Gears...lockers...axles

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rainman
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Gears...lockers...axles

Post by rainman »

Been away for a while (moving was way easier when single lol) but it's time to upgrade the gear ratios in my axles.

Currently running:
Dana 44 3.31 front and rear
4" lift with 33"x10.5" BFG ATs
5.2mpfi/46rh from a 95 ZJ & NP229

Current issue: Overdrive is completely worthless and acceleration is less than optimal.

Planning on 4.56 gears. Trying to weigh cost/benefit of various locker combinations.

Parameters:
-must be street friendly
-must be snow/ice friendly

Manager at local 4WP recommended trutracs front and rear. Further research leads me to believe a front trutrac is less than optimal with full-time 4wd. I was thinking of splurging for ARB's (at least in the front.) I guess if I'm going to spend the money on a full case locker, I might as well spend a little more on a selectable...right?

To complicate matters more I was thinking about a 3/4 ton axle swap before I re-gear. The current 33's are as big as I want to go. I imagine the 44s would be fine (locked 33s) since I don't run any hardcore trails. My biggest fear is losing an semi-float axle while cruising down the highway fully loaded with family and gear. The full float would eliminate that concern.

If I were to upgrade axles I am thinking about:
Front D44 (hp?) from a 80+ J20 (wms-wms~66.5")
Rear D60 from a 80s dodge full size (wms-wms~64.5")
90s dodge 16x6.5 (4"bs) or 2000s 17x7.5 (6"bs) steel wheels
255/85r16 or 255/80r17

Both axles should bolt in fairly easily. This plan looks good on paper but I'm having concerns about the wheel to steering knuckle clearance on the front. Most apparent solution is a high steer setup with angled arms. Seems kinda wasteful on a SUA axle.

I want to use higher backspace wheels to keep the tires under the body. They need to be able to tuck when flexed. According to my calculations my overall width at the tires would be +1.5"-1.75" per side compared to current setup.

Bottom line is I only want to spend money once. Dropping $3k+ on gears and lockers only to need a axle upgrade later is going to be less than optimal. Do it right or do it twice.
1987 Grand Wagoneer
5.2L/46RH/NP229/4"/31s/4.56/ARBs
Current FSJ status: Mostly functional...mostly
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Tatsadasayago
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Re: Gears...lockers...axles

Post by Tatsadasayago »

Glad to see you back Sir!

I agree that the Detroit is not a very good idea for a front axle on a full-time rig. I would go with an OX or ARB or even a Powr-Lok before the Tru-Trac.
If having an extra cable and lever or two on the trans hump the OX isn't a bad choice against the ARB which is higher maintenance overall.

I dunno about the need to go full floater in the rear unless you are planning on running overloaded and pulling a trailer with more than 500 Lbs on the hitch. A properly lubricated D44 in good shape can handle way more constant weight at highway speeds than most realize. It's the worn out and neglected Dana 44s full of water or running without gear oil/bearing grease that has led many people to think it can't handle road trips with a load on.

Anyway, it's good to know you're still around!
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Re: Gears...lockers...axles

Post by Stuka »

With full time, you don't want an automatic locker in either axle. You also don't want a limited slip in front, as it will impact your street driving. The biggest impact is understeer, but can also pull straight if you accelerate.

What kind of off roading are you planning on? For most trails, an ARB in back would be more than enough. In my J10, I am open up front, and detroit in back (but I have a manual trans). It has gone on every trail I have taken it on.

As for axles, what is your final tire size going to be? With 4.56's, I am guessing 35's, maybe 33's. With 35's, the D60 would be a better option in the long run. But, you will also end up with tires sticking out the side of the vehicle, as a J20 D60 is 9.5" wider than a NT D44.
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Re: Gears...lockers...axles

Post by FSJ Guy »

X2 on a selectable locker for the rear. I have one in my Touareg and it is fantastic. Open diff in the front, although it has the "electronic" diff lock feature.

Being able to instantly unlock the rear is very nice to be able to make tight turns without scrubbing tires.
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Re: Gears...lockers...axles

Post by rainman »

Tatsadasayago wrote:Glad to see you back Sir!

I agree that the Detroit is not a very good idea for a front axle on a full-time rig. I would go with an OX or ARB or even a Powr-Lok before the Tru-Trac.
If having an extra cable and lever or two on the trans hump the OX isn't a bad choice against the ARB which is higher maintenance overall.

I dunno about the need to go full floater in the rear unless you are planning on running overloaded and pulling a trailer with more than 500 Lbs on the hitch. A properly lubricated D44 in good shape can handle way more constant weight at highway speeds than most realize. It's the worn out and neglected Dana 44s full of water or running without gear oil/bearing grease that has led many people to think it can't handle road trips with a load on.

