Maximum dyno hp thru pto on JDG

elkcagg

Member
Some guys are saying they're getting 100+ hp out of a JDG & some say even more. I certainly don't doubt that. But harnessing that much power out of the pto makes me not want to go there. I seen 70hp come out of my smaller G and my friend wanted to "lean" into it & I said no. After seeing the mess of shelled pto bevel gears in my other G, I have no way to know how this happened, but my guess is possibly hooked to a baler before it got sent to the salvage yard. Can you dyno off the pulley? How are these folks measuring 100+ hp out of a G when the engineers at Deere were putting out a 38hp pto tractor? The 2 bangers are certainly over-built everywhere else but the pto's are questionable with hp modifications.
 
A while back I bought a m&w dyno that had a adaptor to bolt on flywheel with it. homemade , it adapted flywheel to pto shaft . never used it, sold it with dyno
 
Biggest G I have dynoed was. 600 cubes and was pulling. 118 hp. Multiple times. I know of a few 670-680 cube g's pulling 140+ at 620 pto. They have the big shaft. I've dynoed 5.75 by 9 A's making 90 and they held up. I know of a 45 hp a shattering the gears. My A at half throttle with about 70 hp load, gov popped open and bent shaft side ways and Dyno jumped sideways and killed motor. It's always a risk but the big shaft g's will hold a lot.
 
I think many got broken using things like choppers.. Where you had sudden loads.. Especially when something went wrong (metal going in the chopper) and miss adjusted or no slip clutch.. (This happened to my grandfathers GM )
The Dyno load should be much smoother.. The firing ordered doesn't help the two cylinders any.. Yes we have torn the gears out of a 2 cylinder on the Dyno .. But not a G..
 
Only time i have seen a pto shaft brake was a 5' brush hog behind a 50, hit a large rock moweing in tall grass.
 
(quoted from post at 07:24:23 06/06/14)
Yes we have torn the gears out of a 2 cylinder on the Dyno .. But not a G..

An R maybe????
Yes Sir.. About 80 hp is all the R could handle..

I broke the G again.. Not on the Dyno this time...
 
(quoted from post at 19:36:30 06/06/14)
(quoted from post at 07:24:23 06/06/14)
Yes we have torn the gears out of a 2 cylinder on the Dyno .. But not a G..

An R maybe????
Yes Sir.. About 80 hp is all the R could handle..

I broke the G again.. Not on the Dyno this time...

Oh no! Hopefully not as bad as the time it puked on the dyno.
 
Who's got a pto shaft for a later model G? I thought I had figured out through JD parts that a A and a 60 used the same one. So I found one.....NOT, to small. It's 1 3/8" diameter but to small where it splines into the G spider gears. Any body have one?
 
Well, this certainly raises more questions about the shafts themselves. ( When deere went with the smaller shafts on the Gs.) I have a 50 G with the smaller shaft and my 48 has the larger one & also my 47 which had the busted bevel gears & broke the casting housing. When I switched maincases I had to find a bevel gear with the larger splines. This 47 is 600 cubes
 
Blink It!! 1 3/4" is the flipping large shaft you would want for a G. I need a F649R going by serial number? Any body know of one???
 
I've personally seen just under 150 horse myself! No worries at all. Redline "Heavy shock proof" 75w250 with a couple bottles of friction modifyers seems to work well.
 
My "warmed up a little" '51 G pulled about 6 more horses on the pulley than it did on the PTO with the same dyno which could be rigged either way. I'm sure they lose a little power through that inefficiently designed PTO gearing however rugged it may or may not be. I think it's a definite advantage that the belt pulley is on the crankshaft on two bangers , you get a true engine horsepower indication....no gearing, good or bad, involved. Some say considerable power is lost in the belt connection, but properly sized and tensioned, I doubt it.
 
I can't imagine where any power would be lost on a flat belt connection at all except if it slips but the second they slip you know it. Usually they come off if they slip. My stock B made 26 on the pto & 28 on the pulley, back to back.
 

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