This page is written as a guide to servicing the most common families of vintage Gilson Snowblowers. It relates best to the following machines:

• 1st generation gear drive machines, these were produced between at least 1966 through 1971. These machines are characterized by a cast iron chute base and a 26 inch width. The bottom of the transmission area is open on these machines and there will be 2 or 3 roller chains depending on the exact model. They have forward and reverse and may have a high and low range selector for the ground speed. Horsepower ranges from 5 to 8
• 2nd Generation gear drive machines, these were produced starting in 1972 and into the early 1980s. These machines are either 28 or 32 inches in width. Horsepower is either 8 or 10. The bottom of the transmission area is open on these machines and the will be 2 roller chains and a sealed 3 speed gear drive transmission.
• 1st Generation 3 speed UniTrol, these machines were produced from 1971 through the early 1980s. These machines were almost always 26 inches in width and horsepower ranged from 5 to 10. The transmission area will have a plate that covers the bottom and there will be a large concave depression in the lower back panel.

General Service Procedure (Tune-up)

When I service or rejuvenate a machine I sometimes skip around depending on what I feel like doing and where the risks are. For this presentation I'm going to start at the front and work my way back.

• Starting at the front....
• With the machine still sitting flat on the floor remove the plug from the FRONT of the auger gearcase. It should be filled up to this plug with 30W Non-Detergent oil. If you don't see oil weep from the hole either squirt some in until it flows back out or remove the vent plug at the top and pour some in.
• Check your shear pins they should be 5/16 diameter and of mild steel. If substitutes have been made from hex head bolts make sure there are no hash marks on the head, they indicate a higher grade bolt the will not protect your machine. It's not a bad idea to remove the bolts to make sure they are not partially sheared.
• While the shear pins are out work some oil into the space between the auger assemblies and the shaft. Keeping this area free from rust can be very helpful if you ever need to tear the unit down.
• There is a grease fitting on each end of the auger shaft, grease them with a grease gun until you see a bit of grease moving out.
• Check the drift breaker on your machine. Do you even have one? It serves two purposes. The first is that it lets you twitch drifts so they fall down where your blower can collect and throw them. The more important purpose for this topic is that it also acts as a kick stand, letting you stand the machine up on it's nose. Is yours in good shape? If it's badly bent you will need some good wood blocks for the top of your bucket to rest on when you tip it up, 4X4's often do well. Get some blocks that will let you stand the machine up if your drift breaker is not up to it.
  CAUTION: If you have an early gear drive with the straight vertical front edge on your bucket it will want to roll forward on the auger leads when you stand the machine up, just do it briskly and you'll be OK.
  NOTE: When standing the machine up you want less than 1/3 of a tank of gasoline.
• Speaking of the drift breaker make sure that the mounting bolts are installed with the nuts on the outside.
• Tip the machine backward by tipping the bucket up and prop it with a gallon paint can or equivalent.
• Get a flashlight and inspect the welds where the side panels of the bucket join with the back/bottom panel, especially the last welds near the scrapper bar. If the machine has been scrapping hard these may be broken and need to be re-welded. A MIG welder is nice but an AC stick welder with 1/16 rod can do the job.
• Now, look at the scrapper bar. How does it match up with the lip of the bucket? Is there dirt, rocks, debris etc wedged between the parts? If so it must come apart. The low profile carriage bolts probably won't come apart. A good cold chisel and striking hammer used between the nuts and scrapper bar will get it off in a hurry. Tip the machine up for this task. Using hammers, pliers and a large adjustable wrench you can reform the bucket's lip so it presses tightly against the scraper bar when you re-install it. I like to take the last 1/4 inch and give it a little extra downward bend all the way across. This will force it against the scraper bar when you bolt it back on.
• The scraper bar should be straight and not be grossly nicked. Reinstall it so it is as straight across as possible. If you have a grinder don't hesitate to sharpen it a bit. It's amazing how much better the machine will push through packed snow when this edge is in good shape.
• Skip to your tires for a moment and if they are pneumatic check the pressures are equal and between 12-15 PSI.
• The next thing to do is adjust the skids. I like to set them for 1/2 inch clearance using a few scraps of 1/2 inch plywood. With the machine still up on the bucket loosen the nuts of the skid bolts and drop the skids. Now place the machine down with the scrapper bar resting on pieces of 1/2 inch plywood (or other spacers of your choice). Hold the skid to the floor while you tighten the bolts. The nuts should ALWAYS be on the outside. If your skids are worn through then do something about it or you will cause damage. Replace, repair or fabricate as needed but don't run the machine dead on the scrapper bar.
• Look in through the front and inspect the impeller. The tips of the blades should point ahead in the direction of rotation so they can help cup and throw the snow. If they are bending backwards they can be helped back into shape with a big adjustable wrench or a big pair of pump (Channel Lock) pliers. This may be a sign that a new impeller is in your future of it could last you many more years.
• This finishes up what I look forward inside the bucket area.
• Now the chute section.....
• The most common design for the chute is a stamped steel fine tooth gear driven by a worm gear. The earliest UniTrols used a sprocket affair to drive a matching plate and the early gear drive machines have a cast iron base driven with a pinion.
• On the fine tooth gear models check the 3 hold down plates for tightness. Generally they were riveted though for a brief period pop-rivets were tried. After years of hard service the rivets can loosen. If they do I drill them out for #10 bolts and re-bolt the 3 plates. Make sure everything is flat and deburred before reassembling. Service removable thread locker (Loctite) or lock nuts are good ideas here.