Anyway, it's good to know you're still around!

I figured a trutrac (or any other auto locker) in the front would not work well for me. I kinda looks at Mr 4WP guy a little odd when he suggested it. I assume he thought I had a PT case.

I probably run pretty heavy in the back nowadays. I have my fuel tank underneath and my tire on the back. Long trips will fill up the cargo area. Future plans include a heavy bumper with dual swing outs. Last year I was pulling a car home from SoCal and noticed the handling difference with a full tank vs empty tank. And that was after I blew a tire on the way down substantially reducing the weight of the tire in the back.
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Re: Gears...lockers...axles

Post by rainman »

Stuka wrote:With full time, you don't want an automatic locker in either axle. You also don't want a limited slip in front, as it will impact your street driving. The biggest impact is understeer, but can also pull straight if you accelerate.

What kind of off roading are you planning on? For most trails, an ARB in back would be more than enough. In my J10, I am open up front, and detroit in back (but I have a manual trans). It has gone on every trail I have taken it on.

As for axles, what is your final tire size going to be? With 4.56's, I am guessing 35's, maybe 33's. With 35's, the D60 would be a better option in the long run. But, you will also end up with tires sticking out the side of the vehicle, as a J20 D60 is 9.5" wider than a NT D44.
I've read conflicting stories about auto lockers in the rear in FT 4wd. Maybe I should throw a lunchbox in mine and see what I think. Need to find some snow to play in though.

I would like to be able to run any moderate to boarder-line difficult trail. I'm not an aggressive driver off-road by any stretch and any trail with a high potential for body damage is likely a no-go. At least until I gets some sliders lol.

I'm not going past a 33" tire in this waggy. Math says I'll be cruising at 65 at 2100 rpms with 4.56 and 33s.

BTW, It wouldn't be a d60 rear from a J20, it would be from a dodge d/w250...~65" wms-wms. J20 front 44 would be about the same increase in width (~7".) My math puts me a at 3-4inches wider overall with the proper wheel selection.
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Re: Gears...lockers...axles

Post by Renodemona »

Welcome back, we missed you!
I wouldn't think full time 4wd and auto lockers would play nicely...
Been looking at an Eaton electric for the back but its $$$$
If you did go with wider axles I'm sure we could graft on some wide track flares. Front is easy and the rear shouldn't be too hard either.
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Re: Gears...lockers...axles

Post by derf »

rainman wrote:I figured a trutrac (or any other auto locker) in the front would not work well for me.
The TrueTrac is a limited slip differential, not an auto-locker.

A lot of people have limited slip in the front with no issues.
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Re: Gears...lockers...axles

Post by Tatsadasayago »

I've run several full time FSJs with PowrLoks in the front&rear and only had tissues on ice covered roads when trying to negotiate tight switchbacks. The occasional oopsie on rainslicked roads happened, but that was mostly operator error.
I suppose in those situations even an open diff would not be much worse.
After all these years of wheeling experience, I'd run selectables front and rear if I had the spare change.
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Re: Gears...lockers...axles

Post by Stuka »

rainman wrote:I've read conflicting stories about auto lockers in the rear in FT 4wd. Maybe I should throw a lunchbox in mine and see what I think. Need to find some snow to play in though.
The problem is they dont unlock with fulltime. There is always tension on the driveshaft because of the difference in axle speeds front to rear. Yes the center differential allows for them to be at different speeds, but only because of the drive shaft speeds wanting to be different. Automatic lockers lock when they have torque applied to them. And with full time, there is basically always torque applied, unless you are going perfectly straight.

This is why I advise going with a selectable in back. A limit slip would be fine, and the tru-trac is a great LSD, but it is not as good as a true locker. And the tru-trac only tightens when one wheel spins quite a bit faster than the other. So it normal driving it should be undetectable.

Now if you plan on just being in 2wd all the time unless there is snow, an auto locker is fine. Just be aware of their side effects. Driving in the snow is quirky, and u-joints will wear out faster because of the inherent "slop" that they have. My Cherokee would go through u-joints 1-2 times a year, and basically always barked the inside tire. But my J10 has been much better about it, but I think thats because there is far less weight in back, so slipping the inside tire is not as much of an issue.
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Re: Gears...lockers...axles

Post by rainman »

Thanks for all the wisdom...I will make up my mind in the next week or so. Leaning toward an ARB in the rear only but we'll see.
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What traction device for the front axle?

