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To follow along with my previous thread, I've located a bare 50 inch deck at a reasonable price. I know the pulleys are different sizes on the 46 vs 50 inch JD 318 decks (50 inch deck has larger pulleys I believe due to the longer blades). Does anyone have experience with swapping pulleys?

I would assume that this would raise blade speed when putting a 46 inch spindle and pulley onto a 50 inch deck which could be a good thing; however, I assume the 50 inch belt would be too loose?

Perhaps I could use a shorter belt; however, I have heard that JD belts are significantly superior to any others for this use.

Thanks for any input that you may have!
 

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Can't help on pulleys bore sizes, but JD belts do last longer. The reason for that is because they fir the v-groove in the pulley correctly! JD uses a 38º angle on their pulleys & belts and off the shelf belts are typically 40º. Two degrees doesn't sound like much but when first installed, a 40º belt will only make contact on the top corners of the belt. This is not enough area to properly drive the pulley and the belt wears quickly. Eventually, maybe after a season, the belt will wear enough that the belt will now have a 38º angle & contact fully along the sides of the belt...or bottom out in the pulley groove. Bob
 

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To follow along with my previous thread, I've located a bare 50 inch deck at a reasonable price. I know the pulleys are different sizes on the 46 vs 50 inch JD 318 decks (50 inch deck has larger pulleys I believe due to the longer blades). Does anyone have experience with swapping pulleys?
Nope, no experience. But I did stay in a Holiday In Expre....... But I do have some spare bits from a junk mower to go and look at......

I would assume that this would raise blade speed when putting a 46 inch spindle and pulley onto a 50 inch deck which could be a good thing;
That's the least of your worries, you've got bigger issues... But, PROVIDED that you use all matched pulleys, the center spindle pulley, the double one, will set your speed. The ratio of that top (large) pulley to the PTO clutch pulley will set your RPM. The lower pulley there, and the other two single pulleys, being the same diameter, will keep the same RPM for all three blades. The large pulley between the two decks is kinda close. I'm not sure "exactly" where the belt rides inside those pulleys, but you're probably within 5 or 7 percent on the blade speed, which means that unless the PGA tour is coming play on your front lawn, that part will be fine. The problem is that the pulleys are not in the right place. The 46 inch deck pulleys live closer to the spindle mounting face, and the 50 inch deck pulleys are higher up. There is NOT a lot of room between the blade belt and the top of the deck on either deck. I think that the belt will be resting against the top of the mower deck, The other issue with the height of the pulleys is the double pulley. The spacing between the two pulleys on the double pulley is quite different. Well, somewhat different, but in terms of the space provided under the tractor for the mower to live, and in terms of keeping the mule drive and belt alignment within the allowable out of alignment that goes with raising and lowering the deck, it's a big amount.

however, I assume the 50 inch belt would be too loose?
I dunno.... There's plenty leeway in that blade belt tensioner. I'd bet that could be made to work with minimal to no modifications. I'd call that issue real, but place it on the "least of your worries" pile.

Yeah, John Deere belts are different. Magic? Not really, but they are different. If you're using John Deere pulleys, then a John Deere belt is going to outlive anybody else's belt by five to one, or more. Sometimes way more. It makes them a pretty good bargain. As far as the different sizes, there is NO easy way to do this, but if you bugger around the internet enough, you can find a lot of size belts in John Deere's brand. They are sold as application specific, and any cross reference information goes the opposite way of what you're looking for, so it's cumbersome, and they don't have "every" size, but often enough, they've got one. And again, the leg work is on you, because this off label, this is not as designed, and therefore this is NOT something that the parts counter people can help you with even if they wanted to. Which they probably do, but they can't put hours and hours of work into selling a part that RETAILS for an hour of their time, to put on a one of custom job that they'll never sell another one for.....
 

