What size tires can it handle?
What lockers are available and which are better?
What lockers are available and which are better?
What's the limit of the front diff on the 100?
- Thread starter dennisuello
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
I have been doing some research on this and have come up with this answer. It depends. I think it has more to do with how aggressive you plan to be with the throttle. If you plan on having one front tire off the ground and giving it enough gas to over power the ATRAC, you can break it with the stock size tires. If you plan on driving conservatively and using the ATRAC to get you through, 33s to 35s seem to do okay. Bear in mind this is just me reading on here. The common denominator seems to be when these to things occur at the same time, liberal application of throttle(enough to over power ATRAC) and a fast spinning front wheel that grabs traction all of a sudden.
Pretty much your only option lockerwise is the ARB but that is a pretty good option although one of the aftermarket elockers would be nice to avoid the compressor. I think the LC "weak" front diff is a little exagerated. I think that every differential is subject to the same limits. The ATRAC lets you get into some pretty knarly situations. Once your there you have to realize that you dont have a locker and spinning a front tire that doesn't have traction isn't going to help you much. Taking a 5000-6000 lb vehicle with 33 plus inch tires and getting exuberant with throttle of an engine that makes over 300lb/ft of torque is not the wisest approach.
The Jeep Wrangler is a perfect example. The Dana 30 in the front isn't necessarily weak(atleast compared to the 35 in the back) but Jeep upgraded it to the Dana 44 for the Rubicon. People that want to build it up go rock climbing upgrade to a Dana 60. Can you break a dana 30? yes. Can you break a Dana 44? Yes. Can you break a Dana 60? Less likely because the thing was built for 1 ton trucks but yes. The lockers seem to help on two levels, slightly stronger but more importantly it keeps the scenario described above where one wheel is spinning and grabs all of a sudden from happening. Lockers will inevevitably be harder on other driveline parts like axles and CVs.
I know you were looking a number like 33.8 inches tall where below that number you can't break it but above you can. It is not what I have come up with from researching it.
Pretty much your only option lockerwise is the ARB but that is a pretty good option although one of the aftermarket elockers would be nice to avoid the compressor. I think the LC "weak" front diff is a little exagerated. I think that every differential is subject to the same limits. The ATRAC lets you get into some pretty knarly situations. Once your there you have to realize that you dont have a locker and spinning a front tire that doesn't have traction isn't going to help you much. Taking a 5000-6000 lb vehicle with 33 plus inch tires and getting exuberant with throttle of an engine that makes over 300lb/ft of torque is not the wisest approach.
The Jeep Wrangler is a perfect example. The Dana 30 in the front isn't necessarily weak(atleast compared to the 35 in the back) but Jeep upgraded it to the Dana 44 for the Rubicon. People that want to build it up go rock climbing upgrade to a Dana 60. Can you break a dana 30? yes. Can you break a Dana 44? Yes. Can you break a Dana 60? Less likely because the thing was built for 1 ton trucks but yes. The lockers seem to help on two levels, slightly stronger but more importantly it keeps the scenario described above where one wheel is spinning and grabs all of a sudden from happening. Lockers will inevevitably be harder on other driveline parts like axles and CVs.
I know you were looking a number like 33.8 inches tall where below that number you can't break it but above you can. It is not what I have come up with from researching it.
sleeoffroad
Supporting Vendor
I still think it is the Atrac that breaks them in a lot of cases. We have done quite a few that broke with stock tires / 33" tires in snow conditions on the road. Some with more throttle the others, but none so excessive that you would think the vehicle is getting abused.
We recently did spider gears in a 1998 truck (two pinion) that has never been off-road and has never ran anything larger than stock tires. The only reason we knew it was broke is that when we drained the front diff oil, there was a complete spider gear tooth sitting on the drainplug
We recently did spider gears in a 1998 truck (two pinion) that has never been off-road and has never ran anything larger than stock tires. The only reason we knew it was broke is that when we drained the front diff oil, there was a complete spider gear tooth sitting on the drainplug
I agree 'it is possible to break anything' perspective; however the 100 front diff, IMO, is a manufacturing and/or manufacturers design flaw. I wheeled my 100 with 33" MT/Rs fairly aggressively with the stock front diff assembly. Although I never would allow the front wheels to purposely spin (aka "too much skinny pedal") I drove it into to some places I would have expected, and had front wheel spin, albeit not much, a front diff failure given the facts and experiences of others before me. Rusty_tlc on the other hand broke his in a situation, completely devoid of revving and spinning front tires (I witnessed this 3' from his front bumper when it happened). His is a '98 mine a '99: Supposedly the same front diff assemblies.
Toyota had a heat treating/metalurgy issue with the FJ Cruiser's R&P that shredded a number of R&Ps shortly after it was introduced! Could it be possible that the 100 front diff issue is partly to blame from poor design and/or manufacturing/tolerance variances? Gotta wonder! The "2-pinion" vs. "4-pinion" discussion hasn't proven it is related to either: They both break!
