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Discussion Starter #1
so i have a 78 bronco with a Strange pro 9 inch with 31 spline axles and a eaton Detroit with only 3:50 gears and then 37 in tires. I put and built that strange third member in there because i broke the main cap on the stock one so i wanted to never worry about it... but now i have a fully built edlebrock pro flow 4 fuel injected 460 and zf5. the truck at the dyno made 450 hp and 550 ft... but that was before i tuned it and before upgradeing the spark plug wires and making the rocker lash perfect... now it feels like it has another 50 hp... is this too much power for that axle? ill be putting a dana 60 in the front so i dont think ill be worried about that so much but what about the 9 in? will the strange be strong enough or will i be breaking ring gears or maybe even the 31 spline axles? i have a 10.25 out of a f350 i can throw right under it... but i wont if i dont have to because ill have to regear it and get a new locker... but thankfully it looks like my 88 f350 axle has the exact same perches and shock mounts... i dont mud the thing. mostly i do desert runs or slow rock crawling. i also have a traction bar
 

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I don't think I know anyone who hasn't broken a stock 9" main cap....

I don't think you will be able to break the Strange carrier or the ring and pinion. You might be able to break a stock 31 spline shaft though. I have broken one, but I have 5.13's, dual cases, and 37's, but only a stock tired 351W. So kinda sorta the same thing, but not really....
With 3.50 gears I think you will break driveline u-joints first...
What do you plan to do to match the bolt pattern of the 60 in the front? A 10.25 easily solves that issue.
It seems kinda late now since you already have good parts in the 9", but I know I would have been money ahead if I had just gone with a 10.25 right off the bat
 

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Discussion Starter #3
well then that's where ive got to decide whether its worth doing the swap or just making my 9 inch have 35 splines... the only concern i have is if i do the 10.25 will i need to upgrade parts on that? or will it just be a gear and diff thing? ive heard they draw more power then the 9 inch but its a truck so i dont much care about that ahaha. but ya ahahah when i did the strange case i was really contemplating just throwing the 10.25 under there but i decided not to worry about it yet. but i guess im leaning towards doing the 10.25 just hate to do it if the 9 in will be strong enough... ill lose some ground clearance with the 10.25 right? would be annoying to have to get 8 lug wheels for the front because then i couldn't rotate the tires... i wonder if theres a 9 inch with 8 lug axle shafts...

i do also have a 1350 driveshaft sense i granaded my 1310 4 different times in a couple month period...
 

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well then that's where ive got to decide whether its worth doing the swap or just making my 9 inch have 35 splines

Wouldn't both of these situations require a new locker?

I would imagine in the end it's either run what you have (9", locker, 31 spline axles) or swap in the 10.25 and upgrade that instead of upgrading the 9" twice.
 

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Discussion Starter #5
Wouldn't both of these situations require a new locker?

I would imagine in the end it's either run what you have (9", locker, 31 spline axles) or swap in the 10.25 and upgrade that instead of upgrading the 9" twice.
Ya... you're right hahaha i guess ill just start building the 10.25... anyone got any ideas for what color to powder coat it hahah?
 

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As cobra joe said, if you stay 9” go chromoly 31 spline, they won’t break then. That’s what I did, so now I’m really committed to a 9”.
But I would still go 10.25 if I were you. I don’t think you lose enough ground clearance to make a real world difference, and you shouldn’t be able to break any stock parts. And if you somehow manage to break something, there isn’t a junkyard in the country that isn’t crammed full of spare parts
 

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Yo Harleyabarton,
WELCOME!
For close example of the Strange, Pat P built up his 79 Drag Bronco with:
Hughes Performance C-6 with wide ratio gear kit 2.72 first 1.54 second, transbrake, ATI 9 inch 5000 stall converter, Chrome Moly 4 linked Ford 9 inch with Strange Pro Iron case Strange 4.71 35 spline Pro gears... @ https://www.supermotors.net/clubs/superford/registry/3878
●●●
Gear Ratio Guide for Larger Tires @ http://web.archive.org/web/20060115054646/http://www.roughcountry.com/Gear Ratio Guide.htm
Excerpts, for example:
  1. When ever you change tire size from the original size to another there will be a direct effect on power and drivability. This chart will help you select the optimum gear ratio to put your performance back where you want it.
Using the chart below, first determine your original gear ratio and tire size and follow to the intersection that should be your approximate RPM at 65 MPH. Next find your new tire size and follow that across to the closest RPM to your original and that will be first choice.
If you are interested in a change that will give more power or better fuel mileage use the color coding as a guide.

