My experience with "lunchbox" style auto-locking differentials.

[broncc]

Hello all. Before I bought my locker, I had heard many people complain about them but not provide a satisfactory explanation why. I figured I should type up a short summary of my feelings about these traction devices to help you better decide if it's right for you.

I have a OHV 4.0L and M5 swapped Bronco II. In the back I installed an 31 spline 8.8 with 31s and 4.10 regear. When I did this I installed a Lock-Rite brand differential locker. That was nearly a year ago and over 15,000 miles. This is my daily driver after all

To start; traction is GOOD. Under power the car has a true locked differential. I would argue closing the differential is the second largest traction upgrade you can make after better tires. This type of locker should be durable in RBV applications with less than a v8. I have seen lots of complaints of these breaking, but I feel like if they couldn't stand up to the platform, I would have broken it. I pulled off the differential cover to change fluids recently and the locker isn't showing any wear or damage. Winter driving is much easier and didn't exhibit any of the scary handling characteristics others have reported. It gets much more rowdy when you are doing stunt driving, but is perfectly controllable with normal driving.

Unfortunately, there are a lot of bad things I have to say. This type of locker does not play well with manual transmissions. The nature of how they lock greatly increased drivetrain slack. Clutching too quick can cause the car to lurch forward. Idling along in traffic can hit a resonance where the car can buck forward and back. When I turn sharply, I have to be clutched in or inputting enough throttle to lock the differential completely. Intermediate throttle causes the differential to lock and unlock presumably as the driveshaft is tossed around. (This is embarrassing in the grocery store parking lot!) The car is true one-wheel-drive until its true two-wheel-drive. When you tip into the throttle, the car will pull to one side until the other catches up and locks. This makes highway lane keeping harder, but may affect the Ranger and Explorer wheelbase less. Sometimes on a flat road the differential will attempt to lock on the "tips" teeth. When the locker teeth slip into mesh, it emits a scary popping noise like you just broke a clip or an axle. I pulled over the first time this happened.

The locking action is abusive on the drivetrain and suspension. Offroad, the drivetrain can "wind up" and spring a wheel forward enough to unlock it. Since throttle position remains the same, the whole momentum from piston to other wheel kick the no-longer slipping wheel right back to speed. I have had to retorque my axle u-bolts several times. My transmission mount rubber completely separated from the metal below. The worst damage is taken in the transmission. All thrust surfaces are hammered with each lock and unlock. The junkyard transmission bearings all could do with replacing now. The most vulnerable part of an M5 transmission is the thrust bushings on the reverse auxiliary shaft. I had to reverse out of where I got stuck a few times and the drivetrain shock cracked the thrust bushings. These are no longer available from Ford and don't seem to be reproduced aftermarket. The only place I have been able to source them is a small few NOS listings on eBay and other used transmissions. (for reference they're E8TZ-7N037-A and E8TZ-7N037-C)

Second rebuild update; all the bearing bores are worn out. The most damage comes from the input shaft bearing and the tail housing output shaft bearing. The aluminum center carrier bowed out from shock and seems to have taken preload out of the bearings. I found a steel carrier (97 3.0 4x4 I think) and this will hold me over until I source a new 4.0 case and LSD.

TL DR: Auto differential lockers are the best value-to-traction you can buy. They are not for daily driving or use with manual transmissions.

 

[DRanger024]

You nailed it. I havent had any transmission issues outside of wearing out the rear bearing retainer but everything else is dead on. I feel you eventually learn to drive with it though and I enjoy watching people freak out when the locker loads and unloads in a parking lot. Roundabouts can suck.

 

[broncc]

I'll have to pay close attention to those bearing retainers next time I have it apart. Its good to have more understanding of this!

 

[19Walt93]

I don't like those things. One of my techs put one in his 97 2wd Ranger and it sounded like it was grinding itself to death when he turned corners in the driveway. It's just not hard enough to swap in a traction lok to make it worth putting up with crash-bang-clunk on every turn.

 

[Shran]

If you only have one in the rear, that's why you haven't found out about how fun they are with the hubs locked in adverse weather conditions

I've had a Lock-rite in the front of my crawler for 10+ years. I'm super happy with it. It stays locked and I have not ever heard it ratchet (be that good or bad) but that may be somewhat due to the front axle location. I've wheeled it pretty hard and have broken a bunch of Warn premium hubs and one 30 spline RCV outer axle shaft but never the locker. I do have a manual transmission but it is a NP-435, significantly more stout than a M5OD... I have yet to hurt it and am not worried about that at all.

Driving on dry pavement with the hubs locked in 2wd or around town in the snow/ice in 4wd is horrible. It will pull you all over the road or in directions you don't intend to go. I have to be really careful in slick conditions and it's difficult to steer on dry pavement in 2wd with the hubs locked.

FWIW the Lock-rite, Aussie, Spartan, Grizzly & Detroit all basically function the same way... the latter two are a full carrier replacement.

 

[lowspeedpursuit]

Driving on dry pavement with the hubs locked in 2wd or around town in the snow/ice in 4wd is horrible.

