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Komatsu D21a-7 steering clutch

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
I didn't put grease fittings on the brake control shaft. Since it has seals on both ends i just packed the bearings full of grease. It should last until I'm gone anyway! Tomorrow, I'll lower the covers into place and purge the case with nitrogen. More on this later. I made a nifty lifting sling to allow one person to lower and align the covers. More pics coming tomorrow evening.
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
I devised this little hangar thingy to help suspend the steering case cover while I aligned the brake band controls. The other end I just hooked on an adjusting cover bolt.
DSCN0204.JPG DSCN0205.JPG DSCN0206.JPG
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
I fashioned three stud locaters to hold the cover gasket in place and hold the cover in alignment while the bolts were installed.

After adjusting the brake band and everything is closed up, I’ll purge the cases with nitrogen to remove all moisture.


DSCN0203.JPG
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
Steering clutches rebuilt, closed up, and the brake actuating cylinders also rebuilt while I'm at it. Just waiting for new cross hoses to be built.DSCN0210.JPG
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
This is an easy machine to work on but there are still a lot I have to learn about it. Searching thru the manual but I have not found out anything about this device. Hopefully, someone can shed some light on the purpose of this thing located at the rear under the seat platform.DSCN0211.JPG
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
I finally got my new hoses for the steering brake cylinders installed and the rest of the plumbing in place. Also, I deduced the two solenoid valves have to do with the blade angle control. All I have now is to reseal the spools on the blade control. Hopefully, tomorrow I can crank up and check for drips and squirts. DSCN0217.JPG DSCN0220.JPG I'm looking forward to experiencing the operation after all this rebuilding.
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
I reached the point where I could start the dozer today and all connections were dry. There was only one preexisting slight leak on the bottom of the blade control. I'll have to remove the complete valve assembly to repair so I'll wait until next winter for that. Otherwise, the clutches and brakes worked super smooth and positive control. Even the direction reversing was a lot better with no jerking. All I have now is to install a battery main disconnect switch and the new seat. I'm using a Smitty Bilt seat on a Jeep CJ adjustable frame.
 

darinray

Charter Member
Joined
Nov 15, 2003
Messages
435
Location
Delevan, NY
Occupation
Owner-Equipment & Parts Sales
M10 8.8 structrual steel zinc plated bolt "googled" 30 ft/lbs... Other websites may say differently so I'd compare and use your best judgement.
 

Kevin McCoy

Member
Joined
Jun 6, 2020
Messages
14
Location
Orcas Island, WA.
Hi Don, A very impressive job you have done on your dozer! I am just reassembling a D-21A-6 with support from Darin at DM Machinery 716 942-6318 I know you are in contact with him, I’m posting his number for others as he has been great support With parts and experience on these machines.
Today this seems to be the end of your posting however on Saturday I thought I saw that you got your machine running and were driving it but found it jerky I can’t find those posts now perhaps I’m missing something just curious how things are going and hoping you’ll post some updates.
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
Hi Don, A very impressive job you have done on your dozer! I am just reassembling a D-21A-6 with support from Darin at DM Machinery 716 942-6318 I know you are in contact with him, I’m posting his number for others as he has been great support With parts and experience on these machines.
Today this seems to be the end of your posting however on Saturday I thought I saw that you got your machine running and were driving it but found it jerky I can’t find those posts now perhaps I’m missing something just curious how things are going and hoping you’ll post some updates.
The machine really just needed to be exercised a bit. After a few hours, the jerkiness has disappeared and everything is operating very smoothly. The steering clutches and brakes are very sensitive and positive in action. I didn't even have to "bleed" the hydraulic lines as they purged themselves during operation. Last week I resealed the angle and tilt cylinders and didn't even have to bleed them either.
Darin now has the tools I made to assemble the clutches so contact him for more information concerning their use.
For a relatively small dozer, this D21 is a pleasure to operate. I've been pushing dirt and clearing small trees, bamboo, and underbrush with ease. The joystick controls, to me, are more desirable than lever operation and less fatigue.
The utmost, main thing to consider on clutch overhaul is to positively seal all those bolt holes in the rear of the clutch housing to keep moisture and trash out. Also, new gaskets and seals will result in an air tight assembly.
 

Kevin McCoy

Member
Joined
Jun 6, 2020
Messages
14
Location
Orcas Island, WA.
The machine really just needed to be exercised a bit. After a few hours, the jerkiness has disappeared and everything is operating very smoothly. The steering clutches and brakes are very sensitive and positive in action. I didn't even have to "bleed" the hydraulic lines as they purged themselves during operation. Last week I resealed the angle and tilt cylinders and didn't even have to bleed them either.
Darin now has the tools I made to assemble the clutches so contact him for more information concerning their use.
For a relatively small dozer, this D21 is a pleasure to operate. I've been pushing dirt and clearing small trees, bamboo, and underbrush with ease. The joystick controls, to me, are more desirable than lever operation and less fatigue.
The utmost, main thing to consider on clutch overhaul is to positively seal all those bolt holes in the rear of the clutch housing to keep moisture and trash out. Also, new gaskets and seals will result in an air tight assembly.
Yes I’m sure all those clutch surfaces need a few hours to get seated in, glad things are working great you sure did a fine job, Darin is sending your tools to me today, I am so grateful, they are masterpieces. Thanks for your advice, I really appreciate the time and effort you put into posting this thread the Komatsu books give so little detail
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
The more I operate this machine the more I appreciate the hydraulic power controls, and being an older model, the lack of computer controlled systems, idiot switches, buzzers, and DEF **** fluid. This is the epitome of crank 'er up and get 'er done!
 

William Pedrick

New Member
Joined
Jun 9, 2020
Messages
1
Location
elmira ny 14904
Hi I am Bill Pedrick new member just read post and was in pressed . my 21a quit steering yesterday no power to left track . thinking clutch went on that side will start there . can any one tell me the best place to get manual and parts thanks headed back to farm-camp will check in later
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
Hi I am Bill Pedrick new member just read post and was in pressed . my 21a quit steering yesterday no power to left track . thinking clutch went on that side will start there . can any one tell me the best place to get manual and parts thanks headed back to farm-camp will check in later

Manuals are available on Ebay. Caution on the repair manuals, I have not been able to find one that has any decent pictures. They are all blurry and mostly unusable.
Check with Darin Mitchel for new and used parts. dmmsales.com Also check steeringclutch.com
 
Last edited:
Joined
Mar 9, 2021
Messages
8
Location
Suamico WI
So I installed my rebuilt steering clutches today. Good traction on both sides and good brakes on both sides but neither steering clutch disengages. I am thinking since I had the hydraulic lines off and fluid leaked out I may have air in the lines. Will pull partially apart tomorrow to see if actuators are moving at all. Any thoughts?
Thx.
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
So I installed my rebuilt steering clutches today. Good traction on both sides and good brakes on both sides but neither steering clutch disengages. I am thinking since I had the hydraulic lines off and fluid leaked out I may have air in the lines. Will pull partially apart tomorrow to see if actuators are moving at all. Any thoughts?
Thx.
Remove the rear cover from the brake adjuster and check if you can see the throw out yoke operating the clutches. My control lines seemed to bleed themselves and have worked properly ever since I reinstalled them.
 
Joined
Mar 9, 2021
Messages
8
Location
Suamico WI
My bad, I had read an article stating that when installing new clutches you did not have to adjust the yoke stud. (steering valve assembly)? Anyway, stud was not pushing clutches to disengage. Made some adjustments and works perfect. Now I just need mother nature to get the frost out of the ground up here so I can have some fun.
Thx again.
 
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