4.0 ohv crank timing issue

[TEK4x4]

hey everyone so i have a 4.0 ohv out of a 93 explorer in my 87 b2 i have been having issues with the crank timing gear shearing the pin off and stopping me in my tracks. i have looked all over and only found issues for the sohc timing issues. Has any one herd of this or can explain y it keeps happening. i have torqued the harmonic balancer and crank bolt to spec and have even replaced the crank bolt the only thing performance wise other then stock is a mild low end cam for crawling. any help would be great thanks.

 

[adsm08]

I'm not sure what you are actually breaking.

You mentioned a pin, but the crank sprocket is held in time by a woodruff key.

I have never heard of a 4.0 with problems breaking the keys, Scoobies sure, but not 4.0s.

If you replaced everything else I would guess that the sprocket itself is worn. If the keyway is loose on the key it could round the corners or allow some slap that shears the key off.

 

[TEK4x4]

i wish it had the newer style key way but it a little nub off the back side of the gear that sets into the crank so that as the crank goes around the sprocket does to its only held in there with the pressure of the harmonic balancer keeping pressure on it and sandwiching it between the crank and the harmonic balancer ill try to upload a pic in a bit

 

[TEK4x4]

Here is a couple pics

 

[TEK4x4]

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[adsm08]

Ok, those guys. That is kinda odd. The only reason it should be breaking is excessive drag in the system. Maybe try checking the push rods to see if any are bent.

 

[TEK4x4]

I'm pretty sure I have a bad wrist pin in one piston and I think it's taking out my rob bearing because when I change the oil there is metallic flakes in it. It's only under certain rpm and load that it really makes noise not like a rod bearing when it just makes noise right from start up. So do u think that slapping and jarring of that rod/wrist pin is shearing the pins on the crank gear?

 

[hopster]

sounds more like a thrust issue with the mains. pull the pan. then check your main bearings.

 

[TEK4x4]

Ya but I have to pull the motor for that because of my crossmember I built to clear the d44 if I pull it ill just re build the lower end again