Ford 7710 MFWD Drive Train Ratio

[kjung17]

Why do you need to know the ratio?

Without the ratio of the individual tractor, there is a large hole in the formula.
There is a changeable gear, usually in the MFWD gearcase. The ratio of this gear set determines what tires you can run on your machine. The ratios are stamped on the ID of most tractors. Not sure about the Ford.

 

[kjung17]

Without knowing the circumference of the tires or using the formula you provided, it isn't possible to say whether 70/50 is high, low, or right on. I agree with the 1%-5% front lead.

A 70/50 Front/Rear ratio means that for every full rotation of the front tire, the rear tire will make slightly less than 3/4 of a turn(71%). I am just suggesting that a 29% front tire overrun might cause some performance issues and, perhaps, premature wear. Exact tire circumference can usually be found on the tire manufacturer's website. I have a formula that uses tire circumference to find the desired MFWD ratio, but you have to know both differential ratios. I will find and post it if anyone requests. The MFWD ratio will be stamped on the machine somewhere. It will either give you the number of teeth on each gear (example: 43/33) or a decimal equivalent (ex: 1.303). I like to keep front overrun as low as possible without going negative.

 

[milkman636]

http://www.firestoneag.com/tirelist_pop.asp?ref=112&load=0

SUPER ALL TRACTION II 23ｰ R-1

14.9-28 rolling circumference = 161 inches
18.4-38 rolling circumference = 205 inches

205/161 = 1.273:1 ratio for equal speeds (63.7:50 front/rear ratio)

65:50 would be about 2% overspeed with these tires and a 1.3:1 ratio.

(161 x 1.3) / 205 = 1.02

(front circumference x gear ratio) / rear circumference = overspeed

Knowing the gear ratio is an important part of getting the right tires.

 

[RickB]

A 70/50 Front/Rear ratio means that for every full rotation of the front tire, the rear tire will make slightly less than 3/4 of a turn(71%). I am just suggesting that a 29% front tire overrun might cause some performance issues and, perhaps, premature wear. Exact tire circumference can usually be found on the tire manufacturer's website. I have a formula that uses tire circumference to find the desired MFWD ratio, but you have to know both differential ratios. I will find and post it if anyone requests. The MFWD ratio will be stamped on the machine somewhere. It will either give you the number of teeth on each gear (example: 43/33) or a decimal equivalent (ex: 1.303). I like to keep front overrun as low as possible without going negative.

You are missing the point. The example we are both using does not indicate a 29% front axle lead ratio because the front and rear tires are not the same size. Lead/lag cannot be calculated without axle ratios (including both ring/pinion and final drive numbers) AND tire dimensions. We have neither, only an inaccurate measure of the relative number of front and rear axle shaft rotations.

 

[kjung17]

You are missing the point. The example we are both using does not indicate a 29% front axle lead ratio because the front and rear tires are not the same size. Lead/lag cannot be calculated without axle ratios (including both ring/pinion and final drive numbers) AND tire dimensions. We have neither, only an inaccurate measure of the relative number of front and rear axle shaft rotations.

:laughing:I should probably be fully awake when I do math. Obviously not a 29% overrrun. We'll have to see if he can come up with any actual numbers for that tractor. Deere stamps the front diff ratio on the ID tag. The rear diff and MFWD box ratios are stamped on the rear diff housing.

 

[sandman2234]

I thought we were talking about a Ford 7710, not a Deere 7710?
David from jax

 

[kjung17]

I thought we were talking about a Ford 7710, not a Deere 7710?
David from jax

:laughing:It's true, we are. Under the paint, all tractors are pretty similar. Color makes very little difference with this sort of issue. The math and principles are the same. Most Manufacturers label their machines in some way.

 

[sandman2234]

I hope you don't get run off the board with that type of statement about color choices, LOL. Some of these guys are serious about their color choices and explain the reasons with vast explanations. (However, I think you are right!!)
David from jax

 

[kjung17]

I thought color blindness was encouraged in these, politically correct, days. We are a green dealership, but we see every color in the service dept. The off colors, if you will, are usually the derelicts that the sales staff take in trade. Then we get to try to polish the feces, if you know what I mean.:thumbsup:

 

[Bpp0327]

For the benifit of everybody, below is the technical data of Ford 7710 taken from Ford - New Holland 7710 Tractor Repair Service Work Shop Manual


Tranfer Box ratio = 1:1.144


Front axle Ratio;
Differential = 1:2.16
Planetary Gear = 1:7.33
Overall = 1:15.82

Rear Axle Ratio = 23.76
Final Reduction Gear (Planetary gear assembly) = 4.5




Out of the figures above, I can only confirm the Transfer Box ratio as it is stamped on the nameplate.

BTW my front axle is ZF APL325

Hope this will help figuring out the proper tyre for this type of tractor.