Author Topic: Marlin Crawler's 4.70:1 Xtreme Duty Features in-depth with BigMike  (Read 4347 times)

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BigMike

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Hello Crawler Land!

We have brought back our 4.70:1 XD Gear Set and for the first week are offering them at a $50 off re-introduction sale!

Standard price: $599, One-week Re-introduction sale price: $549!

The audience for this tech article will be 4cyl 1979-95 Hilux Pickup/4Runner, or through the use of bolt pattern conversion plates and a TacoBox, most 4cyl/6cyl/8cyl auto/manual 1979-2018+ Toyota Tacoma, 4Runner, T100, Tundra, FJ Cruiser, Sequoia, and Lexus GX470.

View online here: https://www.marlincrawler.com/transfer-case/gears/hilux-gear-drive/4701-xd-gear-kit



We thought it would be fun to explain some features per day until the week is up, so without further ado, here comes Day #1!
« Last Edit: Aug 13, 2018, 06:12:46 PM by BigMike »
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2016 56-speed 580:1 Triple T/Case 3rd gen Tacoma Rock Crawler   
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BigMike [OP]

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Day #1: Total-Spline Input Technology

To kick things off, let's take a look at Marlin Crawler's Total-Spline Input Technology



When Marlin was developing his very first low range gear set back in 1995, a key requirement was strength. A ratio too low would become too weak, and after careful consideration, the tooth count ratio of 35/20 & 43/16 (creating 4.703125:1) was selected due to it being just before the point where strength began to drop off. And thus the famous 4.70:1 ratio was born!

By this time Marlin's revolutionary 2.28:1 Dual Case setup was nearly two years old and he knew the weak-link would be centered around the t/case input. The reason is two-fold:

First, the input shaft is normally connected to the transmission output coupler and sees a maximum load of engine torque multiplied by transmission gear. As a theoretical example, if your engine at partial throttle is generating 50 lb-ft torque in a 3.95:1 first gear, then the t/case input would see 50 lb-ft X 3.95 = 198 lb-ft torque. Toyota designed for this and all is well but when you place the same t/case input behind Marlin’s brand-new 2.28:1 Dual Case setup, it would now see 50 lb-ft X 3.95 X 2.28 = 450 lb-ft torque! This is like having a 2018 Corvette’s 6.2L LT1 engine[1] at full throttle and peak torque attached to the front of a 40-year old carbureted 4cyl Toyota transfer case....and our example is only at partial throttle! Wow!

Second, if the input shaft does not just simply yield and twist straight off the input gear, then it will all be up to the splines. For the RF1A gear drive t/case, Toyota made two different input spline types where the first (1979-1980) had a spline stepping designed to preload the transmission output shaft and the second (1981-1995), which was manufactured in far greater numbers, did not. The early input is stronger, however, the spline stepping must be ground down in order to fit into late model applications -- as well as Marlin’s new Dual Case Setup. Both shaft diameter and case hardened material is reduced resulting in a weaker-than-stock input which is no good. The second input design was better because the t/case no longer shared thrust from the transmission, but it unfortunately incorporated a much larger engineer’s fuse, which is a failure point designed directly into the factory Toyota input which is not desirable for Marlin’s new hobby he called Rock Crawling.
 
Comparison of Marlin Crawler’s Total-Spline (left) with the most common “fused” Toyota input design that all other manufactures use (right)


What do I mean by an engineer’s fuse? I am referring to the small tapered cross-sectional area between the splines and the input seal surface, which is an inherent weak-link designed to fail. This is a common manufacturing practice with some fuses designed to maximize profit through dealership repairs. But when you’re on the trail 100-miles removed from civilization, the last thing you want is a known weak-link! The idea is that you should not have to repair transmission or transfer case components on any trail. We achieve this with a combination of both (A) moving fuses downstream as far as we can, such as an axle hub gear (which is a piece of cake to replace even in the dark), and (B) by using high strength alloys and oversized outputs and axle shafts: It’s all in the name of making the drivetrain as strong as possible while only having to carrying spares for readily accessible and easy to replace components.

