L3750 gearing

[jsmootz]

Just acquired a 1985 L3750 4wd w/hydraulic shuttle clutch. The tractor is a one owner (neighbor) that I have known since new. It is "barn fresh" with only 477 hours. A really sweet tractor except the rims are rusted from slow calcium chloride leaks.

All info I can find for this tractor shows 13.6 x 28 rear tires and 9.5 x 16 fronts. This particular tractor however has 14.9 x 24 rears and 9.5 x 16 fronts.

It is almost certain that the tires/wheels are original to the tractor. My concern is that the tractor may be fighting itself in 4wd. I can't imagine that Kubota changed the front/rear gearing to accommodate the smaller diameter rears.

Am I just paranoid?

Thanks, SCOTTIE

 

[North Idaho Wolfman]

SCOTTIE,

Your right to question the tire sizes but a little off in the "factory" sizes,
The 13.6x 28 were an option for 2wd.
4wd had 2 options 12.4 x 28 and 14.9 x 24.
So you do have "factory" sized tires on it.

With 477 hours on it, if there was a problem it would have broken something by now.

Are the tire worn super unevenly?
Bald front's or bald rears?
If not then they are matched!

So yes you are "just being paranoid".

 

[jsmootz]

Thanks for the reply. I really do appreciate your input. Could I inquire your source? I have the original operator's manual that came with the tractor and also a Kubota workshop manual (from the dealer). Both show only 13.6 x 28 rears for the 3750 DT.

A neighbor bought the tractor new and it never went outside of his pasture. It could very well have survived 477 hours without serious damage as it has never been used on solid ground surfaces. My concern is that a slight mismatch could be just enough to make the tractor "fight" itself creating inefficiency and possibly real damage in the future.

Regardless I need to drain and dismount the tires, restore or replace rims, and possibly replace the dry rotted tires. It would thrill me to truly confirm the correct size as 14.9 x 24". It certainly would save me $$ if I can get by with reconditioning the existing wheels.

If indeed there was a rear wheel size option for the 4wd I am curious if Kubota provided different gearing for each model.

Interesting side-note: The tractor would not shift into high gear. When I asked the original owner he said, " Don't know if I ever tried it, never had the need". Investigation showed the seat belt bracket had been installed backwards at the factory or dealership and was blocking the linkage. Easy fix, lucky me!

SCOTTIE

 

[ctmike]

Scottie,
I have the same tractor and the same size tires as yours so I think you're good to go.
In my 1991 owner's manual, they do list our sizes in the tires section.
mike

 

[Bluegill]

Dang, that's low hours for a rig that old. Our L3750 has around 3000+ hours.
Don't know what size tires though....

Very good, very strong, heavy tractor! Love that smooth running 5 cly!

 

[North Idaho Wolfman]

Tractor Data . com
http://www.tractordata.com/farm-tractors/001/3/0/1305-kubota-l3750-dimensions.html

The tire and rim sizes can be different and yet still have the same RC (rolling circumference) that is the most important number when trying to figure compatibility, it's a ratio of the front RC and rear RC that has to remain within a proper ratio for everything to work right.

 

[jsmootz]

Still researching. Kubota dealer got back to me. He says the Kubota branded Workshop Manual is usually the last word. The 14.9 x 24 and 9.5 x 16 set is listed as an option for the 3350 but NOT for the 3750.

Workshop manual shows the front axle to be a direct gear drive. 3750 and 4150 use different gears. Unfortunately they don't specify for the 3350. May be the same as 3750, may not. Would need to check parts manual.

Dealer is still researching the serial number to verify. His belief is that the seller or a yard flunky made the switch to appeal to the customer. This area is very hilly and the low, wide look is popular.

There is an 8" difference in the rolling circumference between 14.9 x 24 and 13.6 x 28. This may not be enough to cause severe damage but maybe enough to foster inefficiency and long term wear. ??????

As it stands I will probably go to 13.6 x 28. Hope I don't make an expensive mistake. Sure would pacify my mind to see some early sales literature showing 14.9 x 24 and 9.5 x 16 optional for the 3750.

SCOTTIE

 

[Bluegill]

You definitely want the right size tires!!!! Front end gears and parts are very expensive!

I'll look at our 3750 today and let you know what tires we have.

