M4700 transmission ratios/speeds

[rv7charlie]

I suppose this might be considered a rant in the form of a question, but here goes:
Any thoughts from you 'pro' users on why the M4700 has such a big speed jump from high 2nd to 3rd? Mine gets about 95% of its hours running a 7' cut finish mower. (Mowing ~3 acres of my land, and 20+ acres of a grass airstrip six to eight times a year whenever my turn rolls around.) 2nd gear & 2600 rpm gives a pretty cut, but takes a generation to mow 20 acres. 3rd gear & 2600 rpm gets it done in about 2.5 hours, but gives a ragged cut and the mower tends to deflect the grass at its edges instead of cutting it. (This is with freshly sharpened blades.) Going any slower in 3rd results in the mower turning too slow, making the cut look even worse. When you look at the speed range chart, the speed jumps from about 8 mph to around 12 mph when going from 2nd to 3rd.

Anyone have any idea on why Kubota would have built such a wide gap into their system? I realize that most jobs don't get done in 3rd or 4th, but mowing really does need either a slightly slower 3rd, or a 'variable ratio' PTO rpm. Shelling out the money to replace the tractor with a hydrostatic drive model just isn't in the budget.

 

[newbury]

Your getting into "highway" speed for the tractor. Mine spends it life with me between 1R and 4L. But then all my time seems to be spent in the woods.

 

[TripleS]

Put a shorter tire on it.

 

[Farmer495]

I suppose this might be considered a rant in the form of a question, but here goes:
Any thoughts from you 'pro' users on why the M4700 has such a big speed jump from high 2nd to 3rd? Mine gets about 95% of its hours running a 7' cut finish mower. (Mowing ~3 acres of my land, and 20+ acres of a grass airstrip six to eight times a year whenever my turn rolls around.) 2nd gear & 2600 rpm gives a pretty cut, but takes a generation to mow 20 acres. 3rd gear & 2600 rpm gets it done in about 2.5 hours, but gives a ragged cut and the mower tends to deflect the grass at its edges instead of cutting it. (This is with freshly sharpened blades.) Going any slower in 3rd results in the mower turning too slow, making the cut look even worse. When you look at the speed range chart, the speed jumps from about 8 mph to around 12 mph when going from 2nd to 3rd.

Anyone have any idea on why Kubota would have built such a wide gap into their system? I realize that most jobs don't get done in 3rd or 4th, but mowing really does need either a slightly slower 3rd, or a 'variable ratio' PTO rpm. Shelling out the money to replace the tractor with a hydrostatic drive model just isn't in the budget.

You are into road gear territory, that is why. The gears space nice for upshifting to top speed.

The ratios don't change low range 2 to low range 3, but the multiplier factor of the range transmission spaces them out further speed wise. If 2 and 3 were closer together, they would be almost the same speed in low range. Low range gears might be 1 MPH apart, high range 4 MPH apart.

Most, if not all, tractors with straight 8 speed transmissions have the same set up. Under 5 MPH for low range, 5 to 8 MPH High 1 and High 2, with High 3 and high 4 are highway use. You would need to get into a tractor with another splitter (12, 16, 24 speed etc) to get a better selection in the 5-10 MPH range.

The comment on getting a shorter/smaller rear tire size has merit. Turf special models of utility tractors had short, fat turf tires and the same 8 speed transmission, the smaller rear wheel meant the top speed was considerably lower, and also meant that the high range gears were spaced closer together speed wise.

 

[ptsg]

Turn it into a low rider.

 

[sixdogs]

The others are correct in that the higher gears you're using are preludes to a road gear for highway driving. I have an MX5100, which is mostly the same tractor aqs yours, and would not be able to mow in those high gears.

Most ag equipment is designed to operate at 5mph and that's where tractor makers put their gear ratios. My rear Woods mower--now sold--called for a 5mph max speed. I also got ragged cuts at higher speeds.

I felt the same pain mowing hay in a 3/4 mile long field but when I went faster it left a ragged cut or machinery damage issues. I just slowed down. I also mowed at a higher level and that left the grass softer and that cut a little better at a slightly higher speed.


Smaller tires are an expensive option with not much resale value and a hydro transmission will kind of leave you in the same situation of wanting a higher ground speed.

 

[rv7charlie]

Thank you all for the replies. The smaller tire idea might be worth pursuing, if I ever wear out the existing back tires (or they dry rot ;-) ).

I guess I'm back in rant mode, but it seems nonsensical for tractor mfgrs to devote two top gears for highway use, when (at least with this tractor) it's quite capable of getting under way in high 4th. It would seem logical that high 3rd has no use at all, if it's not for something like mowing. I wonder what the mfgrs think people are using to run 7' & 8' finish mowers, and where those mowers would actually be used.

Again, thanks for the smaller tire idea; that sounds like a potentially workable solution, when I really didn't even expect to hear one.

 

[5030]

Again, thanks for the smaller tire idea; that sounds like a potentially workable solution, when I really didn't even expect to hear one.

If you do that and the unit is front wheel assist, you'll have to change the front's as well to maintain the proper lead-lag ratio or you will destroy the front differential

 

[rv7charlie]

Fortunately (I suppose), it's straight 2WD. It'll likely never happen anyway; I'll probably age out of grass mowing before the tires do.

 

[LouNY]

Thank you all for the replies. The smaller tire idea might be worth pursuing, if I ever wear out the existing back tires (or they dry rot ;-) ).

I guess I'm back in rant mode, but it seems nonsensical for tractor mfgrs to devote two top gears for highway use, when (at least with this tractor) it's quite capable of getting under way in high 4th. It would seem logical that high 3rd has no use at all, if it's not for something like mowing. I wonder what the mfgrs think people are using to run 7' & 8' finish mowers, and where those mowers would actually be used.

Again, thanks for the smaller tire idea; that sounds like a potentially workable solution, when I really didn't even expect to hear one.

If you had a towed load behind it or starting up a hill you'd find a good reason for that 3rd gear.