In conclusion, Marlin’s solution solved both issues simultaneously and he called it the Marlin Crawler “Total-Spline”. The Total-Spline is the only 4.70:1 technology that both (A) does away with the factory engineer’s fuse and (B) has full/complete splines all the way up to the transmission output sealing surface. The splines are 65% longer and the fuse-less shaft has a 15% larger minimum diameter. This means the Total-Spline input is more difficult to strip and more difficult to snap off. An indirect and huge benefit of the longer splines is that they contact more of the transmission output and Dual Case output couplers, rendering both a longer life expectancy and higher ultimate torque loading capability in high torque demand applications such as a Dual Case setup.

The Marlin Crawler Total-Spline is the longest lasting input capable of running the highest amount of torque available today. Invented in late 1995, here is Marlin holding the world’s first ever Total-Spline 4.70:1 prototype gear set which was completed and brought to market in 1996 (images circa early 1996)



Sources:
[1] 2018 Corvette Stingray Specs, https://www.chevrolet.com/performance/corvette-stingray-sports-car
« Last Edit: Aug 13, 2018, 06:06:43 PM by BigMike »
New Instagram: @SlowestTacoma

Check out our new Rock Crawling Videos!
2016 56-speed 580:1 Triple T/Case 3rd gen Tacoma Rock Crawler   
1981 36-speed 511:1 3RZ-FE Rock Crawler
1987 6-speed Supercharged 4A-GZE MR2
Things are only impossible until they are not.
"The worst of both worlds, the best of neither." -abnormaltoy
"An informed question. But difficult to answer. I am what you see." -Nanaki

BigMike [OP]

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Day #2: Countershaft & NEW Input Oil Pumps

Continuing with the input, we are excited to announce that for the first time we have migrated our exclusive XD Countershaft Needle Bearing Oil Pump system over to the input! We now have five specific and completely unique Marlin Crawler oil transfer systems in our 4.70:1 gear set. Let’s take a moment to discuss two of them.

Countershaft Cage Bearing Oil Pump

Fast forward to 2001, and the world’s first Dual Case’d Tacoma was born, aka the Marlin Crawler MC09 TacoBox. We now had larger, heavier 6-cylinder and 8-cylinder (Tundra/4Runner/Sequoia) Toyota trucks using our gear sets and the next weak-link was discovered thereafter.



It turns out that by increasing the torque load at the low range idler gear of a Dual Ultimate setup (see: What are Dual Ultimate and Dual Ultimate Overkill Crawlers?), we saw the factory Toyota stamped-steel lower idler cage bearing fail in extreme use.

To understand this, let’s look at a theoretical torque increase again. When you place Marlin’s 2.28:1 “Crawl Box” (the term Marlin created to describe his Dual Case Low Range Unit) in front of a Marlin Crawler 4.70:1 transfer case, the t/case’s lower idler bearing is seeing a torque increase of 2.28:1 times the 4.70:1 input-to-counter shaft ratio of 1.75:1 (35 teeth divided by 20), which results in 3.99 times more torque passing through Toyota’s light-duty stamped-steel outer race needle bearing.

This is actually what prompted us to upgrade the design of our Dual Case Adapter, also referred to as our XD technology (much more on that here), to have by far the highest load rated machined-steel outer race counter shaft needle bearing on the market by a whopping 52%.

Marlin’s Dual Case XD High Strength Needle Bearing that rules the dual case world


Here is an example of an exploded factory Toyota idler gear needle bearing found wanting. Give that hardworking bearing a break with our XD technology!
 


The crazy thing is that we only saw these failures in rare & severe cold climates specifically from Canadian customers. This was surprising until we considered what was going on.

