I read all over the place people putting in the 8.8 rear end on the 53-56 F100's. Also you read alot about the 9" being put in the truck. What I am wanting to do is put a normal 8" in the truck. Does anyone know what kind of car/truck came with a 8" that would be a direct bolt in?
Only reason I want a 8" is because they are smaller then the 9" and I dont think you need a 9" in the back of a truck. It will just add weight. I have a 8" with a mini spool in my mustang that cost $150 pluss $30 for the spool and I run 12.8 at 107mph and have never had a problem with it.
I dont want to go with a 8.8 because I belive they are weaker then a normal 8". Only thing you are getting with a 8.8 is the disc brakes, in witch I dont think you would need them on the back of your truck.
Also, what rear end came stock in these old trucks? I have a 1955 F100 but I dont have it at my house, its in storage. I plan on starting the build here in the next month or so and I am just trying to educate myself before I start ripping into it.
I would appreciate any help you guys can give me. Thanks for your time!
Only reason I want a 8" is because they are smaller then the 9" and I dont think you need a 9" in the back of a truck. It will just add weight. I have a 8" with a mini spool in my mustang that cost $150 pluss $30 for the spool and I run 12.8 at 107mph and have never had a problem with it.
I dont want to go with a 8.8 because I belive they are weaker then a normal 8". Only thing you are getting with a 8.8 is the disc brakes, in witch I dont think you would need them on the back of your truck.
Also, what rear end came stock in these old trucks? I have a 1955 F100 but I dont have it at my house, its in storage. I plan on starting the build here in the next month or so and I am just trying to educate myself before I start ripping into it.
I would appreciate any help you guys can give me. Thanks for your time!
Posting Guru
Joined: Sep 2006
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From: Bristol TN.
I would say your truck has a Dana 44 rear end in it which I believe is about a 8.5 inch ring and pinion. If your doing a lot of drag racing with the truck it might be a good idea to upgrade but if the truck is just gonna be a daily driver type vehicle and only doing a burnout every once and a while it would be fine. The 57-72 ford truck 9" axles bolt into our trucks which makes things a little easier. I got a axle out of a 71 model f100 and it bolted right in, I just have to figure out my shock mounts cause there a little different.
Hotshot
Joined: Oct 2009
Posts: 16,190
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From: Burbank, WA
There is no 8" rear that would be a direct bolt in. Ford trucks had the axle under the springs and the 8" rear was never used in them. Ford cars that used the 8" rear (compact and intermediates only) all had the axle located over the springs. So even if you could find one that was the correct width (most, if not all will be too narrow), at the very least you'd have to relocate the spring mount pads.
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ah, well you all have good points. only reason I didnt want to go with a 9" is just because they are so big. but, in all reality like you guys said, if im going to go through the trouble of taking one out and putting it in, might as well do a 9" huh? I just dont want to do a 8.8 because I just dont like them.
Now, when you guys lower them, is there a rear flip kit for them? thus making a 8" maybe a good idea if you can find one that fits huh? but once again probly more trouble then its worth. anyway, I thank you all for your time. and I will consider everything you all say. Thanks a bunch guys!
Now, when you guys lower them, is there a rear flip kit for them? thus making a 8" maybe a good idea if you can find one that fits huh? but once again probly more trouble then its worth. anyway, I thank you all for your time. and I will consider everything you all say. Thanks a bunch guys!
I'll have the Roast Duck
Joined: Jul 2002
Posts: 9,622
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From: Northshore, MN
early 9" rears and 8" rears both used the same axle shafts (28 splines) so your strength gain is in the ring and pinion only. The 8.8 in Explorers are stronger than Mustang 8.8's in that the explorer axles are 31 splines, and bigger diameter. There are parasitic HP loss by using the 9" over the Dana 44, though probably not an issue if going with a modern V8.
In a nutshell, the best bang for the buck is a '57-72 F100 9". The Mustang and Fairlane 8" pads are located differently widthwise, than a truck's 9", so you'd be cutting and rewelding no matter what.
EDIT: I forgot to mention the bolt pattern other than the truck's 9" would be non-stock at 5x4.5.
In a nutshell, the best bang for the buck is a '57-72 F100 9". The Mustang and Fairlane 8" pads are located differently widthwise, than a truck's 9", so you'd be cutting and rewelding no matter what.
EDIT: I forgot to mention the bolt pattern other than the truck's 9" would be non-stock at 5x4.5.
Laughing Gas
Joined: Jun 2011
Posts: 1,041
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From: Sterling CO
Here's a couple of really good old articles, well written and organized years ago... back before my time even :P
1953 - 1956 F100 Rear End Selection and Rear Suspension Lowering .: Articles
1948 through 1960 Ford F-1 and F-100 Rear Axle (differential) Swaps .: Articles
I have the flathead straight 6, and opted for the 9" because of the simplicity - straight bolt in no engineering. (I wanted to trade my Dan/Spicer 41 w/ 4.27 ratio down to a 3.0-3.5 ratio, get it driveable above 45mph).
