Front Diff. Gone - Need help understanding some things. (1 Viewer)

[Reno]

2003 LX470

I recently had a bad offroading experience but serves me right and tore through my front stock diff, sounds like third member since when I turn off my diff lock option it sounds like a machine gun going off in my front end. This is why you DONT run 35's without changing your gears I guess but I am looking forward to the build now more. I was looking at 4.88s already anyways so I was already in touch with Opie from Just Diff. From my understanding I can have the option to go with an OBA air locker set up or get a fully built Mopar 8.75" 3rd member, 3.23 Ratio w/ Sure Grip. Which would retain my ELocker from what I understand? This is were I am lost. Is the LC100 same 3rd member/ E locker as the LX470? Maybe PFran can chime in. I saw his video and how he went with the OBA set-up. I want to do it right and do it right the first time im down there. Id like to do the OBA setup so I can have air plumbed through the vehicle in the future. Maybe someone from J.T.s can help me understand as well what my options are. I have tried searching but I feel like I am not getting the right answers. PFrans thread was as close as I got! Sorry if these are ignorant questions I am still new to the forum and very new to gearing, lockers, and options.

 

[AimCOtaco]

Stock front diffs don't lock, which diff lock makes the noise?

A 2003 has a 4 pinion front diff which is middle of the road strength wise, anything will break if missused.

The right gears will give you MORE torque in the diffs and won't really prevent breakage, what prevents breakage is having quality gears correctly set up on a rigid carrier. The lower gearing (higher ratio number) will give you better control offroad which can reduce misuse.

If it is in fact a broken front, the best option seems to be the ARB air locker and new gears. If yours is rebuild-able this should run you about 1500 - 2000 depending on the who and where. You would need an on board air system to operate it but not immediately.

Remember that you will have to re-gear both diffs if you decide to re-gear, both axles need to have the same gear ratio front and back.

I have no familiarity with using a Mopar 8.75" third, maybe it drops in but more likely it fits a new custom rear axle housing? Haven't come across that before around here but I certainly could have missed it. A 3.23 ratio definitely won't get you moving very well with 35's (stock is 4.30 so you need to go up from there with bigger rubber).

I recommend you do a lot of reading around here on similar threads before you hand over stacks of cash in any case.

 

[Trunk Monkey]

First off, I wouldn't drive it with it broken, you can go from bad damage to really bad damage.

Secondly, you don't have an e-locker in the front or rear axle. You do have a locking center differential.

Finally, your best option for replacement is an ARB locker and either replacement gears in the OEM ratio or new gear sets front and rear if you want. The ARB is air activated, so if you want to use it, you'll have to get a compressor, which can provide OBA.

And I have no idea how a Mopar diff comes into the conversation.

 

[Reno]

It only drove a quarter mile at slow speed before i put it into park. With every tire rotation it is a pop or slap almost. When I disengage my center diff lock it wants to come to a hault and rapid loud knocking noise occurs until I turn my center diff lock back on then it goes to making the noise on every rotation. I simply just dont know where to start for parts. I jacked the car up and rotated one front tire and the same grinding and almost impossible spot to continue rotating the tire by hand like it locks up. How would I use the center diff lock would I still retain it if I went with air lockers front and rear. If that was not the case id still do 4.88s while im down there but what would I be looking at if its something in my center diff lock broken? Thanks in andvance and putting up with the questions.

 

[Trunk Monkey]

It's not your center diff, it's the front end, either diff or maybe CV. If you have to move it you should pull the drive flanges and front DS.

 

[Reno]

Thank you guys for the help. It is much appreciated. What im looking to do is 4.88 gears front and rear with the air locker set up. Im working on getting the invoice for parts finalized by mid week.

 

[paflytyer]

Here's a good thread to read....

https://forum.ih8mud.com/100-series-cruisers/736534-4-pinion-diff-snapped-im-stranded.html

 

[Reno]

Thanks for the link I had come across it while searching prior to all this confusion on my end. Did a little more digging and from what I can understand is another way to save a little money would be going with the front and rear ring and pinion kits and doing just the single front ARB locker as having rear will basically make your ATRAC think all wheels are spinning freely and not engage whatsoever and I'd like to retain my ATRAC I think its a good feature. Once I get my parts list I will post it up later today hopefully.

