Tires gear ratio for four wheel drive tires

   / gear ratio for four wheel drive tires #1  

deerehoe

Member
Joined
Aug 27, 2005
Messages
36
Tractor
jd 770
anyone know if the jd 770 is the same as the 790 on ratios? My brotherinlaw has a790 with r4 tires rear 15-19.5 front 25-8.50-14 my new to me 770 with 300hrs has lawn tires 13.6-16 and 25-8.50-14 i would like to find if they would work on my if so where i could to find them or ag tires thank you
 
   / gear ratio for four wheel drive tires #2  
The 670/770/790 Tech Manual doesn't specify the gear ratios, but the rear wheel sizes are the same, the fronts are different. The standard fronts tire sizes are (770) 6.50-10's, (790) 6.00-12. As mentioned, the rears are the same. I'm assuming the standard tires are R-1's for both machines.

It looks like (per the Deere online parts catalogue) all the internal PN's for the MFWD axle are the same.

If you want to do this switch, make sure you swap both front and reat tires. You may have to reposition your fenders for those bigger tires.
 

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