• On the gear drives with the cast iron chute base there a re 3 brass rollers on the 3 bolts you can see from the outside. Remove the bolts and catch the rollers. If they are still round just clean them up oil them and reinstall. If they had been bound up and got flats worn into them you will want to replace them.
• To whatever extent you take the chute apart make it a point to clean all surfaces.
• When reinstalling the chute grease the top and bottom of the ring it runs on. If you do not have to take it off run an oil can around the inside and drizzle some oil down into the gap
• Coat the gear, whatever style with grease
• Give a drop of oil to every moving contact point in the chute control linkage.
• NOTE: If the ring that your chute rides on is found to be cracked you may get it welded. If it broken or if you wish to replace a cracked ring it is available as a service part for both the fine tooth base (700570) and the cast iron base (704164) styles. With a small disc grinder and a welder the machine can be saved. See your local LawnBoy dealer for these parts. If you have your model number have these numbers confirmed. They will not show up on some early parts breakdowns since they did not become available until latter in the product life cycle.
• Finally remove excessive rust from the inside of the chute and spray with a silicone lubricating spray or a polish like Pledge.
• Under the belt cover....
• Let's start with idler rollers. There are two rollers used to apply tension to your belts. Until the late 1970's these were solid steel rollers with an oil impregnated bronze liner bushing. Retaining ring pliers are needed to service these. They should be opened up and cleaned and repacked with a good bearing grease every year or 2 depending on the level of use. A very safe recommendation would be to do this every 10 hours. Later machines use stamped steel rollers with sealed bearings that require no regular attention, they are mounted to a stud with a nut
• On the gear drive models one or two of the idler arms are mounted on bronze bushings that ride on a stationary shaft. When these bushings and the shaft become worn it becomes impossible to keep the idlers tracking correctly on the belt. If these arms are very floppy or if you keep finding the blower idler under the belt when you work it hard this area needs to be rebuilt. generic bushings and common steel shafting are all you need.
• Depending on your specific machine you will have several wire and of flat iron belt retainers. These should be set to have between 1/16 - 1/8 inch of clearance when the belts are engaged. These can be found mounted to the engine near the engine pulley and down below where the belt reaches the large blower pulley. If they are set too loose the belt may flop off of the pulley when disengaged making for an interruption to your snow clearing project.
• When you have the engine ready to run you want to observe the idlers running on the belts. They should be fairly well centered on the belt and the belt should be running in a straight line between the pulleys. If things are in good shape then the idler may need a minor alignment. A large adjustable wrench may be used to hold the arm so you can give it a slight twist to correct the belt tracking.
• This is a good time to get a good look at your belts. The top surface should have few if any blemishes or scars. The bottom side should have no tears or missing chunks. Be sure to check the full length. Sometimes a frozen machine can be started and since nothing can move the engine pulley will burn the belt in a single location. This is easily avoided with proper cleanup prior to storage between storms.
• Inspect any spring ends for wear in the spot where they make contact. Replace as needed and apply a drop of oil to all contact points to reduce friction
• Apply a drop of oil to every moving contact point you can find in this area.
• Now you want to get the machine tipped up on it's nose as mentioned earlier
• On UniTrol machine there is a grease fitting on the left side behind the tire. Give this fitting 10 shots of bearing grease. Inside this case are some big final drive reduction gears. The fitting is positioned such that the grease will be distributed as the machine runs.
• While you're there inspect the screws along this case. This is a rare instance of Gilson using sheet metal screws. While they usually hold up fine if yours are loose or gone they are best replaced with #10 machine screws and lock nuts.
• Now I want to remove your wheels. You have either click pins out at the ends of the axles of clevis pins mounted inboard behind the wheels. Remove whatever pins your machine has. Then remove the wheel making sure you don't take any spacer washers off of the shaft. You may need to twist back and forth to wind the wheel off.
• Take a look at the axle where the pin was passing through it. The hole should be slightly countersunk. If steel has been raised by the pin rocking in the hole when shifting the countersink must be restored. This can be done with a half round or large rat tail file. If this is allowed to go unchecked the raised axle metal can engage the wheel and make removal impossible.
• If the machine is a gear drive the axle bearings have grease fitting. Give these a few shots until movement appears.
• On the UniTrols the axle rides in sintered steel bushings. There is an oil fill hole in the top that should be clear. Give the bushing a few drops of SAE-30 oil. Check the bushings for cracks. If there excessive upward wear of the bushings the clearance between the friction wheel and the axle will be reduced and this can cause premature friction wheel failure. The OD of these bushings is oblong as is the hole they are press into, this prevents roatation of the bushing.
• On gear drives the will be 2 or 3 drive chains seen from the bottom. Coat these with grease all over.
• On UniTrol the bottom is covered, remove the cover. If the friction wheel shows signs of touching the axle it is due for replacement, see above.
• On UniTrols clean the round and hex shafts that the rubber wheel traverses on. WD-40 will cut the gum nicely. Then lightly oil these surfaces. Be sure to keep the drive platter clean.
• In UniTrols remove any nesting material that may be found. Wash your hands after handling such material.
• Put a drop of SAE-30 motor oil on all linkage pivots including in the handle assembly.
• On 3 speed gear drives there is a 2 sprocket cluster running on the cross shaft under the machine. It has a grease fitting that should be greased until response is seen.
• Change your engine oil according to your manufacturers instructions. I encourage you to consider synthetic oil if there is any chance you will use the machine when it is below 0 degrees F.

