I have seen this very often with AllMakes4x4 gears! Heck I even had one that had a wobble in it and I caught it before I put the front cover on. IMHO the original gears are just fine to re-use. I mean vs the crap that is floating around out there a little wear beats a badly forged part if you ask me. I re-use the OEM gears and just replace the chains.

 

Where can I find measurements or wear limits for this? Manual just says "Inspect timing chain gears for wear. Replace components as necessary." Old part doesn't look badly worn, but wear marks from the chain are clearly visible. Nevertheless, I think it is good to re-use. You are right, and re-using worn original parts seems less risky than installing crappy aftermarket parts.

 

I suspect the tolerance specifications for those gears may be locked away in an old file cabinet at Solihull?

It's good to have options, and I usually default to the part that looks and feels better, which is a very subjective decision. Your original gear just looks better to me, with its nice sharp corners.

 

Timing chain system and size is extremely similar to any American V8, SBC, Buick, etc. I would use specifications for one those if you want to go by specs. General rule of thumb is to pull up on chain at mid-point of sprocket wrap. If you can see less than 1/2 a tooth you are good to go. at 112k I doubt it is worn out. I have three in the yard over 215k and all run great.

 

While the gears wear and eventually could pose a reliability or performance problem, it's going to take a long time before that happens. This isn't like a dirt bike where the torque is multiplied driving the rear wheel and worn sprockets become razor sharp if left long enough. Spinning the cam isn't nearly the same level of mechanical stress. Chain stretch is the real problem to overcome.because it affects cam timing. Gears and chains do wear together so at worst you're going to accelerate the wear on each component, but not to the point that it will matter much. I would not use the "new" cast POS. To me that looks like more of a problem due to its crude manufacturing and suspect material composition.

 

I got another sprocket from a different vendor and it looks similar but without the broken teeth. Eurospare, made in China, now I find out I can get it for $7.79. I totally overpaid for it (ebay). A genuine sprocket (BPU has them) would be $51. Since the original 112k miles part looks much better quality and the wear is minimal I will stick with that. Case closed.

 

Good call.