Topic: Broken 23 spline input, looking for real strength comparisons.

[1uzrnr]

I was wheeling pretty hard last weekend in my 1uz powered, one ton 4runner and ended up breaking the rear 23 total spline input.  I was going full throttle backwards up a hill in reverse with the front case in low and rear case in high when it let go.  I tried to call Marlin many times today, but I guess they weren't working. 

What I'm really looking for is a strength comparison between the two competitors 23 spline inputs.  I want real numbers if they are possible, not the nancy thingy gobbler opinions because they like one brand over the other. I need to get my truck running again before I start looking at stronger doublers and rear cases. 

Also, I can't find much on if whether using only the front case in low will always destroy the inputs.  Anyone have real experience or factual opinions on this?









And what they go in.

[Nation]

MC- closed on friday. Wondering the same things. Interested to see what people say. Toyota thinks 23 spline is stronger anyway..

[Cheesemaker]

Looks like after upgrading motor and axles, you found the weakest link in the system. 


They are open Monday thru Thursdays.  They are closed Fridays. 

[jrock]

Maybe try Cryo'ing the input? Curious too.

[BigMike]

Wow nice carnage 1uzrnr and nice 4Runner. This is what happens when you go full throttle

What I'm really looking for is a strength comparison between the two competitors 23 spline inputs.  I want real numbers if they are possible, not the nancy thingy gobbler opinions because they like one brand over the other.

Thank you very much for the pictures. This XD input failed from brute torque; It has a good yield shape that we as manufactures like to see. While we have never done a load test on a TG input vs. a stock Toyota input vs. our Total-Spline input, I can tell you that TG uses a non-molybdenum steel (not Chromoly), the factory uses a high nickle steel (not Chromoly), and both our XD and Competition gears are made from SAE Chromoly steels (XD from SAE 8600-series and Competition from SAE 4300-series).

So right off the back, both our gear sets use steel with higher yield and shear strength ratings than both TG and stock parts, and combining this with the increased diameter of our Total-Spline technology guarantees to be stronger than any competitor. It would be nice to see just how much stronger our inputs are. We have a few places we know of who can do testing for us, and if we did this we'd also test our 135% thicker flanges and oversized 30-spline outputs, which on paper are also much stronger than stock and Longfield components.

I need to get my truck running again before I start looking at stronger doublers and rear cases.

Keep in mind that the gear drive t/case was designed for use behind a 120 lb-ft torque engine in a lightweight pickup with 29" tires. Yes Marlin has taken it to heights Toyota would never have imagined but everything has a limit and it's very well possible you're at that limit, especially if you are going full throttle with a V8 -- what can you really expect. I always describe the best sort of assurance we have in our H.D. gear drive t/case products as follows...
1) they have survived all 8 King Of The Hammers including use in a turbocharged 2.7-liter 3RZ-FE buggy,
2) they have survived multiple Baja 1000s behind high output 4.0-liter inline 6cyls in full bodied Jeeps,
3) they have survived thousands of miles of use in full bodied Supercharged 3.4-liter 6cyl Tundras and 4Runners, and
4) they have survived multiple seasons of Xtreme Rock Racing (XRRA) behind a 4.7-liter 2UZ-FE 8cyl buggy.

But we are full aware of the limit of these cases which is the smaller gear on the 4.70:1 idler gear. It is the first to go when people get really crazy with their trucks -- however to our knowledge this has only occurred when combined with our oversized 30-spline output shafts and their 135% thicker flanges -- more about this later. So we have seen a few of our Competition gear sets fail, which is very rare, but nevertheless fail. As for inputs, we have seen about a dozen 23-spline Total-Spline XD inputs fail, but only 2 or 3 Competition Inputs fail. Breaking a Competition 23-spline Total-Spline input is one of our most rare failures. The Competition Total-Spline input is so strong that the gears inside fail before the input. This is certainly better than snapping off an input, as you can simply replace an input gear and continue on, but it would be really interesting to see how much stronger our Competition gears are than our XD gears, as they are made from a higher grade material...

Also, I can't find much on if whether using only the front case in low will always destroy the inputs.  Anyone have real experience or factual opinions on this?

