seems like gears might last longer, stay in spec longer, and be less likely to break than a chain.

I have seen timing gear replacements for gasser engines...

someone please 'edumacate' me.

thx,
Robert

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Cheers,
Robert

It all has to do with th edistance of the centerline of tha cam and the crank.....you need multiple gears....more than three adn likely 5 to bridge the distance...and with the lash (play or clearance) with gears you would find them being far less accurate than a chain.

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The doc is correct. All MB engines for the last fifty years or so have been overhead cam engines. In this configuration it would take four or five gears to transfer the motion all the way from the crankshaft to the camshaft(s.) With all those gears each requiring a small amount of lash, would add up to lots of slop even when new.

On OHV engines with the cam right next to the crankshaft, a couple of gears is a good choice as was done on early six cylinder Chevies and the 240 and 300 Ford sixes of the sixties, seventies and even used in the nineties.

Another consideration is noise. Timing gears can be pretty noisy, not something desirable in a luxury car. MB uses the optimum timing system for their application, a true roller chain. Some of the engines require more service than others, but even the worst of them beat the heck out of a stupid rubber belt as is found in the vast majority of engines in recent years.

Have a great day,

Yep. The previous posts are right....

In addition to the slop and durability issues, gear drives are VERY noisy too.


Obviously not something you're worried about too much, if you already own a diesel, but.....

Mike

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Cool, thanks to all, makes some sense now, and I had not considered space or sound factors, straight cut gears are noisy.

I puzzled over that one for a while now.

thanks,
Robert

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Cheers,
Robert

If you used straight cut gears it would be very noisy.... these are available for Race Cars...
but I don't know that ' normal ' angled gears would be very noisy... as evidenced by the fact that they were used in normal passenger car engines.

Why would racers ever choose noisy straight cut gears ? It eliminates side thrust.

The option, but way more expensive , for no side thrust ( requireing a thrust bearing ) would be heringbone cut gears. They combine angled interaction with no side thrust.

....and some of those older fiber timing gears used to lose a few teeth once in a while. Can be just as bad as a worn timing chain. My '05 Tacoma V6 engine has gone back to timing chains for the four cams and I feel better with it than I did with the '95 Tacoma V6 with the timing belt.

I'm for chains period. (Although some of those straight-cut metal timing gears can sure make a nice sound.)

Wes