My choice was ease, why brain yourself to death trying to engineer a solution when there are a dozen ready built with no major surgery.
I also wanted to keep 5 on 5.5 instead of doing the 5 on 4.5 - innie nub rims aren't cheap.
1953 - 1956 F100 Rear End Selection and Rear Suspension Lowering .: Articles
1948 through 1960 Ford F-1 and F-100 Rear Axle (differential) Swaps .: Articles
I have the flathead straight 6, and opted for the 9" because of the simplicity - straight bolt in no engineering. (I wanted to trade my Dan/Spicer 41 w/ 4.27 ratio down to a 3.0-3.5 ratio, get it driveable above 45mph).
My choice was ease, why brain yourself to death trying to engineer a solution when there are a dozen ready built with no major surgery.
I also wanted to keep 5 on 5.5 instead of doing the 5 on 4.5 - innie nub rims aren't cheap.
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Logistics Pro
Joined: May 2010
Posts: 3,793
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From: Austin
Hey Newton,
I went with an Explorer 8.8 - giving us rear disc brakes &
the 5x4.5 to match the Mustang II IFS 5x4.5 up front.
I'm not sure it really matters too much it's all in what you want -
getting the right gear ratios out back is the most important thing otherwise you are topping out around 50mph.
Good luck over there.
Ben in Austin
I went with an Explorer 8.8 - giving us rear disc brakes &
the 5x4.5 to match the Mustang II IFS 5x4.5 up front.
I'm not sure it really matters too much it's all in what you want -
getting the right gear ratios out back is the most important thing otherwise you are topping out around 50mph.
Good luck over there.
Ben in Austin
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Elder User
Joined: Mar 2011
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From: Vancouver, WA
I went with a '68 F100 9" rear. Direct bolt in, using stock '56 e-brake cables and all. To accomodate the shock and housing mounting situation I used '58 F100 mounting and shock plates along with '56 U-bolts and tie straps (pieces that sit atop the spring). This allowed me to used stock '56 rear shocks in stock location. I think just the top of the shock is different on your '55 (how it's mounted) but don't quote me on that.
Unless you're gonna lower your rig drastically by way of a flip kit, I would suggest as these guys did and go witht he 9" truck rear. '57-'67 or '68-'72. I break the years up as the '68-'72 rears offer wider rear brake shoes than the '57-'67 rears for improved braking. Chances for gettin a more sain gear ratio with the '68-'72 are better too, chances of hittin a short gear in the early 9" rears are still pretty good.
Unless you're gonna lower your rig drastically by way of a flip kit, I would suggest as these guys did and go witht he 9" truck rear. '57-'67 or '68-'72. I break the years up as the '68-'72 rears offer wider rear brake shoes than the '57-'67 rears for improved braking. Chances for gettin a more sain gear ratio with the '68-'72 are better too, chances of hittin a short gear in the early 9" rears are still pretty good.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
1957/67 F100's have 11" x 1 3/4" rear brakes (same as 1948/52 F1 and 1953/56 F100). 1968/72 F100's have 11" x 2 1/4" rear brakes.
Be aware that there are TWO different 9" rear axles for 1968/72 F100's, one is rated at 3,300 lbs., t'other at 3,600 lbs.
The 3,300 lb. capacity rear axle has 28 splines
The 3,600 lb. capacity has a 9 3/8" ring gear, 31 spline axleshafts and Traction-Lok. Only five parts are the same as a 9.
One: pinion bearing, pinion bearing cup, housing gasket, pinion seal and pilot bearing retainer. EVERYTHING else is different!
To clarify: The only thing that is the same is the spline count itself. The axleshafts themselves are not the same.
8" & 9" Passenger Car (includes Ranchero) rear axles use right/left specific axleshafts.
The 9" axleshafts used in F100's are the same right/left, but are specific to 1957/67, 1968/72. As noted above, 1968/72's could be either 28 or 31 spline.
Be aware that there are TWO different 9" rear axles for 1968/72 F100's, one is rated at 3,300 lbs., t'other at 3,600 lbs.
The 3,300 lb. capacity rear axle has 28 splines
The 3,600 lb. capacity has a 9 3/8" ring gear, 31 spline axleshafts and Traction-Lok. Only five parts are the same as a 9.
One: pinion bearing, pinion bearing cup, housing gasket, pinion seal and pilot bearing retainer. EVERYTHING else is different!
Originally Posted by havi
early 9" rears and 8" rears used the same axleshafts (28 spline).
8" & 9" Passenger Car (includes Ranchero) rear axles use right/left specific axleshafts.
The 9" axleshafts used in F100's are the same right/left, but are specific to 1957/67, 1968/72. As noted above, 1968/72's could be either 28 or 31 spline.
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