[simrokkzz]

Hey Guys
Got to open the 9inch rear of my 79...

the pinion is 12 teeth, the ring 38
Makes 3.16 to 3.17 ratio to me

guessing stock gears in front, so I got some reasoning why 4wd does not work (if in 4Wd Front wheels slip and stop and so on...)
To get the 3rd member out I need to get axles out, what a mess...

but my question:

please recommend a rear Diff set with 3.50 gear set that is locked.
I heard about a Detroit locker but I am far away in terms of knowledge to select this all my own.

engine will be a 400hp high torque 460 hence stockgear ratio should still allow hood power whilst mild off-roading and on street usage.

Thanks in advance guys

 

[Doosenberry]

You probably missed a tooth on the ring gear. The third member I pulled the other day had 39 teeth on the ring gear and 12 on the pinion which is a 3.25 ratio.

If you want good street manners I'd go with a True Trac, which is a limited slip differential and not a locker. If you want something a little more "hardcore", but a lot more "sloppy" for lack of a better word, then an automatic locker like a detroit would work.

Have you seen this video on youtube yet? It's very informative on how all the different diffs work.

When he describes the detroit style lockers that's really what you get. I have the yukon grizzly lockers which are essentially the same thing as a detroit and they introduce a lot of slop, because of how the teeth in the locker fit loosely together.

 

[simrokkzz]

I will have a look into the video shortly.
Counted 2 times 38
But no matter if 38 or 39, it’s too long.
I need 3.50 or more but then I need to change front Ring and pinion as well, which I want to avoid if possible.

being pissed enough about all the new work in front of me, rear was finished I thought

 

[simrokkzz]

Marti stats my car came with 3.50 lock trak in the rear

 

[simrokkzz]

Daniel, so it can be similar to this kit right:

F9-TTGBK-Ford 9" / Eaton Detroit Truetrac / Ring & Pini

www.quickperformance.com

 

[Doosenberry]

I agree that it's too high of gearing (low number).

You could get away with 3.50 and 35's, especially with a fresh engine like that. I would still rather do at least a 4.10/4.11 gear instead though. When you have lower gearing like that it's like free horsepower. It will take some top speed away, but I'm not sure if you'll be taking your Bronco on the autobahn. You could even do 4.56, which is what I did, but the lower you go (higher number) the more top speed you're sacrificing for more low end power.

I haven't used a True Trac, but a lot of guys on here have and they all love them. I just have a hard time recommending a locker like I have, because it's not for everyone, that's for sure. My Bronco, at least right now, would be a lot more fun to drive on road with a LSD instead of a locker. I need to get my new steering components on and hopefully that takes that problem away. It likes to send me off to the side of the road after I make a turn and with a little slop in your steering it's exaggerated a lot more. If my steering was 100% tight I don't think I'd feel the same way and it probably wouldn't be a problem.

 

[simrokkzz]

I just opened front
42/12 oem Dana parts, 3.50

money wise I should stay with that

willing wise 4.10/4.11

what rev I may have at 130km/h (79,45 mph) with 35’s and 4.11 or 3.50

i will take it on Autobahn, but onlyfor travel notfor high speed runs

 

[Doosenberry]

I just opened front
42/12 oem Dana parts, 3.50

money wise I should stay with that

willing wise 4.10/4.11

what rev I may have at 130km/h (79,45 mph) with 35’s and 4.11 or 3.50

i will take it on Autobahn, but onlyfor travel notfor high speed runs

Gear Ratio Calculator

 

[Doosenberry]

Using that calculator, 3.50 with 35's and a C6 transmission gets you about 2800 rpm at 79-80 mph. 4.11 gets you closer to 3300 rpm.

 

[simrokkzz]

Yes, just did the exercise
3.50
Would allow to go 141 mph at 5000 rpm

Well.... crazy
sent you a pm with a pre ass’d 3rd member from JBG

 

[norm]

Since your rear has an odd gear ratio and not 3.50's i would count the axle splines too in case someone swapped the entire rear end.

Don't want you to order a 31 spline diff and have 28 spline axles.

I use a detroit in the rear on mine and that's the only way i would go,personally. Sometimes limited slips can open up at odd times and i don't like that unpredictability.

That being said if you in fact have 28 spline axles i wouldn't go locker.

Quick performance in the link above is a very good vender to deal with.

 

[simrokkzz]

Since your rear has an odd gear ratio and not 3.50's i would count the axle splines too in case someone swapped the entire rear end.

Don't want you to order a 31 spline diff and have 28 spline axles.

I use a detroit in the rear on mine and that's the only way i would go,personally. Sometimes limited slips can open up at odd times and i don't like that unpredictability.

That being said if you in fact have 28 spline axles i wouldn't go locker.

Quick performance in the link above is a very good vender to deal with.

very good idea. It would be hilarious to find that out after new 3rd member arrives.
I will get the axles out tomorrow and will tell.

May this moment I am looking into a set from JBG - as this would not require to setup everything my own, which I have no experience on.

