Jeep Modifications

[Oscar Mike]

I am beginning today to get my Jeep ready for Moab in May. After spending a few days thinking about how to proceed with doing some modifications to my 2005 TJ, I'm thinking that I'll start with locking differentials and some chassis armor (skid plate(s), differential armor) which will cost me a couple of grand... .

My question to the technology inclined is should I install locking differentials front and rear, or is the rear good enough. Is ARB a good product?

 

 

[zmotorsports]

The sky is the limit for differential choices.  I will give you my personal opinions, but remember they are just my opinions.

For selectable lockers, ARB makes a quality component but then you will also have to figure in the cost and installation of a compressor.  Cost wise the ARB is going to probably be the most expensive choice, a good one, but the most expensive.

Next comes electric lockers, the two most common are the Auburn Ected and the Eaton ELocker.  Both are similar in the way they function but slightly different in design.  Both installations are the same and the wiring from the dash to the axle housing will be similar.  I am partial to the Eaton ELocker due to the fact that it uses a four pinion setup vs. the two pinion on the Auburn Ected.  In my opinion it is just a little stronger but I have heard arguments on both sides of their design.  The ELocker uses a ramped cam mechanism that resides next to a drive hub, driven hub and an electromagnet.  When the switch is engaged the electromagnet is energized which pulls the drive hub towards the driven hub.  The drive hub has hardened pins that must engage into the drive hub to be "locked".  This does not happen instantaneously.  Once the electromagnet pull the hub it ramps up into the opposing component until it is fully seated and then it is locked.  This generally takes a few feet.

Most experienced off-roaders will encourage people to engage their lockers when they know they will need them prior to them actually needing them.  This is to avoid damaging them.  I will get lined up with an obstacle and engage the locker(s) as I am approaching the obstacle to ensure the engagement is complete prior to putting any power through the lockers to the tires/wheels to avoid stressing and damaging anything.  The lockers that I have seen people break are due to spinning and then deciding to engage the locker and it grabs and breaks with all of that torque going through them and usually before they are fully locked.

All that said, the one drawback to the Eaton ELocker is its' inherent design with the ramp mechanism.  By design it ramps up and drives the two hubs together.  IF for some reason you are going forward with the lockers engaged and then have to go into reverse, the ELocker will actually "deramp" to the disengaged position and then "ramp" back up in the other direction.  It is not a weak design as some will try to tell you, it is merely the design characteristic of the locker and as long as you know that and drive accordingly it will provide years and years of trouble free operation.  Hammering from forward to reverse will definitely destroy an electronically controlled locker.

Last but not least, let me put a plug in for the Eaton TrueTrac.  This is a helical gear style limited slip, not a locker.  However, they are about bulletproof and depending on your wheeling style may be a much better option because they require absolutely no input from the driver and go un-noticed on the road, great road manners.  I have had TrueTracs in many vehicles over the years and installed many for other people and they love them.  If you wheel in a manner that you do not have a wheel in the air much of the time but just need the added traction, I highly recommend them.  If you are the type of driver who seems to have a wheel in the air a lot this may not be the best option as they do requires some "resistance" from one wheel to transmit the torque to the other in a traction loss situation.

My last Jeep GC I was running a TrueTrac in the front and wheeled Moab for several years without an issue, didn't even have a winch on the Jeep and never got into a situation where I thought I should have installed a true locker.  My son installed Eaton TrueTracs in both front and rear of his 2004 LJ (Wrangler Unlimited) and he loves them.

I hope that was helpful but it was pretty biased based on my experience and opinions.

Mike.

 

[John Canfield]

Great locker synopsis Mike, I learned something.  The 4x4 shop we use in Montrose, CO doesn't like ARB lockers and much prefer E lockers due to "high failure rates of ARBs."  I had a new rear G2 axle with ARB locker installed last year in Moab and it has worked fine for me.  I'm careful to engage it and disengage it when I'm preferably at a full stop because apparently the ARBs suffer when engaged while rolling.  At any rate, I'm very happy with the ARB (my front locker is still OEM.)

