Cracked transfer case-?

Hello jeep people, it's been a while since I've posted but I have two questions that need answers opinions.

First: I cracked my transfer case. It is a Dana 18, and I had previously posted several months ago for some insight on my jeeps top speed and so on and so on. Got a lot of feed back on perhaps the transfer case needing to be rebuilt. Well I was out joy riding on the regular paved roads and hit a bump, nothing big, been over the same bump plenty of times, and heard what sounded like a rock flipping up and hitting the bottom of the jeep. Once I stopped, fluid was flowing out of a big crack on the side of the housing.
With the past history of people suggesting that I should get it rebuilt I was wondering what could have caused this to happen? Now it should be noted that I did drive home (5 miles) with out any issues at all, shifted fine and drove great as usual.
Any suggestions as to what caused it would be appreciated? As well as any suggestions as to getting it replaced.

http://i1346.photobucket.com/albums/p681/rjscj6/359ACD3E-2ACA-4CEC-9375-434AFA4674AD_zps1qeortdj.jpg

2nd question: while wiping down the transmission fluid off from under the jeep, I noticed that the rear differential was hot to the touch, I put a inferred heat gym on it and it read 125 degrees. I know I have fresh fluids in it, but should the temp be this high?

Thanks in advance for all the advice
RJ

 

Let me post another picture of the crack.

 

driveshaft bottomed at the slip joint? ive seen similar cracks after a collision where the shaft gets smacked into the transfer case.

 

No doubt I'll have to replace the transfer case, however, to save the new one from cracking, is there anything that can be done to prevent this from happening again?

 

I've never seen one cracked like that.

 

You could switch to a dana 20 case... I did that with my dana18.... They are quite a bit beefier... But I do agree with posimoto, That is a strange place for a crack. Usually they give out near the PTO opening. -MF

 

Once you take it apart..............carefully & slowly.......while inspecting all the gears and bearings along the way perhaps the reason may show up. The 18's are no question very strong. Maybe a casting flaw that might show up from the inside or once you clean it up from the outside. Look at the drive shaft and yoke and see if it did bottom out.......motor mounts and tranny mounts can also be suspect when things like this happen.

125 degrees is no issue..........normally when warmed up at operating temp. 70-100 degrees over ambient is pretty normal.

 

Always wondered this myself...>Thanks!

 

I had a similar issue with the case originally in my 69. The PO brazed the casting to close it up and it was still in use when I got the jeep...

 

That case can be fixed, once it is apart, a welding shop can preheat it weld and post heat it to let it cool slowly and it will be good as new. I assume it is a single stick case and that may not be easy to find. The twin stick is not the same as the single stick case.

 

Oh by the way, That is a real nice job with the restoration of your Jeep, it is very cool.

 

Thanks guys for the input. Not sure if I'll try try to fix it or find a replacement. It is a single stick which as mentioned may be harder to find.
Thanks for the info tranny99 on the differentials.

RJ

 

Yep, not an area of high stress. They typically crack from the intermediate gear shaft bore. And as said, a D20 case or the large index D18 case used with the factory V6's does have more beef. However, it this is still an F head, a stock case will be fine. And yes, 125 degrees on the axle is not a problem.

 

A twin stick D18 would have the same case as long as it is another large index (4 "). The difference is in the front bearing retainer casting and shifter rods which you would reuse from your old one.
I wonder if a PO setup the output bearing endplay too tight and it overheated/expanded which put that stress on the case causing it to crack. That would also account for the noise you had. See how many shims are under the rear bearing retainer casting when you take it apart.

Don

 

That crack looks to be fairly old.
The Advance Adapter transfer case girdles are intended to stop cracks like that from starting.

 

My guess is the one or both of your drive shafts does not extend enough when the suspension is at full drup.
That would cause the output shafts to want to pull out causing a crack in that location.

 

I think it's possible that a gear tooth has broken off and got jammed in between two gears or the case and a gear.

 

Most of the jeep drive shafts i have seen just pull apart if extended too far.... Do yours have something in place that keeps them from pulling apart? Some shafts have a dust shield but usually a yank and they will slide right off. Maybe yours are a different style....

 

I'll have to check the drive shafts and see how much extension I have, however they are the original stock drive shafts that's been on the jeep.

as far as a tooth breaking off like AKCJ suggest, I'll check that out too, but if that happened wouldn't I have noticed in some kind of way either noise or grinding? And I did drive it home 5 plus miles with no issues at all. A broken tooth my have given me some trouble.

 

That happened to me in a 72 Chevrolet truck with a 205 transfer case.