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John Deere 42 Inch Mower Deck Parts Diagram+ Troubleshooting Guide!

Lawnmowers are extremely convenient equipment and John Deere has always provided the best of best models that make great mowers with great purpose.

But one of the crucial parts of these mowers has to be a deck, something that basically protects a lot of other crucial components while mowing.

Today We are here to sort issues regarding the deck and its parts of the John Deere 42-inch mower basically. We have put a John Deere 42 inch mower deck parts diagram, some notes on each part, and more information that is targeted toward people trying to solve problems with the deck.

Hope this guide gets to you well. Keep On Reading…

Table Of Contents hide

The John Deere 42 Inch Mower Deck Parts Diagram

To know the location and description of the John Deere mower deck parts, we will show a detailed drawing below.

Although it is not mentioned, the yellow board in the illustration is the case of the deck that holds the mechanisms.

John Deere 42 Inch Mower Deck Parts Diagram.

Presenting The John Deere 42” Mower Deck Parts List

Under this segment, we’ll spell out the part’s location for you to know each of them when seeing them.

1 Means Left Hand Belt Cover

As you can see in the above illustration, it stands on the left side. To be more specific, you’ll find it on the left side of the belt.

2 Means Self-Tapping Bolt

This part is easy to tap to ensure better fitting on other components. With a simple twist, you can remove or insert it into the place.

3 Means Lock Nut

Most of the time, it is 10 mm in size that sits inside the hole of the belt cover. This part looks a bit tiny and sleek.

4 Means Idler Pulley

Compared to an ordinary idler, this is slightly bigger and golden in shade. It sits beside the deck belt to support and ensure tension to move freely.

5 Means Flat Idler Pulley

You’ll see it in black color which sits inside to give support on the deck belt outer area. It is smaller than the idler pulley.

6 Means Deck Belt

The only belt you’ll see is the deck or V belt. It will cover all the deck even if the John Deere 42 inch mower deck dimensions are 21” L (length) and 4.97” depth.

7 Means Spring or Rod

Some John Deere 42” mower comes with an extension spring while other use rods to fit into the deck idler arm.

8 Means Spindle Nut

Just like an ordinary nut, this spindle nut fits on top of the drive sheave. It is placed in the mid-point.

9 Means Spindle Drive Sheave

This part looks like a plate that holds a nut and screw. It actually sits in the middle between the nut and the deck cover.

10 Means Bushing

You’ll see 2 bushing in the illustration where one sits below the retainer clip and another one stay under the screw.

11 Means Extension Spring

This component is a little bit longer than usual. It fit on the idler arm edge to get hold and secure the part.

12 Means Idler Arm

It looks like a small guide that holds the tiny accessories to fit on top of the deck cover.

13 Means Rod

This part is long and sleek that seems quite the same as a pipe. It uses inside the brake pad to ensure the components are functioning well.

14 Means Torsion Spring

It is a tiny steel component that has tons of twists sitting on the deck cover. You can locate it if remove the screw, retainer clip, and bushing.

15 Means Retainer Clip

This part is placed right on top of the bushing and below the screw. It helps to keep the screw upholstery in place.

16 Means Screw

You’ll see the special kind of screw that sits on the top of the retainer clip. It is the most visible part which you can locate above the deck cover.

17 Means Brake Pad

This is also known as a thin block that stands on the deck case. It looks like the letter ‘L’.

18 Means Lock Nut

It is a lot smaller than the 3 no lock nuts (in case you are confused). This part fits on the brake pad to support the big rod.

19 Means Bracket

This part contains tons of holes to fit the small components. It carries the self-tapping bolt fit above the mower deck.

20 Means Right-Hand Belt Cover

On the right side of the diagram, you’ll see the belt cover is black in shade. This part holds the idler and other gears to sit on top of the mower deck and support the V-belt.

21 Means Spindle

This component fits in the middle of the tiny gears. You’ll see two holes on the left and right sides.

22 Means 3-in-1 Mower Blade

Below the mower deck, there are some mechanisms and the first thing you’ll see is the large blade. Usually, JD 42” mower contains three 3-in-1 blades.  

23 Means Lock Nut

To carry the blade under the deck, it needs this tiny lock nut. You’ll see it in the middle section.

24 Means Blade Washer

To ensure better tension and grip, this part plays a great role. It sits in between the lock nut and blade to ensure a seal.

25 Means Spindle Shaft

Under the spindle, you’ll see the sleek pipelike object which is the spindle shaft. It sits under the hole of the deck so that blade finds additional space to fit into.