Thanks again for all the help from admin and fellow mudders. I guess this is where the real money pit comes to life. Hopefully stay tuned on my build thread for more upgrades.

https://forum.ih8mud.com/100-series-cruisers/679578-renos-lx470-build-thread.html

 

[Skidoo]

Think you need to read the threads very carefully and maybe do a search on ATRAC.
LOCKERS DO NOT DISABLE ATRAC. They augment ATRAC.
The lowest cost is to replace what is broken in the front diff, ring & pinion or carrier & spiders. For stronger front diff put in an Airlocker and (if they are broken, new ring & pinion).

 

[artwerks]

...just the single front ARB locker as having rear will basically make your ATRAC think all wheels are spinning freely and not engage whatsoever and I'd like to retain my ATRAC I think its a good feature. Once I get my parts list I will post it up later today hopefully.
...

Reno,
Regardless of whether you have just one locker (front or rear) or two lockers, when the locker is engaged ATRAC will not need to function on said axle because ATRAC only works when the wheels are at different speeds on the same axle. If you have only one axle locked, the open axle will still allow ATRAC to function on that axle. This is the best part! You can have ARB air lockers and when they are not engaged the vehicles ATRAC will function as expected.

When my front diff broke, I pulled it out myself to save some money and took it to Slee to have them put in an ARB air locker. I thought about re-gearing to 4.88 as I'm sure I will go to 35s at some point in the near future, but that would have been extra cost since I would've had to re-gear the rear diff too and if I did that, it would only make sense to ARB the rear diff too $$$$
I decided not to re-gear, because I'm already running almost 34s with no gearing issues whatsoever and I've talked to others already running 35s who are not re-geared and also have no issues. I'm most likely not going to go bigger than 35 on a 100 series where re-gearing is really necessary.
So that begs the question... Why do you want to re-gear?

 

[OregonLC]

because your not going to go bigger than 35 on a 100 series where re-gearing is really necessary. I'm already running almost 34s with no gearing issues whatsoever and I've talked to others already running 35s who are not re-geared and also have no issues.
So that begs the question... Why do you want to re-gear?

I'd probably differ on that opinion. 33 is right on the border of needing to gear with the 4spd, especially when heavy. 34s and 35s definitely can benefit from lower final ratios, they get very piggy. 1st is like starting out in 2nd.

 

[artwerks]

I'd probably differ on that opinion. 33 is right on the border of needing to gear with the 4spd, especially when heavy. 34s and 35s definitely can benefit from lower final ratios, they get very piggy. 1st is like starting out in 2nd.

Good point.
Except we are talking about an '03 with a 5spd.

 

[Reno]

I have continued to do research on all this and yall are very right I am having trouble grabbing all the threads and putting them into one to make this understandable in my head I fell I understand one concept but then it gets washed by another. For example the difference between the 4 gear guys vs 5 gear running 4.88s or the LC vs LX which I have memorized the page on Slees website explaining the differences. I also found more info on ATRAC and running dual lockers after talking on the phone with the guys at Just Differentials, who have been crazy helpful to a new guy, and even go as far as putting you in on a group call so I could ask my questions to actual LC owners. If I am going to pay for these parts, I want to go with lower gears, and as far as lockers, I got both front AND back after talking to Opie and some guys from JustDiff. I understand that this will actually replace the carrier for the R&P which is initially what can cause the failure.

I plan on driving to work which is in Moab home is in Houston, TX. Once in Moab I travel up and down from the city to Dead Horse Point every day for around a 30 day period so a lot of inclines on the road. While I am home I pull a boat during the more warm months. I love my LX and don't think that now is the time to duck out after my first big repair. So after the re-gear I want armor which is more weight so everything I am trying to do is to help compensate a little for future modifications. I also understand that gears/lockers wont compensate for a dumb irresponsible driver, so these threads have definitely helped me see how the 100 series is properly used offroad and kept from expensive repairs.

