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Discussion Starter · #1 ·
Hey there! This is my first time ever asking for help on a forum, so hopefully it'll pay off.

I've got a 1984 CJ7 that I've been wrenching on for a little over a year now, fixing issues that were on it when I bought it, things the previous owner did, making it more reliable, etc. It is now finally time for me to address the gearing and axles on it. I've still got the stock axles, Dana 30 up front, AMC Model 20 in the rear. I've done a semi "scientific" check to see what gears it has in it now, which I believe to be 2.72s. Needless to say with 33s, 4in lift, and a 5 speed manual, the gearing is not very good.

Im thinking 4.56s for the gearing, but being that Im going to be in the axles replacing the old gears, now is the time to install lockers as well. I'm on a decently tight budget, so I was thinking about doing "lunchbox lockers" in both axles. but it was brought to my attention that in the rear when i would make a sharp turn that the inner tire could chirp/hop.

I have no idea what I'm doing when it comes to things like this, as I'm new to all of this, but what all setups are you guys running and any ideas/help with what I should go with would be much appreciated! I'm running the 258 (4.2L) that came in the Jeep as well.

Thanks!
 

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Staying 33s? Don't go 456. I've got 456s on 35s and it's great offroad but on road 1st gear is useless and it's rapping out at 65.

Axle wise I'd do trutracs if you want to spend the money. 410s and for sure one piece shafts in the rear.

If you want to go the cheap route research lunch box lockers.

If you drive on street and get any snow or even wet asphalt you will not like a non selectable or LSD type of diff.

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Discussion Starter · #3 ·
Staying 33s? Don't go 456. I've got 456s on 35s and it's great offroad but on road 1st gear is useless and it's rapping out at 65.

Axle wise I'd do trutracs if you want to spend the money. 410s and for sure one piece shafts in the rear.

If you want to go the cheap route research lunch box lockers.

If you drive on street and get any snow or even wet asphalt you will not like a non selectable or LSD type of diff.

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Yeah, I am planning on staying with 33s for the forseeable future. I've got the one piece shafts in the rear axle already thankfully. forgive me for not knowing, but what do you mean by 410s for the rear?

I'm looking at the lunchboxes, just wasnt sure about them with my jeep being a daily driver. It spends 90% of its time on pavement, but im hoping that will change in the future once i get these upgrades. its also spring, so it rains quite a bit here.
 

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I have a warmed up 258 in my CJ5, so it's likely got a little more power than yours...
I regeared to 4.56 for my 35's, with a T5 it's almost ideal on the road. For you with 33's, you might rather go with 4.10 gearing.
I also have Lock Rite's front and rear, for the last 20 years. They've held up just fine, but I absolutely cannot use 4wd in the snow. Even wet roads in 2wd can be a fish tail experience.
As far as chirping the inside tire on turns, I can if I want to. If I stay light on the gas, or better yet, clutch in coast around street corners, it's no big deal.
Keep in mind that an automatic locker will lock with applied torque, whether accelerating or engine braking. I have let some uninitiated folks drive my CJ and they have quite a herky jerky time around sharp corners.
It's not a big adjustment, but it is an adjustment.

One last note, if you do install any sort of lockers, be sure to upgrade your axle shafts. Stock shafts won't last very long.
 

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Gears, 410s would be the lowest I'd go. You'd probably be good with 373s honestly.

Definitely recommend a LSD type for you then. If you got trutrac when you're offroad you can brake modulate(torque) them to get them to almost act like a 100% locker.

Although with a 3rd pedal it takes a whole lot of skill.

I've got a lunchbox in the front and spool in the rear of mine but I'm completely fine with driving it the way it acts but I don't drive in snow or rain now.

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I have a Spartan lunchbox locker in my 20. If it's a DD, I wouldn't use one in the rear. It will pop and jerk in slow speed turns, It's fine at speed though. You will also have have to change the carriers in both axles. I would go LSD in the rear, the front is fine with a lunchbox locker, as it wouldn't be in 4x4 all the time.
 

