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Just how crappy is a lunch box locker in the rear axle?

welndmn

Well Done Man
Joined
May 21, 2020
Member Number
1008
Messages
667
Loc
Concord, CA
I have owned a few lunch box lockers in front axles, and I really hated them all, the pops, the clicks, the strange pulling when driving at speed in 4x4, but I've never owned one in the rear.
My 47 CJ2a is being used more and more and as much as it pains me it could really befit from a rear locker. The issue is it has a Dana 41, so the only option is a lock rite locker, if there was a limited slip option (Stupid rare) i'd buy it, but there is not.
So with 80" of wheelbase, how much will hate that decision to run a lock rite in the back?
Maybe put it in the once every 5 years I run a hard enough trail that I need it?
 
For what its worth, I ran a spool on my street driven Samurai and barely even noticed it.
 
The times I have driven one on street was less than fun, especially in intermittent snow/ice conditions. The popping and unlocking was pretty hairy at times.
 
I swapped from a welded diff to a Detroit in the rear of my CJ7 because it was supposed to be more streetable and tire friendly. It liked to lock/unlock and cause darting left/right when shifting and was less predictable in the snow.
 
I'd consider a spool or even cutting brakes as a possibility. Spools suck on the road but atleast they are consistent in their behavior. If you have no other option I guess that's what you get to use unless you swap in a normal axle.

Can you put a selectable in the front?
 
I've got a lock rite in the rear D44 in my CJ-5 and I can tell it's there on the street when shifting under power, like when you're accelerating to get onto the highway. It will shift the CJ to the left and you have to be paying attention to the steering wheel to keep it in your lane. The Jeep spends 95% + of its life off road to I can live with all that. Dirt road, gravel, wheeling and in the snow as my hunting rig that rear locker is not an issue at all. If I had a rig that spent more of its time on the highway I might look at an LS instead.
 
Is it impractical to put a 44 rear in and be able to run whatever diff you like?
I've run Lockright and Detroit rears in 103" wheelbase much heavier than a flatty and got popping/banging/jerking a bit, usually reliably enough to be able to scare passengers any time I had one. I don't imagine it'd be a lot of fun in something that short/light.
 
I have ran a lunchbox and also a spool on the street. The biggest downfall of the spool was tight turns and parking lots. The tire chirping and hopping tires gets old. It also speeds up tire wear. Out on the road and under 90% of normal driving I dont know it is there. The lunchbox locker was a no-slip and was pretty smooth especially if you learned to coast through tight turns. It didn't seem to be as bad as some of my friends lock rights.
 
I have a spartan on my street driven toyota truck and it's ok. It was kind of rowdy when it was new and I was on 33s. It does get weird if the tire pressures arent the same, they do suck in the snow as well. Saying that 99.9% of the time I dont even know it's there unless I am pulling into a parking spot.

I like them because they work offroad.
 
Got F/R lock rights in my cj-8, once you get used to not getting on the throttle when making a tight turn, it's not that bad IMO. Just recently put spartan lockers in both ends of a samurai, wow, you thought the rear axle was coming apart in that thing! :eek: After 500 miles or so it finally has broken in a smoothed out much better, but still not as good as the lock rite in the jeep.
 
I actually prefered the 2 spartans I've had vs the 3 Detroits I've had. Both spartans and 1 Detroit was in the front though.

I've driven my buddies Sami with a lock rite rear quite a bit and I can't say I ever noticed it.
 
I feel that they are weaker and will water out sooner in the rear. I have broke a few and due to their design, they are just weaker than a Detroit style locker.

As for DD a locker in the rear.... just learn how the rig works. It’s not the same as a open diff... learn what it does and get over it, I have in mine.
 
Rear lunchbox locker was the best $250 I've ever spent. I don't even notice it lock and unlock. You're on the gas and it's basically a spool. You're off the gas and it's basically open with a little clicking noise.

Lunchbox in the front is way clunkier.
 
We're missing some info here.

Auto or manual rig?

I've run both, with the automatic rigs, I'd rarely notice the lunchbox in the rear except for in the parking lots. I had always assumed that with the auto putting constant pressure on things it helped tame down some of the lunchbox characteristics.

