Lubricating for crawl box?

[superyota]

Do you get proper oiling to the crawl box if you run the crawl box in low, and the rear case in high?  The only reason why I ask is I want to put 4.7's in my rear case, but at the same time, I use my stock low a lot(snow, mud, etc), and want to keep the gearing if possible.  Been thinking about doing triple stock cases just so I can keep the different gearing options, but going to a dual ultimate would be easier.  If I go 4.7's in the rear case, I would have the rear in 4H and the crawl box in low, and running gears 1-4 on the road in snow mainly.  I just don't want to burn up bearings and gears doing this because I'm afraid it won't lubricate correctly.  Any insight would be appreciated.  

Edwin

I posted this up on pirate also... http://www.pirate4x4.com/forum/showthread.php?t=1019420

[fordh8r]

Makes no difference what 'range' you select...all the gears are spinning in either range and the oiling is the same. 

[superyota]

I was under the impression with running the front in low and rear in high, the front would be spinning too fast, causing it to get too hot and possible ruining it.  do you run yours this way?  I do a lot of snow trips to mammoth in the winter time where I take my truck, and the only way to get around on sloped roads there is 4low for me.

[fordh8r]

Yup!  I run the crawl box in low most the time and then drop the rear in low when things get more technical. But when you consider that the input is the only part that spins faster in low, chances are it will never spin faster than it normally would at highway speeds at high RPM since it is directly related to engine speed (depending on trans gear selection) But most the time you're in first and the input isn't spinning very fast anyway. They realy don't get that hot and the 90w is good at those temps anyway. 

[superyota]

I found this thread on pirate.  it says by running it in low at high speeds flings the oil faster than it can lubericate, causing it to burn up.  this is my concern.  I think I'll post this up in the tech support section.  here is a link to the thread on pirate...  http://pirate4x4.com/forum/showthread.php?t=903790&highlight=crawl+box+oiling

[fordh8r]

  The only logical arguement that I read in all that was the guy who mentioned doing long hill climbs and the oil washing into the rear case resulting in starving the front case for oil. And the guy running the V8...that one makes some sense.  

 The way I see it is when you look at the fact that no matter which range you're in (hi or lo) ALL the gears ar still spinning and the oil level (as long as it is correct) will still be splashing and oiling just the same. That said, the fastest the t-case will ever spin is in 5th at highway speeds. But in low range the only speed that changes is the output speed (starting at the countershaft). So, why wouldn't it starve and burn up then when running down the highway? I DD mine and if that were true, mine shoulda burned up long ago.  

 Unless, the only other logical possibility is that the gear on the countershaft (the low range gear which is larger and should sit deeper in the oil level) spins slower in low range which could minimize oil splashing around and possibly starving the case for lube for extended periods. That might make some sense but I believe this would also have to be coupled with the 'hill climb' scenario to make this true. Granted, the power flow through the t-case changes when you shift into low and the dynamic load does change on the input bearing so it would seem there could be more to it than just an oiling situation.  

 The next thought would be...why would this happen only to a crawl box when it never seems to be an issue with a single case.   But since I've never had this problem in all the time I've had mine, I can't say that I've had one on my bench to do a fair and just failure analysis.  I can say this...I've wheeled my truck in low for hours at a time at Hollister, Rubicon and Truck Haven Hills with absolutely no issues.

 The only thing I don't like about threads like that is the variables in the rigs of folks who say they had this problem but fail to mention what those variables are i.e. Drivetrain combo (4 cyl, V6 V8 and so on...) and it's easy to forget that they could be overly abusing their equipment due to Driver input or improper procedures (oil level checking on a slope) or how often they may service their rig or.... well, you get the idea. Without that info I immediately start asking these type of questions and start thinking only about the ones that are closer to what I'm running for a fair comparison of what I should expect from my rig.    

  So again...  

 

[superyota]

I understand what your saying.  When you have the crawl box in low, and the rear case in high, your going to be turning the input on the crawl box a heck of alot faster than the input or output on the rear case.  the crawl box doesn't hold very much oil, and I don't think the oil can travel back and forth between the crawl box and rear case easily, it does, but only through where the bearing is if i'm not mistaken.  the faster you turn the input on the crawl box, the more oil your going to need up there to help lube and cool things right?  My concern is turning it so fast, for extended periods of time, is it going to starve the crawl box of oil? 
by the way, i'm running a stock 22re, 5.29's and 40's with dual stock cases right now. 

on a side note(this might have to get a new thread started for it), i know almost everyone puts the 4.7's in the rear case, but a few guys i know run them in the crawl box.  I know running them in the crawlbox puts a lot of stress on the input of the rear case, but enough to be of concern?  sorry for all the questions.  I like to do my research to it's full extent before making changes to my drive train.  and i want it to last.  thanks again for your feedback fordh8r, i appreciate it.

[fordh8r]

Yeah, no sweat! I always like logical and progressive thinking when it comes to a problem that doesn't seem to have a clear cut answer. 

