rear differential blown, what now?

[SRath]

Actually, Tippin Spotted Cow, I believe you are thinking of an ARB Air-Locker. There are also electric lockers and OX lockers (mechanically controlled with a cable). They, too, are true Lockers, but they function very differently from a Detroit Locker.



All of these function as an open differential until the driver engages them. Then they fully lock both wheels together like a spool using air, electricity, or a manual cable. There is no "in-between" or wheel speed differentiation at all. You will go straight, and nothing but straight. No cornering without tire scrub.



A Detroit Locker is not controlled by the driver. It delivers full torque to both wheels at all times. It will allow one wheel to coast faster than the other (so you can corner) but as soon as both wheels are going the same speed again(straight) it engages and drives both.



It works like a ratchet. If one wheel needs to go faster than the ratchet is turning, the ratchet will just click away and allow it to while still driving the slower wheel. As soon as the coasting wheel slows down to the same speed as the slower wheel, both are receiving equal torque again. In this way, it does offer an "in between". Locked like a spool when going straight, but it allows for different wheel speeds on corners.



Detroits are legendary for their strength and absolute reliability. When they were introduced in Mopar muscle cars, they were called "No-Spin" differentials. There are no air lines, wires, cables, clutches, etc. Just 100% of the engine torque to both wheels at all times. For that reason, they are not very "front axle friendly". They prefer to go in a straight line like any locker or spool and tend to fight the steering wheel when you turn tight.



On the rear, you will learn not to power through corners, or you will scrub and chirp your tires because you did not release the tension driving the outside wheel. And every now and then (for me it was maybe once every 5 or 6 months), just to see if you're paying attention, it might disengage or re-engage with such a "BANG!" that you will swear you just left chunks of steel strewn down the road behind you! Nothing ever breaks from that, though.



Supposedly, if you carry very heavy loads, it is capable of breaking axle shafts if you power too hard through a corner and don't allow it to disengage, I'm told. Something has to give, usually the inside tire which will then try to spin at the same speed as the outer wheel causing tire scrub, but I have heard of guys breaking axle shafts that way, too. But you won't break the Detroit. I never had anything break at all and I could go places in 2wd that my buddies couldn't in 4wd.



A very similar, though not as reputable, locker is the PowerTrax. Click here POWERTRAX BY RICHMOND VIDEO DEMOS to go to their website and watch the Dodge videos and see what a 2wd equipped with a rear locker can do that even a 4x4 with limited slips in both axles cannot do. A very cool demonstration!



These are all very different from "Limited Slip" or "Posi" differentials, which use various clutches, ramps, and other internal gizmos to divide the torque between the two wheels. They cannot give both wheels 100% of the torque like a locker or spool and some work far better than others. Many are prone to clutch pack wear. All will leave you helpless if one wheel is in the air or on a very slick surface. The PowerTrax demo I linked you to above demonstrates how worthless those can be in simple everyday situations. But they are OK (and better than nothing) for front axle use if you cannot afford the $1000 price tag of a selectable (ARB, Electrax, OX) locker for the front. They'll give you @ "3 1/2 wheel drive" when used in conjunction with a rear Detroit Locker, which can help keep you out of trouble in the first place.



My dream setup is a Detroit Locker in the rear and an ARB, Ox, or Electrax Locker in the front. What I will actually be settling for in my Dodge, at least for now, is a PowerTrax locker in the rear and a PowrLock limited slip in the front (mostly because: 1> I already have them and 2> because Detroit does not make a Locker for my 3. 54 gear ratio in my Dana 80 and 3> my best lottery ticket so far has only netted me $7).



Anyway, this is what I think I know about lockers! Hopefully it helps...

 

[tugboatphil]

SRath, you may not believe this, but I think I understood what you were saying. Why is this axle not used in more applications? Is it a lot more expensive? Was it ever an option for our trucks?

