Topic: locker theory

[chrisfranklin]

Lets say you are running a stock Jeep CJ/Wrangler 4 or 6.  You've got the D35 axle, which is prone to break, but you want to get a locker.

Here's a Hypothetical situation, one locker, rear, & D35 axle:

When you are off-road and transfer case is engaged, you're going to distribute torque to both the front and rear axles.  But, you're climbing and a front wheel leaves the ground, thus causing you to lose the unlocked front end.  All of the engine torque is then transferred to the locked rear axle and D35.  And depending on other variables (tire size, power, gearing) you may get breakage.

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So, wouldn't it make sense to never run a CJ/Wrangler with a D35 with lockers unless both axles are locked, not just one?  Wouldn't this help to insure that the engine torque is always evenly distributed between the front and rear axles off-road, thus reducing opportunities for the D35 to get overloaded (tires size, power, gearing notwithstanding)?  

(Or, maybe you could also just do the front, too, and count on weight shift and articulation as enough to keep the rear end planted and torque evenly distributed?)


Nah, nah, nah, grumble, grumble, grumble  

[SMC4WD]

ARB has the 'Super 35' locker.  It takes the 27 spline side gears and upgrades them to 30 splines.  Same as a D44.  No-one makes stock 30 spline D35 axles, so your only choice are high alloy, chromoly or something.  Go easy on the hill climbing and you should be ok.

D35 pinions brake all the time.  So do the axles (not the clips, but the axles).  If an axle brakes, there's nothing to keep it attached to the housing, and out it comes.  If you can keep the axle, and the carrier (or pinion gears) from braking, you've eliminated a few of the D35 quirks.

Start with the rear.  Save money and build something.  Then sell that D35...   You can end up even, or at least not be out that much.

[Jeffy]

Not really since the NP/NV231 does not have a central diff so it acts like a spool in the drivetrain  This is why you shouldn't run 4wd for very long on dry pavement.

Also, if there was a central differential that wasn't lockable, if you got the front axle in the air all the power would go to the front axle.  Power travels to the end with the least resistance.

[SMC4WD]

Oppp's.....  

Did I entirely miss the question?

[chrisfranklin]

Are we talking about the same things here?

I was thinking, in the hypothetical, that if you unweight one wheel on an unlocked front (and no manual hubs), then you lose the axle.  So, the entire power of the engine is going to go to the rear wheels, provided they have contact or are locked, right?  Which means the D35 gets all the burden as a result.

But, if you were running front and rear lockers (say auto) and a front wheel became unweighted, you'd still have power getting to the ground in the front.  Thus the rear wouldn't be takng all of the torque, but would be sharing the load with the front. And, the D35 would be taking less of the load.  

So, it makes sense to run front and rear lockers, not just rear,  if you are using the D35 rear axle.  That way you make sure that the rear end will never be doing the work alone and will thus may face less chance of breakage.

No center diff (i know).  And, transfer case is effectively a spool.   :?  

[Jeffy]

Are we talking about the same things here?

I was thinking, in the hypothetical, that if you unweight one wheel on an unlocked front (and no manual hubs), then you lose the axle.  So, the entire power of the engine is going to go to the rear wheels, provided they have contact or are locked, right?  Which means the D35 gets all the burden as a result.

Power will still go to that axle and no matter what.  Power will be wasted because it will go to the tire that's in the air but power is not redirected to the rear.  The rear still has 50% of the power. It does not gain 100% becuase the front axle isn't touching the ground.

[SMC4WD]

Ok...  Front axle, open diff.  One tire in the air will lose any traction to the front axle.  The power will still be split from the transfer case, but the power going to the front axle will do nothing but head towards the spinning wheel. Least path of resistance.

More power will not be forced to the rear axle.  Since the transfer case is splitting the power between front and rear, the rear will not get more of the power.

But, since the rear is doing all the work, whether it's locked or open, it is more likely to break.  If it was locked, it could put more strain on it, therefore the strain makes it even more likely to break.  