26 Means Cover Rod

This part is solid and cylinder-shaped that fits directly in the hole of the lefthand belt cover so that the cover sits on top of the mower deck.

Riding Without a Deck – Needs A Little Consideration

All that troubleshooting and repair or replacement can wait, right now you want to ride the mower without a deck.

Now will a riding mower run without a deck, or is it impossible? Well, it will run without a deck for sure unless there’s a safety mechanism meant to stop such riding.

Now, can you drive a riding mower without a deck?

Something you can do is not always something you should do. And that’s what is the case right here. You can drive a mower without a deck, but try to never do that. This will be clear if you know the purpose of that deck for the lawn mower you are riding.

It basically

  • Holds the blade safely by covering it.
  • Helps in protecting the rider as well as the mower itself.

If You Ride a Mower Without a Deck Then

  • Debris will fly from all sorts of places toward you.
  • Grass clippings and rocks will be all over the yard making a mess.
  • Risk the operation of the lawn mower itself.

The blade will be prone to faster wearing out as it’s exposed to corrosion, rust, and rain.

So, obviously, you should consider always securing the deck to the mower before running it.

But if you have absolutely no choice, and you must run the mower without a deck, then do it with extreme caution to keep the chances of risks a little lower.

If it is for transporting the mower to a different location and not to use on the lawn, then also you need to be aware of its legally allowed.

According to AVVO,

“Riding lawnmowers are for riding on lawns, not roads. You have to have a slow-moving vehicle symbol on your riding lawnmower to drive it on the road.”

And that simply means you need to take certain steps and know precisely about those to legally move a riding mower on the road.

However, if you are mowing the lawn, going without a deck is just inviting risks. And you should always consider mounting a new deck as your best choice for such a situation rather than finding ways of using the mower without a deck.

There are so many reasons for that, and mostly it’s due to damaging the blade and other crucial components that the deck protects.

Since the blade is at most risk when you skip the deck, how about also skipping the blade. Can you ride a lawnmower without the blade?

Yes, absolutely! You can run the thing without the blade. But there would not be any action. So, it’s going in vain basically.

Running the lawn mower without a blade for troubleshooting or repairing a certain issue is the option. But for using the mower without a deck, you removing the blade will make it unusable.

Also, there are some lawnmowers that come with an auto shut-off feature. And that means whenever the blade is stuck or caught, it will be triggered to signal the engine to turn off. That means you won’t be able to turn the engine on without the blade.

Those who need to ride the lawn mower without using the blade can try raising the deck higher, as much as possible. Not needing the cutting action is applicable for transporting the mower or maybe to tow a lawn sweeper.

This Is How We Would Troubleshoot a John Deere 42 Inch Mower Deck

I’m guessing that your reasons for looking into a john Deere 42 inch mower deck parts diagram could simply be due to a need for troubleshooting the deck. And if that’s the case, we would love to help you a little here.

There was a time when a 42-inch mower deck was considered to be less standard, it was more of an extra wide size option.

However nowadays 42 to even 52 inches decks are the real standards. And this new standard also accompanies double sometimes triple blades for the mower to give a shorter order making capability for a huge lawn.

And that’s why the now-normal but quite high-cutting swatch requires dynamics that are also extra and not to mention the need for more moving components.

It’s true that the components are assured with a similar guarantee. However, it’s not shocking to discover one or more deck parts eventually meeting failure due to usage and over time wearing out.

A number of problems will start appearing with the parts. And eventual it will make the wide cutting equipment problematic to use.

A troubleshoot of a john Deere mower deck can really help here. As you will be isolating the deck to diagnose the existing issue.

Let me walk you through the steps one by one, try to not skip not a single one.

Make Sure There are No Bent/Damaged Components

One of the common issues that can happen is too much vibration. And this can seriously cause bent or damage to the existing mower deck components. That’s why you should consider starting this troubleshooting by checking the mower blades.

Important – The engine must be shut down while you are checking the blade!

If you find out any sign of bending or damage, it will simply need a replacement. And yes, the entire set needs to change.

This is because most mower blades are not easy to repair after being bent or damaged. And that means, even with a single blade going bad, the entire set will need replacement.

Are The Blades Sharp Enough?

Okay, maybe the blades are not bent or damaged. But there’s one more thing you need to make sure of.

And it’s whether the blades are sharp enough or dull to the point that the grass ends up being brown. Sometimes you’ll notice the tips being abnormal after mowing. That’s also a huge sign.

