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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.
I would be interested in the sourcing information.
I recently had a sheave failure and had it repaired at a local machine shop for less than the cost of a new one.

BTW, has anyone installed a tach on their 430 and would share the information. I like to have a tach on all of my engines.
 

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The picture is deceiving for 420,430 gear box, the 27 tooth gear is the input, for the 18 is output and puts the gear box into overdrive
I have mine torn apart right now (430 60" deck and the 18 tooth is on the input shaft and the 27 tooth is on the output shaft. I don't know if it has been opened before, but that's how it is at present. Are the gears interchangeable? Could mine be assembled improperly? Mine is a Peerless 1100 - 003. No serial number on the deck but the S.N. on the tractor indicates it is a 1988 model 430. I am confused by these postings and replies. All I really know is that it doesn't cut bahia grass stalks worth a darn even with newly sharpened blades. :)
 

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Can you tell anything about the extra load this gear induction puts on the engine and PTO drive vs the gear reduction as designed? Wouldn't it be like running your vehicle in overdrive all of the time? I think I will try this out. JD engineers always over built things in the earlier model machines.
 

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This is the pulley mounted to the gearbox, correct? If so, what part number is it?
Watch the proximity of the gearbox pulley to the deck spindle pulley when you go to a larger one. They are very close as it is and the larger pulley will increase the probability and a degree of damage that will be caused by larger debris getting between them. Also, any slack in either pulley may cause inadvertent contact of the pulleys.
 

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I think a 6.5" pulley is the max diameter that will fit. I have a 6 incher on it now that has enough clearance and it looks like a 6.5" might work but I haven't verified that yet. I know a 7" pulley won't work because I tried one off a 400 deck. Another issue is clearance with the belt where it crosses the deck under the gearbox mount along the back.




No part number. It's a generic mix and match type pulley. The type with different sized hubs that can be welded to different sized pulleys. The groove isn't exactly the same as the stock pulley. Not quite as wide so it's only using the sides of the grooves for grip. So far so good though, It's been on there since last fall with at least 50 hours use this year and the belt still looks fine. I'm not using a non-standard pulley by choice. I'd put the correct one on it if one was available new in the larger diameter I need to compensate for the slower gearbox on it now. The groove profile (on the generic replacement pulley) will undoubtedly affect the belt longevity. But.. I bought one 400 with a deck belt that had no V shape left at all. Looked like a black 3/8" rope but amazingly still worked.

I actually put another drive pulley on my 420 deck before I started trying to speed it up. The speed was actually excellent till I replaced the gearbox with one that's only a 1:1 ratio (vs the 1:1.5 ratio) on the original 420 gearboxes. I initially replaced stock pulley because the bore was wallowed out badly. The keyway on the shaft was buggered up too.
The JD standard pulley is very expensive. I have had the pulley and shaft repaired at my local machine shop.
 
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