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As for the comment on stock shafts... your milage WILL vary. It depends on how you drive and what you do. I went 12 yrs on my stock D30 with lunchbox and 35s no breakage. I'm on year 9 with a WT D30 out of an 86 CJ with no breakage.

Just got back from my 6th trip to EJS... so going on 20 yrs with locked front on 35s with a V8 and I've had no shafts or joints let loose. I don't drive it easy but I don't run around like a drunk hillbilly niether.

I will say I'm honestly surprised I haven't broken anything yet.

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Discussion Starter · #8 ·
So it's looking like with my 258, t5 tranny, 33s and 4in lift, I shouldn't go any lower gearing wise than 4.10s correct? It's also sounding like a lunchbox would be good in the front.

So let me ask yall this, how does a LSD do off the road, out in the woods?
 

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Discussion Starter · #9 ·
I think if I recall correctly I have the Yukon one piece shafts in the back. Not sure about the front, haven't had to pull them yet. Had to replace axle bearing seal after I bought the jeep cause it was leaking badly.

Would those Yukon shafts hold up ok?
 

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The Yukons will be fine. The problem will be finding gears for the 20 in the right ratio, quailty parts are some what scarce as the 20 isn't as popular as the D30 or D44. Try to steer clear of the Crown or Omix brands as quality is very low.
 

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Absolutely stay away from crown and omix if at all possible.

Don't get fooled into paying $500 for yukon gears niether. They ain't made in the US. As long as you confirm gears are country of origin of Korea mainly, Italy is better. No Chinese, Taiwan, India, etc.

Elite gear and Revolution are strictly Korean gears and they are the best bang for dollar.

Bearings are mainly Koyo now which are Japan counterparts to US Timken. Timken are preferred but most install kits state they ship either Timken or Koyo depending on stock and most stock is Koyo.

Performance of an LSD offroad will depend on which one you get. Trutracs are best because they're gear driven, torque sensing so no clutches to wear out. But unlike a clutch pack you can't tighten them up to work more better.

I'm assuming you're looking through gear charts and calculators... just keep in mind that most of those "stats" are good on paper but lots have found that the perfect stated ratio was indeed a little too deep for them.

I also ran stock 331s for those first 11 yrs before my axle swap and only stalled the jeep out once on 35s. It was way more drivable on the street but she really woke up offroad with the 456s.

That's why I state if you're driving a lot on road I'd lean towards 373s on 33s. But the t5 may have a higher 1st than I'm used to which would skew the results.

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So the question is:
What do you want to do with your Jeep.
This will drive all your decisions.

You can build for:
Daily driving
Mud
Fire roading/hunting
Rocks and technical wheeling
Snow and ice
Etc............

Each build will be unique with different traction devices, lifts, motor upgrades, and transmissions.
 

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If your going to spring for a true track at about 750 an OX or ARB locker runs about 1000 last I checked (depending on what type you buy there may be other stuff ya need to buy). It is a bit more but it's only a few hundred away to have a selectable locker...especially in the rear diff where folks are talking about adjusting to driving. If you go with a spartan that's a different story cause they only run about 300. It's a pretty big expense to open up the axles in general, but it's not something you're going to do often.

Just my .02 cents and a different take from what's already been posted...decide what you really want/need and save to get it since it' can get expensive either route. When I did mine I bought each piece one at a time (front locker, rear locker, front axle shafts, rear axle shafts, etc.) and just put them on a shelf until I could afford the install...but I knew I wanted selectable lockers...so I just dumped it all in my garage over about 6 months or so.
 

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Discussion Starter · #15 ·
So the question is:
What do you want to do with your Jeep.
This will drive all your decisions.

You can build for:
Daily driving
Mud
Fire roading/hunting
Rocks and technical wheeling
Snow and ice
Etc............

Each build will be unique with different traction devices, lifts, motor upgrades, and transmissions.
So right now I'm aiming for more of a daily driver, but I do want to be able to go to places like Stoney Lonesome or Choccolocco Mountain and do those places fairly easily.

