Pronto M71 -Does the larger round grease seal have to be replaced from the inside (of the motor arm() it does no seem to want to press into place from the outside.

The service and repair manual with diagram will help you to locate and fix the problem on your own and you will get the manual from the given link http://toolsnyou.com/

It seems to be a known issue. Is it the black disc by the axle in this image?
https://www.monsterscooterparts.com/brands/invacare/models/pronto-m51/motor-and-gearbox-for-the-invacare-pronto-m51-and-pronto-m61-power-chairs.html

I would put a large hose clip around it. If you have the old one, you can probably get a replacement from Home Depot, or contact the company for a free one.

http://www.invacare.com/cgi-bin/imhqprd/contact.jsp

More info and manuals etc

https://www.google.com/search?q=Invacare+Pronto+M51+gearbox+grease+oil+plug

..

see this causes and use the common sense.God bless you
If your dishwasher seems noisy, check these: Water-inlet valve Motor Heater fan Pump Water-inlet valve An aging water-inlet valve can sometimes fail slowly, rather than all at once. It can shudder on and off rapidly, causing the incoming water lines to shake, rumble, and rattle--sometimes violently. If yours is doing this, replace the inlet valve. Motor If it's the motor that's noisy, either of these may be the "culprit:" As motor bearings wear out, they can become quite loud when the motor runs. They wear out quickly if they frequently get wet, because the water washes away the motor bearing grease. Bearings can get wet if the spin seal is defective. Then there will also be water leaking onto the floor beneath the dishwasher. Replace the seal if it leaks (read about the main tub seal in the "It leaks" section, later). If, from beneath the dishwasher, you can see a round, plastic disc that's mounted to the top of the motor (a "slinger"), it may have broken free of the motor shaft. If so, it could be rattling around the shaft while the motor is running. If that's the problem, you need to replace the motor. Heater fan If the heater fan bearings are rusted or worn, they may squeal, or scrape loudly during the drying cycle. If this is the problem, replace the fan motor. Alternatively, the fan blade may be loose. If so, you need to replace it. Pump Small fruit pits, toothpicks, and fragments of glass sometimes get stuck in the pump. When this happens, open the pump and remove the debris. The pump is usually mounted directly to the motor, then attached to the bottom of the dishwasher. To get to the pump, you usually need to remove the lower rack, the spray arms, and the spray arm support from the inside of your dishwasher. A dishwasher pump isn't obvious. Look for an impeller--a round, plastic fan blade-type device that spins around and pushes the water toward the drain. When you can see the drain impeller, you should be able to see the clogging debris

To perform the following procedure, the lower control arm must be removed from the vehicle. Refer to Removal And Installation for that procedure.

1. Using a screw driver or other suitable tool, pry the seal boot off of the ball joint assembly
2. Position receiving cup, Special Tool 6758 to support lower control arm when removing ball joint assembly. Install Remover, Special Tool 6919 on the top of the ball joint assembly.
3. Using the arbor press, press the ball joint assembly completely out of the lower control arm.

NOTE: When installing ball joint in lower control arm, position the ball joint in control arm so notch in ball joint stud is in the direction shown. This will ease assembly of the ball joint to the steering when installing pinch bolt.

1. By hand, position ball joint into ball joint bore of lower control arm. Be sure ball joint is not cocked in the bore of the control arm, this will cause the ball joint to bind when being pressed into control arm.

 

1. Position control arm with installed ball joint, in an arbor press with Receiving Cup, Special Tool 6758 supporting the lower control arm. Then center Installer, Special Tool 6908-4 on the bottom of the ball joint
2. Carefully align all pieces. Then press the ball joint into the lower control arm until it is completely seated against surface of lower control arm. The ball joint is correctly installed when there is no gap between the ball joint and the lower control arm. Do not apply excessive force against the ball joint or the lower control arm.
3. Install a NEW seal boot by hand as far as possible on the ball joint. Installation of the seal boot is to be with the shield positioned as shown.

CAUTION: Do not use an arbor press to install the sealing boot on the ball joint. Damage to the sealing boot will occur if excessive pressure is applied to the sealing boot when it is being installed.

1. Place Installer, Special Tool 6758 over seal boot and squarely align it with bottom edge of seal boot. Apply hand pressure to Special Tool 6758 until seal boot is pressed squarely against top surface of lower control arm.

CAUTION: A replacement ball joint is not pre-lubricated. Properly lubricate the replacement ball joint using Mopar Multi-Mile grease or an equivalent. Lubricate ball joint after seal boot is installed but prior to top of seal boot being pushed down below notch in ball joint stud. Air must vent out of the seal boot at notch when grease is pumped into ball joint, failure to do so will balloon and damage seal boot. Do not over grease the ball joint, this will prevent the seal boot from pushing down on the stud of the ball joint.