Now locked in the front, the power ratio from the T/C hasn't changed (still 50/50), but the locker eliminates that 'least path of resistance' theory.  Traction to at least one tire in the front will assist the vehicle, making it easier to progress up the obstacle.  Easier work for the rear axle could help in reducing the chance of breaking.

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Did I get it right this time??

[wrangler387]

I believe what you are trying to say is... if you had a locker in the front and rear, then the front 50% would aid in pulling the jeep, whereas with only a rear locker, you'd have to give it more gas to make the rear axle do all of the work to move the jeep since the front axle is rendered useless with one wheel in the air and then no locker. Am i following your train of thought SMC4WD?

[chrisfranklin]

SMC4WD, Wrangler 387, yeah, that's the idea that was coming to me  :D.  Just, you said it more correctly.

[jackhammer]

wow I think I almost learned something there.....hypathecally. are you really trying to justify not swapping axles by adding lockers front and rear.  I could be mistaken but isnt the height of the tires averaged into the dana 35 breakage history. I have a 95YJ 2.5 auto 3.73. I just put my TJ flares on and I came across some 30x9.5 BFG ATs that was a deal I could not pass up on tj 5hole rims.I am leaning toward an 8.8(disc)and HP dana30 w/44 ujoints both geared at 4.10 for my next upgade after a trans cooler . I hope this will give me a better base to build upon later(such as lockers and regearing fo possible bigger tires therefor eliminating a fear of breaking dana35 axles

[chrisfranklin]

(tire size, power, gearing)

Did kinda mention the other variables, JackHammer.

But, it would seem that running front/rear lockers could safeguard the D35 a little more, all else being equal.  Heck, with front and rear lockers you could probably successfully get away with running an axle "weaker" than the D35 (if there is such a thing   ); this, of course, provided that tire size, power, gearing were within reason.

Would be interesting to see, but wonder how many of those folks who break their D35s were running a locker in the Rear, only.  Probably quite a few.

[jackhammer]

I see what you are trying to say. Are you planning on stayting on 29"s? The way I feel is I will eventually go bigger then the 30"s I just picked up and I dont want to pay for lockers twice. So I think the axle swap will work for me to start. It is like a triple upgrade. rear disc,added strength, and 4.10 over 3.73.  But I will head to your theory when I do lock it up I will lock both at once. probebly detroit rear and selectable front.

[wrangler387]

^ i agree with you completely. I have 31" tires on my jeep now (came on there) and when these wear out i'm going to jump up to 33" tires. But definately have no intentions of keeping the D35.

[Jeffy]

I guess I see where you're trying to go but I don't think it will work.

There is one thing that will get you into trouble.  That's you.  A locker will get you deeper into trouble then open diffs.  Without any locker, you won't be breaking axle shafts.  With a locker, you are more prone.  Add larger tires and it's just a waiting game.  Now if keep both tires down on the front, having it open won't be a problem.  I don't think you'd start picking up the wheels unless you're on a trail that's 3 out of 5.  Now with one locker, you will probably end up trying harder then you would with both ends open.  This means you'll probably ride the throttle a lot more when stuck.  This is when you can really get into trouble.  All the hopping and high RPM.

Now if you have two lockers, you can still get into a senario like the one before.  Although the front locker might get you a bit further without getting you frustrated.  Still when climbing up a tall stairstep or getting one wheel in the air, you don't have that much extra traction from the front.  Most of the weight will still be on the rear axle.  Power will still be divided 50/50 to each axle but those fromt tires will be spinning and not hooking up.

So what am I saying?  If you want more strength, get more strength.  Thinking that two locker will save your D35 will give you a false sense of securiety that could leave you high and dry.  Or more realistically, cold and wet.

[chrisfranklin]

Would be interesting to see, but wonder how many of those folks who break their D35s were running a locker in the Rear, only.

Yeah, how many of those photos in your D35c FAQ write-up do you think were doing just the forementioned. Not going to put you on spot with your own experiences...  :wink: [/quote]