7710 II wheel size

MNfarmer

Member
Just curious if there was a correct rear wheel size for this tractor with fwa? I have 18.4-38's on mine and my neighbor has 34's on his. Both tractors have 14.9-24 fronts...was the ratio for the front end changed for the bigger rear wheels or did someone put 38's on it not realizing it could change the ratio?? Thanks
 
Normally.... the 7710 had 18.4-34 rears. Early models with the ZF axle had 13.6-24 fronts. Later models with the Carraro axle had 14.9-24 fronts. At least that is what I have observed. It is possible (because I've learned that nothing in the Ford world was ever absolute) that some models may have been equipped with different ratio transfer boxes to feed a different set of front skins. I also believe that the 8210 was equipped with 18.4-38 rears and 14.9-28 fronts.... and I expect that it either had a different transmission output ratio or different crown wheel ratio to achieve that difference.... in which case it likely had a different transfer box to make up the front difference. Point of what I'm trying to say is that somewhere along the way, someone may have mixed and matched some parts to make something work out...

Rod
 
The axle ratio will be stamped on a tag... probably on the left rear side of the axle near the diff on the carraro. The transfer box will have a similar tag with it's reduction or transfer ratio. For calculating the rest of it..... I usually use the transmission output ratio and known rear axle ratios combines with tire stated circumference to calculate relative travel speeds for front and rear. That information and probably a formula for comparing ratio's is printed in the transmission section of the service manual.

Rod
 
Rod, I found the tag on the axle and some numbers stamped on the transfer box but no tag. I'll see if I can get the pics to load.
 
Can't get the pictures to load, here's the front axle ratio...1:17.4545. These are the only numbers I found stamped on the transfer box, didn't find a tag..1 127 and 43/43
 
I don't know what to tell you there... is the tag missing or does it appear to never have had one?

Rod
 
Yes, as far as I know... but you should see a flat spot with the rivets remaining if the tag is gone...

Rod
 
I stopped and looked at my neighbors 7710 today. He has 42/43 stamped on his transfer box and has 34" rears. I have 43/43 on mine with 38" rears. Both have the same front axle and front tire size. Would that make sense?
 
Forgot to add...I stopped at the dealer today and looked in one of their books and there were three driven gears available for the transfer box. 42,43, and 44.
 
It probably makes sense.... It could be either a .97 ratio or a 1.02 ratio depending on which is the drive and which is the driven in that set... and seemingly it could be either way with the combinations listed. All we know is yours is a direct drive....
I wouldn't get too worried about it unless it won't steer in FWD or it's scrubbing the tires in a turn. That would suggest to me that the front doesn't have sufficient lead.

Rod
 

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