Assembled Center Section for Ford 9" 31 Spline Eaton TruTrac - Broncograveyard.com

New 3rd member with a 3.50 gear ratio and 31 spline Detroit Truetrac carrier ready to install.br Features a new ring and pinion, detoit truetrac clutchless limited slip, and bearings.br NOT WARRANTIED OVER 33 Inch TIRES!br

shop.broncograveyard.com

As an alternative the set above from
Quick performance May be good

 

[CrazyBRONCOguy]

Agree with Norm that it needs to be looked into on what you currently have. I say this as someone who has ended up having to buy things 2 times before...

I have had a Full Detroit locker, TrueTrac, and Spool. I like the trutrac on the street and its been fine for what I use that truck for which is a little dirt/mud/sand. It does take a few spins to make both sides work. I prefer a spool over the full locker, but im willing to live with the street manners associated with it too.

That 3rd member should be drop in ready, no setup needed. However I would strongly recommend getting one made with a Nodular case and Daytona Pinion Support as well with shims instead of a crush sleeve, its not a bunch more money to have the strongest stuff you can get, if your already looking at 1200 for that JBG one anyways... Moser, Strange, Currie, Yukon (i think now has one) etc... should be able to get you want you need.

FWIW, I have 4.10's and 35's on my 78 and its about perfect combo for street able but still good offroad bronco. If your trans needs rebuilt, you could go to a wide ratio gear set to get a little better off the line power.
Personal opinion though would be that you will be fine with 3.50 and 35's (with that engine) you just might have to use 4lo when off-road, all the time

 

[norm]

Graveyard is most likely buying it from someone and marking it up and selling it would be my guess.

Quick or any other gear/diff specializing business assembles them to order.

 

[norm]

Ha, I'm the opposite. I ran a spool for one summer and hated it.

Where I hated it was very slow driving, parking spot turn in. Anything above that slow speed it was ok and felt fine. A locker opens up at the super slow speed tight turn in stuff, just easier on things and not near as much effort to go.

If i didn't drive it as much as i do a spool wouldn't bother me.

 

[Doosenberry]

I agree that for off road use you can't really beat a locker of some sort. Mine work great in that department. I just think an LSD would be better if you're doing mostly street use. It just depends on what you plan on doing with it and you'll have to be honest with yourself. Are you really going to need one? That sort of thinking. If I was driving on ice and snow a lot I'd have to at least swap out my rear locker. It gets really squirrely in those situations.

Of course, I'm going based on my own Bronco and my own experience and I think having a manual tranny, especially with a heavy mechanical clutch, has a bit to do with the added quirks of my setup.

 

[Gondal]

If you want best of both worlds spend a little more and get a selectable locker
I love my ARB locking diffs. Just flipping a dash operated switch let’s me go about 50% of the trail that needed 4x4 with open diff

 

[slimpartywagon]

If you want best of both worlds spend a little more and get a selectable locker
I love my ARB locking diffs. Just flipping a dash operated switch let’s me go about 50% of the trail that needed 4x4 with open diff

This actually the best option, weather ARB, Detroit E-Lock, or other brand, having a selectable locker give you the best of both worlds without a compromise.

 

[Gondal]

I might add that I put an ARB locker my 78 bronco in the mid 90s
It still functions perfectly. Over the summer I pulled out the third member and installed 4 46 gears. While I was in there I replaced the actuator seal in the locker just because it’s rubber O ring that I figure must fail eventually
Other than that no other maintenance or repairs to the locker
Just routine gear oil changes every year or 2
i don’t go out hard core wheeling or thrash on it. Moderate off road.
but really the lockers make the obstacles so much easier you don’t have to trash the bronco. It oretty much just climbs and crawls whatever you need. Some people say lockers take the fun out of wheeling
Makes it too easy

 

[simrokkzz]

That 3rd member should be drop in ready, no setup needed. However I would strongly recommend getting one made with a Nodular case and Daytona Pinion Support as well with shims instead of a crush sleeve, its not a bunch more money to have the strongest stuff you can get, if your already looking at 1200 for that JBG one anyways... Moser, Strange, Currie, Yukon (i think now has one) etc... should be able to get you want you need.

that may be the way to go for me.

our focus at the moment is to get the car finally on the street.
We spend well above 10k already incl.
The new motor, which was not planned.

in case the Profile I use the car for shows I need lower gearing we may upgrade to 4.11 at some point, for the moment I think I need to talk to Quick for the tru trac

it will rarely see heavy off roading, but at least some steep trails which may be wet and slippery, there I need grip for the heavy car.

from the calculation of tire/gear ratio 3.50 seem to be ok, 4.11 still as well, however going 4.11 now will be more costly

selectable lockers will best - that is true!! At this moment too expensive doing that overall as I will need some additional devices as well - in the end this may break my plan with having a historic car certification, as electronic lockers are far from being 78/79 tech.

If any can recommend a direct contact to a shop doing the above please let me know.