True Trac vs Open Diff

KYC

Adventurer
#1
Read many threads on lockers vs lsd. So this isn't a question regarding what is better.

I'm wondering if there is any reason to choose an open diff vs installing a true trac?

The true trac is the only option I am considering. I'm not considering any other "LSD" units.

Does a true trac suffer from "randomly engaging" on tight slippery turns? or are these instances over-stated?

My rig sees highway and light off road. I've never been stuck due to traction issues, but would like the option get on some less maintained roads.

I do not rock crawl at all. I'm worried about the occasional stream crossing, mud, wet sand and maybe some slick rocks.

This would be installed on a 2wd van.

So simply put, I want to know is there are any negatives with the true trac vs open diff. Is true trac better than an open diff 100% of the time in a 2wd RWD vehicle?
 
#2
Any halfway decent or better LSD will absolutely be better than an open diff. And the true-trac is a pretty good LSD. I've got one in the front of my Jeep. The D30 application for it has some preload (a few versions of the true-trac do, most don't) so you can feel it a little in the steering but it's otherwise pretty transparent in 2wd or 4wd. In the rear, I'd say it'll definitely help. Engagement is smooth, no jerks or anything that I've found. I've never gotten mine to bind or chatter in a tight turn (that would be more noticeable up front and the preloaded unit would be more prone to it).
 

KYC

Adventurer
#3
Any halfway decent or better LSD will absolutely be better than an open diff. And the true-trac is a pretty good LSD. I've got one in the front of my Jeep. The D30 application for it has some preload (a few versions of the true-trac do, most don't) so you can feel it a little in the steering but it's otherwise pretty transparent in 2wd or 4wd. In the rear, I'd say it'll definitely help. Engagement is smooth, no jerks or anything that I've found. I've never gotten mine to bind or chatter in a tight turn (that would be more noticeable up front and the preloaded unit would be more prone to it).
would you say that the true trac would perform better on the highway and city driving than an open diff?
 

Buliwyf

Viking with a Hammer
#4
Better in city, no difference on the highway.

Do a few donuts in the mud or snow when you get it in. Just to get a feel for it. Should be very seamless.
 
#5
In highway or city driving, you won't be able to tell any difference at all. The TrueTrac is actually just a helical gear differential, but the side gears are designed to cause some level of binding with the case as torque is passed through it. The more torque, the more binding, which usually encourages both wheels to spin rather than just one on all but the slickest of surfaces. In a rear axle, you can "fool" it into binding more by applying the parking brake gradually if you are stuck with one tire having no traction and the other having some.

I'm running one in the front of my Jeep as well, and will put one in the rear of the Comanche if I ever get into it. There is NO soother, more invisible option, and I find the TrueTrac to be an outstanding performer in all but absolute rock crawling. The best part is that there are no clutches to wear, and no special fluid to run.

Since you asked, there is ONE condition where an open diff might be considered by some to be preferred over a traction diff of any kind... That is on snowy or icy roads, if you have zero experience.

With an open diff, you will likely only spin only one tire, while the other remains in static contact with the road. You may not go anywhere, but the tire that is not spinning keeps the back of the vehicle stable. With any sort of traction diff, both tires will spin, and the rear of the vehicle may "fishtail" some until you get out of the throttle and stop spinning the tires. Spinning both tires can happen with an open diff too, but it isn't nearly as likely. IMO, this is not a big concern, and any fishtailing is easily corrected by lifting off the throttle.

IMO, you won't be going wrong with a Truetrac for mild offroading.

The other choice that I think would work even better for you is a factory G80 code "locking diff", which is known as a "Gov Lock". It's a limited slip, but if one wheel spins too much faster than the other, it will lock fully, and you will spin both tires. They don't hold up well to heavy right foot abuse with larger tires, but for mild use, with a driver who understands not to just flat out floor it from a stop if stuck, they will last forever. A G80 will get you out of far worse jams than any limited slip, since it in effect becomes a locker if you are spinning only one tire.