This chart is based on 65 MPH and a gear ratio of 1:1, on a manual transmission in 4th gear. Please NOTE: If you have an automatic transmission your RPM will higher due to slippage in the transmission and the torque converter. With an overdrive transmission your RPM in overdrive will be 15% to 30% less than indicated."
●●■●●
1978 Bronco Dealer Brochure via Indybronco
1978 Bronco Emission Component Location Diagrams via 78brncoxlt

1978 Ford Bronco & Truck Wiring Diagrams by Ford via Bronc Mom @ https://drive.google.com/file/d/15KEp-dmAewg_76EfeIPysZGftmGiO7fN/view


1979 Bronco/F Series Electrical & Vacuum Troubleshooting Manual via topsig (Ziggy); similar to 78.

1979 Wiring Schematics, Connector Pin-outs, etc by Ranger429 @ https://www.fullsizebronco.com/forum/6-1978-79-bronco-tech/223050-79-wiring-schematics.html
Similar to 78

Bubba's M-Block Ford V8 Workshop by Dave Resch @ Bubba's M-Block Ford V8 Workshop

MANY 78 Parts Break-Out Diagrams by Indybronco (Lula Mae) @ pictures, videos, and sounds | SuperMotors.net

78 351M/400 Engine Exhaust Emission Control Information Decal & Timing by member grovermyson @ https://www.fullsizebronco.com/forum/6-1978-79-bronco-tech/505882-timing-do-i-need-do-anything.html

C6 Auto Transmission, if equipped, Description & Operation, Adjustments, Diagnosis & Testing (partial), Disassembly & Assembly, Parts Break-Out Diagram, Hydraulic Control System Diagram, Removal & Installation & Specifications @ https://redirect.viglink.com/?format=go&jsonp=vglnk_155464716156516&key=6ed47b392b9edfe394b9e89b72717104&libId=ju70qeuf01000bgv000MAb4isjltc&loc=https://www.fullsizebronco.com/forum/6-1978-79-bronco-tech/210246-c6-rebuild.html&v=1&opt=true&out=http://www.thedieselfiles.com/Ford/C6%20Automatic%20tranny.pdf&ref=https://www.google.com/&title=C6 Rebuild - Ford Bronco Forum&txt=Description & Operation, Adjustments, Diagnosis & Testing (partial), Disassembly & Assembly, Parts Break-Out Diag...

Partial Chilton Manual for 1978, 1979, 1980, 1981 Bronco. Scanned by broncocity.com @ https://web.archive.org/web/20130419152159/http://www.broncocity.com/66-81manual.htm

Ford Shop Manual Diagrams: 1978-1979 Full Size Shop Manuals, partial @ https://broncograveyard.com/rt-1273-technical-diagrams-archives.html
My Tablet takes too long to download, so try the first in this list as long as you have Adobe Acrobat 9 installed. Let me know if the downloads are worth the effort.
Includes:
Wiring Manuals & Diagrams Download PDF
This complete manual for the 1972-1979 Ford Bronco Includes Rear Lights Diagram
Motor Manuals & Diagrams Download PDF
This complete manual for the 1972-1979 Ford Bronco Includes Air Cleaner Diagram
Chassis Manuals & Diagrams Download PDF
This complete manual for the 1972-1979 Ford Bronco Includes '78 Brakes Diagram, Gas Tank Setup Diagram
Body Manuals & Diagrams Download PDF This complete manual for the 1972-1979 Ford Bronco Includes; Upper Body Diagram, Front Clip Diagram, heater Ducts Diagram, Tailgate Diagram, Console Diagram, Front Clip Diagram, Grill Setup Diagram, Heater Controls Diagram, Interior Trip Diagram, Rear Sheetmetal Diagram, Tilt wheel Diagram, Tire Rack.

