Ford 7710 MFWD Drive Train Ratio

[Bpp0327]

I have just purchased a Ford 7710 '82 MFWD. Trying to figure out the actual drive train ratio so I jack the whole tractor up to raise all 4 wheels, run the engine and count the actual wheel rotation of both front and rear wheels. The result turns out the front wheel rotates at much slower rate, out of 100 rear wheel rotations the front wheel rotates only 70 rotations. Is this normal for MFWD or something wrong with my front drive? Any advice/suggestion/comments will be much appreciated.

 

[RickB]

If, when you did your test, only one rear wheel was turning but both fronts were, the open rear differential tripped you up. Had both rears been turning at the same rate, the number of rear wheel revolutions would have been cut in half. 70 front/50 rear is much closer to reality.

 

[Bpp0327]

Thanks for the info. Yes, one of my rear tyre are touches ground and the front tyre are both raised by dozer blade.

Hope others can learned from this.

 

[kjung17]

There should be a tire chart and formula for calculating overrun in the operators manual. 70/50 seems very high. Front tires should only turn 1%-5% faster than rears. Never slower.

This formula is out of a JD manual, but will work, if you can find your tractors ratio. Static loaded radius is the distance from the floor to the center of your axle. This number will vary slightly with tire pressure, so correct your pressure before you take your measurement. You should also load your machine as you will be using it most. Load in bucket, bale on spear, etc.

1 — (minus) REAR STATIC LOADED RADIUS/FRONT STATIC LOADED RADIUS x MFWD RATIO = “X”

IF “X” IS BETWEEN .010 AND .050 THE TIRE COMBINATION IS ACCEPTABLE. IF “X” IS NOT BETWEEN .010 AND .050, THE TIRE COMBINATION IS NOT ACCEPTABLE.

 

[RickB]

70/50 seems very high. .

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.

 

[Toddao]

Why do you need to know the ratio?

 

[Bpp0327]

I did the test just trying to validate if the tyre combination put by the tractor dealer on my tractor is good. BTW, out of the 3 test I did, the front wheel revs varied from 60-70 revs (70, 60, 64). The tyre is 14.9R28 Front and 18.4R38 Rear Michellin Tyre.

 

[sandman2234]

The tire sizes listed are definitely different from my 7710, about the same year.
David from jax

 

[D7E]

all the 7710's i've had were 16.9 38 rear

 

[sandman2234]

Just walked out and checked mine. They are 18-4-30 rear (duals)and 12-4-24 fronts.
David from jax