CAUTION: After the ball joint is properly greased, clip the end of the grease fleeing off below the hex. The ball joint seal boot is non-purgeable and further greasing is not required and can result in damage to the seal boot.

1. Reinstall lower control arm on vehicle.

Sounds like you have a blown seal on your left gearbox. The only permanent solution is to replace the left brake/motor gearbox assembly. Not exactly a do-it-yourself repair. to verify, you can pull the seat off to inspect with a flashlight or tip the chair up at 45 degrees on the right drive wheel to inspect.
In my experience this is a common problem. It may take some time for enough gearbox grease to ooze out and cause the gearbox to fail. If you run the chair inside the house it will get messy very quickly and the grease stains are difficult to remove. If the chair is upwards of 4 or 5 years consider replacing left and right motor/gearbox assemblies. Hope this helps.

It's noisy If your dishwasher seems noisy, check these: Water-inlet valve Motor Heater fan Pump Water-inlet valve An aging water-inlet valve can sometimes fail slowly, rather than all at once. It can shudder on and off rapidly, causing the incoming water lines to shake, rumble, and rattle--sometimes violently. If yours is doing this, replace the inlet valve. Motor If it's the motor that's noisy, either of these may be the "culprit:" As motor bearings wear out, they can become quite loud when the motor runs. They wear out quickly if they frequently get wet, because the water washes away the motor bearing grease. Bearings can get wet if the spin seal is defective. Then there will also be water leaking onto the floor beneath the dishwasher. Replace the seal if it leaks (read about the main tub seal in the "It leaks" section, later). If, from beneath the dishwasher, you can see a round, plastic disc that's mounted to the top of the motor (a "slinger"), it may have broken free of the motor shaft. If so, it could be rattling around the shaft while the motor is running. If that's the problem, you need to replace the motor. Heater fan If the heater fan bearings are rusted or worn, they may squeal, or scrape loudly during the drying cycle. If this is the problem, replace the fan motor. Alternatively, the fan blade may be loose. If so, you need to replace it. Pump Small fruit pits, toothpicks, and fragments of glass sometimes get stuck in the pump. When this happens, open the pump and remove the debris. The pump is usually mounted directly to the motor, then attached to the bottom of the dishwasher. To get to the pump, you usually need to remove the lower rack, the spray arms, and the spray arm support from the inside of your dishwasher. A dishwasher pump isn't obvious. Look for an impeller--a round, plastic fan blade-type device that spins around and pushes the water toward the drain. When you can see the drain impeller, you should be able to see the clogging debris.

it takes a ball joint press which can be purchased at harbor freight. you should purchase "moog problem solvers". they are your best bet for trouble free repairs.

If your dishwasher seems noisy, check these:

Water-inlet valve
Motor
Heater fan
Pump
Water-inlet valve An aging water-inlet valve can sometimes fail slowly, rather than all at once. It can shudder on and off rapidly, causing the incoming water lines to shake, rumble, and rattle--sometimes violently. If yours is doing this, replace the inlet valve.

Motor If it's the motor that's noisy, either of these may be the "culprit:"

• As motor bearings wear out, they can become quite loud when the motor runs. They wear out quickly if they frequently get wet, because the water washes away the motor bearing grease. Bearings can get wet if the spin seal is defective. Then there will also be water leaking onto the floor beneath the dishwasher. Replace the seal if it leaks (read about the main tub seal in the "It leaks" section, later).
  
  
• If, from beneath the dishwasher, you can see a round, plastic disc that's mounted to the top of the motor (a "slinger"), it may have broken free of the motor shaft. If so, it could be rattling around the shaft while the motor is running. If that's the problem, you need to replace the motor.
  
  

Heater fan If the heater fan bearings are rusted or worn, they may squeal, or scrape loudly during the drying cycle. If this is the problem, replace the fan motor. Alternatively, the fan blade may be loose. If so, you need to replace it.

Pump Small fruit pits, toothpicks, and fragments of glass sometimes get stuck in the pump. When this happens, open the pump and remove the debris. The pump is usually mounted directly to the motor, then attached to the bottom of the dishwasher.

To get to the pump, you usually need to remove the lower rack, the spray arms, and the spray arm support from the inside of your dishwasher. A dishwasher pump isn't obvious. Look for an impeller--a round, plastic fan blade-type device that spins around and pushes the water toward the drain. When you can see the drain impeller, you should be able to see the clogging debris.

If it is coming from your motors, it could be very bad. i.e. motor replacement. Sometimes on the side of those motors there is a black plastic cap about the size of a quarter or half dollar, those fall out sometimes and allow gearbox grease to come out. This should`nt be confused with your motor brush caps which are about the size of a pea and have a small **** in them for a screwdriver.DO NOT TAKE THESE OUT.  If the large cap has come out just stick it back in. If you can`t find it you`ll ned to call a dealer to get the part replaced.    If you can still find no prob,your probably going to have to go to a dealer.