New owner operator, have issue with clutch

Long story short, I began trucking in the summer of 2014 with a tri axle dump truck, fast forward to today, I recently bought a 2004 Kenworth W900 with a Cat C15 475HP engine with a 8LL transmission and 4.10 rears 7 axle super dump. I've had the truck for about two months now and besides basic maintenance, she has performed well despite her age. The truck has about 690k miles and the clutch/master/slave cylinder are original according to my old boss when he bought this truck new all of those years ago and I never had this issue for the year I drove this truck before I bought it for a very good deal. Now, this issue began on Monday, when I take off from a dead stop in 1st gear and even low gear to a somewhat lesser degree, if I let the clutch out like normal, the truck seems to jerk/bounce like as if I let the clutch out too fast when it's about half way depressed still. This happens more frequently when I take off going uphill and have even stalled a few times because I'm feathering both the clutch and accelerator to avoid that sudden jerking/bouncing motion and to prevent the clutch from burning. The gears shift fine, they don't pop out, there is no clutch slippage, the clutch brake engages fine, the air pressure is normal and there are no leaks, the PTO engages/disengages fine and I also smelled a hint of what seems to be hydraulic/brake fluid when this first began inside the cab shortly after taking off. This happens when I'm loaded, since I usually take off in 2nd gear when empty, the clutch behaves nearly normally with a hint of that issue at times. At times, when I'm maneuvering in tight places, the clutch feels normal but then sometimes, it feels as if it's pushing back against my foot and this only happens when I'm in 1st gear and such going really slow entering construction projects and such. I inspected hydraulic fluid used for the PTO/bed and it's all in working order with no leaks and operate fine when dumping my loads. My initial thoughts are that could it be the master/slave cylinder that's going bad? My father is an auto mechanic and also a trucker but he is across the US right now, so he isn't around to take a look at the problem and won't be in my region for another three weeks.

I'm barely beginning to learn how to do all the basic maintenance myself but I would like to know what this issue could be before I take the truck to a shop and avoid being ripped off and such.

 

The clutch is original and once the truck is moving, even double clutching feels normal, that issue happens when taking off from a dead stop. If the truck is in motion, even when I downshift to first gear, there is no slippage of the clutch and such as long as the truck in in motion and I have no issues shifting and such in heavy traffic as long as I don't stop on an uphill. Also, when I said about that jerking motion, it feels as if the truck is trying to stall and that jerking/sudden bouncing motion happens once and not bouncing like a lowrider car or rodeo ride. I mean that when I'm taking off with my feathering of the clutch, it will feel like it suddenly wants to take off as if letting the clutch out too fast to stall a vehicle when one is learning to drive a manual if that makes sense to you. One other thing I didn't mention is that the clutch peddle sometime doesn't quite depress normally meaning that sometimes, you can kinda feel a clicking kinda feeling when depressing the clutch. Hard to try to put to words when it's much better to drive the truck loaded to feel what's wrong.

What about that smell of hydraulic/brake fluid I smell inside the cab shortly after this happens when I take off up a hill?

On the 8LL note, it's not too bad when you go into muddy construction projects and such, I can see why many dump trucks have them. Though, I would have preferred at least a 13 speed or 18 I drove before buying this truck. But this 8LL allows me to cruise at 65-70 without having the engine screaming.

When I get the chance, I'll have the shop take a look at the mounts you mentioned. It's not a serious issue as it's relatively minor push back against my foot.

 

Hmm, that sounds reasonable because there are times when the truck takes off normally, so it's random I guess.