Post by jpswapmohn »

Bringing this back up as I have a similar question:
I am trying to decide what type of diff to put in my front axle.

J-20 axles acquired to go into my GW. The rear D60 has a Grizzly installed by previous owner with with 0 miles on it.
The front is apart and needs a rebuild.

This will not be a heavy trail rig. I have the YJ mutt for that, and will have way too much blood, sweat and lunch money in this thing once "finished". I run ARB's front and rear in the YJ and love them. I engage/disengage the front on the fly as needed to retain turning radius/steer-ability. Can't really justify ARB's for the GW.

I built and installed NP242 to retain some "AWD" capability. Lockout hubs will be engaged if AWD or 4WD use is anticipated.

A selectable locker in front makes sense, but for the expected use, it is hard to justify the cost.
The TruTrac seems like a good compromise, but above, some of you indicate a LSD-type diff is not recommended for the front in AWD.

Currently, I have a LSD carrier from a Rodeo rear D44 in the front NT D44, also with locking hubs. Pretty sure the clutches in it are shot. Have not had issue with it, but have hardly run in 4WD since install. It was fine in 2WD before I put the locking hubs on. Would the trutrac be similar?

Just watched the Crawlpedia video explaining different lockers. Had no idea traditional LSD clutches only lasted ~20k miles! The guy did say he ran TruTac's in both axles on his Cruiser.

options:
1. Remain open
2. clutch-type LSD (undesirable if clutches need replacement every 2 years)
3. TruTrac (better than open or clutches)
4. Selectable ($$ and will sit unused for most of its life)
5. Aussie or similar (I could see this being an issue in AWD)
Other recommendations?
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Re: Gears...lockers...axles

Post by REDONE »

The TruTrac is awesome in AWD vehicles and rather than just say so I'll tell you why. You may have already seen it in that video but I'll explain it here anyways. Torque sensing (Torsen) differentials like the TruTrac don't have clutches to wear out because they use hydraulic resistance to deliver the forces to opposite axle shafts.

The best explanation I've come up with is this. Image a rotary pump is attached to one axle shaft. The handle that DRIVES the pump is attached to the opposite axle shaft, and the outlet of the pump is a tiny little hole, and for the purpose of this thought exercise, the suction of the pump is always below the oil, so it never sucks air. When the two shafts are turning the same speed, the pump isn't pumping so nothing happens. Once one shaft starts to turn faster than the other (going around a corner) the pump starts to pump oil, but it's not that much so it flows through the hole just fine. Now say you're doing a burn-out and tire breaks loose. That tire is going to turn MUCH faster, so now the pump is trying to pump a LOT of oil through that tiny hole. This makes it much harder to turn the handle, which is how the force is transferred to the tire that still has traction.

The difference between this example and the actual TruTrac is that it's not a tiny hole, it's the clearances between the sideways gears and the housing. Those sideways gears are screw-type pumps that deadhead against the housing, so what fluid they do pump (since they are not submerged in oil) has nowhere to go except through the clearances (if they were used as pumps this would be called pump-slip).

I've had two TruTracs through the years, on in a 9" and one in a D44, and I like them for what they are. If one fell in my lap I wouldn't hesitate to run it in the front of Money Badger (I also have a Grizzly in the rear). I'm holding out for a screaming deal on a PowrLok so I can tune it just shy of being a locker, but Money Badger is a toy, not something I plan to commute in on icy roads. ;)
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Re: Gears...lockers...axles

Post by dodgerammit »

Ran a truetrac in the front of my W350 (D44 with 4.56 gearing) the 60 Rear had a powrlok, but at times I'd like the true trac in both ends. No issues with plenty of winter roads driven. It is not a locker and therefore doesn't behave as one. It is excellent for a steering axle. I loved it, and when it is time for Radio Flyer's axles to undergo the knife, I have no doubt as to what differentials will be going in. Just gotta decide on 3.31 or 3.54 gearing.

I highly recommend true tracs for milder rigs.
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Re: Gears...lockers...axles

Post by Tatsadasayago »

I run super tight PowrLoks in my Chief and they are so friggen cool. Nothing quite like that SnapSnapSnap sound when crawling over rocks almost as big as the jeep. :)
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Re: Gears...lockers...axles

Post by Stuka »

Tru-Tracs are the best LSD IMO, but as I mentioned above, if you ever drive in snow, leave the front open, or put in a selectable.
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Re: Gears...lockers...axles

Post by derf »

I have an XJ with the NP242. I put TruTracs in front and rear. I don't have much experience with them yet as I just got the Jeep up and running a couple weeks ago. And I haven't had them in the snow/ice yet. Though this weekend promises a day of snow so I'll be out playing around in it to see how things go. I can say with certainty that for normal driving day to day on dry pavement you can't tell that they're there. The Jeep rides and drives just like it has open diffs. But that's what a limited slip does. It really doesn't kick in until you start to lose traction.