Order a Ford authorized repair manual other than the EVTM, either a Bishko or a Dave Graham from rockauto.com in Literature section or other source. If it's a CD, ask if it will run on your device.

For any Bronco issues or to chat about it's planned modifications or build, it's better to post each seperately in Noobie Bronco Tech Questions. Flame free zone. This will get more attention and you can build up your post count to get into other sections such as Build section that requires a 30 post count & Bronco and Ford Parts/Accessories (75 posts required to view).

To save you time and for better responses, please fill out your Signature with location, year, engine size, transmission type, transfer case type (manual or electric shift), locking hub type (automatic or manual) info & major mods such as a Lift, etc. .
From the navigation, near the upper right-hand corner, click on your avatar and then select “Account Settings” from the drop down menu.

From your “Account Settings” page you will then see more navigation option of the left side. Select “Signature”.

Now you can simply enter your signature information in the text editor and click save.

Our Forum faqs @ https://www.fullsizebronco.com/help/faq/
Includes for example:
How To Upload Images To Posts & How to Use Search
See more tips!

Baba Looey's Favorite FSB Links (lots and lots of tech links) @ https://www.fullsizebronco.com/forum...ech-links.html


Look at some Technical Service Bulletins @ http://www.bbbind.com/tsb-wiring-diagrams-database/

Try to find time to Participate and VOTE in our Full-Size of the Month (F.O.T.M.) & Full-Size of the Year (F.O.T.Y.) Contests @ https://www.fullsizebronco.com/forum/27-f-o-t-m-voting/
Full-Size of the Month (F.O.T.M) contests will be held in JANUARY, MARCH, MAY, JULY, & SEPTEMBER. Each month in-between will be used for nominating contestants to run in the following Month.
You will get ideas by those competing. Also see the prizes. They are awesome as compared to other sites' "contests"!
Full-Size of the Year (F.O.T.Y.) contest is ongoing now.
 

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Registered
Joined
·
10 Posts
Discussion Starter #9
Yo Harleyabarton,
WELCOME!
For close example of the Strange, Pat P built up his 79 Drag Bronco with:
Hughes Performance C-6 with wide ratio gear kit 2.72 first 1.54 second, transbrake, ATI 9 inch 5000 stall converter, Chrome Moly 4 linked Ford 9 inch with Strange Pro Iron case Strange 4.71 35 spline Pro gears... @ https://www.supermotors.net/clubs/superford/registry/3878
●●●
Gear Ratio Guide for Larger Tires @ http://web.archive.org/web/20060115054646/http://www.roughcountry.com/Gear Ratio Guide.htm
Excerpts, for example:
  1. When ever you change tire size from the original size to another there will be a direct effect on power and drivability. This chart will help you select the optimum gear ratio to put your performance back where you want it.
Using the chart below, first determine your original gear ratio and tire size and follow to the intersection that should be your approximate RPM at 65 MPH. Next find your new tire size and follow that across to the closest RPM to your original and that will be first choice.
If you are interested in a change that will give more power or better fuel mileage use the color coding as a guide.