 

[ENGINE er]

what part of houston are you in? Its sounding much more complicated than it actually is.

 

[OregonLC]

I have continued to do research on all this and yall are very right I am having trouble grabbing all the threads and putting them into one to make this understandable in my head

Don't worry about everyone else's opinions, look at what you want to do and what your current experience is. In the absolute simplest sense:

Lockers

Was ATRAC working for you sufficiently before? If not or if in the future you expect to run on more aggressive terrain then get it locked. ATRAC does a very good job at simulating a locker. There are situations, however, where being 100% locked makes the difference. The locker will not in any way decrease your ATRAC functionality; if you want ATRAC just unlock that axle. Nor will it affect the other axle.

Gearing

Was it peppy enough before or was it a pig? Do you want tall highway gearing? Does it tend to hunt between 5th/4th or does the TC stay locked? Are you increasing tire size or vehicle weight? The 5spd does have a lower 1st gear which helps off the line but there's also the affect on the highway on slight inclines. Never having owned an A750 box, my gut tells me that anything over a 33 on a built rig would benefit from shorter gearing. If you're over 33 then it's probably not a highway cruiser anyway. If you're at 33 then you just need to figure out the ultimate direction you want to go. Do consider the 'while you're in there' component; less cost and less hassle to do now.

 

[LandCruiserPhil]

Changing your gears to 4.88 will increase your RPM ~16% at the same given speed with stock gears.

 

[rusty_tlc]

My Opinion:


GEARING:

You want to maintain the correct tire to gearing ratio, this will minimize wear on the axles, transmission and the rest of the drive train.

To calculate what gears you need for a change in tire diameter:

NEW SIZE/OLD SIZE EX: the stock tire diameter is 31" you want to put 35" tires on

35/31~= 1.13 or a 13% increase in tire diameter

To find the correct gearing: X=1.13*stock gear ratio

X=1.13*4.30= 4.86

The closest gears available are 4.88.
​

LOCKER;

If you broke the OEM front carrier once you will probably break it again. Get the ARB locker and don't look back. Putting the OEM carrier back in is going to be a waste of money.
​

 

[LandCruiserPhil]

My Opinion:


GEARING:

You want to maintain the correct tire to gearing ratio, this will minimize wear on the axles, transmission and the rest of the drive train.

To calculate what gears you need for a change in tire diameter:

NEW SIZE/OLD SIZE EX: the stock tire diameter is 31" you want to put 35" tires on

35/31~= 1.13 or a 13% increase in tire diameter

To find the correct gearing: X=1.13*stock gear ratio

X=1.13*4.30= 4.86

The closest gears available are 4.88.
​

LOCKER;

If you broke the OEM front carrier once you will probably break it again. Get the ARB locker and don't look back. Putting the OEM carrier back in is going to be a waste of money.
​

The OP has a 2003 with a 5speed and 4.10 factory gearing

 

[rusty_tlc]

The OP has a 2003 with a 5speed and 4.10 factory gearing

That's why I put the EX: in there, it was just an example of how to calculate the gear change required for a change in tire size using numbers off the top of my head.

For the 2003:
According to Tire Rack there were two OEM tire sizes;
Converting 275/65-17 to Standard 30.6
Converting 275/60-18 to standard 29.5

so lets assume a 30" OEM tire diameter.

35/30=1.16

So X=1.16*4.10=4.78

4.88 is the closest available gear ratio.

The transmission is irrelevant IMHO. If you increase tire diameter without re-gearing you get "rubber overdrive" which is likely to result in poor performance on road and increased breakage off road.

 

[LandCruiserPhil]

The transmission is irrelevant IMHO. If you increase tire diameter without re-gearing you get "rubber overdrive" which is likely to result in poor performance on road and increased breakage off road.

Yes and no
Yes - Looking at final drive I agree 100%
1st gear is a different story
A 5 speed has a 18% lower first gear then a 4 speed.
With increase of tire size you effective 1st gear ratio with a 5speed and 35 is lower then a 4speed with stock tires (If my paper napkin calcs are correct)
I think we will all agree 35's increase breakage no matter what gear you run