If you can afford to have lockers on front and rear, go for it.  If you can only do the rear axle, that will take care of 90% of the need to lock axles.  The advantage of doing both axles is that will be a perfect time to regear to 4.88 if you have an automatic transmission.  The gears themselves aren't expensive but the labor can be on the costly side.

 

[zmotorsports]

Thanks John, you pointed out an important issue that I forgot to address.  Gear ratios.  I would highly recommend regearing at the same time as installing the lockers as the labor is the same and this would avoid having to do it a second time.

As far as the ARB lockers, I don't think they are bad or weaker than the other options by any means, just more expensive initially.  The ARB's that I have worked on with issues were due to improper installation by the owner or shop and an O-ring was nicked or cut which resulted in an air leak or the copper air line internally was not routed properly and came in contact with the ring gear.  Other than that they are a great locker, it is just I think there are better options with less moving parts and less cost out there.

Mike.

 

[Oscar Mike]

I used Detroit Lockers in the 1974 CJ5 that I built several years ago in the front and rear, and I never had any problem. I tow this Jeep four-down so my next question would be: Do the lockers in anyway impact normal driving/towing?

Gear Ratios: You mention 4:88 and I would ask "why?". Is there a big impact to highway driving using 4:88 gear ratio? What is involved in changing the gears? Will I need to change axles when I change the gear ratio? Should I run 4:88 in the front and rear? I have lot's of questions that I don't even know to ask.

Thanks in advance for all of the guidance.

 

[Photog]

I don't think the lockers will affect driving or towing.  However, if you re-gear, both front and rear need to be the same.  The 4.88 gears work better on larger tires if you are going to 35" tires it would be less expensive to put them on the same time as the lockers.

 

[Oscar Mike]

I called a local shop to get an idea of cost to do what I want to do. If I install ARB lockers front and rear with 4:88 gearing I am looking at $4,500.00 +/-, and if I go with E lockers I am looking at $3,800.00 +/-.

The shop also suggested a 4" lift and installing 33" tires to be better prepared for Moab, and of course the appropriate wheels which would run about $3,000.00 for the package.

Do these numbers sound like they're right?

I bought the Jeep for 15K, plus these mods and I am still way under a new Rubicon...

What I don't want is a radical Jeep, too high and so forth would be a bad thing. Is a 4" lift getting too high?

 

[zmotorsports]

I used Detroit Lockers in the 1974 CJ5 that I built several years ago in the front and rear, and I never had any problem. I tow this Jeep four-down so my next question would be: Do the lockers in anyway impact normal driving/towing?

Gear Ratios: You mention 4:88 and I would ask "why?". Is there a big impact to highway driving using 4:88 gear ratio? What is involved in changing the gears? Will I need to change axles when I change the gear ratio? Should I run 4:88 in the front and rear? I have lot's of questions that I don't even know to ask.

Thanks in advance for all of the guidance.

Detroit lockers in a fairly heavy vehicle are usually fine but in a light vehicle like a Jeep they can cause a lot of stress on things like axle shafts before the clutches slip such as going around a turn/corner.  That said, I have played with springs and clutches in some, but I just feel there are much better choices than the Detroit locker unless it will be strictly a trail rig or trailer queen.

With selectable lockers or the Eaton TrueTrac limited slip you will not need to do anything special for daily driving or flat towing.  The selectable lockers will not be engaged when towing so it will be like a standard "open" differential.

You will not need to change axle shafts when upgrading to lockers or gears "unless" you decide to go with a stronger axle shaft, ie higher spline count.  Many limited slips and lockers come with the OEM spline count but I know ARB requires the axle shafts be upgraded to the 32 spline in most applications.

The gear ratio will be based on what diameter tires you will be running.  For the 4.0 I6 engine on 33" tires or even 35" tires the 4.88 gear ratio is a very popular and wise choice.  Reason being is that not only are you changing the effective diameter of the tires, you are also changing the frontal area of the Jeep when installing a lift kit which will result in a higher coefficient of drag and therefore require a little more RPM to push that brick through the air.  Another thing to consider is the armor, ie weight, that is being added so the Jeep could again benefit from a few more RPM going down the road.

