Crawler Box Splines keep stripping.

Have three sticks poking through the floorboard, i can say for sure no vibrations. But from day one I could always hear the gears howling.

One piece driveshaft custom made for my application. Im hoping the fabricator measured and approved my angles.

I didn’t use anti-seize but did use Marine Grease when coupling, recommended by my fabricator.

 

I understand 2 of the failures happened on the highway. That doesn't mean that they weren't caused by using 4wd. It just means they totally failed when you happened to be in 2wd. Pull both driveshafts and do a spin test in the front and rear. If the spin test shows different gear ratios you found the issue. That's the first thing I wold check after a single failure. You've had 3. lol

 

Your splined shaft and female side are just way to short to deal with a lot of stress. Hell, my zero turn lawnmower has a far longer spline engagement for the deck shaft [uses a 2 piece driveshaft, not belts] Once you get a bit of slop in the spline engagement, it'll trash itself in short order.

That's just a piss poor design.

 

Stock (3.73:1) in the rear, bought the front diff used. Never dug into it so hoping the same. Will do a spin test this weekend.

I understand what you are saying, and will look into it this weekend. I just don’t see how different ratios will stress out the front input shaft. The power is split front/rear after this input shaft has transmitted power to the tcase. I can see that if an output shaft keeps failing.

 

I'll respectfully disagree. Theres nothing wrong with the spline design, length, or depth. That's a factory toyota input that they have put in tens of thousands of trucks for 15+ years.

 

If that used diff is 4.10 that's a 9.91% difference in ratios and easily enough to cause issues in 4wd. That causes binding in the case. That binding gets transferred back to the input shaft each time it unloads. Your basically creating a shock load in the t-case and the weak link is the input shaft and coupler.

 

I'd put a case and a half. Glad to hear that Atlas is working out for you. I thought about one but TG adapters and an old gear driven case where way cheaper with way less fab work for my 97 4Runner. lol

 

I knew there some people smarter than me that could offer some suggestions

Sucks you had to go through all this OP. I am sure those inputs werent cheap.

 

Good looking out man. I only found this thread because you linked it in the Crawlbox BS thread.

 

I do appreciate everyones input, I will look into the differential ratios. And yeah sucks to go through a lot of parts but now I am at the point I just want to have a reliable truck lol.

 

Please let us know what you figure out. I'm certainly curious.

 

this. the wear looks like its in one direction, which would be caused by front and rear axles spinning at different rates.

 

For front diff ratio

 

Nope, nobody wheels Toyota duals hardcore....




No, they aren’t going to hold up to 42’s and an LS. But in a mini truck/4Runner/Tacoma with 40” or less tires and a Toyota powertrain...they work pretty well. A little common sense goes a long ways with them too. It’s kind of like the mentality that you have to have tons and 40’s/42’s if you’re building a crawler and anything less is for the dumb peasants



I am curious as to why OP keeps stripping cases. Definitely a ton of fretting. May have been answered already, but was the female coupler replaced and anti-seized each time the input stripped?

 

My 1st thought was that the damage looks like what you'd get if operating in 4X4 on pavement. Some guys seem to think that is OK. But different axle ratios front and rear would do it too.