ADJUSTING a 3 SPEED UniTrol SHIFTER

• Tip it up on it's nose
• Open the bottom
• Loosen the two carriage bolts on the lap joint in the linkage.
• Slide the wheel all the way to the left (full reverse) as viewed from the bottom with the machine tipped up on it's nose.
• Place the control lever over the reverse position.
• Spread the linkage at the lap joint to remove linkage slop and hold the joint fairly straight. The goal is to set the mechanism so that the friction wheel is as far from center as possible in reverse. this will give you the fastest possible reverse. The forward speeds will fall into place.
• Tighten the joint
• Make sure you don't land in the hole as you shift
• Make sure that the friction wheel is not in the center hole of the platter when in first gear
• Make sure the wheel lifts from the platter
• If not adjust the clevis on the left side of the handle.
• That's about it.

3 SPEED UniTrol BELT CHANGING

• Remove the top belt cover.
• LOOSEN the 3/4 inch bolt on the engine that holds your belt guard, just loosen it a enough to pivot the guard.
• Look down near the big impeller pulley on the left side, use a 7/16 wrench to loosen the little belt retaining finger.
• Look in the same place on the right hand side. If you have a similar finger loosen it. Newer machines have a brake mechanism, leave it alone.
• Tip the machine up on it's nose, if the drift cutter is not there or good enough to support it then position wood blocks to support the top lip of the bucket.
• Remove the bottom cover
• Look at the base of your handle assembly on the left hand side, there should be a hair pin cotter.
• Remove the pin and release the linkage from it's hole.
• You should now be able to reach into the machine and lift the friction wheel from the platter far enough to pass your belts through.
• Mark your belts in some way so you won't get them confused, B for Blower & T for Traction for instance.
• By rolling the pulleys slowly you will be able to get them off and on the pulleys. You will also move the idlers so they are behind the belts and then place them back on top in the end. This part is mostly common sense and defies verbal explanation!
• This is a real good time to grease your idler rollers if they are the solid steel type held on by retaining rings, they should be opened up and greased every year or 2. If you have the sheet metal idlers with sealed bearings held on by a nut then you're all set.
• With the belts in place reset the belt guides for 1/16- 1/8 inch clearance when the blower is engaged.
• Reverse the balance of the procedure.
• That's about it, the hair pin cotter is the key.

