Problem with router WRTU54G-TM

Im using router WRTU54g-TM and I have the following problem: when I don't use the router and connect my internet cable directly to the lan card of my PC I get 36mb download and 60mb upload speed but when I connect my internet cable to the router and then my PC to the router that speed drops down to 20-28mb download and 20-30mb upload. I did a factory settings restart on the router and reinstalled it but the problem is still there. I would be grateful to anyone who can help.
Thanks.
 
I assume we're talking about only wired here, no wireless, at all.

Let's remember, a router does add some overhead to your connections to support NAT, the firewall, perhaps parental controls, etc. So you would expect some loss. However, I wouldn't expect THAT much loss either.

If I had to guess? Since this a router that comes w/ support for VOIP, it's my guess the router has QoS (Quality of Service) enabled. What this feature does is lower your top-end bandwidth so when and if it needs to give phone service higher priority, it can. IOW, it essentially reserves some bandwidth for itself. Exactly how much bandwidth you will lose is hard to say since each VOIP router determines this for itself, usually based on measuring the available bandwidth when the rooter is initialized, then lowering it by some percentage (say, 15-20%).

Another problem is, something these routers reserve TOO MUCH. Many were produced at a time when ppl had far less bandwidth than you have. And reserving 15-20% wasn’t a big a hit. But then take that same router and use it w/ the kind of bandwidth you have today, now it’s a big hit! In that case, you want a smarter router, one that doesn't overdo it.

Again, I'm just speculating here. If the router supports disabling the VOIP, try that if only to see if the problem goes away and confirms my suspicions (esp. if you’re not using VOIP anyway). The router might even allow you to reconfigure these settings and raise your top-end. Or maybe you can disable QoS altogether.