I've always wondered about this. It's not supposed to do that, it's supposed to ratchet smoothly and not lock or bind at all in 2wd. The front lunchbox in my jeep never binds in 2wd. But the one in my TTB always binds on a tight-enough turn with the hubs locked.

I guess there's "enough" drag somewhere in the axle assembly, but I question if it's user error in the setup somewhere, or just an inherent quality of the TTB.

 

[Shran]

I've always wondered about this. It's not supposed to do that, it's supposed to ratchet smoothly and not lock or bind at all in 2wd. The front lunchbox in my jeep never binds in 2wd. But the one in my TTB always binds on a tight-enough turn with the hubs locked.

I guess there's "enough" drag somewhere in the axle assembly, but I question if it's user error in the setup somewhere, or just an inherent quality of the TTB.

I've had people comment that it should be ratcheting but it doesn't. I know what that sounds like & feels like... I also know what driving a vehicle with a spool or welded diff is like, and it's exactly like that, it never unlocks. For my wheeling purposes it's not a problem at all.

I kinda wonder if it is just too tight or something. I don't recall there being any shims, it was basically just the four big pieces and some springs & pins.

 

[lowspeedpursuit]

Honestly, since I trust myself to have done the install right, and I have manual hubs, I've put in exactly zero troubleshooting on it. If I lived somewhere with, say, heavy snow, and I wanted to leave the hubs locked regularly, I'd probably care more.

It's come up in other topics, but the Aussie lunchbox specs thinner side gear thrust washers than stock, which they sell separately. Googling it now, I'm seeing multiple people with D44 TTBs who I guess read the directions, but didn't know about the thinner washers. Stockers were obviously too tight, so they're just running without thrust washers entirely. It's possible that's the move, but the D35 TTB pumpkin is such a pain in the dick to drop, I probably won't change it until I have another reason to be in there.

I guess the c-clip eliminator could also be a source of tighness, since that spring constantly pushes in towards the diff?

 

[Shran]

Mine is in a 78/79 Dana 44 solid axle. It's been in there so long that I don't remember what I did with thrust washers... I bet it just has the stock ones or nothing. I just don't care enough to pull it apart, it's not super hard but I have to remove the ring gear in order to get the lock-rite out.

 

[bobbywalter]

if you need traction because your unloading wheels you need a locker.... or some sort of traction control system.

best is a selectable unit. better then anything open or locked.



there are trade offs for maximum traction when using low dollar cost effective stuff.

i have several.....and have had many over the years. real detroits are best as far as life cycle. with these low dollar options the carrier takes an ass whooping with a drop in. so you are wearing it out over the long haul.

it is a trade off. for 18 dollars i have a mini spool in the 9 and 280 dollars i have a spartan in the d44 ....when you do that you have actual traction.


and there are alot of downsides to full time traction.

this is often why my first suggestion is a winch unless you are willing to live with a locked diff. they cost about the same and a winch ha alot of potential.

i live with the issues.....so really....there there are no issues because i understand what they are and why i have it. .

traction loks are for pavement. i have destroyed too many differentials trying to get by with those turds. great for a mustang....not for a truck. a torsen... or a tru trac otoh.....not as fragile and not for a true wheeler...but a do all truck.

until i can afford a selectable....i will deal with poppy mc bang bang.

and if you dont like poppy mc bang bang...dont get a autolocker.

 

[Curious Hound]

Wow! Reading all this brings on such a negative feeling. I have Aussie lockers in both of my diffs and I love them maybe I just learned a better technique of driving with a lunchbox locker. Mine ratchets fine around corners. If yours does not release and ratchet around corners (with no power applied) then it probably isn't set up properly. My Aussies do everything I want them to do on and off road. Maybe it depends on which brand you have.

 

[bobbywalter]

well....sometimes there is no way to set one up perfectly because of carrier tolerances ect.

you end up needing a different carrier/axle.... at that point rebuilding the diff brings different options.

i run stock available gears specifically so i have low dollar axle swap options. you cant rebuild a trak loc for cheaper then i just swing in a jy rear 60...or 8.8. no such thing as a 9 inch around here....but i have spare carriers.

that is why you check the tolerance.

i like this thread. good work Broncc bringing it up.

the one in my rear 60 is on the loose side and pops more then i would like but works perfectly. the one in the 9 couldnt get dialed with the carriers i had as the holes were egged a bit and they side gears were tight...

so just living with the mini spool for now.

there is added maintenance with these to be certain... even drag racing running a spool eats up mounts and breaks stuff from actually getting traction..

you always have to nut and bolt any rig that gets used hard.

 

[DRanger024]

I don’t regret my Aussie one bit. It made the truck WAY more fun to drive. You really just have to learn to drive them.

 

[00t444e]

I have daily driven for years with an auto locker in the rear of manual and auto vehicles, I wouldn't have it any other way. Every vehicle I own gets an auto locker in the rear, I wouldn't put a selectable locker in the rear if it was free. Many of the issues you described sounds like driver error or you have something else wrong. I have no problems driving around in parking lots, turning, going around corners, or backing trailers with them. I use 85w140 gear oil and you can't even hear them unless you are actually listening with the windows down then it's just a faint click when you go around a turn. They haven't increased wear on any of my transmissions or drivelines either.