first reduction gears jd a

[jd88640]

can anyone tell me hou much slower a 1948 jd a
would be if i change the pully gear and the
first reduction to the later a say a 1952.
i know the 1948 is about 2.5 mph in first
gear and the 1952 is about 1.5 with 13.6-38.
do not know if the reduction gears do all
this or the trans. gears play into this.

 

[Mike N Mo]

The late A reduction gears will slow a 1948 A down by about 8-9%. The transmissions are different between a "2-stick" transmission and a creeper gear (single stick). Reduction gear tooth counts are 36/86 for S/N under 648,000, and 34/88 above 648,000. 620/630 gears are 33/89 teeth. Mike

 

[jd88640]

thanks mike for you"re help. pull the 1948 a
at 5.5 mph class. looking for a little more
rpm response at the end, think this would
help a little all the way down the track.
then when the load starts coming i might have
more throtel to give. comments on this if
you understand what i mean would be helpfull.
thanks jd88640

 

[jdajdgpuller]

We just did this to our '51 A, but we made the opposite switch to make it faster. It was indeed about a 9-10% speed increase.