3 SPEED UniTrol IMPELLER CHANGE

• Remove the auger shaft bushings.
• Remove the belts. See Here
• Tip the machine up on it's nose. If you have the original drift breaker it will act like a kick stand. Otherwise use a 4X4 wood block or something similar depending on your exact model.
• Remove the bottom cover plate, click pins, wheels and any thin shaft spacers.
• Disconnect all of the linkages to the mechanisms. Unbolt the bellcrank mounted to the inside of the big dimple on the back of the machine.
• Remove the bolts securing the side plates that the axle bushings are in.
  • Do not remove the hex head sheet metal screws for the inner gear cover on the left, this can stay together. However as part of this job it's suggested that you disassemble this final drive gearcase to clean and regrease. The grease has probably lost a lot of it's oil content and there may be considerable sand in there.
• All of the guts, axle, and side panels will now come off as one.
• Remove the internal retaining-ring that secures the drive platter to the main shaft, slip it off and keep track of the spacers above and below it.
• Lossen the 2 blower pulley setscrews then use a puller to remove the blower drive pulley.
• You will now see a bearing with a retaining collar, loosen the set screw and use a drift pin and hammer or spanner in the plain hole to release the eccentric locking collar, try CCW but it could be the opposite. Remove the collar. If it is siezed then you may have to grind one side away to free it.
• Now remove the 2 nuts that secure the flange of that big center bearing and remove the flange.
• Prop the auger leads so that the bearing rises up away from it's seat and use a puller to remove it from it's shaft. If you cannot get a puller in there you can take an air hammer or punch and striking hammer to shatter the bearing outer race. It is suggested that this bearing be replaced when doing this job. This will leave the race on the shaft which can be split with a small disc grinder.
• Lay the remains of the machine back down and the auger/impeller assembly will slide right out!
• Loosen the 2 square headed set screws on the impeller and find a way to pull it off. I'm working on a puller design and I'll share it if it works. As time goes on these get harder and harder to remove. You may need to use a small disc grinder to strip the impeller down to the core. Then slit the core lengthwise with the grinder to release it. Be careful to limit nicks to the shaft.
• Reverse the procedure and you're done!

3 SPEED UniTrol FRICTION WHEEL REPLACEMENT

• Tip the unit up on it's nose.
• Remove the bottom cover plate
• Remove the Right wheel, keep track of any small spacers, if the wheel won't come off read my FAQ on the topic.
• Remove any bolts that secure the right side plate, the plate the axle bushing is in.
• Pull the axle towards you to get it out from under the lip that retains it at the top.
• If this feels to stressful remove the left wheel and loosen those side plate's bolts.
• Slide the RH side plate off of the axle.
• There will be a cotter pin on the RH side of the friction drive module, remove it and any space washers
• There is a small carriage bolt on the RH side of the friction drive module remove it. NOTE: If your machine is from the first year of this model (1970) you will not have this feature. You will need to remove both side plates and everything in between them and release the hex shaft from the bearing to slide it clear to allow removal and replacement of the friction wheel.
• You have one more thing that has to go right before you're home free, if you're so inclined say a prayer.
• Wiggle the end plate that you removed the carriage bolt from. The bearing at the top end has to slide off of where you removed the cotter pin. Don't force or distort it.
• Did it come off? If yes take a deep breath.
• If not here's where you have to be careful and clever with pullers and such. Odds are very good it will come right off. See below for what I use/
• Hold the hex shaft with a closely set big adjustable wrench.
• Remove the 3 bolts that mount the friction wheel.
• Remove the friction wheel
• Clean all sliding surfaces with WD-40 or some solvent that will cut gummy old oil.
• Clean the platter with brake cleaner, denatured alcohol, lacquer thinner or anything else that will leave it absolutely clean. If it's rusty sand it first.
• Reverse the procedure to put it back together
• Lightly oil the sliding surfaces including the hex shaft, wiping them with oily fingers will help prevent over oiling. I like top use Mobil-1 5-30 oil for this. I think the synthetic behaves better in the cold and over time.

The alternative is to unbolt both side plates and disconnect all of the linkages grab it by the axle and haul the whole pile of guts over to your bench, for a simple friction wheel change this usually does the trick.

Pulling the End Bearing on a UniTrol Transmission.
The spanner is made from 2 lengths of 1/4 X 1 flat steel bar and two 5/16 bolts. It lets you get behind the bearing plate and attach a commercial puller. Works great!	Install the puller so it mates up with the hex shaft, center it and tighten the nuts just finger tight. Install a common small gearpuller and remove the end plate and bearing with the puller. Be sure to touchup the shaft so it's a clean fit for next time.

