So I decided to change out the UHMW / Plastic Impeller on my 47 snowblower for piece of mind. Not that I've had any trouble with it yet; but have heard some horror stories about these plastic fans going South for various reasons. My old 47 snowblower had the steel impeller and I never did have a problem with it at all. Ordered the replacement impeller, p/n AM109105 from Green Farm Parts and it arrived a few days ago. $252.86 including shipping.
For some who may be interested, here's what it took to get the job done.
Remove the snowblower from the quick hitch and roll it forward so the drive shaft is facing up. Remove the safety wire and drive-out the roll pin that retains the implement driveshaft yoke to the drive sprocket shaft:
Remove the implement drive shaft.
Loosen the (4) Nuts (1/2" wrench) that secure the drive sprocket shaft bracket, slide the bracket towards the large driven sprocket. This will loosen the drive chain. Remove the drive chain from the driven sprocket.
Loosen the (2) 3/8" square set screws on the driven sprocket hub. Remove the sprocket from the shaft.
Loosen the 5/32" set screw and remove the retainer collar from the shaft.
Roll the blower back unto its base and remove (3) bolts (1/2" wrench) that attach the auger shaft end bearings at the flange retainers on each side of the blower housing.
Remove the two bolts that attach the gearbox to the support bracket (1/2" wrench)
You can now remove the auger assembly, gearbox and impeller fan forward and out of the blower housing.
Slide the plastic impeller from the shaft. Remove the shear bolt (7/16" wrench) that attaches the flat bracket to the drive hub and remove the drive bracket.
Loosen the 1/4" set screws that attach drive hub to the main shaft.
This photo shows both impellers for comparison. The steel impeller is considerably heavier than the plastic impeller.
Replace the steel impeller onto the shaft and retain with the shear bolt previously removed. Leave the drive hub set screws loose at this time. Position the auger assembly, gearbox and impeller in front of the blower housing in preparation to reinstall in the unit. It may be helpful to tip the blower housing back unto the rear brackets to make placement and reinstallation easier.
Reinstall the entire assembly into the blower housing. You may need to rotate the impeller to clear the support bracket. Guide the shaft through the rear support bearing at the back of the impeller housing. Install the auger shaft flange bearing spacers by tilting the assembly left to right in order to gain necessary clearance. Reinstall the flange bearing and gearbox retaining bolts. Once all bolts are in place tighten securely to ~ 25 Ft. Lbs. Push the impeller back into the fan housing until it bottoms out and tighten the 1/4" set screws on the drive hub.
Rotate the entire blower housing forward so the drive end is facing up. Reinstall the shaft retainer collar with the recess facing towards the bearing. Rotate the collar clockwise until it locks, then tighten the 5/32" set screw.
Reinstall the driven sprocket w. key onto the shaft but do not tighten the set screws. Reinstall the drive chain between the sprockets. Adjust the slack out of the chain by moving the input shaft bracket away from the driven sprocket. Use a small straight edge to align the sprockets. Tighten the driven sprocket set screws using a 3/8" wrench. Adjust the chain tension so there's about 1/8" deflection on each side. Tighten the (4) 1/2" nuts to ~25 Ft. Lbs.
Install the implement drive shaft yoke with key onto the drive sprocket shaft and reinstall the roll pin. Safety wire the roll pin into place and that's it. Reattach the blower and test it out.
Had a few other photos to post but reached the maximum of 15 attachments. Hope this helps others who may be interested in replacing their 47 / 54 snowblower impeller. It's not cheap but you can't put a price on reliability and piece of mind, not to mention downtime at the worst possible time.