 

[SRath]

I should mention that the Detroit Locker is a complete, ultra-strong differential carrier that replaces your weaker factory open or limited slip carrier completely for all applications EXCEPT the GM Corporate 14-bolt (10 1/2 inch).



The 14-bolt is the ONE application where the factory carrier is retained and the Detroit Locker components are installed in it. That is because the 14-bolt carrier is very strong to begin with and it also makes it the cheapest and easiest rear axle installation for a Detroit Locker.



The PowerTrax has a less stellar reputation because it installs into the factory open carrier in ALL applications, just like the Detroit in the GM 14-bolt. That leaves the factory carrier case the weakest link, but keeps installation difficulty and expense to a minimum.



The PowerTrax components are much stronger than the factory carriers. So when you start adding modified engines, big tires, and locked traction, you will inevitably break some of the weaker factory carriers.



If, however, you have a big beefy unit like a Dana 80 (or 60 or 70) to begin with, there is little chance of breaking anything.



PowerTrax are often called "lunchbox lockers" and if you hear bad things about them from time to time, this is why. They themselves are plenty tough, but the carrier they get installed in may not be.

 

[SRath]

I don't know about trucks, but I'm pretty sure it was a Mopar factory option in some muscle cars a long time ago.



Axle manufacturers like Dana and Eaton would rather sell the car and truck makers (and you) their own limited slips and lockers as options.



In fact, Eaton recently bought Tractech, the company that makes Detroit Lockers and several other lockers and limited slips. So far, it has just meant an increase of $100 in the price. "If you can't beat 'em; buy 'em!"



Many folks would find the "aggressiveness" and occasional quirk and noise objectionable. The same lame thinking and catering to folks who want mushy, but seamless-shifting, automatics and car-like rides in pickups that brought about the demise of tried and true tough stuff like REAL Dana 60's and leaf springs up front and 205 t-cases, is what gets you limited slips that do more slip than anything else (mine is a good example). They won't even stack the factory clutch packs to be halfway decent in the factory limited slips for fear of offending someone with any type of "harshness".



GM sold thousands of pickups with factory Gov-Loc lockers. They were a fairly effective locker that used flyweights to detect and stop wheel spin by locking the differential.



If you do much offroading or find yourself in low-traction situations frequently, and you ever try a Detroit Locker, you will never want to be without one. A selectable locker might make more sense for guys who tow and load their trucks real heavy most of the time and stay primarily on-road. But a Detroit can keep you out of trouble as opposed to trying to get yourself out of trouble after you lock your differential in the same way that it is better to enter a situation in 4wd than to wait until you're stuck to engage your 4wd.



Current cost for a Detroit Locker ranges from @$400 for a GM 14-bolt to $500 or $600 for most other applications (best guess). About half the price of a selectable locker.



Edit: I took the time to do a little research and I was wrong about it coming in Mopar muscle cars. It came in Ford muscle cars. Sorry. I'm a '69 Z/28 guy... here's what some literature says:



"The legendary Detroit Locker began the revolution in performance differentials and still leads the industry today as an Eaton brand. The Detroit Locker is the most durable and dependable locking differential available.



The Detroit Locker maximizes traction by delivering 100% of the torque to both drive wheels. It is engineered to keep both wheels in a constant drive mode, and has the ability to automatically allow wheel speed differentiation when required. Applications are also available for C-Clip style axles.



No other performance differential has the reputation for delivering traction in mud, snow, rocks and on the track. The choice of professional racers and off-road enthusiasts around the world! The durability of the Detroit Locker is unmatched!"

 

[JGrefenstette]

i found a Detroit Locker for out D70's 3. 54 gear. its $599... .

 

[SRath]

I completely forgot until driving all night: Throughout the '70's and '80's (when chevy still made a real truck) our military bought thousands of Chevy 1-ton, single-rear-wheel, 4x4 pickups. Most all of them were specified and ordered with Detroit Lockers in the rear axle. That says alot, given that GM offered it's GovLoc as a regular option...



Too bad those trucks came mostly with the junk 6. 2 diesel instead of a Cummins!