My son's mileage and overall driveability went up when he went from the OEM 3.73 gear ratio to the 4.88 gears when we installed his TrueTrac's.  Before it couldn't get out of its' own way and afterwards it actually had some "pep" back into it.  If a Jeep can actually have "pep" that is. 8)

Mike.

 

[Photog]

I have a 3" lift which works fine with the 35" tires.  If I had it to do over, I think I might do a 4".  I would recommend 35'" tires over the 33s.

 

[zmotorsports]

I called a local shop to get an idea of cost to do what I want to do. If I install ARB lockers front and rear with 4:88 gearing I am looking at $4,500.00 +/-, and if I go with E lockers I am looking at $3,800.00 +/-.

The shop also suggested a 4" lift and installing 33" tires to be better prepared for Moab, and of course the appropriate wheels which would run about $3,000.00 for the package.

Do these numbers sound like they're right?

I bought the Jeep for 15K, plus these mods and I am still way under a new Rubicon...

What I don't want is a radical Jeep, too high and so forth would be a bad thing. Is a 4" lift getting too high?

Sounds about right.

On a side note that is almost exactly what we did to my son's 2004 LJ.  He wanted a nice clean daily driver and weekend wheeler which is what he built.  Nothing too radical but still overbuilt for what he will use it for. 

Here is a link to his complete build thread if you wish to check it out.
http://www.forbiddenjeeps.com/jeep-builds/2916-project-un-limited-funds.html

Mike.

 

[zmotorsports]

I have a 3" lift which works fine with the 35" tires.  If I had it to do over, I think I might do a 4".  I would recommend 35'" tires over the 33s.

Keep in mind Bill that he is talking an 05 TJ which is a different platform that your JK.  Slightly different animals when talking gear ratios.

Mike.

 

[Oscar Mike]

I have a 3" lift which works fine with the 35" tires.  If I had it to do over, I think I might do a 4".  I would recommend 35'" tires over the 33s.

Why would you suggest 35s over 33s?

 

[Photog]

The 35" tires will give you better ground clearance on the axles and differentials.

 

[zmotorsports]

Depending on which 35" tires you are looking at, some measure closer to 34" than 35" so a 33" tire will be less expensive and they will be close enough that it won't really matter.

Also the short wheelbase of the TJ has a good breakover angle so the only place to really benefit is from the differential clearance moreso than the frame clearance. 

My son has 33" tires on his LJ which doesn't have quite as good of breakover angle by design but we installed a tummy tuck on it which helped immensely due to the fact that we removed about 3 inches of crossmember and skid plate that hung down underneath and tucked it all up nice and tidy to the body.

As a general rule of thumb, for every inch you can eliminate from the midpoint of your Jeep (breakover angle) you get the same net benefit as going up two sizes in tires.

I hope that helps and doesn't confuse you.

Also, on a side note it will also greatly depend on "how" you wheel.  I know people who insist on running 40" tires so they can drive over anything, and I mean over it.  They want total clearance.  That is all well and wonderful but if you want street manners, you will be giving up or compromising with 40" tires on the street, not to mention the power to turn them.

The way I wheel I generally will place my tires directly on the rocks to make certain I do not drag a differential or catch anything such as a shock mount or something on the rocks.  My son does the same, places the tires on the rocks rather than straddling them.  Nothing right or wrong, just different off-road driving styles/techniques.  I like to keep a fairly low center of gravity on a Jeep so it doesn't feel so "tippy" on off-camber situations and is still 100% streetable.

Mike.

 

[Oscar Mike]

Sounds about right.

On a side note that is almost exactly what we did to my son's 2004 LJ.  He wanted a nice clean daily driver and weekend wheeler which is what he built.  Nothing too radical but still overbuilt for what he will use it for. 

Here is a link to his complete build thread if you wish to check it out.
http://www.forbiddenjeeps.com/jeep-builds/2916-project-un-limited-funds.html
Mike.

I skimmed through your son's Jeep build and I was very impressed, it looks like a nice job. All it takes is cash.

 

[Oscar Mike]

I hope that helps and doesn't confuse you.
Mike.

I am easily confused, because I don't have a clue about the mechanics of it all. I am really good at preparing for the outback, i.e., gear and such, but when it comes to the technical aspect of the Jeep, I am a complete novice.

