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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
A little more cleaning and painting this week. Maybe I'm going a bit overboard but, at least, reassembly will be clean. I rigged a sleeve to protect the final drive oil seal and wrapped some rope caulk around the oil seals to protect them during sand blasting. A rinse down with paint thinner and a coat of paint.DSCN0141.JPG DSCN0142.JPG DSCN0144.JPG DSCN0145.JPG
 

cxprestige

Member
Joined
Jul 21, 2019
Messages
14
Location
central NY state
A little more cleaning and painting this week. Maybe I'm going a bit overboard but, at least, reassembly will be clean. I rigged a sleeve to protect the final drive oil seal and wrapped some rope caulk around the oil seals to protect them during sand blasting. A rinse down with paint thinner and a coat of paint.

Nice looking job! Some people might think it's pointless to paint inside where nobody will ever see, but a smooth painted surface will rust a lot less (hopefully not at all). Rust absorbs moisture and begets more rust, so the bare metal clutch discs and brake drum should last longer in this compartment.
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
I made a list of gaskets and seals needed and the prices thereof. Since the cover gaskets were 25.41 each I invoked my shade tree skills and made a pair!DSCN0146.JPG DSCN0148.JPG
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
I got the last of my steering clutch parts beadblasted and painted. Just waiting on new parts to arrive. In the meantime I cleaned and chased the threads of all those 16 holes in the back of the steering clutch cases. Originally, they were plugged with cork and over the years some of the cork plugs were removed. These holes are a prime source of moisture and dirt entry and future clutch and brake failure. Pressure washing doesn't help either! I purchased some M18-2.5 bolts, applied pipe dope on the threads and torqued them in place. Along with new gaskets and seals, my clutches should remain clean and free for many years to come.
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Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
Before ordering new steering clutch springs I decided to check the originals. Not having the Komatsu specs for these springs I decided to make a comparison test. Free length was 2 13/16" on all of them, compressed to 2 1/4" they all read 85 lbs. Since they all read the same I feel confident they are good to run.
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cxprestige

Member
Joined
Jul 21, 2019
Messages
14
Location
central NY state
Before ordering new steering clutch springs I decided to check the originals. Not having the Komatsu specs for these springs I decided to make a comparison test. Free length was 2 13/16" on all of them, compressed to 2 1/4" they all read 85 lbs. Since they all read the same I feel confident they are good to run.
View attachment 207676

The service manual for 6 series gives a free length of 70.6mm, compressed 51mm with 60 Kg force. That works out to 2.77", 2.01" and 132 lbs. The spring part # is the same for 6 and 7 series, so these numbers should work for yours.
I think you're right that matching is more important than absolute length.
I've wondered about those corks from the beginning--why wouldn't they have put the bolts in and left maybe one small vent? Maybe they wanted the steering clutches to breathe, like a fine wine.
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
The service manual for 6 series gives a free length of 70.6mm, compressed 51mm with 60 Kg force. That works out to 2.77", 2.01" and 132 lbs. The spring part # is the same for 6 and 7 series, so these numbers should work for yours.
I think you're right that matching is more important than absolute length.
I've wondered about those corks from the beginning--why wouldn't they have put the bolts in and left maybe one small vent? Maybe they wanted the steering clutches to breathe, like a fine wine.
I reset my tester to 2" and rechecked the springs. All tested at 130-131 lbs except for one spring came in at 128. I think that will work nicely. Thanks for doing the math for me!

As far as venting the steering cases, I'm going for the sealed version. Maybe put a couple of desiccant bags in for good measure. My way of thinking is 'no vent, no moisture'.
 

cxprestige

Member
Joined
Jul 21, 2019
Messages
14
Location
central NY state
As far as venting the steering cases, I'm going for the sealed version. Maybe put a couple of desiccant bags in for good measure. My way of thinking is 'no vent, no moisture'.

