8N Replacement

[PaulL2]

I've always been interested in these sub-gearboxes. It always seemed funny to me to have 4 forward, 4 reverse, then a range selector to give you 3 more (so 3 x 4), then a shuttle as well. Sounded like 3 gearboxes.

The description above from @SDT makes sense - it's not really yet another gearbox, it's an adjustment in the hydraulic. So it's basically an HST + a tricky vane adjustor + a range gearbox.

 

[Fallon]

Fallon,
I have not driven a Korean made tractor. Are you saying they can not be shifted easily between ranges? Which brands/models did you test?

TYM, LS & Kioti are Korean. Only 1 dealer in Colorado sells them. They are several hours away & I wasnt super Impressed with them. The tractors were solid & good value not to mention noticably cheaper though.

As far as poorly shifting HST transmissions... Economy Kubota, Grand Kubota, 2 speed economy JD, premium 3 speed, LS, TYM & probably a few others. I've owned both Kubotas & test drove or operated a pile of the others with HST transmissions.

For every single one shifting could often be problematic. It was sometimes sticky to shift out of gear, but never to bad. The problem is always shifting into gear. Sometimes the straight cut gears dont line up & you can't shift into gear. Or it slides in then out of gear as you overshoot. You need to bump the go pedal, clutch, or let the tractor roll slightly. Not super hard to work around, but annoying.

 

[rScotty]

Correct. It's basically a tweaked L3200 (32hp). They played with the numbers to get it below the 25hp limit where you need emissions equipment. I hear they did a poor job often resulting I'm a more powerful machine than expected. It develops power at a lower RPM than the rest of the Ls.

It's a little low on power, but not to bad. A really good compromise for those wanting a bigger machine without emissions stuff.

They wouldn't have to tweak the engine, just the advertised specs.
The L3200 makes its power at 2800 rpm. If we can assume that the torque curve is fairly flat with respect to RPM, all you have to do to "tweak" that engine is have the advertising department rate the same engine's HP at a lower RPM.
In the case of the L2501, it would be tempting to rate that same engine at only 2200 RPM - which meets the emissions HP requirement for not needing emissions controls.

I'm not saying they did it that way; that's just the easiest way to do the job. There are other & more expensive ways to go about changing HP mechanically. What I am saying is that anyone can change the rated HP output to be anything they want simply by changing the RPM where HP is calculated. It's that simple.
rScotty

 

[PaulL2]

What I am saying is that anyone can change the rated HP output to be anything they want simply by changing the RPM where HP is calculated.

I've heard this mentioned before, and I think it makes sense, although I have no way to verify it.

Problem is, I don't know how you'd go about taking an L2501 and running it at higher revs. I think they're governed and don't rev any higher - so whilst it can make more HP, you can't actually get at it? Or do they "redline" at 2800 revs, but just not talk about it? I also presume that the PTO is rated for 25HP @ 540 / 2200 engine RPM. So if you were to rev the thing to 2800 RPM you'd now have (say) 32 HP, but your PTO is now doing 690 RPM instead of 540, so that's not as useful as it could be.

So I guess the process to turn an L2501 into an L3201 would be to change the rev limit, but then also change PTO gearing and hydraulic pump gearing? Or maybe only PTO because when you're doing hydraulic work like loader work you're not really HP limited anyway, so you just run at lower revs? Or perhaps those PTO implements that need lots of HP are also happy to run faster - I could probably run my chipper at 690RPM and that'd be good because it'd move more air and clear better, and maybe the same for my mower - more tip speed?

All a bit academic for me, they don't sell the L2501 in NZ, but it seems to be a question a lot of people are asking and nobody seems to have a clear answer on.

 

[PHILIP8N]

I retired my 1950 8N with a 2009 Kubota GL3940HST. Both operate a 72" rear discharge finish mower, but now I can run a 6' bush hog off of the Kubota. Philip.

 

[PHILIP8N]

It is usually more than just the pump. Also replace relief valve, lift piston, and lift piston rings. I just honed out my lift cylinder. There is a pretty good video by 2 guys (out of michigan?) that goes thru the rebuild of the pump and lift system components. I did mine over Thanksgiving holiday, HUGE improvement. Philip.

 

[SDT]

It is usually more than just the pump. Also replace relief valve, lift piston, and lift piston rings. I just honed out my lift cylinder. There is a pretty good video by 2 guys (out of michigan?) that goes thru the rebuild of the pump and lift system components. I did mine over Thanksgiving holiday, HUGE improvement. Philip.

I always replace the early style lift piston and steel rings with the later NAA style lift piston and neoprene seal.

SDT