REPLACING THE ROPE IN A RECOIL STARTER

This is written based on the Briggs & Stratton L Head engines that are commonly found on these vintage machines. The procedure is similar on most small engines.

• You have to remove the recoil housing which means removing the heater box and removing 3 of the head bolts. After that it's just 4 small bolts (7/16 wrench).
• With the assembly on your bench you will need a tool that plugs in where the starter clutch goes in the center, a broom handle ground or sanded to the shape will do fine.
• Get some good quality braided nylon cord of the matching diameter and melt one end to a nice clean point.
• Nail the assembly to your bench or get a helper to hold it.
• Insert the tool into the pulley and wind the spring up then back off until the hole in the pulley lines up with there the rope enters the recoil housing.
• Thread the pointed end into the housing and over to the hole in the pulley.
• Fish the rope up through the hole with needle nose pliers.
• Tie a good knot.
• Pull the knot down to the pulley.
• Slowly let the spring wind the tope into the pulley.
• Slide the handle onto the rope.
• Pull a little rope out of the housing so there will be some tension when at rest.
• Tie the rope around the handle pin.
• Trim the rope.
• Test it. It should pull back in readily and have adequate length when out.
• Reinstall on the engine.
• Be careful where here it meshes with some sheet metal parts, make sure it's together as you found it.
• Evenly torque head bolts to 165 inch/pounds or 140 inch pounds if 5 HP or smaller.
• That's all there is to it!

ADJUSTING YOUR CARBURATOR

This is written based on the Briggs & Stratton L Head engines with FloJet carburetors. These are bowl type carburetors with a visible adjusting needle at a 45-degree angle.

Well assuming that the ignition is good and the carburetor is free and clear here is what I do...

• Get it to run for about 5 minutes to warm up.
• Run it to full speed
• Turn the high needle (the diagonal one) in to where the engine falters (note where you are)
• Run the needle out until it again falters, note how far it was from the other extreme, move to the midpoint.
• Drop the engine to idle
• Repeat with the low speed needle (not the idle stop screw), it's up in the heater box and barely reachable with finger tips.
• When doing a cold restart you might need to make a slight correction on the high needle to sweeten the setting for a cold engine.

Replacing a Gear Drive Impeller or Main Bearing

In general the gear drive machines split in 2 tight behind the impeller. This makes impeller / bearing service quite easy. The hardest part is dealing with the effects of aging that tend to make certain things not want to come apart. I always replace the main bearing if I'm in this deep.

• Remove the belt cover
• Remove the blower belt
• Remove the 2 side acorn bolts below the belt cover
• Remove the 2 top acorn bolts and catch the drive end of the machine as it tries to fall away.
• Next you remove the big pulley, loosen 2 set-screws and use a big gear puller to grab the center hub.
• Now remove the 2 auger support bearings up front.
• Use a file to remove any set-screw divots the pulley left behind.
• On the input shaft there will be a black eccentric locking collar with a set-screw, remove the set-screw.
• Find the drift pin hole in that collar, whack it CCW and it should loosen. If all else fails try CW. It could have been tightened in either direction.
• Remove the collar and touch up the set-screw divot
• Now its' time to get that bearing free......
• Remove the 2 nuts that secure the bearing flanges. remove the top flange.
• Get a board to put under the augers. You want to force the augers to the back of the bucket to lift the big bearing as high as possible.
• If you can get a puller on the bearing, do so and remove it. You might get lucky carefully prying. If not you need to get rough.....
• Put on some safety goggles. Using an air hammer or cold chisel and striking hammer shatter the outer bearing housing and dissect the bearing. This will get it out of the bucket assembly!
• Now you just need to remove the inner race from the shaft, try tapping it. If that doesn't work you can gently grind it with a small disc grinder until it splits open. Don't cut into the shaft.
• Mark the augers as left and right. Remove the 2 shear pins and auger assemblies.
• Remove the 2 impeller set-screws. Get the assembly into a hydraulic press and support the center hub of the impeller. Press on the input shaft. The first few movements may make a frightening snapping sound! Be sure to have something soft to catch the worm drive. Soaking it in something like Kroil penetrating oil in advance can't hurt.
• Using a file dress the 2 impeller set-screw divots
• Now you can service or replace the impeller. If you work on the impeller try to maintain the balance. Use a lawnmower blade balancer if nothing else.
• When reassembling make sure you get the auger leads back on the right sides.
• Install the auger support bearings before the main center bearing. The auger bearings will set the shaft projection. You should now be able to introduce all of the bearing parts in order and reverse the rest of the process.