Timing belts I have a 2000 Volvo S40 with 74,000 miles. When do I need to replace the timing belt?

It has a belt. If cracked, replace it immediately! Go to Matthews Volvo Site and look for: 99' S80 T6 Cam Seal Replacement/ Oil Leak Repair,Timing,PCV

Below is the master help link provided to go through belt routing diagram:---Timing belt, drive belt, serpentine belt, accessory belt, fan belt, engine belt routing diagrams for all types of car models?
Click the link below: ----

http://carbeltrouting.blogspot.in/2012/02/timing-beltdrive-beltserpentine.html
----------This will help. Thanks.

Do it at 60,000 miles, it is cheaper than a damaged engine-Volvo had different recommendations:
All models - 1999MY: Replacement of timing belt and tensioner every 80,000 miles or 8 years.
1,6/1,8/2,0 - 2000-01MY: Replacement of timing belt and tensioner at the following intervals:
90,000 miles/8 years.
186,000 miles/16 years.
1,9T/2,0T - 2000MY: Replacement of timing belt and tensioner at the following intervals:
66,000 miles/6 years.
138,000 miles/12 years.
210,000 miles/18 years.
2,0T - 2001MY: Replacement of timing belt and tensioner at the following intervals:
90,000 miles/8 years.
186,000 miles/16 years.
All models - 2002MY : Replacement of timing belt and tensioner every 96,000 miles or 8 years.
The previous use and service history of the vehicle must always be taken into account.

Volvo recommends for Volvo S80, changing the timing belt every 105,000 miles. Needless to say, they are pretty religious about this now.
The B20, B21, B23, and B230 engines are non-interference engines, meaning that the camshaft can be rotated independently of the crankshaft and no damage will result to the engine. That is, if the timing belt breaks, the valves will not hit the pistons; the engine will simply stop.
On the other hand, the B234 16-valve engines and any of the other Volvo multi valve engines are interference engines. Loss of the timing belt in these engines will result in severe or fatal engine damage.
Your car might be fitted with:
2.8L (VIN 90, 6th & 7th digit, B6284T eng, turbo)
2.9L (VIN 94, 6th & 7th digit, B6294S eng)
To get more information you can download the Owners manual at:
http://new.volvocars.com/ownersdocs/2001/2001_s80/01s80_08b.htm

I would replace it as soon as possible. 105k is kind of pushing it. No later than 90k.

Yes it is, replace the belt!

Yes it is ok till there is no problem with the belt...You can carry on for another 20,000 miles and then replace it..

if that belt breaks and you have an interference engine the valve can be damaged because the piston comes up and hits the valve that is left open when belt breaks

timing belt replacement is 168,000 km

error definitely some issues with the early six-cylinder timing belts. There were some updates, including a dampener for one of the cams. See if you can get copies of the service bulletins for your engine. I think the belt may also be somewhat wider on the later engines. DO NOT use the later interval.