A dull blade can:
  • Temporarily damage the entire lawn.
  • Cause shock and diseases.

So, without making any delays, sharpen the mower blades asap.

Is The Deck Un-level?

Uneven cuts are a big sign that the deck needs some inspection for level. Because a 42-inch John Deere deck is quite expansive on its own, there’s a big chance for it to easily become unlevel. And of course, it can end up wreaking chaos.

Do This:

  • Bring the mower on the level ground first.
  • Now take measurements from the outside edge of the deck to the ground. You want to do this for each outer edge.
  • Find out the difference between both measurements. It should be less than a quarter inch.
  • If it’s not less than ¼” then you need to make some alterations. Bring the deck’s lowest end upward for the adjustment.
  • This adjustment applies on each side of the mower, close to the lift yokes.

Are The Deck Drive Belt Stretched or Worn Out?

You will most likely hear a squealing type of noise whenever the mower deck is operating. And this is a big indicator that the mower deck drive belt is in trouble. Most probably the belt has overstretched. Or it can simply be damaged.

If the belt stretches, then it can slip on deck pulleys. And that is why such a sound happens. Another sign is discovering cracks and flat spots on the belt right along the edge inside.

You must change the deck drive belt. And make sure the new one is an original John Deere belt for no compromise in performance.

Keep In Mind – Cutting dry grass will help in sidestepping any bogging down issue of the mower. Also, for an even lawn cut, keep the driving speed slow. A little cautious usage can prevent all these issues.

Further Evolution of Other Parts Before Swapping the Deck

Once you are sure that the deck needs a replacement, take another additional step beforehand of the swapping. And that’s going through other critical components and ensuring those are working fine.

Why is that important? Let me answer by giving you an example. Imagine your lawn mower does not simply have a worn-out deck but also a failing drive system. Or to make it even worse, a failing engine.

And if that’s the case, changing the deck won’t solve the problem. Engine and drive systems, both are expensive to fix, and without those sorting out first, you cannot think about a deck swapping just like that.

I’ll keep this really simple, but you can also find more in-depth by researching on troubleshooting all these parts individually. But for now, let me give you a brief guideline on what parts to check before confirming a deck swap.

Make Sure the Drive System is Doing Fine

One of the expensive repairs is done for the drive systems. Self-driven mowers will need a well-functioning drive system. One of the common issues is having a leaking drive system.

You want to make sure the operation is smooth when driving, if the mower is struggling to pull in areas such as hills, then that can be a sign.

Also, if there’s any noise particularly that you head when driving. A grinding or squealing noise is a huge sign. Checking for oil leaks in the trans axle is also necessary.

And so is checking the condition of a drive belt. If you don’t already know both of these parts, wheels, and pulleys basically make the drive system.

The more common type of drive system issues is damaged wheels, transmissions, wheel drive gears, and drive pins. It can also be faulty pulleys, braided drive cables catching frays, or damaged belts.

Make Sure the Engine is Doing Fine

And by that, we mean, the engine health needs to be topnotch. You can look at the oil quality, it should not be grey or black (that’s a problem indicating sign). Also, look into the oil level, a higher level may mean a problem with the carburetor.

Mower oil leaks can also be a case, something that often takes place in crankshaft seals. You also want to make sure:

The engine is starting without difficulties. Hard to start may indicate a need for carburetor replacement or even tune-up.

The engine needs to escape misfire or spluttering issues. If it does, get a tune-up. But sometimes luck does not favor and it ends up being an expensive repair.

If there’s any surging with the engine rev then a new carb will be necessary.

The smoking engine can also mean trouble. Sometimes it’s simply an overfilling of oil. But it can also mean wear on the engine.

Keep In Mind – The less worrying or easy-to-sort types of engine faults that won’t be a hindrance in getting a deck swap are basically shear key broken, a damaged coil, carburetor failure, or dirt build-up and pull starter damage.

Apart from the drive system and engine, you should also check the controls, blade, handlebars, blade boss, grass box, and grass flap. You’ll need to spend quite a lot on replacing drive controls.

Also, these parts are not too high-risk components. But you should still consider the repairs before jumping into a deck swap to get smooth results after the replacement.

If You Must Replace the Mower Deck

Sometimes replacement becomes unavoidable. Because the deck itself entirely has gone out of order. And it’s not just one or two parts that need to be treated for the deck to work like before.

So, if the deck has almost zero chances of recovery, it’s time to think about switching the riding mower’s deck.

Now one question that is often asked during such situations, are riding mower decks interchangeable?