The motor in my CJ7 is fairly stock, it's got a holly carb, dui distributor and hotter spark plugs.
Still have the stock t5 and transfer case. 4 in BDS suspension lift on 33s. Poison spider roll cage and harness seats.

I state all that because in addition to changing out my gears and installing lockers, is that I'm gonna upgrade my braking system. So that is cutting into my budget, making it harder to decide on what lockers to get. I really like the idea of a selectable in the back, and a lunchbox up front, I guess I just need to crunch some numbers.
 

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Discussion Starter · #16 ·
Absolutely stay away from crown and omix if at all possible.

Don't get fooled into paying $500 for yukon gears niether. They ain't made in the US. As long as you confirm gears are country of origin of Korea mainly, Italy is better. No Chinese, Taiwan, India, etc.

Elite gear and Revolution are strictly Korean gears and they are the best bang for dollar.

Bearings are mainly Koyo now which are Japan counterparts to US Timken. Timken are preferred but most install kits state they ship either Timken or Koyo depending on stock and most stock is Koyo.

Performance of an LSD offroad will depend on which one you get. Trutracs are best because they're gear driven, torque sensing so no clutches to wear out. But unlike a clutch pack you can't tighten them up to work more better.

I'm assuming you're looking through gear charts and calculators... just keep in mind that most of those "stats" are good on paper but lots have found that the perfect stated ratio was indeed a little too deep for them.

I also ran stock 331s for those first 11 yrs before my axle swap and only stalled the jeep out once on 35s. It was way more drivable on the street but she really woke up offroad with the 456s.

That's why I state if you're driving a lot on road I'd lean towards 373s on 33s. But the t5 may have a higher 1st than I'm used to which would skew the results.

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I'll look into the gearing a bit more then. I know as of right now with the 2.72s or whatever highway gears I have now, 1st gear is about like second gear, third is kinda like 4th gear, 4th is like 5th, etc you get the idea. (1st:0-~17mph. 2nd:17-~34mph. 3rd:34-~60mph. 4th:55-~70mph. 5th: ???can't use it)
 

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I have a Detroit Locker in the rear and a Tru Trac up front. The only thing about the rear locker I can say as being a negative is wearing the rear tires faster. I have heard it chirp a few times and felt it but nothing bad. Nothing adverse in slowing to a stop or speeding up either. I sure like not running out of traction because I have a tire or two off the ground.
 

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I have a Detroit locker in the rear and open diff up front. I do very well off road but will add a locker in the front someday. The driving I have done in 20 years has never really made me feel like I really needed it.
 

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I have a Detroit locker in the rear and open diff up front. I do very well off road but will add a locker in the front someday. The driving I have done in 20 years has never really made me feel like I really needed it.
Same with me. When I swapped to WideTrac axles, my AMC20 was already loaded up with 4.10s, Moser 1-piece axles, a Detroit, and welded tubes. When I built the WT D30, I used 4.10 Yukon gears and that's as far as I got. The Detroit does fine off road and rarely unloads (pops, bangs, or 'chirps' the tires) on the pavement thanks to my driving style (coast around the corners, don't drive like a speed demon).

Of course, 4.10s and 33s will have you running out of rpms really quickly. Mine originally started out with 2.73s (like yours) and when I put the 33x15.50 TSX Swampers on, I lost all low-end grunt, it wasn't happy on the freeway going any slower than 75mph, and the speedometer would read 65 but I was really doing 72mph. When I swapped to 4.10s, the pendulum swung the other way: now I couldn't even get across the intersection without grabbing 2nd, the engine was screaming just to maintain 65mph, and speedo showed 75mph while doing so.

Personally, I want streetability in addition to off-road capability ('capability,' not dominance). Matching up tire size to gear ratio is super-important toward finding the happy medium in that case. It was my daily driver when I installed the 33s, but then became a toy later. Now, I want to drive it to work every now and then, but when the opportunity comes up to hit a trail or two with a buddy, I definitely don't want to be smoking and slipping any clutches just trying to get moving, nor burn all my fuel just getting to the trails and back.

I agree with jeep_boy02 that 3.73s are what's needed for 33s (4.10s are better for 35s).
 
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