 

[SRath]

"i found a Detroit Locker for out D70's 3. 54 gear. its $599... . "



My guess was pretty close on the price, then.



That Dana 70 Detroit Locker, when ordered for a Dana 70HD, instead of a regular Dana 70, can supposedly be made to work in a Dana 80 by simply drilling and retapping the ringgear bolt holes to the larger Dana 80 size.



If I did not already have a PowerTrax to try, that is what I would do. And if I don't like the PowerTrax, that is what I will do.



Maybe I should do it anyway, since I do love the detroit... ? I could recoup some of the $600 by selling both the PowerTrax and the factory limited slip unit currently in my axle...



Detroit lockers are available for the Dana 80, but only for 4. 10 and higher (numerically) gear ratios. which makes no danged sense since many or most Dana 80-equipped trucks (Ford and Dodge) are also diesels and have lower (numerically) gear ratios like 3. 54 and 3. 73. Someone in marketing is asleep at the wheel I think...

 

[Tippin Spotted Cow]

I work with a guy who tells me about how his '95 2500 bangs like that once in a while. Is there any way to tell by jacking it up and spinning the tires by hand, whether hes got a detroit or just a regular limited slip?

 

[SRath]

Not that I know of, Tippin, but maybe someone else knows an easy way? I would take the cover off and look. Even then, you would need to know what that particular axle's version looked like.



Does his '95 have the D70 or the D80? What gear ratio?



I ask because if it is a D80 with 3. 54 or 3. 73 gears, it would have to be one of the home-modified D70 Detroits.



I just emailed eaton to ask why they don't make one for D80's with 3. 54 or 3. 73 ratios. Told them about the current conversions of D70HD units being done. Maybe they will even answer...

 

[JGrefenstette]

why is it that some axles, when suspended, if you spin one wheel the other goes in the oposite direction???

 

[Tippin Spotted Cow]

Only in park, or in gear with the motor off on a manual. Thats the way a diff works. When the driveshaft turns the gears in there, it turns the wheels forward, ideally at the same speed when going straight. They way the gears are set up, the wheels can turn at different speeds for cornering. The problem with this is that means on an open diff, theres nothing to say one wheel cant turn and the other one sit still. Heres a real strange trick too, if you hit the gas and only one wheel spins, that means that particular wheel is moving at twice what your speedo is reading. If you want them both to spin the same way with the motor off and the rear jacked off the ground, you need to have the transmission or tc in neutral. If the driveshaft is allowed to spin, you can get both wheels going the same direction.

 

[tugboatphil]

So the Detroit Locker is an internal replacement unit for the ring and pinion set of a LS differential? The stub axles would go into it just like they do now?

I went to that Eaton website and couldn't find anything. It must have been too modern for my 1983 Tandy TRS-80 computer.

 

[SRath]

That Tandy is real collector's item now, isn't it ? I'll bet you still have Pong installed on it? That was cool stuff...



Yes, for most all applications it will completely replace your factory carrier. You will reuse your ring gear and won't need to touch your pinion. You should be able to just have your gear lash reset by shimming the new carrier since replacing just the carrier should not affect your pinion depth. Your stock axle shafts will remain the same, too.



But it is extremely important to have that gear lash set properly and to have the tooth contact pattern checked!



Then just seal 'er up, add good gear lube, and go! No special friction modifers or additives needed.



I agree about eaton treating their new aquisition like a redheaded stepchild. Their website leaves much to be desired, but if you go to some of the larger gear specialist companies like Randy's Ring and Pinion, you will find much more helpful info about the Detroit and many others.



Just do a web search for "Detroit Locker" and avoid the eaton hit. Ebay has many auctions for them, new and used, and the sellers there (stores and private individuals) often have some advertising and fitment info on them, too.



A local drivetrain specialist store in Cedar Rapids (Sadler Powertrain) actually sells them on Ebay, too, and has good pricing. They have a different seller name there though and I can't think of it right now.