The one good thing about the rear case in high range is that it bypasses the weakest link of a Marlin Crawler Total-Spline 4.70:1 gear set, and that's the idler gear. I single out a Marlin Crawler gear set because competing products will strip-out both input & dual case coupler before getting to this point. This is a typical issue with TG parts because 1) they do not have our Total-Spline technology, 2) have 8 times less coupler support (source), and 3) their couplers that are NOT made from SAE Chromoly steel like ours. (I see you also have our MC07 adapter which is awesome.) Competing products do not face this because they already fail in other locations beforehand. But the low range gears are bypassed in high range and therefore the weak link becomes the input shaft.

In low range the outputs are having to deal with torque loads 4.70 times greater than the input, so it is more common to break outputs. Even Longfield Chromoly outputs break -- we have three broken samples at our shop. But after we created our oversized 30-spline Chromoly outputs (57% larger rear (source), 67% larger front (source)), no one in the world has managed to break one. Now what we are seeing is that people are managing to break 4.70:1 idler gears.

It's all a game about hunting down weak-links. First it was the input gear, that was solved with our Total-Spline technology. Then it was outputs breaking. That was solved with our 30-spline output Technology. Then it was flanges breaking. That was solved with our 135% thicker HD flanges. Now it is the low range gears themselves. We have done some work towards this issue with our XD gear sets, which feature 42% wider idler gear teeth and an oversized shank diameter (see points #3 and #4 here). This is a great approach at the next weak-link, but what we haven't done is applied our XD technology to our Competition gear set....yet. That would be the ultimate as we'd combine the XD features with our Competition's best SAE certified material available.

In the end we will openly admit that if you find yourself breaking t/case parts over and over then you should consider moving on to something stronger than the 4cyl Toyota t/case. Swapping out to our Competition Total-Spline 4.70:1 gear set is definitely the strongest gear set in the world -- on paper -- and would give better results than our XD gear set you are using now. Only time would tell as to if you are able to break even our Competition gears or not.

Toyota thinks 23 spline is stronger anyway..

The 23-spline gear set not only has more spline engagement & surface contact area but it has a larger diameter which is where it gains the vast majority of its strength over the 21-spline. Rather, 1uzrnr is asking about a comparison between Total-Spline and non-Total-Spline 23-spline inputs.

Maybe try Cryo'ing the input?

Remember cryogenically freezing materials primarily increases fatigue limit, not ultimate strength. It is a process that attempts to shrink grain boundary size by reducing irregularities in the crystal structure, which may result in fewer dislocations in the crystal structure, which may reduce the chance of fracture propagation (cracks). This is primarily beneficial only over similar repeating loads, not sudden spikes in loads. Cryo-freezing an input shaft or an output shaft will enable the teeth or bearing races or shift hub splines of the shaft to wear longer against their counterparts, but will still exhibit ultimate yield and shear strengths at comparable levels. For this reason you find cyro services for ring and pinion gear sets or other components which undergo millions and millions of cycles. But it isn't so beneficial to input, output, or even axle shafts when it comes to dumping the clutch at 5,000 RPM or having an accelerating airborne 40-inch tire come crashing down onto a high traction surface.

Regards,
BigMike

[BigMike]

Ah, as I mainly only offer tech support, I forgot to mention the most important thing to you 1uzrnr and that is I don't know if you are outside our one year warranty or not, but our sales department is usually compassionate to any broken parts and will most likely work with ya on getting a replacement input. We are here to take care of our customers who share our confidence in and run our products

Give us a call on Monday for sure.

Regards,
BigMike

[1uzrnr [OP]]

Ah, as I mainly only offer tech support, I forgot to mention the most important thing to you 1uzrnr and that is I don't know if you are outside our one year warranty or not, but our sales department is usually compassionate to any broken parts and will most likely work with ya on getting a replacement input. We are here to take care of our customers who share our confidence in and run our products

Give us a call on Monday for sure.

Regards,
BigMike

Thanks for taking the time to type all that out Big Mike.  Just to clarify, I'm running two stock geared cases.  The front has a TG 23 spline input with their tacoma adapter and the rear is, as you saw already, a MC adapter with 23 spline input and a longfield output.  If you have a Comp 23 spline in the stock ratio I may be interested in that just for a little more piece of mind.  My warranty has long been past due so I will be buying a new input for sure. 

