Converting a 451 blower into a 450?

[medic75]

After driving 250 (500 round trip) miles for a 450 snow blower, I found it was a 451. The only difference I can find in these two models are the gear ratio. After attempting to order the 450 gears and shaft, I found that they are no longer available and were quite expensive also. This created plan B - a smaller pulley. With the gear ratio of the 451 being about 2.58:1 and the 450 being about 1.86:1 (0.535) it makes sense to me that I should be able to go from the stock 7 inch pulley to a smaller 5 inch pulley and solve the gear reduction problem. This change, if my calculations are correct, should give me a 40% increase in speed on the input shaft and create a speed which is slightly faster than the 450, simulating a gear ratio of 1.84:1 (0.542).

Any thoughts?

[Matt G.]

Only problem I can think of is that the belt may slip because it has less contact area. It might be easier to put a different PTO clutch on. What model of tractor are we talking about here?

[medic75]

It's a 782. I really don't want to touch the tractor side because I use it to mow too and I don't want to screw everything else up.

I had thought about the belt slipping but then I figured that the belt would have contact with at least half of the pulley so there shouldn't be a problem. Then after figuring it out, you may be right. I am losing almost 30% of my belt contact area. Is this the reason for the larger PTO's on the newer tractors? I am far from an expert when it comes to gear ratios, but I think my calculations are correct.

I have read about people swapping gears, but I have never seen where anyone has swapped a pulley. I can't even find where someone has tried it. I couldn't figure out why considering that it is probably the easier alternative and definitely the cheaper alternative.

[Matt G.]

The PTO clutch pulley on a 782 is pretty small, and so is the pulley on the QA36A and QA42A, so not much belt contact area there. If you use an OEM belt, you should be alright. I've destroyed 2 Gates green belts with my 782 and QA36A. It's cheap to change the pulley, so I'd suggest trying that first. If all else fails, change the gears.

[medic75]

Originally Posted by Matt G.

If all else fails, change the gears.

That was my original plan. It was kinda ruined when my local CC dealer told me that the entire input side of the gear box is no longer produced or available for the 450. I'm stuck with the 451 gears unless I can find some old stock somewhere.

[Matt G.]

Either that, or someone trying to turn a 450 into a 451...

[Iowa Farmboy]

well what did you do?
Did you change the pulley? If so how did it work?
I have the same problem 451 that I need to run on a 2072

[ol'George]

A 5" pulley should do the job as there is sufficient wrap of the belt, so slip is not an issue.
IIRR my Qa42A on my 782 uses a pulley similar to that.
I had an issue last year with a bad gear box gear, and went to a tiller box with a different ratio.
In order to use it, I just changed the auger drive sprocket to get the correct rpm,as it is a single stage thrower.
I have since purchased a used thrower gear box from evilbay and returned to origional gearing.
I found no difference in performance with either setup.

[Frank1541]

Medie75,

If you are still trying to make this work, I have a 450 gearbox and I need the 451 gearbox for my application. I have a 450 that I need to adapt for the newer large pulley on the Cyclops GT. The gearbox is in good shape. How about a trade?

John