There are usually rebuilt units on ebay for less than the cost of a TrueTrac, or any junkyard can probably find you a complete axle to swap in, which would likely be cheaper than doing gears and diff in your current axle. If you go that route, just pop the diff cover off and make sure it's all there, and no pieces are stuck to the magnet before you leave the yard, or have them offer to replace it if you find it's broken when you get home. PM me for further details if this sounds like an option you might like...

FWIW, I've run three gov locks in three different trucks. They all work great, and I've had zero issues. As with the TrueTrac, you cannot tell they are there in normal driving.
Good Luck
 
#6
The only negative is price vs an open diff.

I'll echo everyone else's comments. Invisible when you don't want it, there when you need it.

I have them in both axles of my Dana 30 swapped Explorer- 8.8 rear end. Considering one for the rear of my Expedition
 

KYC

Adventurer
#7
Thanks for the replies everyone.

I'm planning to do a re-gear and would like some kind of traction while they are in there.
 
#8
If you're re-gearing to a ratio that was offered from the factory, I still suggest your best bang for the buck is a Junkyard axle.
I had assumed for no reason you were talking about a GM van, but I see you actually have an E150...

I'm sure Ford offered an LSD as optional in the vans, so if they also offered the ratio you want stock, it's the cheaper way to go than buying and installing into your axle...

EDIT: Just checked car-part.com. Looks like axle ratios varied by year, with some years offering 3.55/3.73/4.11. There's also a heavier E150 axle listed, with a 9.75" ring gear instead of the 8.8". Doesn't list the LSD separately, but I would still be it was an option, you just need to find a tagged axle...

I'll be quiet now... :)
 
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#10
Definitely a good choice and probably the best choice for your purposes. I just installed one in my expo camper build rear end and will be doing the same in the front eventually. The only drawback is if you lift a drive tire off the ground, they don't work but applying the brakes a bit fixes that so it's not a big deal for slow speed stuff where you might lift a tire.
 
#11
The only time I notice the true trac in my Dodge 2500 (factory installed lsd) is on a tight off camber turn at low speed. I can hear the inside tire scrubbing. My wife doesn’t notice it at all...
 
#12
I would be interested to learn if the trutrac might possibly be a disadvantage on icy paved highway where tire traction could be momentarily lost when power is transferred to other wheel.
 

Comanche Scott

Expedition Leader
#13
I would be interested to learn if the trutrac might possibly be a disadvantage on icy paved highway where tire traction could be momentarily lost when power is transferred to other wheel.
Look at the applications this differential is made for, and you'll see it is doubtful, unless the vehicle is driven recklessly.
http://www.eaton.com/Eaton/ProductsServices/Vehicle/markets/index.htm

Most likely a competent driver following the Basic Speed Law in that condition would never know when it is biasing the torque. The vehicle would just feel well controlled.

So it's not a panecea to race from the Bay Area to Heavenly after work for a long weekend of skiing, but when driven correctly will definitely get you there in a more controlled manner. :)
 
#14
A limited slip in the rear will make the vehicle more capable on snow, ice, etc. But it can make it a little harder to drive until you're used to it, as you'll be more likely to push the tail out in a turn with power rather than just spinning the inside wheel. But if traction is fairly even side to side and you spin them while going straight, you'll tend to go straighter than with an open diff (rear end won't have as much desire to walk sideways).

Given a little time to get the feel for it, I don't see a downside to a limited slip in snow / ice. I will say the front true-trac in my Jeep can yank on the steering a bit as it tosses power around if you get heavy-footed with the throttle on unevenly slippery surfaces in 4wd. Under lighter throttle, with more consistent traction or in the rear, it'll be much less noticeable.
 

Factoid

Three criminal heroes
#15
I have a 1988 LR Defender 90 that had a 2.5TD with an open 3.54 front and rear. I recently installed an LS3/6L80 from a 2012 Camaro and a truetrac with the stock ratio in the rear and no change to the front. That takes my 90” wheel base vehicle from about 90hp to 400hp. The truetrac has been flawless and it's been in mud and on ice with zero issues, clunky locking events, or noticeable wheel biasing. I'm very impressed and plan on installing one in the front diff as soon as funds allow. Highly recommended.
 
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