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Yo. Me again. Continuing to gather gracious answers from my elders while I slowly resuscitate my 79 wag. You guys have been very helpful. Anyway, was wondering about opinions on lockers/ lsd diff setups that would be amenable with the old bw 1339. I want to keep the case a full time unit as it was designed. I would also like to install traction devices when I regear in the distant future. I have heard tell that this case may not like a locker in the front. How about a detroit tru trac front and back? Of tru trac front, locker back? Thanks.

I have seen AMC comments to not use traction devices on QT equipped Jeeps. But when I thought about it more, why not? Since then I helped a friend put a lunch box locker in his rear axle. He is running a part time kit in the QT. It works fine. If I were to want axle traction device(s) on a stock QT, I would go with limited slip front and/or back. I don't think you can go wrong with that. There is a certain amount of shock load and driveline binding to consider with lockers. That could be a problem for the QT brake cone splines.

Thank you, Mr. Moderator. I do want to run it stock, assuming it's in good working order. It's not yet on the road, bur 95,000 miles on the odometer hopefully speaks to a t case that has plenty of life left in it. Unless somebody put the wrong fluid in it...

The rear axle should be fine. But do not put an automatic locker in the front.

Even certain limited slips up front with a full time setup will make the steering less than ideal. And before you ask, yes, there are FWD and AWD vehicles with front limited slips, but they are typically only 1 way limited slips, not two way, which is all thats really available for our axles. A one way will only tighten up under acceleration. Under low throttle or coasting, it acts like a normal differential. A 2-way will tighten up in forwards or reverse.

Thank you gents for this thread - exactly the info I was looking for!
Stuka, your explanation and comment has finally made it clear to me why I should not put an automatic LSD in the front with a stock QT T.case
Thank you all very much.

Selectable locker is always an option as well. A bit more expensive but I think they are worth it.

Excuse me, Mongo no understand. Why is an automatic LSD no Bueno for a q-trac?

In the front, I mean.

Jeep only offered the open differentials with the Borg-Warner Quadratrac. Jeeps from the era without the QT came with the optional TracLock limited slip differential (LSD) for the rear axle only. The TracLock is effective but not aggressive, and does not seem to affect handling adversely when installed in the rear axle. I kinda think the TracLock would be ok in the rear axle of a QT Jeep but it could have an effect on handling.

A locker in the rear axle can cause handling problems, esp. when there is ice. Possible the QT would experience problems in patch ice on pavement with a rear LSD? Don't know. Certainly a LSD in the front axle or a locker in either axle would change the steering response and handling of the QT Jeep depending on the conditions. This is true for part-time Jeeps too.

I run a lunchbox locker in the rear with my 1339 QT. No problems. Goes everywhere. Only thing with the one I have, be prepared for the 'click click click' sound when turning. Even the slightest turns ... she clicks in order to slip.

Yeah, sometimes I think, " hang it! I'll just lift the thing, throw on some tires and a lunch box, and go!" But 3.54 gears, 35s, and the hills in western Oregon may not be a great combo, I fear...

Yogi wrote: ↑Tue Jul 13, 2021 9:13 pm Yeah, sometimes I think, " hang it! I'll just lift the thing, throw on some tires and a lunch box, and go!" But 3.54 gears, 35s, and the hills in western Oregon may not be a great combo, I fear...

Been there. They aren't.

Running 32x11.50-15's on mine. Click-click locker in the rear no problem. Went through 16" of snow in Edrive like it wasnt even there.

How do you like the click-click locker on dry pavement? Lotta people say it's no big deal at all, others seem to hate it.

You have to be willing to accept the noise on turning. I had the rear diff cover off and inspected the unit for any problems and I'm told by the manufacturer that it's doing what it's supposed to do. A healthy unit WILL click on dry surfaces (no slippage under tires) when you turn. Not gradual turns, but slower more angular departures.

Ok, time to resurrect this tread, if I may. *ahem*
Can anybody explain clearly to this newbie why front and rear lockers, particularly the fronts, are especially hard on the bw 1339? I understand that a rear is ok, but considering that many other full time transfer cases seem to handle f/r lockers ok, why is the front such a no-no for the QT? I've tried to read up on this one, but I still don't quite get it.

I should have specified; selectable up front only.

Been doing some more reading through old treads from ifsja.org since my last post. I suppose my main question is, when the t-case is locked in e-drive, in what way can the clutch cone mechanism be affected by heavy use of lockers? I would think it would only put extra stress on the chain, since the limited slip is locked up and the cones aren't doing anything. Yet I've heard tell of leaving dual ARBs locked up for an extended period while in e-drive and frying the cone. How can this happen?

I can see the front output shaft, brake cone and bevel gear in the sprocket being damaged, I would think the rear output shaft, brake cone and bevel gear may remain unscathed due to the fact that the rear shaft is mechanically locked to the sprocket by the collar. This would transfer any drive shaft stresses directly to the sprocket itself. The front shaft is only locked due the inability of the rear output shafts bevel gear to rotate, of course the entire assembly transfers torque between its components any time torque is applied to any part of it. So which part would fail first is a bit of a crap shoot. I cant see how the brake cones would fry in the scenario mentioned, but a damaged sprocket ? yes I can see that. I can envision the splines stripping out of the front brake cone and bevel gear. Thing is no one really knows IF the drive sprocket brake cones are serviceable or not without dropping a drive shaft and performing a Torque Bias Test, simply driving the beast is not an indicator of the transfer case operating as designed. We should remember this unit was never designed to still be in service 40 years after the last time it was manufactured new. It is tough, but just how much is too much? Unfortunately that question too often gets answered way down the trail with fading sunlight....

A selectable locker up front is much less of an issue than an automatic or limited slip, as its up to the driver to enable it. E-Drive will protect the clutch cones. I think my concern would be the QT chain, the e-drive coupler. The QT is kind of unique in that both front and rear outputs run off the chain, and that the differential receives all the engines torque, including low range where that is multiplied. I have heard of people stripping the e-drive collar. Its actually pretty common for the MM PT kits as they have poor engagement. You can see all sorts of failure photos here: https://jubileejeeps.org/quadratrac/gallery.htm

With more modern cases, like the NP229, the chain only drives the front axle. And there isn't a mechanical differential, it uses a viscous coupling in full time mode, and locks it up in part time mode. In full time mode, the rear axle never has the ability to have any slip. It has a mechanical connection to the main shaft in the t-case. The front axle receives power through the viscous coupler, which doesn't have a mechanical connection to the main shaft. The coupler is filled with a fluid with a series of metal discs that transfers power to the front if the rear spins faster than the current speed of the front. If both front and rear outputs are moving at the same speed, the front axle is actually not receiving any power.

So for regular driving, a selectable front locker will not impact the QT at all. And in most cases, a front locker is rarely needed. But if you do have a locked, just take things easy, and chances are you will be fine. Check for shift collar wear if you happen to rebuild the t-case ever.