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46 (M00595, M00596) & 50 (M01011, M01012, M01013) decks use the same blade to blade belt - M41668.
Spindle assemblies between the decks are all the same.
The outer pulleys are sized different - 4 1/2" vs 4 3/4" OD. However, if you hold them up side to side, you will see that the ID, where the belt rides, is practically the same.
The 46 & 50 center double pulleys are different. The distance between the CTC of the 2 pulleys is where the difference is. The bores are all the same on all the pulleys.
"Up" and "down" orientation of outer pulleys differ also. Tall hub on 50 goes down; tall hub on 46 goes up.
 

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Condensing all of this advice may be difficult.

The net-net here is that you can move almost everything from the 46 over to the 50.
You would need the correct 50 center double pulley, as the 46 center pulley is different.
(I believe someone here, or on the other forum, offered one up).
The 50 center double pulley is AM39954. The 50 center "speed up" double pulley is AM116141 (the top pulley is a smaller diameter).
You can use the outer 4-1/2" spindle pulleys from the 46. Flip them over so the tall hub side is facing down.
The ID (where the belt runs) of the 4-1/2" vs the ID of the 4-3/4" pulley is almost identical, so swapping them will not make much of a difference.
 

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Can you use the speedup pulley on a 46 deck by reversing the two outside pulleys? It seems to be possible from this discussion.
 

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Doug - that's a very good question. I think Cliff has hit on two of the likely issues.
However, I am just about finished up with one full 46 resto, and have started to tear down another 46, also for resto.
I have a standard 46 center pulley, 46 belt covers, a 50 standard center pulley, a 50 speed up pulley, and various outer pulleys.
Soon, I will be able to do a test fit on your suggestion. I will fit it up, but I will not actually install and mow with it as I don't need that kind of setup.
I will post up what I find.

cruisin - I don't have any direct experience with the earlier 140 decks, but I believe it will work. I think Bob might have mentioned this earlier.
You only need to change the rear draft arms to the spring loaded type from a 300 series.
 

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I haven't tried it but probably. The deck covers might not fit. The idler pulley might need to be spaced up as well.
Not using deck covers and I think I might modify the existing ones to make clean out easier. Washers will change the idler pulley height.
 

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Discussion Starter #13
Doug - that's a very good question. I think Cliff has hit on two of the likely issues.
However, I am just about finished up with one full 46 resto, and have started to tear down another 46, also for resto.
I have a standard 46 center pulley, 46 belt covers, a 50 standard center pulley, a 50 speed up pulley, and various outer pulleys.
Soon, I will be able to do a test fit on your suggestion. I will fit it up, but I will not actually install and mow with it as I don't need that kind of setup.
I will post up what I find.

cruisin - I don't have any direct experience with the earlier 140 decks, but I believe it will work. I think Bob might have mentioned this earlier.
You only need to change the rear draft arms to the spring loaded type from a 300 series.
Thanks for the input. I now think that the model 48 tag was installed from another deck during a restoration, as it has front and back wheels and i believe the original model 48 jd 140 decks didn't. So maybe it is a replacement 46 inch (for the JD140) like my 318 original deck.
 

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Can you use the speedup pulley on a 46 deck by reversing the two outside pulleys? It seems to be possible from this discussion.
As mentioned earlier, I am just finishing up the resto work on a second 46 (M00596X) deck. Today as I was installing the pulleys, idler, etc, I did some testing.
You indeed can install a speed up 50 center pulley, AM116141, on a 46 deck. You then need to reverse the outer pulleys from the normal way they go on a 46 deck. Put the tall hub side down, like they would go on a 50 deck. You likely will have to adjust the height of the idler arm, idler, etc, to match your specific deck, and how much wear the arm has. But, this approach will work, and you can install the speed up pulley on a 46 deck.

I did not test fit any belt covers, but I suspect they will not fit properly. If someone installs a speedup pulley on a 46, perhaps they can test fit the belt covers.
 
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Thanks Ken for the information. I have a 46 deck waiting new bearings. When I do that then I will install the speedup pulley and check deck covers.
 
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