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Discussion Starter · #1 ·
I just finished rebuilding the gearbox on my 430 with 60" deck. There seemed to be a lot of play in the driveline and gearbox. All that was fixed with new woodruff keys.

In doing research, I found out the 60" deck on 420, 430, and 755 all have 18 tooth input and 27 tooth output. In looking at almost all other deck gearboxes (50" and 72" on just about everything including front mowers,) they have 25 and 26 teeth respectively for about 1:1 ratio. Any ideas why only the 60" deck on these machines would have the blade speed reduced? It seems if I used a gearbox from a 50" or 72" deck I could get faster blade speed on my 60" deck.

My first thought is that the 420, 430 and 755 have about the lowest horsepower of machines using these 60" decks and maybe the thought was to not overtax the engines.

By the way, I have sourced all the parts needed to rebuild these gearboxes and will supply the info if anyone is interested.
 

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Discussion Starter · #4 ·
The 18 tooth gear is on the driveshaft input shaft and the 27 tooth gear is on the pulley output shaft. Deere uses the same nomenclature as Peerless which is contrary to the application.
 

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the 18 tooth gear goes on #M87228 shaft which the parts book says is an output shaft. the 27 tooth goes on M86843 which is the input shaft.
That is the same thing I found, at least for my 1990 420 with 60" deck.

(RPM speeds corrected from 3450 to 2000)
Which is a 1.5:1 gear ratio. So with a front PTO input speed of 2000 RPM the output speed would be 3000.

If the gears were reversed, as mentioned earlier in the thread, with an input speed of 2000 RPM the output speed would only be 1333 RPM.

 

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According to all the websites I have found, the stated front PTO speed is 3400-3450 RPM. The rear PTO speed if equiped is 2000 RPM.



 

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Just to be clear, the rear PTO is 2000RPM only if you have the gearbox reducer. If it's just the PTO clutch it's still 3450, or max engine RPM. The driveshaft into the hydro pump has a passthrough with a spline on the back of the pump. All 1:1.

For front PTO, I am unsure. But the PTO will still turn engine RPM since it's directly bolted to the crankshaft (like the driveshaft to hydro pump).

-Aaron-

Sent from my SM-G781V using Tapatalk
 

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On a 420/430 the pto input is about 2000 rpm at 3450 engine rpm. The engine pulley is smaller than the front pto pulley.
Charms is correct.
The front PTO is belt driven from the electric clutch on the engine, not the drive shaft. The pulley on the electric clutch is about 3 1/2" diameter and the pulley on the front PTO shaft is about 6" diameter. So at 3450 engine speed the front PTO would be turning about 2000 RPM as Charms stated. It is interesting that all the tractor data sights list it at 3450 RPM.

So with the input shaft to the deck gearbox turning at 2000 RPM the output shaft with the 1.5:1 gear ratio would be turning at 3000 RPM almost the same as engine speed. (I corrected my numbers in post 7 above)

As for blade speed that would depend on the pulley diameters on the deck gearbox and the spindle pulleys, and I haven't checked that.
 

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Discussion Starter · #13 ·
The nomenclature in the parts book uses the same descriptions as Peerless,, however it is opposite for this application.

The PTO input driveshaft connects to the M87228 shaft which has the 18 tooth gear installed.

The pulley is installed on the M86843 shaft with the 27 tooth gear which is the output to the deck.

My pulley was the AM117851 which uses the split bushing. Here is the description: (4L or A, 5L or B Belt Section, 1 Groove, 4.9000 in (A) 5.4000 in (B) Pitch Dia., 5.4500 in O.D., Split Taper Bushed, H Series Bushing, Cast Iron Material.)
 

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Discussion Starter · #14 ·
Here are the specs on the spindle pulleys.

John Deere Blade Drive Pulley - AM35307
Specification
Belt SectionHB
Effective Diameter6.000 IN
Groove Width0.630 IN
Angle34
Bore Size0.986 IN
Key Width0.251 IN
Length1.000 IN
MaterialSTEEL
 

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Discussion Starter · #15 ·
Here are the specs on the electric clutch pulley.
  • Replaces OEM : AM100848, AM101137, AM104238, AM104896, AM39329
  • Specs: 1.438" Crankshaft, 4.875" Pulley
I can't find the diameter of the driven pulley on the driveshaft. Mine looks to be around 6" or so.
 

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Discussion Starter · #16 ·
Here are the parts I needed:

DescriptionJD #QtyAftermarket
O-RingU444962#1512.987"ID0.103" C/S
SealM868491SKF 101111.987OD x 1 x 1/4
SealM868501SKF 99981.756OD x 1 x 1/4"
Woodruff Key26H824#8071/4" x 7/8"
 

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The nomenclature in the parts book uses the same descriptions as Peerless,, however it is opposite for this application.

The PTO input driveshaft connects to the M87228 shaft which has the 18 tooth gear installed.

The pulley is installed on the M86843 shaft with the 27 tooth gear which is the output to the deck.

My pulley was the AM117851 which uses the split bushing. Here is the description: (4L or A, 5L or B Belt Section, 1 Groove, 4.9000 in (A) 5.4000 in (B) Pitch Dia., 5.4500 in O.D., Split Taper Bushed, H Series Bushing, Cast Iron Material.)
Good Luck,
 

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In JDparts, for a 420/430 decks, there is a early version for deck serial # up to 525,000, and a later version for serial # over 525,000. The gearboxes are different, but the gearbox pulley numbers are the same.
I have a later 420/430 deck in the shed, so I had a look and, turning by hand, the gearbox pulley output definitely turns faster than the driveshaft input. So on that deck, the input shaft would have the larger gear.
On that deck, I agree that the pulley output would be about 3000 rpm. The drive pulley on the gearbox is a little smaller than the deck pulleys, so blade rpm might be around 2500.
Edited
 

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Discussion Starter · #20 ·
My mystery is solved! For reference, mine is the late model deck.

Thanks to all that responded, specially Burned 300 for trying to get the light bulb to go off in my head. I just couldn't wrap my head around the fact that the gears would be installed the way they were from the factory, but that's the way it came to me. I knew like everyone else that the 27 tooth gear should be on the input shaft. So I had to look elsewhere to figure it out.

Here is what happened. When I purchased the 430, it had a 50" deck on it (which I was not interested in as I have a 50" deck on my 332 that I mow with now.) The 60" deck was not installed. The PO had inherited the tractor it from his father who got it from a neighbor that bought it new. The PO told me, even though they had a very large yard, they only used the 50" deck because the 60" deck didn't mow very well. I should have figured something was wrong then, but I didn't. It looked Ok. Well now it is obvious someone had installed the gearbox incorrectly which, I assume, is why it didn't mow well, and I was trying to put it back together the way it came to me.

I only removed the gearbox assembly to install a new belt and noticed it was leaking at the pulley seal and had a little "slop" in the gears. The bearings were all good to go, so new seals and woodruff keys for less than $30 and I am back in business.

Thanks, again to all who provided input.
 
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