Four wheel drive is great. I really like how it makes my Jeep transform from 1 wheel drive to 2 wheel drive. I am interested however in increase my number of driven wheels to 3 or 4. I mainly bought the Jeep to be my winter car but going up hills with the front left and rear right tires spinning isn't super effective. So I've started looking at lockers and LSDs.
Primarily this is a road car driven with all seasons or M+S tires in the stock size. A main goal would be to keep road manners. This pretty well rules out a rear lunchbox. This had me thinking TrueTrac. The issue then becomes that I have a 27 spline 8.25 diff and from what I can find, the TrueTrac is only available for the 29 spline 8.25 diff. So for a TrueTrac I'd have to swap to a later 29 spline rear which would be money. The only other rear diff option that makes sense is a TracLok. Just like a TrueTrac I'd still have to have my gears set up which would add to the cost a good bit(I'm cheap). The third option is a front lunchbox locker. It's a cheaper piece of kit and wouldn't require gear setup. It would only lock up in 4wd which would keep the road manners good. The downside is that I've read they push really bad which makes sense as it's pretty much a front spool when you're in 4wd. I've also read that lunchbox's are a bit rough with manual transmissions.
I'm pretty much set that a rear TracLok or a front Lunchbox would be the most cost effective option but I'm willing to hear other people's input or other options that I haven't thought of.
Honestly, your best bet is going to be a rear LSD of whichever flavor you prefer. It will help all the time, not just in 4wd, and it will lessen the need for 4wd as well. Even the die hard off-roaders that run front air lockers will only engage it when absolutely required; it goofs with the steering too much.
Yup, rear LSD will transform the Jeep. If you buy a used axle, budget a rebuild of the LSD. They really only last about 100K miles
You didn't specify what year your xj is, or more to the point whether it has the axle disconnect or not in the front. If you have a later one without the disconnect then any front locker is going to adversely affect handling all the time, 2wd or 4wd, unless you install lockout hubs. If you have the axle disconnect and want to deal with that kind of understeer in 4wd you might as well weld the spider gears or put a spool in the front because pretty much everything is going to work the same and you might as well save some money and have the handling be consistent.
No front lockers in snow, certainly not auto lockers. If it's locked and you're in 4wd, you pretty much can't turn. A selectable locker that you can leave open in the snow is fine, but if you're not off-roading, it's not much use either.
My ZJ has a trac-lok in the rear and it's pretty darn competent in the snow in 2wd. I added a true-trac to the front and in 4wd, it's darn near unstoppable in snow (with snow tires on). A few minutes ago coming into the parking lot at work I drove it through about 10 inches of heavy, wet snow in 2wd with no issues and when I got into the deep spot (somewhere in the 15 inch ballpark I think), it moved along just fine in 4wd.
The true-trac up front is pretty invisible in 2wd. In 4wd it's well mannered, but if you get on the power a bit and get some wheelspin you'll feel a tug at the steering here and there depending on how uneven the traction is up front.
What about swapping a Ford 8.8 rear out of an Exploder? See them all the time for around $100 and they seem to be pretty widely available with LSDs, plus gets you rear disk brakes as well. Gearing may be the only issue, if your XJ is a 5 speed it should have 3.08 final drive gearing and I'm not sure the Exploders had gearing available that tall. I do know they had 3.55 and 4.10 options though, which means you could grab a D30 front from either an auto or 4 cylinder XJ to match those ratios. If you can fab and weld spring perches, I bet this could be done cheaper than even a lunchbox locker if bought well. Or just weld the diff.
That being said, I never once got my XJ stuck in snow, including driving it out of the 1/4 mile gravel driveway at my old place in over 30" of snow, and that was on E36 M3ty all season car tires and before I lifted it.
My Jeep is an early 96, 5 speed, 4.0 with 3.07 gears and a Command Trac (NP231). So it sounds like proper LSD in the rear is the correct option. I can do that. I'll look into getting a TracLok for the 27 spline 8.25 diff.
Unless there exists a TrueTrac for my diff which I would jump on in a heartbeat.
If I wanted to go to a 29 Spline and TrueTrac, can I just grab 29 spline axles and the truetrac carrier? Or is there a lot more involved?
I don't know for sure with the 8.25, but I'd be pretty surprised if that wouldn't work. A true-trac and the 29 spline axles should all fit together and work in your current housing.
But if you can get a trac-lok and new clutches cheaply, that's not a bad option either (and the trac-lok doesn't go open on decel like the true-trac, so I somewhat prefer it in the rear for predictability).
Plus, the trac-lok might be better on patchy ice, as it has some preload (only the D30 and a couple other versions of the true-trac do, most aren't preloaded so one tire on ice or in the air means you're not moving much, especially if you don't drag the brakes).
TrueTrac is a torsen, correct? With no friction surface they act like an open diff, right? If that's true, I'd opt for a clutch type LSD. The preload can help in low/no traction situations.
TrueTrac is a torsen, correct? With no friction surface they act like an open diff, right? If that's true, I'd opt for a clutch type LSD. The preload can help in low/no traction situations.
True-trac is a helical "torsen" style, yes. The reason they work well in the front is that they don't change the steering much. A clutch pack will make the truck more prone to understeer. You can drag the brakes slightly to help the diff if you get to that scenario.
On the XJ I'm building for a friend, he chose to go with a Trac-lok in the rear and a True-trac in the front for maximum winter ability with the minimum of side effects.
Yes, the true-trac is a torsen. The D30 application (for the front) does have some preload, so it does slightly increase the steering return to center force even in 2wd. But that's also good for traction on patchy ice, etc. (and it's not nearly as annoying or understeer inducing as a clutch type in the front would be). I think the 8.25 application is one without preload, so it'll act open if one side has no traction at all.
Agree with the rear lsd
But wouldn't 4 dedicated winter tires be cheaper and easier ?
My KJ had TracLoc and with all seasons it wasn't that great, even in 4wd. Tires would still spin easily. A set of winter tires cured the beast.
In reply to iceracer :
Snow tires and LSD(s) is even better.
Woops. I was thinking of s clutch LSD for the rear only.
What about an air or E locker on the rear?
I have studded snow tires. They made a huge difference over my ATs that were on it at first.