 

[BAP]

If you load your new tires, make sure you don't use the calcium chloride. Use something like beet juice, citrus juice or Rim Guard that is ballast that won't freeze and also will not rust your rims out again.

 

[Bluegill]

Our old L3750DT Hydro shuttle has 14.9 x 24 rear & 9.5 x 16 front. R1 ag tires.
Rims look original...

I would not put the larger wheels/tires on the rear of yours...

 

[jsmootz]

Our old L3750DT Hydro shuttle has 14.9 x 24 rear & 7.5 x 16 front. R1 ag tires.
Rims look original...

I would not put the larger wheels/tires on the rear of yours...

Except that mine has 9.5 x 16 fronts. The combination on your tractor is listed as an option for a 3350 in the WSM. My combination doesn't match to anything. I'm pretty sure that I need to up the rears or lower the fronts. The WSM pairs 13.6 x 28 with 9.5 x 16 as std. on a 3750DT and 12.4 x 28 with 8.3 x 16 as an option.

 

[hodge]

"There is an 8" difference in the rolling circumference between 14.9 x 24 and 13.6 x 28."

That is a lot of difference, and if there is a discrepency, you would feel it while driving. Does it bind up? Do you get a lot of tire slippage when turning?

 

[North Idaho Wolfman]

jsmootz,
I don't know where you got your info that the 13.6 x 28 and the 14.9 x 24 had 8" of RC difference?

The 14.9 x 24 and the 13.6 x 28 are the same RC.

 

[jsmootz]

jsmootz,
I don't know where you got your info that the 13.6 x 28 and the 14.9 x 24 had 8" of RC difference?

The 14.9 x 24 and the 13.6 x 28 are the same RC.

View attachment 9395

I would be thrilled if the 13.6 x 28 and the 14.9 x 24 shared the same RC. It would save me lots of work, money, and retain my peace of mind.

My source was a phone conversation with an engineer/consultant at Titan Tire. He said RC of 13.6 x 28 is 158" and 14.9 x 24 is 150".

What is your source? (I really am hoping you are right)!

As a last resort I am going to pull a tape around a rear on my father's Deutz (13.6 x 28) and compare it to mine.

 

[North Idaho Wolfman]

I got it strait of Titans site.

Real simple to find out if it's set up right, put the tractor and a flat hard surface in neutral and engage the 4wd, if you can push the tractor its fine.

There is also an acceptable range of 5% in the tire ratios.

 

[jsmootz]

North Idaho Wolfman,
Boy do I feel stupid! I just noticed your attachment. You have provided me with exactly what I need. Thanks much.

Evidently the Titan representative I spoke with did not understand my issue or he was a little incompetent.

My tractor wheels/tires sizes will stay "as-is". Now to the task of restoring/replacing these nasty wheels. Thanks to all, especially North Idaho Wolfman, for your patience and consideration.

 

[Bluegill]

Except that mine has 9.5 x 16 fronts. The combination on your tractor is listed as an option for a 3350 in the WSM. My combination doesn't match to anything. I'm pretty sure that I need to up the rears or lower the fronts. The WSM pairs 13.6 x 28 with 9.5 x 16 as std. on a 3750DT and 12.4 x 28 with 8.3 x 16 as an option.

I screwed up, mine has 9.5 x 16 fronts. Sorry...

14.9 x 24 rear & 9.5 x 16 front.

 

[ctmike]

I got it strait of Titans site.

Real simple to find out if it's set up right, put the tractor and a flat hard surface in neutral and engage the 4wd, if you can push the tractor its fine.

There is also an acceptable range of 5% in the tire ratios.

I did the math on our tires and got 2% ratio.

 

[freewheel3]

Its been my experience that if the front / rears are not the correct ratio, you will definitely feel it when in 4wd. Get the tractor moving in gear and then push in the clutch - it will stop almost as if you have applied the brakes. It is binding up. This is evident even when there are no other obvious symptoms such as wheel slippage etc.
Another dead give away is to try engaging or disengaging the 4wd while the tractor is moving in gear, if the ratios are correct it will slip in / out like butter. If not, not.
These are 2 easy, quick and free ways to check. No tape measures or fancy math involved.

 

[jsmootz]

I did the math on our tires and got 2% ratio.

How did you figure that? Do you have the gear ratio for the tractor? I havn't found it in the WSM.