Reading all of the discussion about TruTracs on various forums, I have basically uncovered that there are two types of people who respond.

1. People just repeating what they hear about stuff. From these people you get a great variety of what driving it might be like. But when pressed, all they can say is "that's what I've heard". And what they have heard varies from person to person.

2. People who have actually installed and used them in their own vehicles. What you get from these people is pretty consistent. First is that off road, they are just like every other limited slip. They help more than an open differential but aren't true lockers so they only help so much. So they're not good for heavy rock crawling and the like but decent for mild/moderate trails. Second is that they work great in snow and ice so long as you're not driving too fast for conditions. i.e. they won't suddenly make you be able to take hard corners fast on ice. They're only good for helping you get moving. They can't make you stop or turn faster on snow and ice.

Assuming the snow forecast holds up and we get enough for it to accumulate, I'm going to be out playing around to see how well they work.
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Re: Gears...lockers...axles

Post by Stuka »

derf wrote:I have an XJ with the NP242. I put TruTracs in front and rear. I don't have much experience with them yet as I just got the Jeep up and running a couple weeks ago. And I haven't had them in the snow/ice yet. Though this weekend promises a day of snow so I'll be out playing around in it to see how things go. I can say with certainty that for normal driving day to day on dry pavement you can't tell that they're there. The Jeep rides and drives just like it has open diffs. But that's what a limited slip does. It really doesn't kick in until you start to lose traction.

Reading all of the discussion about TruTracs on various forums, I have basically uncovered that there are two types of people who respond.

1. People just repeating what they hear about stuff. From these people you get a great variety of what driving it might be like. But when pressed, all they can say is "that's what I've heard". And what they have heard varies from person to person.

2. People who have actually installed and used them in their own vehicles. What you get from these people is pretty consistent. First is that off road, they are just like every other limited slip. They help more than an open differential but aren't true lockers so they only help so much. So they're not good for heavy rock crawling and the like but decent for mild/moderate trails. Second is that they work great in snow and ice so long as you're not driving too fast for conditions. i.e. they won't suddenly make you be able to take hard corners fast on ice. They're only good for helping you get moving. They can't make you stop or turn faster on snow and ice.

Assuming the snow forecast holds up and we get enough for it to accumulate, I'm going to be out playing around to see how well they work.
If you guys end up with any hard pack, this is where a front limit slip will be more noticeable. In deep snow I doubt it will be. But on hard pack, it can cause a lot of under steer. Although in my experience the vehicle wont crab walk like it would with a locker up front. A front auto locker (or spool) on hard pack snow is a nightmare. Going in the direction that you want to go in is nearly impossible.
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Re: Gears...lockers...axles

Post by derf »

Stuka wrote:If you guys end up with any hard pack, this is where a front limit slip will be more noticeable. In deep snow I doubt it will be. But on hard pack, it can cause a lot of under steer. Although in my experience the vehicle wont crab walk like it would with a locker up front. A front auto locker (or spool) on hard pack snow is a nightmare. Going in the direction that you want to go in is nearly impossible.
I would believe that this would be more of an issue with a clutch type limited slip over a torsen style like the TruTrac.
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Re: Gears...lockers...axles

Post by Stuka »

derf wrote:
Stuka wrote:If you guys end up with any hard pack, this is where a front limit slip will be more noticeable. In deep snow I doubt it will be. But on hard pack, it can cause a lot of under steer. Although in my experience the vehicle wont crab walk like it would with a locker up front. A front auto locker (or spool) on hard pack snow is a nightmare. Going in the direction that you want to go in is nearly impossible.
I would believe that this would be more of an issue with a clutch type limited slip over a torsen style like the TruTrac.
So if the clutch style is tight, it can act more like a spool on low traction surfaces like hard pack snow. This is obviously bad for turning, as it will cause massive under steer.

With a torsen, both tires will always spin, its impossible for one to spin without the other. A torsen only allows for a tire to spin faster than the case, but never slower. With an open center differential like an NV242, the center diff should be able to absorb this, even on low traction surfaces. With a part time case (and to an extent a viscous coupler), this cannot happen. The front "slow" tire has to spin at the same speed as the rear tires. This will result in it breaking traction when you turn on the front inside tire. On high traction surfaces a VC will absorb this, but unlikely to do so on a low traction surface. That tire breaking traction is what causes the under steer.
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