Sealing it up is a good idea--I'll probably do the same. There's enough air in there that, even with a big temperature swing, there shouldn't be enough change in pressure to hurt seals or pull fluid from the ring / pinion case. The dessicant should reduce condensation damage.
I'm also trying the Vapor Corrosion Inhibtor capsules--supposed to be good for 2 years in a sealed space--to prevent surface rust on the clutch discs. Zerust is the one I got--there are others of the same chemistry.
But the best rust prevention of all is USE. Look at the brake rotors on a car that sits just a few weeks--already covered with rust (at least in this climate--central NY state).
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
I got all the new parts in today from the good folks at SteeringClutch.com . Tomorrow, I have to build a tool to assemble the clutch pack and start back together. It's certainly nice to have everything clean and painted for reassembly. DSCN0183.JPG
 

cxprestige

Member
Joined
Jul 21, 2019
Messages
14
Location
central NY state
It's certainly nice to have everything clean and painted for reassembly.
Those parts look way too nice to bury inside the clutch case--maybe you should make a window in the cover so as to watch everything turning!
Do you plan on coating the splines and other bare metal with anything? The drums and clutch discs would wear clean, of course, but anywhere else it might help.
 

Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
All threads and splines are coated with never seize. Today, I built a compression tool and assembled one steering clutch. More pics and progress tomorrow evening.

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Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
A compressor tool is needed to assemble the clutch pack. This is my rendition of the “A” tool as mentioned in the Komatsu service manual. I made the two guide pins from M8 fine thread by 4.5” bolts.
1- Place the spring collar on the tool base and install two guide pins. 2- Place all springs and spacers in position and install the spring bolts, (less flat washers), only about two threads.
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Don Shilling

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Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
1- Lay the inner hub in position, install upper compressor adapter and compress the springs until the spring spacers are slightly proud of the surface of the hub and remove the bolts but leave the guide pins for now.
Install the plates starting with a friction and ending with a friction.

2- Lay the thrust plate into position. There is only one position where the bolt holes and inner teeth align. Rotate the plate until everything lines up.


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Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
1- Align the external teeth and install the brake drum.

2- Remove the guide pins and install all eight bolts and tighten to specs or your “feel”.

3- Remove the tool, install the brake band and you’re ready to go!


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Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
The clutch throwout assembly has been beadblasted, no damage found, painted and is ready for assembly. The bearing is assembled on the gimbal and clutch fingers and this is mounted into the throwout lever. All pivot and sliding points are greased and the bevel gear flange is fitted into position.

At this point, a neat modification has been added. Cxprestige offered a suggestion concerning the ball and socket at the bottom of the throwout lever. The ball doesn’t ride in the bottom of the socket but, rather, is suspended in the bore of the socket and the whole throwout assembly is suspended on the bevel gear flange. Grease can be placed into the socket and a boot assembled over the ball and socket to prevent any trash from entering the socket. This boot is derived from an early Volkswagen axle but we’re not exactly sure which model.


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Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
The clutch throwout arms are installed and ready for the clutch assemblys. There is a world of difference in the smoothness of the action before and now with everything clean and lucubrated.

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Don Shilling

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Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
A rainy, drizzly day is always suitable for inside work! The throwout assemblies installed and ready for the steering clutches. I attached two 3/8” lifting eyes on the opposite flange wheel and inserted a pipe to lock the bevel shaft while we tightened the first flange.
Due to the restricted clearance between the two flange wheels, I shortened a 2 1/8” socket just enough to grab the nut.

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Don Shilling

Well-Known Member
Joined
Aug 10, 2019
Messages
147
Location
Texarkana, Texas
Occupation
Retired, multi occupation
At this point, it cannot be stressed enough to pay attention to the orientation of the brake band on the drum. It would be a shame to get the clutch in and tightened and then realize the brake is on backward! Been there, done that on other similar projects!

Lower the clutches into position using a comealong. Instead of using a bottle jack to rotate the track I used a pinch bar and levered the sprocket teeth to align the bolt holes in the flange wheels. A lot easier and quicker.


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darinray

Charter Member
Joined
Nov 15, 2003
Messages
435
Location
Delevan, NY
Occupation
Owner-Equipment & Parts Sales
Bravo Don, Wow you made this process look easy and fun. :) Glad you got the girl back up and running. Did you drill and tap grease fittings on the housings? One note that you may not ever need to know but people reading this may is.. On both the final drive and bevel gear flanges Komatsu put 2 threaded holes used for large nut lock that can aid in pulling the flanges off. Just use longer bolts than you took the lock cap off bolts. Built in puller really..
 
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