     Let me just say this, you say the input is spinning much faster...when, actually, the inverse is true...it's the output that is spinning slower because the input is still the same given engine RPM and trans gear selection. For example (for easy numbers) 4th gear is direct (1:1) so what ever your engine RPM is so is the T-case input, correct? We'll just say 1000 RPM engine speed which means Trans output is 1000 RPM (in 4th) and t-case input is 1000 RPM and t-case outptut (in High which is also 1:1) is 1000 RPM and t-case output (in low) will be 2.28x slower, correct? So given this example it isn't the input that's different it's the output. But think about how much slower the input is spinning in 1st gear VS 4th in this example. It seems heat shouldn't be a problem. 

  Otherwise, to say that the input is spinning faster you would have to be spinning the engine 2.28x more RPM, no? So if the output of the t-case in low were still 1000 RPM you would have to be spinning the engine at 2,280 RPM in 4th gear...but then figure what that would be in double low and first gear in the trans. That's a lot of engine RPM! But that's why we're running these gears in the first place for torque. You don't get that with the engine alone.  Besides, even if we had an engine that could do that kinda work in 1:1, I would still prefer the gear choices.

[superyota]

sorry for not clarifying.  I'm speaking in regards to the input on the crawl box, not on the rear transfer case.

[fordh8r]

sorry for not clarifying.  I'm speaking in regards to the input on the crawl box, not on the rear transfer case.

Exactly! Crawl box or single case will make no difference in this scenario. 

[BadnewsBob]

I don't have any tech to add to this but....I know a lot of people running crawl boxes around here and I have never seen or heard of one burning up from poor oiling, I wouldn't worry about it.

[superyota]

Exactly! Crawl box or single case will make no difference in this scenario.  

I can see it not being an issue with a single case, being your oil is all coming from the same case and only one input.  vs. with duals, if you have the front case in low range, running 4th gear at 3k RPM, and the rear case in 4h, the output of your crawl box is not going to be turning at 3k, and neither is your input or output on the rear case.  although in input on the crawl box will be at 3k.  I hope that made sense.  The guy on the pirate forum said he talked to marlin in regards to it, and here is what he said, from 85McFly on pirate... http://pirate4x4.com/forum/showthread.php?t=903790&highlight=crawl+box+oiling

"Marlin says the front and rear cases share oil but i wonder if there is a inherent oiling problem with the front box since it only relies on oil slinging to lube the gears and bearings. Marlin Crawler says by driving it fast in stock low, the oil is flung too fast or out of the way to properly cool the front box. I relies every thing has its limit but maybe they should provide a warning with purchase if this is the case. I almost just want a single case unit back if this is going to continue. I will be pulling the whole crawl unit out for shipment back to marlin for repair."

Could someone from the Marlin crew please give us some input in this?

[fordh8r]

I can see it not being an issue with a single case, being your oil is all coming from the same case and only one input.  vs. with duals, if you have the front case in low range, running 4th gear at 3k RPM, and the rear case in 4h, the output of your crawl box is not going to be turning at 3k, and neither is your input or output on the rear case.  although in input on the crawl box will be at 3k.  I hope that made sense.  The guy on the pirate forum said he talked to marlin in regards to it, and here is what he said, from 85McFly on pirate... http://pirate4x4.com/forum/showthread.php?t=903790&highlight=crawl+box+oiling

Yes, makes perfect sense. But back to what I was saying when you compared those same RPM's to Highway driving... how do they relate?

"Marlin says the front and rear cases share oil but i wonder if there is a inherent oiling problem with the front box since it only relies on oil slinging to lube the gears and bearings. Marlin Crawler says by driving it fast in stock low, the oil is flung too fast or out of the way to properly cool the front box. I relies every thing has its limit but maybe they should provide a warning with purchase if this is the case. I almost just want a single case unit back if this is going to continue. I will be pulling the whole crawl unit out for shipment back to marlin for repair."

I do know that both cases share the same oil and while I will certainly not discredit Marlin's statement here, I'm sure he must know something more than I do on this specific unit, I must ask though, How could it be spinning too fast? Given the relative engine RPM the gears are still moving slower when in low range and slower yet when in first gear in the trans. My thought would be more on the side of lessened RPM causing less oil splash being the cause of an oiling issue and not caused by overspeeding. In which case, the reason that overspeeding would make sense is that no matter how fast you sling oil around the case it still only flows back to it sump point at the same rate so you could possibly "suck it up" faster than it will flow back to be "sucked up" again but you'd be talking some real speed here. The only way for the input to run faster on the t-case than the engine, would be for the trans to be in 5th (OD)...but again, back to the highway scenario. 

  The only real possibility I see here is if the stock t-case uses a pump for lubrication and not dependent on "Splash Oiling" then I can see how the front box might suffer since it becomes a "splash Oiling" type system. In my mind, that wouldn't explain all the crawl boxes that haven't failed. 

