B7800 Drive train ratio/Inter-axle ratio?

[Work-too-much]

Hi everyone I am new here.
My B7800 came with 4 ply Titan Track loader NHS 23x8.5-14 front tires and Goodyear Super grip 12.4-16 rear tires. They are both R4 tires. I do loader work, snow blow the driveway and mow my lawn with the tractor. The fronts need to be replaced and I would like to try the R14T's. I was told the R14T is not as aggressive when mowing the lawn (I make real wide turns when mowing the lawn). The rolling circumference of the fronts are 70.34" and the rears are 110.14".

I am looking at putting R14T 88A8 23x8.5-12, which have a rolling circumference of 68" on the front. My issue is I cannot find anywhere what the drive train ratio is for my B7800? I want to confirm what the lead/lag would be with the original tires and with the R14T to be sure they fall within the specified percentage.

I called Messicks and they said to replace both the front and the rear with R14T tires. The rears probably have 70% of the tread on them so I don't see that as a good option. It doesn't make sense to mark the tires and roll the tractor with worn out front tires to get a drive train ratio.
Any help would be appreciated!

 

[Work-too-much]

I also wanted to add I have the service manual and the operators manual and I could not find the drive train ratio listed in either manual. Also I believe the B7800 runs the same engine/transmission as the B2710 and the B2910 tractor because the manual covers all three models of tractor using the same tires on all three.

Thanks

 

[Henro]

I believe the B7800 is identical to the B2710 and B2910, as Work-to-Little (sorry, could not resist ) stated.

You can calculate the desired ratio using the diameters of the originally installed tires. That would include a slight over speed built in for the front, which seems to be standard. You can google what the standard range is, but I think the front over speed is something like 3 to 5 percent. But don't quote me on that just what I THINK I remember.

Another way to get a close estimate of the front/rear speed ratio due to gearing might be to jack the tractor up on one side, and with both wheels off the ground on one side, run the tractor in 4 wd and count the revolutions front and rear. And see what the ratio is. Might need four eyes to accomplish it. BUT it could be done. Count ten or a hundred on the back, and get the number counted on the front during the same time.

Myself, I would probably just check the standard diameters of the front and rear tires and try to match it pretty close, and expect the results would be satisfactory. Without a bit of over speed on the front when in 4 WD, steering becomes an issue.

 

[Henro]

By chance, I noticed this thread and post #2 may answer your question:

Tractor Wheel Database Somewhere?

I would like to know the specifics of the rear wheels on my B2910. Of course I could measure and hopefully accurately determine the wheel lug bolt (and stud) hole circle diameter and the wheel pilot size. But I think to get an accurate measurement I would have to remove a loaded tire. I would...

www.orangetractortalks.com

Edit: there is a later chart in this thread that shows the b7800HSD has the same ratios...not unexpected...

 

[Work-too-much]

By chance, I noticed this thread and post #2 may answer your question:

Tractor Wheel Database Somewhere?

I would like to know the specifics of the rear wheels on my B2910. Of course I could measure and hopefully accurately determine the wheel lug bolt (and stud) hole circle diameter and the wheel pilot size. But I think to get an accurate measurement I would have to remove a loaded tire. I would...

www.orangetractortalks.com

Edit: there is a later chart in this thread that shows the b7800HSD has the same ratios...not unexpected...

Thanks Henro! That is exactly what I was looking for! My B7800 is a HSD.

 

[Henro]

Thanks Henro! That is exactly what I was looking for! My B7800 is a HSD.

I see the chart in post #7 specifically calls out the B7800HSD. No surprise that it is the same as the B7800DT and B2710/2910.