When you are in good quality light and powdery snow, the kind of snow that few of us Central California wheelers have ever seen in our lives, that stuff gets packed up into every nook and cranny under your rig and will cause havoc on mechanical components. The reasoning here is twofold:
  • If you’ve ever wheeled in deep snow then you know how much throttle and effort is required to go anywhere. There are many negative factors at play, such as higher than normal resistance to motion and low average speed resulting in low air flow. These combine for a drivetrain that is under high levels of stress with elevated heat soak, and
  • As snow is packed around your transfer case, particles in contact with hot aluminum housings will melt, and combined with rapid cooling from evaporation will re-freeze into a sort of ice blanket for your t/case.
Now you’re out there flooring it, working the truck forward and rearward over and over, spending ten minutes just to go 100 feet, all the while your t/case is baking away with no heat dissipation from the environment. If you are a fan of Rallycross like myself, then you’ll know of the struggles teams have with overheating in the snow and ice. It seems counter intuitive but it’s a real problem!

The same principle applies with mud bogging and is one of many reasons why you should never do this with a Toyota. Mud packs up and around your transfer case and because dirt has very good thermal insulation (think adobe huts) it reduces heat exchange away from your drive train resulting in elevated gear oil temperature and increased bearing stress. As the saying goes in the machine industry, heat kills!
While we can’t change the elements, we can improve oil flow! Perhaps the top of your t/case is still conducting heat, and if we can get some circulation going maybe juuuuuust maybe we can save your t/case!

Spoiler alert: After the creation of our Xtreme Duty products, we have a 100% success rate in all sever weather climates!

What we have done is an ingenious little oil pump integrated right into the counter shaft. Below is a close up picture of what it looks like. What happens is that as oil gets squished between the teeth of the low speed and idler gear shown, it becomes highly pressurized and instantly pumped directly into the center of the needle bearing.

The Marlin Crawler 4.70:1 Counter Shaft is the only one of its kind in the world that has this feature. Even if you don’t play hard in the snow or mud, you can still have great piece of mind knowing that you’re extending the life of your idler gear needle bearing.



ALL-NEW: Input Shaft Pocket Bearing Oil Pump

Ok guys! This is insanely great! We have applied the same oil pump design to our Input Gear which pumps oil directly to the smallest bearing in the entire transfer case, and not only that, but consider the following:
  • For 1988+ Chain Drive Applications
    Should you have a Xtreme Duty 4.70:1 Dual Case Unit (all 1988 and newer chain drive applications, such as the MC09, MC10, and MC11 Marlin Crawler TacoBox), then for the first time in history you have a Toyota Dual Case setup with an internal Coupler Oil Pump!
  • For oil-pump-less Chromoly Output Shaft users
    Should you have a transfer case equipped with a discontinued All Pro off-road or Bobby Long output shaft that lacks the factory Toyota oil pump, then you can now have for the first time ever a proper oiling to the tiny input pocket bearing!
This is great news for many rigs out there and is the only twin-solution on the market that restores proper pocket bearing oiling with oil-pump-less HD outputs as well as providing oil to a Dual Case coupler, depending on application.

Here is what our NEW XD Input Gear looks like. Combined with our Total-Spline technology, it’s an incredible input unlike any other:


…and here is what it will avoid in certain applications! Yikes! Don’t let something like this happen to your 1988-2018+ modern Dual Case setup! Get some freak’n oil flow in there with the Marlin Crawler XD technology!

« Last Edit: Aug 14, 2018, 06:44:15 PM by BigMike »
New Instagram: @SlowestTacoma

Check out our new Rock Crawling Videos!
2016 56-speed 580:1 Triple T/Case 3rd gen Tacoma Rock Crawler   
1981 36-speed 511:1 3RZ-FE Rock Crawler
1987 6-speed Supercharged 4A-GZE MR2
Things are only impossible until they are not.
"The worst of both worlds, the best of neither." -abnormaltoy
"An informed question. But difficult to answer. I am what you see." -Nanaki

BigMike [OP]

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(edit: if you got here early, sorry I forgot to post this first and have shifted my original reply down)

Before we get into today’s topic, I want to reiterate just how important the Input Gear Oil pump is… The below image comes directly from our website confirming the two key points above.