Is the stock idler gear a weak link like with the 4.7 gear set?  If so, I would guess I could break either the input or idler gear.  Have anymore thoughts on dual stock geared cases with the front in low and rear in high?

I was definitely flogging on it in reverse, I'm not afraid to admit that.  I haven't had a serious break until last weekend and I've done a lot stupider things with my 4runner.

I'll be calling Monday morning.

[BigMike]

Just to clarify, I'm running two stock geared cases.

Ahhhhhhh Yes, I see the 2.28:1 gears now. Sorry, with a truck as built as yours, I instinctively assumed it was an Ultimate setup.

If you have a Comp 23 spline in the stock ratio I may be interested in that just for a little more piece of mind.

Unfortunately we only make our Competition gears in a 4.70:1 ratio. Our 2.28:1 Total-Spline input is only made using our XD material (8600-series SAE Chromoly).

Is the stock idler gear a weak link like with the 4.7 gear set?

While the stock material is weaker, I'm going to say the weakest gear on the stock idler is less likey to fail because it has larger and wider teeth, and it is undergoing lower levels of torque. Please keep reading...

There are four gears in mesh with this low range system. The first pair is the Input->Counter, and the second pair is the Counter->Low Speed gear. This second pair is the weak link of the reduction gears themselves because it has the smallest individual gear of them all, regardless if 2.28 or 4.70. However, keep in mind that this 2nd pair of our 4.70:1 gears has more torque passing through it because the first pair of gears in our gear set is a lower ratio than the first pair of gears in the 2.28:1 ratio. So the counter shaft of the 4.70:1 has a higher torque load passing through it by default. So not only does the smallest gear of the 2.28:1 gear set have larger teeth, but it also has less torque passing through it.

Have anymore thoughts on dual stock geared cases with the front in low and rear in high?

1uzrnr, Woah, actually, this is very important and is something I should have asked above. Can you please verify if this is how you had the cases engaged when our input snapped? There is a very important thing to consider and that is how your engine torque is being multiplied through your drive train. We strongly advise to keep your largest gear reductions as far down stream from the engine as possible. This is why it is advised to NOT run 4.70:1 gears in a Crawl Box when in front of a gear drive t/case and I'll explain. Let's assume you have a R150F behind your 1UZ-FE, a maximum of 261 ft-lbs torque at full throttle, and theoretically speaking please consider the following:

Option 1: 1st gear with your 2.28:1 MC Crawl Box in High Range and your 2.28:1 T/Case in Low Range:

Combined T/Case Gear Ratio: 1.00:1 * 2.28:1 = 1.00 * 2.28 = 2.28:1

Torque Loads:
261 ft-lbs TQ -> 3.83:1 1st gear -> Crawl Box Input Gear -> 1:1 Crawl Box -> MC Total-Spline Input Gear -> 2.28:1 T/Case -> Output shafts
For the Crawl Box Input:
= 261 * 3.83 = 999.63 lb-ft TQ
For the T/Case Input:
= 261 * 3.83 * 1.00 = 999.63 lb-ft TQ

So you can see both inputs are experiencing the same load. This is very nice. Now lets consider the alternative:

Option 2: 1st gear with your 2.28:1 MC Crawl Box in Low Range and your 2.28:1 T/Case in High Range:

Combined T/Case Gear Ratio: 2.28:1 * 1.00:1 = 2.28 * 1.00 = 2.28:1 -- the same as above

Torque Loads:
261 ft-lbs TQ -> 3.83:1 1st gear -> Crawl Box Input Gear -> 2.28:1 Crawl Box -> MC Total-Spline Input Gear -> 1:1:1 T/Case -> Output shafts
For the Crawl Box Input:
= 261 * 3.83 = 999.63 lb-ft TQ -- the same as above
For the T/Case Input:
= 261 * 3.83 * 2.28 = 2,279.16 lb-ft TQ much higher than above

So as you can see that even with the SAME combined gear ratio, the 2nd input is dealing with 2.28 times more torque when the front Crawl Box is in low range. If the end result is still an overall reduction of 2.28:1, then there is nothing but disadvantages here and therefore don't do this short of just moving your truck around in camp or doing very basic, slow speed wheeling.