[Slolyfe]

Best thing to do to prevent under oiling is to, pull your crawl box shifter(the front one)and pour oil in until it almost over flows. Don't fill it the last inch otherwise when you put your shifter back in it will over flow. Your welcome.

[fordh8r]

Best thing to do to prevent under oiling is to, pull your crawl box shifter(the front one)and pour oil in until it almost over flows. Don't fill it the last inch otherwise when you put your shifter back in it will over flow. Your welcome.

Is this before or after you fill the rear case? 

[jrock]

By how few have had this problem I would take it that it isn't a common problem. Im totally with Fordh8r on this. The crawl box might not be getting the same oiling as it was when it was attached to the front of a 4wd section but nothing else changes.

The post on Pirate does not say how much angle he has on the drivetrain. If there is an engine lift there would be more tendency for the oil to drain to the rear case just as when he does hill climbs. Plus, hill climbs put a ton of force on everything, hence his V8.

[fordh8r]

What if the bearings in the failed cases happened to be purchased all around the same time? Could they have been a bad batch of bearings from the bearing supplier during the building of those case adapters? Quite possibly. But like Jrock pointed out, why so few failures? How could something that is common to every last crawl box cause such an uncommon problem? To me,these are the kinda questions that should be asked if someone were to fully investigate this issue. 

[blackdiamond]

Here's the math behind the RPM in the crawl box:

(1) The RPM in the crawl box at 70 MPH in 5th gear with 32 inch tires and 5.29 gears is 3309/0.851=3888 RPM.

(2) With the rear t-case in 4.70:1, the RPM in the crawl box at 22.5 MPH in 5th gear with 32 inch tires and 5.29 differential gears is 5,000/0.851=5875 RPM.  This is 50% faster!

(3) To not exceed the highway RPM in the crawl box the fastest you could go with the rear t-case in 4.70:1 would be about 17.5 MPH.

I've had no issues traveling between Washington State and Utah or California traveling 60-80 mph over several trips.  I'm running an Inchworm unit but would assume that Marlin's crawbox will perform equal or better.  There's always a factor of safety in a design, but 50% is fairly significant.

Hold on a second...

Ok, I think the numbers are correct.

If you run with the front case in 2.28 the rear case will have a lower RPM than in 1:1 so that shouldn't be an issue.

[superyota]

alright, you guys got me convinced.  thanks for the input everyone.  I won't worry about it.  Now it's time to get the 4.7's and install them 

[superyota]

Best thing to do to prevent under oiling is to, pull your crawl box shifter(the front one)and pour oil in until it almost over flows. Don't fill it the last inch otherwise when you put your shifter back in it will over flow. Your welcome.

hey austin, i'm assuming when you say "overflow" you mean out the fill plug on the rear case, right?

[Slolyfe]

hey austin, i'm assuming when you say "overflow" you mean out the fill plug on the rear case, right?

No. Fill that biatch to the top of both cases. You wont have to worry about lubrication again!!!

[superyota]

No. Fill that biatch to the top of both cases. You wont have to worry about lubrication again!!!

I like this idea!  I'm going to do it.

[freds40]

Running the front in low and the rear in high has never given me issues. I've never thought about it really but honestly until I do have an issue, I probably won't. 

[BadnewsBob]

 :thumbs:X2

[blackdiamond]

No. Fill that biatch to the top of both cases. You wont have to worry about lubrication again!!!

You really think that this is necessary or even a good idea?  Why don't you trust the factory oiling design?

[blackdiamond]

Here's a few more numbers to help determine if the RPM in the drivetrain should be a concern.

I assumed that the worst case that we should consider would be stock 28 inch tires traveling at 80 mph in high range.  In this situation, the engine would be turning 5,078 rpm and the t-case would be at  5,968 rpm.  So we can assume that the factory oiling should be able to handle 6,000 rpm.

With the crawl box in 2.28 and the t-case in high the worst case would be at about 48 mph where the engine would be turning 5,173 rpm and the crawl box input would be 6,079 rpm and the crawl box output turning 2,666 rpm.

With the crawl box in high and the t-case in 4.70 the worst case would be at about 20 mph where the engine would be turning 5,078 rpm and the crawl box and t-case input would be turning 5,967 rpm with the t-case output turning 1,270 rpm.

With the crawl box in 2.28 and the t-case in 4.70 the worst case would be at about 9 mph where the engine would be turning 5,210 rpm and the crawl box input would be turning 6,122 rpm with the crawl box output and t-case input turning 2,685 rpm and the t-case output turning 571 rpm. 

So what does this mean? You shouldn't have to worry about oiling in the crawl box or t-case as long as you keep the engine rpm to no more than 5,000 rpm.  I'm sure almost everyone is running larger tires which would increase the final mph but not change the relationship in the gearing.

[blackdiamond]

By the way, running in a gear other than 5th in the transmission will only reduce the relative speed of the crawl box to the engine.  Lower gears slow everything down that is behind it.