When I wrote “insanely great” I wasn’t just quoting the Phantom Phreak (great movie), I was being quite serious: For the first time since Marlin created the entire Rock Crawling industry we now have a Toyota Dual Case / Crawl Box where the splines of the Output Coupler and T/Case Input are oiled!!

More than two decades of designs have come and gone from multiple companies trying to minimize coupler spline wear and we now finally have the industry’s first oiling solution when you place our 4.70:1 Total-Spline input gear into your Dual Case Unit,

…which as most are aware is only practical in front of a chain drive t/case

……which means the Marlin Crawler TacoBox Supreme is the ONLY late-model Toyota Dual Case setup available that properly provides oil to the Dual Case Coupler and T/Case input shaft splines!



(Spoiler #2: Our Competition Gears have had this input oil pump feature for more than a year now. More on this at a later date!)
« Last Edit: Aug 15, 2018, 07:01:30 PM by BigMike »
New Instagram: @SlowestTacoma

Check out our new Rock Crawling Videos!
2016 56-speed 580:1 Triple T/Case 3rd gen Tacoma Rock Crawler   
1981 36-speed 511:1 3RZ-FE Rock Crawler
1987 6-speed Supercharged 4A-GZE MR2
Things are only impossible until they are not.
"The worst of both worlds, the best of neither." -abnormaltoy
"An informed question. But difficult to answer. I am what you see." -Nanaki

BigMike [OP]

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Day #3: Slow Speed Oil Transfer & Cage Bearing Oil Pump Systems

Now that we’ve got oil to the inner diameter and pocket bearing of either the t/case output shaft or the dual case coupler, we now need to figure out how to keep the Low Speed Gear’s cage bearing lubricated. Enter the two solutions only found with the Marlin Crawler Xtreme Duty 4.70:1 Gear set.

This next technology was developed during Marlin Crawler’s six consecutive top-20 finishes in the annual King Of The Hammers event. On the left is our leaf-sprung 3-time National Champion Formula Toyota and the right a linked Turbocharged 3RZ-FE Marlin Crawler X-Chassis competition rig. Both running our Dual Ultimate Transfer Case setup which combined for a record six consecutive top twenty King Of The Hammers finishes for a Toyota platform



Non-stop testing in the hot desert led to the discovery of an oiling need to the Low Speed Gear’s cage bearing at low RPM use. The reasoning is that the internal factory oil pump of the transfer case only functions when you have sufficient RPM at the output shaft necessary for the oil pump screw gear to pressurize the inner passage of the output and provide oiling to its four cage bearings. But now that we are going so slow, and worse, climbing up steep obstacles so slow that was previously literally impossible without the Marlin Crawler, we’ve got a twofold issue:
  • One: Not enough shaft RPM for the factory t/case oil pump to function
  • Two: A previously impossible ability to slowly climb steep angles requiring oil to travel against gravity to lubricate critical components

When you break it down it becomes clear how important this is:
With our most typical Marlin Crawler Dual Ultimate setup, at an 800 RPM idle the factory t/case oil pump is only rotating 18.89 RPM. Only nineteen revolutions per minute! This is an oil pump that is almost 50-times less effective than 5th gear highway use ((common 1st gear * Crawl Box * T/Case) / 5th gear high-range = (3.95*2.28*4.7)/0.85*1.0= 49.798). Then on top of this we regularly pit this absence of oil pump pressure against gravity in steep climbs.

The factory t/case oil pump needs help on the trail during slow Rock Crawling. Here is my Triple Marlin Crawler Transfer Case (2.28:1 MC08 + 4.70:1 TacoBox) 2016 3rd gen Tacoma at such a steep angle my engine’s low oil pressure warning light was on. At angles like these, a transfer case oil pump has a lot of gravity to contend with.