Yes, riding mower decks are interchangeable if you manage to get the exact dimensions and bolt placement right. But that’s also quite difficult to figure out. And so, you should always try your best to purchase a specifically meant for your lawnmower deck. Focusing on the make and model is key here.

To get the perfect deck sway you can:

  • Try looking for a pre-loved mower that will have the same deck specs. Some owners will have a blown engine and so they might have kept it unused. And then, it makes sense for them to sell the other components that are still doing fine, including a deck. You can look for such a deal.
  • Or simply contact the dealer and find a new deck that is meant for the mower. Most manufacturers have no sort of standard deck spec to meet.

And that is why the designs are common and often shared. So, finding an identical deck fit is not that hard for a different manufacturer. So, this route is also valid if you have an understanding of matching the deck precisely.

Keep In Mind – A deck smaller than what your mower needs will make the blade awfully scrape it. Eventually, this will fasten the wearing out of your blades by making it dull and less effective. This also negatively affects the belt and springs. And if the deck is too big, the mower will keep bumping into everything.

Apart from the interchanging eligibility, there are more things that are critical and directly related to deck replacement that you must know.

These Are:

  • Your drive system will not transfer across if you cannot match the new deck with the old one.
  • The handlebar mounting points need to be the same.

You are all ready to find out about the removal & replacement process.

Here’s What to Do:

  • Make sure the mower is on a flat level surface. You want to gauge the parking brace and also ensure the blade control switch is not engaged.
  • Get the key out after turning the engine off. The cut lever height needs to be at its lowest position.

Important – You must always read all the safety-related information and instructions inside the operating manual. Servicing your lawn mower will be safer that way.

  • You will see a cotter pin in the front support rode. Remove it. You also want to take out the rod from the deck bracket.
  • Now bring the deck front lower to the ground. And then the mower deck needs to be lifted up. Also, the hanger brackets. This will make sure these are clear from the left rod on the rear.
  • Now carefully bring down the deck’s rear to the ground. You want to gently slide the deck into the machine’s rear side. This will help you to easily bring out the mower belt from the engine pulley.
  • You are ready to carefully slide and remove the deck from beneath the machine. At this point, complete all the maintenance you may have in mind such as cleaning the blades or adding a recycler kit.
  • Get the new deck right beneath the machine. And you want to push it in a backward direction. So that you can change the engine pulley’s belt.
  • You need to get the deck into a position from where it is liftable in the back end. For that, you need to move the deck forward. And this will allow you to re-hang the deck with the help of a support bracket on the back.
  • You want to secure the front support rod with the deck using the clevis pin and cotter pin. Make sure the belt is onto the engine pulley.
  • Give the whole thing a final check, and make sure the deck is sitting right with all idlers and pulleys in place. Then you are ready to turn it on and start mowing.

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Frequently Asked Questions (FAQs)

Are 42-inch mower decks interchangeable?

Yes, 42-inch mower decks are interchangeable. But you must match the deck’s common specs otherwise blade won’t be able to work right and also the drive system can face troubles. Engine swap won’t be an issue even if you have interchanged deck.

What size belt does a John Deere 42-inch deck take?

The exact size for the belt of a John Deere 42-inch deck is BB 5/8″ x 153-3/4″.

Why does my mower deck wobble?

There are many sources of this wobbling deck problem. But it can be due to the blade not being balanced. Also, pulley or mandrel damage can cause it.
Sometimes it’s due to pulley catching dirt or even a blade belt failure. Vibration can also take place due to nuts or bolts getting loose in blades, pulleys, and mandrels.

Why is my mower deck squeaking?

It can be due to the cutting belt getting engaged for the first time. That’s when the belt may give a short chirp or a squeaking-like sound.
This is common with new components. But otherwise, this can be a sign of some underlying issue.

Do you have to remove the mower deck to replace the belt?

Yes, you have to remove the mower deck to replace the belt. This is because the removal will help in accessing the belt better. And so, the replacement will be easy as well as quick.

Wrapping Up

And just like that you now have a much of resources. Including the john Deere 42 inch mower deck parts diagram, their brief explanation, troubleshooting of the deck itself, understanding of the matter of replacement, and more.

Hopefully whatever issues you are facing with the deck will soon meet a solution after this. If you cannot still come up with a proper fix for the situation, then getting expert help is highly recommended.

Decks are a pretty important part of the whole mowing system. So, it definitely needs some solid attention to participate in the mowing chore you will need to do a lot inside your lawn.

Good Luck on That!

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