With the manuals rigs, the "Ill behavior" of a lunch box makes itself apparent (pops, surprise lane changes, etc). The comment about getting good at coasting through tight turns with the clutch in is very spot on.

Personally, I wouldn't hesitate to run another lunch box in the rear again as it never really bothered me that much, though I can see why some people can't stand them back there.
 
I DD a 85 toyota with a detroit out back 5:29’s and 33’s for years. Took about 6 weeks to break in and get used to it, after that just drive it. A bit of clutch around a tight corner seemed to quiet it down a bit if it was a concern. Otherwise it was super predictable, not great in inconsistent snow and ice for on road driving but nothing that you cant get used to.

All that said I am going selectable F&R on my current project.
 
My lunchbox locker didn’t last 2 weeks. I rounded the teeth clean off.
 
Your in a flatfender I dont think hearing noises are gonna be noticeable. What I worry about is the 41.. the axles are tiny even being full float they are small course spline. I want to say you could use the power locks out of Dana 30's and use course spline 44 side gears. But shoot that was 25 yrs ago so I'm not sure I'm remembering that swap correctly. When I was young I got away with a lock rite in a course spline 44 with 2 piece axles with a small block and 35x15.5 sx's on it. It ran mostly mud and would spin the outer hubs off alot but surprisingly the axles held for awhile. While I ran that horrible math my flatfender buddies were having a hard time keeping axles in their open 41's. If I were you, I'd keep the 41 open and lock the front 25 and stuff some 27 axles in it for a little more strength.

... oh I never broke that lock rite with the course spline shafts. They are way stronger in that application. Wasn't till I built a 30spline 44 that I started breaking the lockrites. So strength of the locker for you will be more than adequate.
 
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Your in a flatfender I dont think hearing noises are gonna be noticeable. What I worry about is the 41.. the axles are tiny even being full float they are small course spline. I want to say you could use the power locks out of Dana 30's and use course spline 44 side gears. But shoot that was 25 yrs ago so I'm not sure I'm remembering that swap correctly. When I was young I got away with a lock rite in a course spline 44 with 2 piece axles with a small block and 35x15.5 sx's on it. It ran mostly mud and would spin the outer hubs off alot but surprisingly the axles held for awhile. While I ran that horrible math my flatfender buddies were having a hard time keeping axles in their open 41's. If I were you, I'd keep the 41 open and lock the front 25 and stuff some 27 axles in it for a little more strength.


I do have the 19 spline dana 44 axles swapped into the Dana 41, so swapping in a dana 44 really only gets me locker options, and I just don't know if that worth the cost.
It's only on 33's.
Yup, I do have willys truck dana 27 U joint axles swapped into my dana 25.

From the all the responses, it sounds like it's just not worth the trade off to put a lunch box locker in my flat fender.
 
I do have the 19 spline dana 44 axles swapped into the Dana 41, so swapping in a dana 44 really only gets me locker options, and I just don't know if that worth the cost.
It's only on 33's.
Yup, I do have willys truck dana 27 U joint axles swapped into my dana 25.

From the all the responses, it sounds like it's just not worth the trade off to put a lunch box locker in my flat fender.

Oh.. you converted to 44 shafts.. run it.. you'll be fine. Just carry an extra carrier pin with ya. That's about the only thing they break. You wont be disappointed with it.

hahahaha.. oh and never listen to toyota guys on jeep advice :flipoff2::lmao::lmao::grinpimp:
 
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Ran one for a few years. In parking lots turning sharp it will unlock and click click click click. In a sweeping turn it will unlock on the deceleration and relock on the acceleration, causing it to jerk halfway though the turn. If your rear tires are at unequal pressure it will cause some weird driving problems. When accelerating though a turn it can unload with a loud bang.
You get use to it after a while, it's just annoying. They are good offroad, never had a problem with traction.
 
I ran lock rights in my Sammy front and rear. I drove that thing everyday from home to work then school and back at 65-75. I never noticed them if my tires pressures were equal.
 
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