direct gear drive

The fly-boys use the belts. More reliable than a jury-rigged gear drive.

Hi Clare,

That, I would not have thought. But, jury-rigged in not a good idea in the air.

Do the fly boys have better belts that last longer?

Many thanks,

-T

I think Gates and perhaps others offer a 'racing' belt. But I have no idea if change interval is longer.

Hi Lucky,

Thank you and Rats!

-T

Belt drive, as designed by Subaru, is what the fly-boys use. The change interval in hours is less than half what it would be in a car.

Belts are actually VERY reliable - and easier to change than chains or gears. There is a good reason auto manufacturers use them

At 92,000 miles they break throwing valves into your cylinder heads. Pretty much ruining your engine. So, reliable is in the eyes of the beholder.

According to my local subi dealer, the new engines have gone to direct gear drives.

I dislike having to change the rubber band every 90,000 miles at $1000.00 a pop. And if I can't afford it at the time and I miss a few 1000 miles, OH HOLY CRAP!

They use them because they make less noise and they are cheaper. Give me steel gears any day!

It is EXTREMELY rare for a belt to fail in less than the recommended change interval - there was a year or two of Daewoo (Chevy) production where belts were failing early, so the change recommendation was moved up. In aircraft use 500 hours is a LOT of flying - so changing a belt every 500 hours is no big deal - and that's only 30,000 miles in a car. In a homebuilt plane, it is about 5 years of flying.

google up "timing chain failure"

That is why I prefer "gears"

The other thing is, it is usually recommended to replace the water pump at the same time as the timing belt. No point in having a good timing belt (or gears / chain) and a failing pump, especially on an aircraft engine.

BTW, I lost the timing belt in my 1995 Legacy; it did not destroy a piston(s). That was the only belt I have lost in five Subarus, with two of them going over 200K miles.

The valves-hitting-pistons problem is not caused by the belts -- it is because of the engine's "interference" design. There are plenty of other engines in which total failure of the belt driving the cams has no such effect. In one of those cars you just remove the failed belt, re-set the cams and crankshaft to the proper relationship, install a new belt, and drive away. If the failure occurred in traffic you probably need to change your shorts too.

Hi John,

Does this engine have this problem (Forrester 2006)?

I really dislike the rubber band design. Subi does too or they would not have dropped it on their new engines. I really do love this car though. Subi can make one goof and be forgiven.

I wonder if I ever have to replace the engine, if one of those new ones would fit?

-T

It is going to be a pretty complex gear train to drive 2 overhead cams, each about a foot from the crankshaft.

My parts guy at the local subi dealer said the new engines are direct drive. I wonder what the did to solve the problems you speak of?

Nobody said they HAVE solved the problems. These are new engines - little experience to go by. And when your local Soob guy says "direct drive" he's blowing smoke. It is not gear driven, and it is not "direct" drive. It is chain driven, with a PAIR of hydraulically tensioned chains. The jury is still out. And by the way, a GEAR driven cam on that engine would be quite noisy.

When my timing belt broke, the engine simply stalled and would not restart. It wasn't a catastrophic event; I simply pulled over to the side of the road.

Agcoauto.com says Subaru DOHC engines are Interference while SOHC engines are non-Interference; I believe my old Legacy was SOHC so no problem there, unlike my 2005 WRX which is DOHC. BTW, Cars101.com says "6 cyls have timing chain, should not need replacement".

I wonder which 6 cylinder engines they are talking about. I believe the forst 6 cylinder engine in the Tribeca had a chain? I ask that because when my son bought his 2008 Tribeca, I asked about it having a chain or belt and the response was "this one has a chain, the older ones have a belt". Also, the Kia Sedona I had had a 3L six cylinder engine and it had a timing belt.

The early ohc six was belt drive. (the ER27) SOHC. The DOHC H6 3.0 (EJ30?)is chain drive. This was required to get the 6 cyl down to only