I really do appreciate the input from everyone.

 

[zmotorsports]

I skimmed through your son's Jeep build and I was very impressed, it looks like a nice job. All it takes is cash.

Thanks.  Money is one thing but knowing what works and what doesn't as well as having a game plan is more important.  Otherwise you could be throwing good money after bad rather.  I always tell people to decide EXACTLY what you want the vehicle to do and then plan accordingly.  I see way too many people say they want a daily driver/weekend wheeler and then they start throwing parts at it that don't support that plan.  Before long they have a vehicle that must be trailered to the trail and that is not very street friendly.  I see it way to often.

On a side note, my son was looking at Rubicons but they were bringing in stupid money and he found a fairly good deal on a Sport model.  He spent $15k on it and now has spent just over $5k on parts and has a Jeep much nicer than any of the Rubicons he looked at previously.  The Rubicon is an excellent package but it is not the only platform to build a Jeep out of, just a better starting point in several aspects.

Mike.

 

[zmotorsports]

I am easily confused, because I don't have a clue about the mechanics of it all. I am really good at preparing for the outback, i.e., gear and such, but when it comes to the technical aspect of the Jeep, I am a complete novice.

I really do appreciate the input from everyone.

That is what we are here for.  Glad to help.

Mike.

 

[Oscar Mike]

Depending on which 35" tires you are looking at, some measure closer to 34" than 35" so a 33" tire will be less expensive and they will be close enough that it won't really matter.

Also the short wheelbase of the TJ has a good breakover angle so the only place to really benefit is from the differential clearance moreso than the frame clearance. 

My son has 33" tires on his LJ which doesn't have quite as good of breakover angle by design but we installed a tummy tuck on it which helped immensely due to the fact that we removed about 3 inches of crossmember and skid plate that hung down underneath and tucked it all up nice and tidy to the body.

As a general rule of thumb, for every inch you can eliminate from the midpoint of your Jeep (breakover angle) you get the same net benefit as going up two sizes in tires.

I hope that helps and doesn't confuse you.

Also, on a side note it will also greatly depend on "how" you wheel.  I know people who insist on running 40" tires so they can drive over anything, and I mean over it.  They want total clearance.  That is all well and wonderful but if you want street manners, you will be giving up or compromising with 40" tires on the street, not to mention the power to turn them.

The way I wheel I generally will place my tires directly on the rocks to make certain I do not drag a differential or catch anything such as a shock mount or something on the rocks.  My son does the same, places the tires on the rocks rather than straddling them.  Nothing right or wrong, just different off-road driving styles/techniques.  I like to keep a fairly low center of gravity on a Jeep so it doesn't feel so "tippy" on off-camber situations and is still 100% streetable.

Mike.

I agree with your idea of a build completely, I want a very street-able Jeep.

When I go off-roading, if I can't go around, I too would place my tires on the obstacle instead of straddling the obstacle. I've got a few weeks to figure it all out. Working backwards from May 11, 2014 (Moab rally), I'll need to have the work done by April 11, 2014 so I will have a chance to take it out and drive some obstacles.

 

[Oscar Mike]

I always tell people to decide EXACTLY what you want the vehicle to do and then plan accordingly.  I see way too many people say they want a daily driver/weekend wheeler and then they start throwing parts at it that don't support that plan.  Before long they have a vehicle that must be trailered to the trail and that is not very street friendly.  I see it way to often.
Mike.

I've been thinking about this exact thing for a while now. This Jeep is not my daily driver, but it IS my toad, so when we are traveling it is my daily driver. We bought this Jeep with the express purpose of being towed. I also have to consider my "white knuckled" wife, who will refuse to go trail riding with me if it is too radical looking. When we do off-road it is usually on cow paths, forest service roads, and such, even then my wife is easily frightened. Seldom would I do complicated trails that exist in places like Moab, but in the event we happen on to an obstacle, I want my Jeep to be handle it with relative ease, based on my driving ability and the Jeeps mechanical ability. Some obstacles it is better to just turn around/go around.

Smaller tires do mean less clearance, and yet I don't think I should be too concerned with the clearance thing, but it should something I am conscience of when I am in the outback.