Questions about TruTracs and Dana 35s and Axle Shafts

Breto31

Breto31

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2005, 4.0, 3.73 gears, 6-speed, Dana 35 rear…. I’ve been researching my next project a little bit, and I figured I would get some opinions from you guys….. I am wanting to get some sort of locking diff or a LSD for the rear. I have read a lot of good things about the Eaton TruTracs, and I am kind of leaning towards that based on price, and reviews.

Most of my driving is on road, with a wheeling trip every few months. Typically no rock crawling, but more so deep ruts/washouts, hills, and southeastern mud.

WHAT I KNOW:
  • I’m not ready for a regear.
  • I am not swapping axles.
  • I would like to maintain good on-road performance, while gaining traction off-road (I’m tired of hammering the throttle off-road because of my open diffs).
  • I do not want to break the bank for a selectable locker.
  • I am only planning on locking the rear.
QUESTIONS:
  • Using a LSD, should I upgrade to chromoly shafts? I know the answer will be “yes”, so does that shaft upgrade require any further upgrades to make them work, or is a straight up plug-and-play (pull the old shafts out, put the new ones in)?

  • Some of the videos I’ve watched appear to show the TruTrac not engaging as the other wheel loses traction - or it appears that the Vehicle still has open diffs as it loses traction. This is until the driver changes the technique, and stops and applies the brakes. That seems weird to me. I would think that the LSD would engage the other wheel to pull as you apply more gas and the one wheel loses traction - I would think that’s it’s an automatic thing as one wheel spins, the other engages. Seems counterintuitive to have to stop in the middle of the obstacle, apply the brake, and then start again to get the LSD to work (I also don’t fully understand how a LSD works, so there’s that).
 
Typically a Dana 35 with stock shafts holds together fine with a Truetrac LSD, I wouldn't worry about upgrading the shafts so long as you're not running anything larger than 33" tires. A pair of Truetracs front and rear was my first TJ's upgrade and its original Dana 35 never gave me any problems with the Truetrac and 33" tires that I pushed fairly hard at times.

And should you some day decide to upgrade your Dana 35's axle shafts the replacements must be made from 1541H steel, not chromoly like 4340 or 4310. The type of outer bearings used in a Dana 35 have no inner races so the bearings ride directly on the shaft and chromoly doesn't have sufficient surface hardening for that but 1541H does.

I wrote an article on how they work and why/how adding brake pressure helps LSDs work better. The thread title may not seem related to a LSD but it specifically talks about them in the middle of it after explaining concepts that make the LSD information understandable. See if this answers your questions... https://wranglertjforum.com/threads/how-is-torque-delivered-to-the-wheels-on-a-4x4.1738/
 
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Breto31 said:
Using a LSD, should I upgrade to chromoly shafts? I know the answer will be “yes”
Click to expand...

Using a dana 35 that answer is NO. It's been covered elsewhere on this forum, the 35 needs a 1541H axle shaft due to the bearings riding on the shaft, which has been demonstrated to wear into a chromoly shaft.

Breto31 said:
I also don’t fully understand how a LSD works, so there’s that
Click to expand...

A TruTrac is a Limited Slip Differential, not a locker. A locker physically locks one axle shaft to the other (a spool is a dedicated locker, selectable lockers can toggle back-and-forth between open and locked) A Limited Slip Differential does just that, it limits the slip, not stop it.

Breto31 said:
I’m not ready for a regear
Click to expand...

Installing a new carrier, LSD or locker, will require pulling the gears and at minimum require basic setup checks if reinstalling the same gear. You might want to consider a full gear ratio change if you have any intentions of doing so in the future.
 
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I'm on 33s with 4.56 gears and truetrac in the rear, open in the front. Just got back from SMORR and it performed amazing. Just be easy with the skinny pedal. edit: Dana 35 on stock axle shafts but I'm planning on upgrading to 1541H at some point.
 
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Jerry Bransford said:
Typically a Dana 35 with stock shafts holds together fine with a Truetrac LSD, I wouldn't worry about upgrading the shafts so long as you're not running anything larger than 33" tires. A pair of Truetracs front and rear was my first TJ's upgrade and its original Dana 35 never gave me any problems with the Truetrac and 33" tires that I pushed fairly hard at times.

And should you some day decide to upgrade your Dana 35's axle shafts the replacements must be made from 1541H steel, not chromoly like 4340 or 4310. The type of outer bearings used in a Dana 35 have no inner races so the bearings ride directly on the shaft and chromoly doesn't have sufficient surface hardening for that but 1541H does.

