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NP205 Yoke broke

K5Cobb

K5Cobb

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I have just finished up with a sm465/np205 swap from a 700R. I haven't had it out of my shop 2 days and I have already broken 2 yoke's on the back of the 205. I have just been driving it around the yard and on the farm and every time it gets any pressure on it other than normal riding, it breaks. The sm465, np205, 12bolt, and 38.5 tsl's came out of a 78 k10 that never had this problem. The k5 has around 6 to 8 inches of lift, does anyone know where I can get a stronger yoke, or know where my problem may be.

Thanks for your help.
 
drive line angles / maxed out u-joints binding and poping apart.

it is just the yokes or also the u-joint ?

and what size u-joints 1310 or 1350 ?
 
The drive line isn't bad at all, and It shears two of the ears off the drive shaft side and it breaks the yoke where the u-bolt holes are. I put a normal 1310 precision u joint in it the first time, the second tome i put a "super strength" percision 280. The second time it broke, it was half the stress as the first time. aslo I have shimmed the rear axle and dropped the transfer case as much as i could to minimize driveline angle
 
Got enough travel in the slip yoke? Or is your 205 fixed output?
 
Do you have any slip built in to the shaft? Maybe thats binding in some way.

Z
 
Hmm :thinking:

Doesnt look like a whole lot of travel in the slip portion. Maybe an inch or two when fully connected? But you arent really flexing it out though. Just driving around the property, right? Maybe its just enough to bind up and break.

Z
 
the 4th pic is of a the yoke where it would be locked down, the 5th pic is of the the yoke compressed all the way. it has plenty of travel out, and it never goes any further in there where it is in the running pic.
 
attachment.php


This pic looks like the rear axle is pointed @ or above the transfer case with the blocks and the big tires you may have enough axle rap to be binding the drive shaft.
 
ChrisPerry said:
attachment.php


This pic looks like the rear axle is pointed @ or above the transfer case with the blocks and the big tires you may have enough axle rap to be binding the drive shaft.
Click to expand...

It is pointed dead towards the t-case. it has 4" blocks, 4" drop brackets, and factory springs. what would you suggest to correct this. I also forgot to add that it broke the same one both times and did the same thing to both u-joints.
thanks for yalls response
 
4X4HIGH said:
The slip yoke end should be at the axle also.
Click to expand...

I was told that one time be for and i tried it, but i ended up building a new shaft b/c i kept getting dirt in the splins, what are the pros of running it backwards of the way i have it?
thanks christian
 
Only thing that hasn't been mentioned that I can think of is if you are tightening those ubolts down way too much. They actually take barely any torque. I noticed the caps were still stuck in the ubolts is why I thought of that...Does the ujoint rotate freely in the caps once you put the ubolts on there?

You'd have to torque those ubolts down really, really hard though...I'm not sure you wouldn't strip the threads off before you could actually seize the ujoint in the cap.

I'm betting on yoke binding of some sort though. There's no way a brand new 1310 ujoint would fail just from torque that easily. Hell, I've driven home on just my front several times on an old ujoint (still have the stock 1310 up front and I have 40s).
 
owenst7 said:
Only thing that hasn't been mentioned that I can think of is if you are tightening those ubolts down way too much. They actually take barely any torque. I noticed the caps were still stuck in the ubolts is why I thought of that...Does the ujoint rotate freely in the caps once you put the ubolts on there?

You'd have to torque those ubolts down really, really hard though...I'm not sure you wouldn't strip the threads off before you could actually seize the ujoint in the cap.

I'm betting on yoke binding of some sort though. There's no way a brand new 1310 ujoint would fail just from torque that easily. Hell, I've driven home on just my front several times on an old ujoint (still have the stock 1310 up front and I have 40s).
Click to expand...

Well.......:whistle: I got on them with the wrench and a cheater wrench, but I dont think I got them that tight. I havent checked to see how easy they spin though. thanks christian
 
The torque spec for U-Joint U-bolts is only 15 ft/lbs, any tighter and you start to distort the cap of the U-joint and they will fail.
 
wow that isn't much, I got them as tight as I could with 2 wrenches. this is my fist go around with u-bolts, which is better, u-bolts or straps?
 
K5Cobb said:
wow that isn't much, I got them as tight as I could with 2 wrenches. this is my fist go around with u-bolts, which is better, u-bolts or straps?
Click to expand...

U-bolts are far superior to strap and bolts. Straps will stretch out of shape and not hold the u-joint cap from spinning and that can wipe out a u-joint earlier than it should.
 
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