To make it worse, with the Crawl Box in low range you are transferring the load through the low range gears yet they have less gear oil (~0.8 qts) to dissipate heat than compared to the gears in the t/case (~1.7 qts). Yes, we have built a lot of oiling features into our adapter plate, but what happens when you are in a long uphill climb? All that oil is going to flow out of the Crawl Box and into the T/Case. Now you are pushing torque through the front low range gear set that has very little oil while the very same low range gear set is just idling in the t/case that has an over abundant amount of gear oil.

Always, always shift the T/Case into Low Range first, and then if you encounter a need for lower gearing then engage the Crawl Box. Sure there are exceptions to this, such as if you have a 2.28:1 Crawl Box and a 4.70:1 T/case and you didn't want to use your 4.70:1 gears, then obviously your only choice is to use the front 2.28:1 Box, but in the scenario where the two cases have the same low range gear ratios, you should always use the T/Case as the full-time low range box and only engage the front case when you need the extra gearing.

For me I have Triple Cases in my truck as follows: 2.28:1, 2.28:1, and then 4.70:1. So if I wanted to use a 2.28:1 ratio, I would without question select the second case and leave the front case in high range until I absolutely needed it. For me it's even worse as oil from both my front cases can flow to my back case so I need to be sure that if I want to use the front case on a long uphill climb, I probably shouldn't be in 4th of 5th transmission gear because those gears would be singing-away at high RPM while starving for oil.

I could offer you additional assurance of our gear drive t/case products and that is both myself and Marlin. I've been running my 2.28-2.28-4.70 triple setup since 2004 without any problems and Marlin has been running his 2.28-4.70-4.70 triple setup since 1995 without any problems. Look at Marlin's scenario. With all of his t/cases in low range, if he were to floor it under full load -- which is something I can firmly say he has never done -- then he'd be passing 9,768.17 lb-ft TQ through the input gear of his T/Case, which is 329% more torque than what your V8 can muster.

This is synonymous to your 1UZ-FE having a peak torque output of 1,119 ft-lbs. That is truly how far Marlin has taken this 4cyl t/case. It can survive behind a 1,100+ TQ V8 engine ........ so long as you don't flog the hell outta it!!

This is a fun discussion. These are the topics I enjoy getting carried away with

Regards,
BigMike

[Nation]

I love it!  BigMike the rock star!

[1uzrnr [OP]]

Do you guys ever answer the phone?  I've called a lot of times and it's always the high volume of calls recording. I just want to know if the 23 total spline input is in stock and how much the shipping is.  I need to get my 4runner mobile again since it's sitting on the side of the street.

When I broke, I had the crawl box in low and the transfercase in high. 

Here is a short video of what I was doing a couple of minutes before it broke.


Thanks again for your input BigMike

[Nation]

Umm..... that'll do it.

[Cheesemaker]

Yeah, its not often you can bounce off rev limiters like that, and not have anything break!!

[1uzrnr [OP]]

Yeah, its not often you can bounce off rev limiters like that, and not have anything break!!

I do it all the time, its the only way to get up some of the hills around here.  Think east coast style but lots of trees and roots instead of rocks.

[Nation]

I like your style 

[Cheesemaker]

The PNW its alot of the same.  Just ask Bigmike about when he went to a Memorial for Bobby Long in Washington state!    He realized how much skinny pedal is needed in our wet environment. 

Like this!





I'm a low impact type of wheeler.  I'd rather winch instead of tearing up the trail trying to get traction.  I've seen way too many trails get ruined and then ultimately closed. 

[1uzrnr [OP]]

I like your style 

Thanks!

The PNW its alot of the same.  Just ask Bigmike about when he went to a Memorial for Bobby Long in Washington state!    He realized how much skinny pedal is needed in our wet environment. 

Like this!




I'm a low impact type of wheeler.  I'd rather winch instead of tearing up the trail trying to get traction.  I've seen way too many trails get ruined and then ultimately closed.

Most of the trails are on private land that we have permission to be on and they come out and beat on their trucks just as hard.  If we all winched the hills there would be no reason to even drive back there.