I wrote an article on how they work and why/how adding brake pressure helps LSDs work better. The thread title may not seem related to a LSD but it specifically talks about them in the middle of it after explaining concepts that make the LSD information understandable. See if this answers your questions... https://wranglertjforum.com/threads/how-is-torque-delivered-to-the-wheels-on-a-4x4.1738/
Click to expand...

The write-up makes sense. Thanks for that….. It seems like a LSD would work my style of wheeling.

I’m on 33’s, with no plans to increase the size.
 
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I have TruTracs (TT) front and rear and you're right - they will let one wheel spin like an open diff from time to time. And they will do that every time you have a tire in the air. They need resistance at both wheels to work, unlike a locker. That's why the brake trick works. Watching videos of my rig I often see one tire spin and the other remains stationary, like an open diff, and then after a moment the TT sends power to the stationary one and I am moving again. Sometimes the TTs just take a moment to work. I have also successfully used the "brake trick" without stopping the vehicle, or more often my rig is not moving forward but my tires are still spinning. Keep in mind that the brake trick is not some magical thing to be relied on, but it does sometimes work enough to make the difference.

I don't often lift tires off the ground and I do often drive on snow-covered roads so I am extremely happy with my TTs. They make a huge difference offroad until you get a tire in the air. I like that they just work and are "invisible" on the road. I also like that they don't stress the axle shafts as much as a locker, so I am less likely to break them offroad. I may be wrong about that, though, so please someone correct me if I'm wrong.
 
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BlueC said:
How have these affected your turning radius? I'm considering putting one up front, but I do a lot of tight maneuvering on trails.
Click to expand...
Not that I remember when I had them front and rear on my previous TJ. But for the front they're not really that helpful, I'd suggest a lunchbox locker in the front instead. They don't affect steering in 2wd and if you go with the No-Slip lunchbox locker from Powertrax you won't even notice it when driving around town as it is noise and click-free. Most other lunchbox lockers make soft clicking/ratchetings sounds during slow-speed turns like in a parking lot. When I got rid of my previous TJ's Truetracs the front got a No-Slip lunchbox locker and I loved it.
 
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Why not just do a locker in the Dana 30 and get "true traction" then later do the truetrac in the rear if wanted.
 
Great info! Will be watching this thread. I have pretty much the same goals/concerns. LSD seems perfect for what I'd want to do. Understanding the 'braking' concept, seems to make sense. Front lunchbox locker sounds good too. 👌👍
 
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BlueC said:
How have these affected your turning radius? I'm considering putting one up front, but I do a lot of tight maneuvering on trails.
Click to expand...

No affect on road or off. It's pretty dang nice in tight spots offroad when other Jeeps are doing multi-point turns and I can just whip around in one go.

I agree with Jerry that a lunchbox in the front is superior offroad. Lunchbox front/Trutrac rear is what I would do if I were doing it over again. I do love the TT in the front when I'm in 4 high on snowy roads but I have been told that with some modified driving habits a lunchbox in the front handles OK in the snow as well. I would not want one in the rear for a daily driven rig though.

My wife has a TJ as well which is open/open dana 30/35 and I am probably going to go lunchbox front, TT rear rear for her. Either that or wait longer and get the best thing: selectable lockers. :)

Edit: One pro about the lunchbox is it's an easier install. I am no expert but I believe with the Trutrac you need to at least check the backlash after and maybe adjust it. You are replacing the carrier and spider gears. With a lunchbox you are just replacing the spider gears so nothing changes with your ring and pinion. The best budget option which is also a huge boost offroad is to simply put a lunchbox in the front and leave the rear open.
 
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I'd hold out for the No-Slip locker which performed brilliantly in my previous TJ with no clunks, clicks, or ratcheting on the street. I couldn't even tell it was there when in 2wd. I've driven a TJ with a Spartan front lunchbox locker and it was nowhere nearly as well behaved or as perfectly quiet as the No-Slip is.
 
Jerry Bransford said:
I'd hold out for the No-Slip locker which performed brilliantly in my previous TJ with no clunks, clicks, or ratcheting on the street. I couldn't even tell it was there when in 2wd. I've driven a TJ with a Spartan front lunchbox locker and it was nowhere nearly as well behaved or as perfectly quiet as the No-Slip is.
Click to expand...

Some of the reviews mention clicking or up to 1000 mile break in? Then others say it seemed perfect...
 
I was going to go with a lunchbox locker up front and a TT in the rear but from reading looks like if you drive in snow covered roads you are better off the TT front and rear, is that correct?
 
Pantera99 said:
Some of the reviews mention clicking or up to 1000 mile break in? Then others say it seemed perfect...
Click to expand...
The ones mentioning clicking are likely talking about the Powertrax Lockrite. Reviews are often combined for the same manufacturer. No break-in is required.
 
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