How common are those composition molded gears? Can anyone say if they’re in the D3400 or D4600 or even all D4400’s?

Mike, you may need pushrods and or rocker arms.

"ccjersey" wrote:

How common are those composition molded gears? Can anyone say if they’re in the D3400 or D4600 or even all D4400’s?

Mike, you may need pushrods and or rocker arms.

You are right Jim, with that oil sitting on top of the aircleaner, it's obvious valves and pistons have gotten out of time.

"RAX200" on here has a shed full of D4 tractors and he tells me none he has worked on have fibre gears, though when you look at the 4G and 7J parts book, the diagram of the cam gear has odd cross hatching, suggesting it's a composite gear, all the other gears in the parts book have simple diagonal lines. My buddy who is sending me a used gear tells me that one is steel, so I wonder if they were a aftermarket replacement people used when rebuilding the engine?

Seems hard to understand why Cat would bother trying to save 30 cents back in 1939 by using fibre to create that gear, rather than steel, but interestingly there is a smaller gear mounted on front of that camshaft gear, and that one is steel, is it possible there was a theory fibre gears absorb the thrust or vibration of the camshaft better than steel?
Regards
Mike

In later years the 6 cylinder Ford engines had the fiber camshaft gear. It was supposed to be used to quieten down the gear noise of the engine when used in passenger vehicles. The industrial version of the same 240 and 300 cubic inch engines had a steel gear.

The fiber gears were original Caterpillar, only early engines received them. Too many problems, and Cat switched to Steel. I believe thought was fiber gear would make gearing quieter.
It is uncommon to find a engine with a fiber gear, this late in life.
Either your gear, failed due to material, or something in the accessory drive locked up.

a fibre gear in the valvetrain......yikes:jaw: in an interference engine??

The teeth on that old fiber gear are very thin at the tips almost opposite where the teeth broke, so it has done a million hours, I can see where the engine has been rebuilt / reconditioned previously, for example all the head studs had pipe wrench bites in them, and the new liners were sitting a bit higher than spec when everything was measured, so I suspected the block had been decked.

I just pulled the pushrods and rolled them along the fender, they are all straight, I can't see any obvious bends in the rockers, and all the valve stems appear the same height looking along the top, I find it hard to believe I've dodged a bullet on this one, I'll find out when I get it back together and try and fire her up.

I have a highly respected ACMOC member about 3,000 miles west of me, who is kindly sending me a steel gear out of one of his D4 wrecks, I have nothing to lose by fitting that and just seeing what happens when I try and fire the engine up, though knowing the postal system here in Oz, it will be a month before I get the gear from my buddy....

Thanks for your input everyone, my old great friend had a large 4 X 4 drive International truck on his farm when I was a kid, I got to drive it couple of times, I remember Gwyn saying it had a fiber timing gear that was dodgy and ready to let go at any time, he said it was a weak spot in those engines.
Mike

I quietly rolled the engine over and have good compression on all 4 cylinders, as each piston came up to TDC I could hear air slowly leaking past the rings on all 4, this engine has new rings and liners with only 8 or 10 hours run time.

Once I try and fire her up I'll find out for sure, piston crowns may well be cracked, but you do have to be lucky once in a blue moon don't you?
Mike

-maybe the logic is the fibre lets go before other forces increase and does more damage to other pieces....but that still doesn't put an interference valve engine in the clear...necessarily..

-i'm pulling for you Mike, you deserve a break..

-even a blind squirrel finds the odd nut