Damage to the timing belt drive gear

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Gyre
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Joined: Wed May 06, 2026 11:58 am
Hi!

Recently removed the timing belt drive gear from my 944 S2. The car has been sitting for a over a decade before I got it, so the gear was really on there! When it finally came loose I noticed that the gear puller had caused a couple of splines to deform slightly where it pulled. See attached picture. The second picture is of a part of the gear that is not damaged.

Considering the wear marks and pictures I took before removing the belt, it seems like the belt won't even get in contact with this part of the gear. Not really sure what to do here. Do I run the part like this? Smooth out the shark edges first? Try to whack it back? Please advice :)

The part (94410512505) is NLA and I'm not sure the second hand once I can find is in any better condition.
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#1

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walfreyydo
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I wouldnt worry too much about it, but if you are, used gears are fairly plentiful on ebay and not terribly expensive. You could even file those down slightly if needed to bring them back to shape. Either way probably not a huge issue
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#2

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Tom
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walfreyydo wrote: Tue May 12, 2026 6:44 am I wouldnt worry too much about it, but if you are, used gears are fairly plentiful on ebay and not terribly expensive. You could even file those down slightly if needed to bring them back to shape. Either way probably not a huge issue
I agree. Maybe dress any sharp spots with a file, then run it and forget it...

#3

dr bob
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Are the gears the same as on the 928 engines? If so, take a look at 928srus.com for options. Roger commissioned a run of gears a while ago, and I'm very happy with them both fit and function. Harder aluminum and a much tougher wear coating vs. the original pieces.
dr bob

1989 928 S4, black with cashmere/black inside
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#4

Gyre
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Thanks for the quick replies! I'm leaning towards using the one I got. Filed down the sharp bits and it looks a bit better now. Considering that the belt most likely wont even touch the damaged part of the gear I feel pretty confident.

We'll see in a few months if this comes back to haunt me :)

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I agree that you should be fine based upon the wear marks. The belts don't shift forward/back significantly in most cases, they tend to run along the flange for the tensioner roller and settle in on that line across the other pulleys. Just make sure the crankshaft pulley is reinstalled in the correct orientation with the flanged side facing forward/away from the engine.

#6

dr bob
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At this point, most of our cars are past 'regular driver' duty, so belt wear and life are less critical. From the V8 crowd, we started with some concerns for belt life on drivers, with the concerns about the factory 60k change intervals for the V8. We determined that the 60k number was good for engines that have still-perfect gears and rollers. Wear on gear teeth moves the load faces around some, and the question then went to how much is OK. Most of the decision is based on some crystal-ball prediction of what the pieces and wear will be like at the end of the next cycle. Same issue on bearings and pivot bushings in rollers; feels OK now but how much more before they show wear signs sufficient to affect the life of the belt?

The gear you show has a LOT more wear than the ones I replaced on my V8 car. Mine were swapped before the anodizing was worn through, the point beyond which it's tougher to re-coat the gear teeth. Same decision process as described above -- would they last through another 60k without risking extra wear on the belt?

There are a LOT more 944/951/968 cars than there are 928's, though they use only 1 cam drive gear vs. the 2 used on the V8. The 944/etc. engines are routinely revved higher though even in 'normal' driving. Is there a good market for 944 gears, if they are not the same as the ones used in cousin-once-removed 928 engines?

----

My car is on a maybe 8-year belt change schedule, more for belt and rollers age rather than for belt wear and stretch. The grease in the sealed ball bearings deteriorates with age, doesn't flow or lubricate as well as it does when new. The belts have certainly improved a lot since the cars first made it to market, evidenced some by the last few I took off. No visible wear at all on the teeth where they drop in between the gear teeth on the sprockets. Were it not for the concern about replacing bearings in the rollers, and based on the visual inspection of the belt, it would have been easy to decide to just button the covers back on and drive the car. Don't be fooled by a simple visual, unless you have a better crystal ball for seeing at least one belt cycle into the future. I borrow one from my great-aunt Claire and Uncle Ed (Claire Vuoyant and Edsel Murphy), cloudy for me but clear to them. Then install new pieces, including gears that are even a tiny bit suspicious.
dr bob

1989 928 S4, black with cashmere/black inside
SoCal 928 Group Cofounder
928 Owner's Club Charter Member
Former Ex Bend Yacht Club Commodore Emeritus

Free Advice and Commentary. Use At Your Own Risk!

#7

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