This chart is based on 65 MPH and a gear ratio of 1:1, on a manual transmission in 4th gear. Please NOTE: If you have an automatic transmission your RPM will higher due to slippage in the transmission and the torque converter. With an overdrive transmission your RPM in overdrive will be 15% to 30% less than indicated."
●●■●●
1978 Bronco Dealer Brochure via Indybronco
1978 Bronco Emission Component Location Diagrams via 78brncoxlt

1978 Ford Bronco & Truck Wiring Diagrams by Ford via Bronc Mom @ https://drive.google.com/file/d/15KEp-dmAewg_76EfeIPysZGftmGiO7fN/view


1979 Bronco/F Series Electrical & Vacuum Troubleshooting Manual via topsig (Ziggy); similar to 78.

1979 Wiring Schematics, Connector Pin-outs, etc by Ranger429 @ https://www.fullsizebronco.com/forum/6-1978-79-bronco-tech/223050-79-wiring-schematics.html
Similar to 78

Bubba's M-Block Ford V8 Workshop by Dave Resch @ Bubba's M-Block Ford V8 Workshop

MANY 78 Parts Break-Out Diagrams by Indybronco (Lula Mae) @ pictures, videos, and sounds | SuperMotors.net

78 351M/400 Engine Exhaust Emission Control Information Decal & Timing by member grovermyson @ https://www.fullsizebronco.com/forum/6-1978-79-bronco-tech/505882-timing-do-i-need-do-anything.html

C6 Auto Transmission, if equipped, Description & Operation, Adjustments, Diagnosis & Testing (partial), Disassembly & Assembly, Parts Break-Out Diagram, Hydraulic Control System Diagram, Removal & Installation & Specifications @ https://redirect.viglink.com/?format=go&jsonp=vglnk_155464716156516&key=6ed47b392b9edfe394b9e89b72717104&libId=ju70qeuf01000bgv000MAb4isjltc&loc=https://www.fullsizebronco.com/forum/6-1978-79-bronco-tech/210246-c6-rebuild.html&v=1&opt=true&out=http://www.thedieselfiles.com/Ford/C6%20Automatic%20tranny.pdf&ref=https://www.google.com/&title=C6 Rebuild - Ford Bronco Forum&txt=Description & Operation, Adjustments, Diagnosis & Testing (partial), Disassembly & Assembly, Parts Break-Out Diag...

Partial Chilton Manual for 1978, 1979, 1980, 1981 Bronco. Scanned by broncocity.com @ https://web.archive.org/web/20130419152159/http://www.broncocity.com/66-81manual.htm

Ford Shop Manual Diagrams: 1978-1979 Full Size Shop Manuals, partial @ https://broncograveyard.com/rt-1273-technical-diagrams-archives.html
My Tablet takes too long to download, so try the first in this list as long as you have Adobe Acrobat 9 installed. Let me know if the downloads are worth the effort.
Includes:
Wiring Manuals & Diagrams Download PDF
This complete manual for the 1972-1979 Ford Bronco Includes Rear Lights Diagram
Motor Manuals & Diagrams Download PDF
This complete manual for the 1972-1979 Ford Bronco Includes Air Cleaner Diagram
Chassis Manuals & Diagrams Download PDF
This complete manual for the 1972-1979 Ford Bronco Includes '78 Brakes Diagram, Gas Tank Setup Diagram
Body Manuals & Diagrams Download PDF This complete manual for the 1972-1979 Ford Bronco Includes; Upper Body Diagram, Front Clip Diagram, heater Ducts Diagram, Tailgate Diagram, Console Diagram, Front Clip Diagram, Grill Setup Diagram, Heater Controls Diagram, Interior Trip Diagram, Rear Sheetmetal Diagram, Tilt wheel Diagram, Tire Rack.

Order a Ford authorized repair manual other than the EVTM, either a Bishko or a Dave Graham from rockauto.com in Literature section or other source. If it's a CD, ask if it will run on your device.

For any Bronco issues or to chat about it's planned modifications or build, it's better to post each seperately in Noobie Bronco Tech Questions. Flame free zone. This will get more attention and you can build up your post count to get into other sections such as Build section that requires a 30 post count & Bronco and Ford Parts/Accessories (75 posts required to view).

To save you time and for better responses, please fill out your Signature with location, year, engine size, transmission type, transfer case type (manual or electric shift), locking hub type (automatic or manual) info & major mods such as a Lift, etc. .
From the navigation, near the upper right-hand corner, click on your avatar and then select “Account Settings” from the drop down menu.

From your “Account Settings” page you will then see more navigation option of the left side. Select “Signature”.

