Crawler Box Splines keep stripping.

I have an idea of what is going on with your splines. (Been a Mechanic for over 35 years ) My question for you is this. Are there alignment pins ( dowels pins ) anything other then just the bolts holding the two cases in alignment ? If there are no Pins then that is more then likely is your problem .

 

Ok so much for my idea .

 

I am all up for ideas, even the simplest thing could be my issue. Right now im leaning towards lack of lubrication, so will probably top fill the crawl box, the question is how much gear oil? According to marlin I need to fill to the fill port level, drive around and re-fill so no precise capacity.

 

I’d put around 3 qts or so in. If it starts puking out the shifters drain a bit out via the fill port. More oil is better in this application. On a R&P, not so much.

 

Sorry I am late to the game on this one .
Is there an air vent on the top of this crawl box that allows this gearbox to vent to atmosphere ? If there is a vent hose , are you sure the tube is clear from obstructions ?
Got any specifications for the Marlin crawl box we can have a peek at ? I am interested in the end play adjustments and how the end play is adjusted as well as checked ?

 

There isn’t any vent on the crawl box. Atleast my doesn’t have one.

 

There should be a vent to atmosphere .
If for some reason the crawl box didnt have a vent , there would be no room for expanision and contraction of fluid during heating cycles unless the crawl box uses the factory transfer case vent as its way to vent ? I highly suggest the OP looks at this !!!!!
Sorry for the stupid questions , but I am diagnosing this problem from an OEM standpoint .
Having never used an aftermarket crawlbox from Marlin , I go back to the basics of OEM standards for all vehicles .
All automatic transmissions , all manual transmissions , all transfer cases and all differentials must have a vent to atmosphere in order to function correctly .
If you Plug a vent to atmosphere on any of the above , you are asking for serious trouble very quickly .

 

Let’s assume there is no vent. How would that cause the issue he’s having?

 

OK , Lets assume there is no vent to atmosphere .
What happens when the fluid inside the Crawl box gets hot ? In most OEM instances , you blow all your seals but it gets much worse .
The fluid needs to expand but the fluid cant expand because the fluid cant push the hot air out of the crawl box .
From this point , everything inside the crawl box gets hotter and hotter , the rotating metal parts inside the crawl box expand with heat . Yes guys , we have ourselves a pressure cooker
If the internal parts inside the crawl box continue to expand with heat , lubrication ports become blinded off and the end play adjustment in the gear assembly diminishes to a zero set point .
Not saying this is the OP,s issue , but it is such a common problem on OEM 4x4 trucks that play in the mud , I thought I should bring it up .
For the 4x4 guys who play in the mud and water and take the time to run your OEM atmospheric vents up to your firewall !!! your doing yourself a big favor

 

mine has one on the shifter base

 

I can buy that.

 

Mine doesn’t. U also got the super duper short shifter that marlin had for like 10 secs they no longer sale.
This is my shifter base


With how much these things leak u really don’t need a vent

 

Lot of members here involved in trying to solve this . Great to see Could it be something as dumb as a plugged vent ? Only time will tell

 

i suggest drilling and tapping a vent into this critter and it wont leak anymore !

 

I’ve actually solved my leaking problems. Gotta be deliberate as fuck when sealing.

 

I wish I had two of these Marlin boxes in front of me . One of them built for an automatic and one that Marlin builds for a manual . Op says the one built for the automatic has constant lube . I would love to compare the differences

 

Also just looked at a pick I got. Think the crawl box would vent out the transmission tail housing. There is a vent tube off the tranny and pretty sure the crawl box isn’t “sealed” from the tranny tail housing.

 

There is no difference in a manual vs auto crawl box other than the spud adapter that fits over the crawl box input shaft going into the manual tranny

 

You are correct . I went back to the OP,s first set of pictures and I can see a vent to atmosphere in picture . Is it plugged up ?