It’s a very big misconception that people believe the modern reels don’t carry the same level of quality as the older ones. As far as bait runners are concerned I’ve owned 3500b’s 5010’s and 4000Ds.
There isn’t much I don’t know about any of the above because I don’t just use my reels I strip them, I clean them I service them and if need be I repair them. My 5010’s I knew inside out,back to front, upside down they’d been apart and serviced every year for over 20 years. I can tell you now that the design and general material quality of the mechanical parts inside any of the above reels is no better or worse than one another. All use high grade metals for the gearing, worm drives, shafts and bearings. That’s fact.
The designs are different though as the older series reels use 2 worm drives 1 for rotating and one for up and down. The modern reel uses 1 for rotating but the up and down is done with another gear and a carriage located on that gear. This only means when you remove the main gear it must go back exactly in the position it came out or it will jam up after half a turn. Not a weak point just a design change and it still works
The 5010 has a small slither of stainless steel spacing out two parts of the body, it’s held in place when the case is shut. It always falls out into the reel and can go undetected on rebuilding so again not a weak point just something to watch. Unfortunately no reel is perfect. I still can not believe shimano took a couple of grams off the 4000d by reducing the bail arm diameter. Yet they gave it a beautifully solid stainless steel handle. Why not make that a mm thinner. Madness!!
Yeah I know it doesn’t cause people problems but it will if you accidentally drop it from waist height I can guarantee you that. The 5010 got cast aluminium handles!!! Again why? One good drop they bend. Don’t attempt to straighten it. Ask me how I know.
A little tip if you have rear drag reels you can improve the smoothness of that drag a lot by applying graphite powder to the drag washers very sparingly indeed. You don’t want it in the reel body. This actually improves the drag 100% more. 3500b was a awesome reel
It has no weak points at all. However the line lay was shoddy to say the least and it was just too dam heavy for smaller rods imo.
4000d spool prices get mentioned a lot and again I think it’s because it’s misunderstood what your buying. Your not just buying a spool your buying a beautifully machined very high tolerance anodised aluminium spool with a complete drag system built inside. Bargain at £30.
For me the 4000d isn’t perfect but it ticks more boxes than the others.
I’d love a pair of Thunnus reels but they rock up at another £100 on top and you don’t see many spares on offer in this country. A few extra bearings and a few ounces lighter ain’t really the changes I would make to a 4000d to make it better.