Now you can simply enter your signature information in the text editor and click save.

Our Forum faqs @ https://www.fullsizebronco.com/help/faq/
Includes for example:
How To Upload Images To Posts & How to Use Search
See more tips!

Baba Looey's Favorite FSB Links (lots and lots of tech links) @ https://www.fullsizebronco.com/forum...ech-links.html


Look at some Technical Service Bulletins @ http://www.bbbind.com/tsb-wiring-diagrams-database/

Try to find time to Participate and VOTE in our Full-Size of the Month (F.O.T.M.) & Full-Size of the Year (F.O.T.Y.) Contests @ https://www.fullsizebronco.com/forum/27-f-o-t-m-voting/
Full-Size of the Month (F.O.T.M) contests will be held in JANUARY, MARCH, MAY, JULY, & SEPTEMBER. Each month in-between will be used for nominating contestants to run in the following Month.
You will get ideas by those competing. Also see the prizes. They are awesome as compared to other sites' "contests"!
Full-Size of the Year (F.O.T.Y.) contest is ongoing now.

ok! ya thanks for letting me know about that drag truck! gives me more info on what to do! i actually have a zf5 transmission with first is super low like 7:1 or something and with my 3.50:1 gear ratio i actually really like it because i daily this truck and i only have to turn the engine at 1500 rpm going 75mph on the highway! im getting about 11-12 mpg which is insane for a 460 making 500 or so hp! and with 600 ft of torque i think ill stick with the 3.50 gears untill i start needing more gears.. but i think with the granny low in first gear a and then the np205 having a wonderful low range ill be just fine! i dont do mud bogging or anything. just hard core overlanding and baja and some rocks. at the moment the trucks 0-60 is somewhere around 5.5 which is DUMB!!! i do not need to go even THAT fast in a lifted 78 bronco ahahahah
But like i said thank you for letting me know about that drag bronco that gives me a lot of confidence in the 9 inch!
 

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Yo Harleyabarton,
YW!
Glad to help!
BTW, the "strange" in your post rang a "strange" bell in my mind, causing me to think of Pat!😎
Looking >>> to your future posts!
 

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Discussion Starter #11
As cobra joe said, if you stay 9” go chromoly 31 spline, they won’t break then. That’s what I did, so now I’m really committed to a 9”.
But I would still go 10.25 if I were you. I don’t think you lose enough ground clearance to make a real world difference, and you shouldn’t be able to break any stock parts. And if you somehow manage to break something, there isn’t a junkyard in the country that isn’t crammed full of spare parts
ok! ya i might as well do the 10.25 if im doing the dana 60... just to keep the bolt pattern. but if there are upgrade parts i will go ahead and get them... i break enough things on this truck... id rather a 1 ton axle not be one of them. ahahah ill be driving this thing east and west in the spring time. from Florida to eureka California. hitting all the off road courses i can! so if i can rule a axle breaking out of the equasion i will...
if anyone knows what i might need to upgrade on a 10.25 let me know... its a 1988 f350 with dually hubs... i'm assuming ill need to change the hub? or can i run a normal tire on a dually hub???
the truck only has 15,999 orginal miles and was used on a farm its entire 5 year working life and then sat in a ranch for 15-20 years... so im assuming the axle is in perfect condition... everything else was... it even has the original motor craft spark plugs... and serpentine belt!
 

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I would also go with the 10.25 if I had one.

That being said, the 9" is a wickedly strong axle in terms of torque. The large pinion offset lowers the stress on the gear teeth, allowing people to run lower gears than most other axles without compromising on gear strength. The extra pinion bearing helps too. Personally, I think the biggest downside to the 9" is the semi-floating axles shafts. Sure you can get chromo or 35 spline shafts, and they are retained better than in an 8.8, but the shafts are still in combined bending and torsion. You say you're into overlanding, so you probably carry a lot of gear... keep in mind that the GAWR for a 9" is at most 3600 lb (sticker in my '78 says 3580 lb), and the 2nd gen Bronco eats up a lot of that when empty. Floater kits for the 9" are available from Currie (I'm currently dreaming of a full-floater F9 axle, so I can stick with 5 lug...) but they're pricey.