Just for general information: I would not recommend an automatic locker up front (I am not aware of an electric type locker readily available for the front 100...but any manual locker, air, electric, cable would be best IMO). There are numerous occasions on the trail you do NOT want the locker engaged. A selectable locker is best for multi-purpose rigs such as the 100. I also believe lockers help distribute the drivetrain stresses over more parts/great surface area in general. When 3X engaged I can feel my drivetrain working more efficiently with less stress to the entire system. The ARB locker seems to have increased the overall integrity of the front diff even when not engaged....however, again, I believe an engaged locker, all things being equal, distributes drivetrain stresses more effectively. But...I'm not an engineer...I'd like to hear more about this topic from the "experts"!
In terms of "over-exaggerated front diff issue": It IMO is a solid preventative type upgrade if you want to virtually eliminate a known issue. The problem with waiting until it fails is it will probably fail when recovery is not easy (or cheap!) and the damage/cost multiplier comes into play once it does fail. If you take care of it before catastrophe you're just paying for the ARB locker and set-up...otherwise the collateral damage adds up: R&P, case damage, etc. This is an issue each owner will need to weigh for themselves. But for where I drive my rig I wanted to eliminate as many known issues to enhance the overall reliability to help prevent disaster in remote areas.
Also there appears to be some evidence the ARB carrier provides better support/rigidity to the ring gear. Although it would be best, given the history of the 100 front diff issues, to run more challenging sections of a given trail with the CDL and front diff locked I do believe the front diff is inherently more reliable because of the ARB carrier. And as Darren (ats4x4.com) has stated: Great care and precision when setting up the ARB and diff assembly goes along way to mitigating a 'soft' design. Per Darren: Machined pinion spacer, bearing preload, checking and correcting the ARB carrier run-out, etc. Apparently this type of attention to detail eliminates the front diff issues with the 100 as Darren states they have never had a front diff failure after he installs an ARB per his recommendation and procedures. Coming from an Aussie 4x4 shop instills confidence in me that his set-up works!
Edit: I think 33" impart less stress to the rig particularly the steering rack assembly. Christo originally told me, when I was considering going to 35"/315, that he thought 33" are the biggest without the concern for increased wear/tear. Having said that I need my 35"/315 and have resigned myself to the fact steering/front suspension components will wear more rapidly...I'm starting to experience this! I'll have to weigh in after another year to see if it is a reasonable trade-off. That's where the SAS, I think, would be more tolerant/better suited for 35"/315 for the type of trail use I subject my rig to.
Last edited:
Many run 33's, some run 35's. I can't afford to regear, so 33's for me.
ARB and ARB.
hoser
SILVER Star
TJM will be releasing it's Pro Locker for the IFS 100 soon.
I agree that it would be nice if the front diff was stronger but all I meant with the exagerated comment was that some people post that that the front diff breaking is inevitable and will happen to everyone eventually but it just isn't true. I started the poll a month ago and found that about 20% had broken there diff but for a website such as this(that advocates going offroad and specifically rock crawling), I dont think it means a diff breakage is inevitable. I would like to know what the new Tundra has for a front diff and how it relates to the LC as for as compatibilty.
The poll
https://forum.ih8mud.com/showthread.php?t=181611
The poll
https://forum.ih8mud.com/showthread.php?t=181611
Granted amid 'MUD folks "only" 20% of the front 100 diffs have failed. And considering the larger total population of 100 owners that don't even know about 'MUD and the poll the number of failures gets reduced quite significantly I'd say in relationship to the total units sold stateside. But its something to at least be aware of so one can make/take they're own assessment/pre-emptive measure.
Threads like this are great if nothing more than to bring awareness to all potential issues!
Man I thought for sure Shotts would have already posted in this thread! haha.
I figure 35's are about the largest, and ARB is obviously the best locker out there. I think if you are easy on the pedal you can go a long way without breaking stuff on your vehicle. Knock on wood, I haven't had any issues with the new FJ and I am pretty easy on the throttle. I follow the 'as slow as possible, as fast as necessary' philosophy. Also, I am wondering why everyone is feeling that ATRAC is breaking stuff. Land Rover has been using their version - ETC, for years and I have not heard of anyone crunching gears in their diffs because of traction control.
I figure 35's are about the largest, and ARB is obviously the best locker out there. I think if you are easy on the pedal you can go a long way without breaking stuff on your vehicle. Knock on wood, I haven't had any issues with the new FJ and I am pretty easy on the throttle. I follow the 'as slow as possible, as fast as necessary' philosophy. Also, I am wondering why everyone is feeling that ATRAC is breaking stuff. Land Rover has been using their version - ETC, for years and I have not heard of anyone crunching gears in their diffs because of traction control.
Man I thought for sure Shotts would have already posted in this thread! haha.
I figure 35's are about the largest, and ARB is obviously the best locker out there. I think if you are easy on the pedal you can go a long way without breaking stuff on your vehicle. Knock on wood, I haven't had any issues with the new FJ and I am pretty easy on the throttle. I follow the 'as slow as possible, as fast as necessary' philosophy. Also, I am wondering why everyone is feeling that ATRAC is breaking stuff. Land Rover has been using their version - ETC, for years and I have not heard of anyone crunching gears in their diffs because of traction control.
The diff issues are related to ATRAC and non-ATRAC LC 100's. Too much skinny pedal is probably to blame for a some if not a majority of the front diff failures.
hoser
SILVER Star
There was another poll awhile back about broken differentials. Probably not of much significance because of the small sample size but...
https://forum.ih8mud.com/showthread.php?t=75567
https://forum.ih8mud.com/showthread.php?t=75567