A saving grace could be that “Hey, we are going incredibly slow so it’s okay” but what one forgets is that this particular cage bearing that we want so badly to oil, the Low Speed Cage Bearing, sees the highest amount of torque from any bearing within the reduction housing precisely because the Low Speed gear is the last of the reduction gears and the one generating the final torque for your tires. Using our 50 lb-ft example from reply #1,
  • As mentioned the 4.70:1 T/Case Input sees 450 lb-ft of torque (engine * trans * Crawl Box = 50 lb-ft * 3.95 * 2.28 = 450.300 TQ),
  • The 4.70:1 T/Case Countershaft sees 788 lb-ft of torque (450.30 * (35 countershaft teeth / 20 input teeth) = 450.30*1.75 = 788.025 TQ)
  • And finally the Low Speed Cage Bearing, which supports the Low Speed Gear, sees 2,118 lb-ft of torque (788.025 * (43 low speed gear teeth / 16 countershaft teeth) = 788.025*2.688 = 2118.211 TQ….at only partial throttle!)
Result: The most heavily loaded reduction housing bearing also happens to be the last bearing to receive lubrication from the (no longer functioning) t/case oil pump. This cage bearing is the last line of defense between engine and reduction housing torque output and it could use some big-time help and this help has come in the form of the Marlin Crawler Xtreme Duty Slow Speed Oil Transfer & Cage Bearing Oil Pump Systems.

Xtreme Duty Slow Speed Oil Transfer



Pictured above is our Xtreme Duty 4.70:1 Low Speed Gear. This is the only 4.70:1 gear in the world that has not one but two integrated oil pump systems.

The first is what we call the Slow Speed Oil Transfer System and is best illustrated in the below animated image. When the rotation of the XD Low Speed Gear is reduced to go as slow as possible for maximum Rock Crawling effectiveness with the highest torque load present, the slots, which we have intentionally designed as straight, horizontal holes rather than smoothly rounded go-fast holes, collect, carry, and deposit gear oil directly on top of the output shaft assembly.



From here, the oil needs to make its way down and into the cage bearing of the Low Speed Gear, and for this may I introduce our second integrated oil pump system which we call the Cage Bearing Oil Pump

Xtreme Duty Cage Bearing Oil Pump

Once oil has slowly been lifted up and deposited atop the output shaft assembly, it then gets directed through wide and angled oil channels on both the front and back side of the Low Speed Gear shown below:



Contrast this with factory and attempts at copying Marlin’s original 4.70:1 gear ratio and we find there is no comparison. At left we have the factory low speed gear cage bearing oil transfer port design, at center we have our most common competitor’s low speed gear cage bearing oil transfer port design (smaller than factory), and at right is our exclusive, angled, and wide-mouth Xtreme Duty 4.70:1 Marlin Crawler low speed gear cage bearing oil transfer system that we incorporated on both sides of the low speed gear.



Now that we have returned oil to the mainshaft assembly, we can now resume supplying oil to the important bearings left stranded by the inactive factory oil pump, namely the two 4WD idler gear cage bearings, the low speed gear cage bearing, and the input pocket cage bearing.

Hopefully it is becoming clear that the original 4.70:1 gears that started it all are designed with the same love and passion that Marlin used when he created the Rock Crawling movement a quarter of a century ago, and why they are the clear winner for mixed trail and highway use.
New Instagram: @SlowestTacoma

Check out our new Rock Crawling Videos!
2016 56-speed 580:1 Triple T/Case 3rd gen Tacoma Rock Crawler   
1981 36-speed 511:1 3RZ-FE Rock Crawler
1987 6-speed Supercharged 4A-GZE MR2
Things are only impossible until they are not.
"The worst of both worlds, the best of neither." -abnormaltoy
"An informed question. But difficult to answer. I am what you see." -Nanaki

bigwill837

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Great info and cool products!

 
 
 
 
 

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