BTW, nice Bronco. Orange is fun (y)
 

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Discussion Starter #13
thanks for the advice! ya someone near me is selling a floating 9 in out of a race car for only like $900 but i wasnt sold in it sense i might do the 10.25... i will most likely do the 10.25 because of that GAWR.. but i also thought of making a custom axle girdle or even just custom axle tubing. but sense im gonna do the dana 60 in the front.. unless i can get a 5 lug hub for the dana 60 i might as well keep both of them the same bolt pattern

and thank you! its a color i bought it as. never would have picked it my self but now that its orange im inlove... and i dont want to change it ahaha
 

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Harleyabarton
Just chiming in here with my 2 cents

I am building my 93 bronco with a 408w stroker and running a 91 f250hd ff 10.25 with 4.10 gears welded and the dana50 4.10 pumpkin with the pass inner shaft and slip shaft with the c-clip delete spring in my 44ttb for now. But I am having solo build me dana50 beams with +3 width and the radius arm mounts to get my 8 lug and as much beef as a ttb can possibly provide.
That said I will be running a floater 9" eventually from Shreiner Enterprises with 35 spline inner and 40 spline outer with 8x6.5 lug pattern to get my ground clearance back and save 100lbs of unsprung weight in the back.
They can build you a complete floater housing with axles, sans the 3rd member for around $2500(listed prices are a tad lower but don't show option for 8 lug, just call and talk to them, they will build whatever you want/need). And when you get a custom 9 housing with larger OD and/or thicker tubes and and on top of that run ff hubs. The gawr of a stock 9" effectively doesn't matter anymore because you have a way beefier housing and bearing setup.
It may not be the budget option for the time being but considering you already have a Currie 3rd member that is much stronger than even nodular iron stock castings you would still need a new 35 spline locker. But this would give you the ultimate Ford 9 that will hold up to 550hp and 600ftlb turning 37-40's on any terrain for years to come with maximum ground clearance and minimal weight under those leaf springs which helps when bombing through the desert with stability and ride quality. Doesn't matter some much in the rocks or mud.

Shreiner Enterprises is based in Arizona and they have been building 9floaters for trophy trucks for over 30 years. Great reputation and unbeatable pricing compared to all the other big name companies like Currie that are out there.

Stock Ford 9 axle weighs aprox 190lbs
8.8 around 170
10.25 is 330-360lbs
Fab 9's with thicker and larger diameter tubes and ff hubs will add some weight, but counter that with an aluminum 3rd member and should be under or right at 250lb.
 

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I swapped a 10.25 into my bronco. There are two generation of 10.25 but I don't remember the cut off for the years. I want to say 87 or 91 was end of 1st Gen. Number of splines where the yoke attached is the major difference. 2nd Gen pinion is longer. Also 10.25 came with 3.55 or 4.10 from the factory. May be more ratios available but those are the two I always ran into.

1st Gen 10.25 has a shorter pinion shaft than the 2nd Gen 10.25. Most ring and pinion kits include the ring and pinion from the 2nd Gen 10.25 which solves the issue of pinion shaft failure.

You may want to Google or search the forums. There is an article/post describing the difference between both generation of 10.25 and the 10.50.

The 10.5 has much larger ring and pinion gears but the pinion bearing is smaller to allow the larger pinion to work in the housing.

So to paraphrase the article I read:

1st Gen 10.25 prone to pinion shaft failure. Replace with 2nd Gen ring and pinion and proper yoke for that setup.

2nd Gen 10.25 solved the issues of the 1st Gen 10.25. still not as strong as the 10.50 in regards to ring and pinion only.

10.5 strongest ring and pinion but at the expense of smaller pinion bearing.

Those are comparing stock parts. Aftermarket could change all that but I only plan 35's on a street queen so stock is fine.
 
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