[aussie Evan]

g,day sam (cletracboy)

I never expected such a quick reply. Thank you
yes, we modified to suit a 2 peice seal & have reassembled all but yet to try

I am a farmer in victoria, cattle sheep & cropping, age 35, & am always interested in old machinery

This Oliver DDH has serial No 2L4726 so from what I read on this site must be 1950/1951

Next problem may be clutch as it was slipping in 4th gear (which seems very fast for a dozer) I have a workshop manual for a BDH (previously owned by my father) but not for a DDH. Is the clutch replacement done the same way?
Maybe somebody has a workshop manual for a DDH?
Evan

[Robert Barbour]

The DD has a double clutch, it can be changed without removing the engine throu the cover on the top of the clutch housing.  You will have to remove the fuel tank and support structure to get access but that is easier than removing the engine.  It is similar to the BD.

[Blake Malkamaki]

Does that have a spring pressure clutch, or an over-center clutch? In either case, I believe they are all double disc clutches.

[Robert Barbour]

The DD clutch is a double plate spring type with foot pedal, the OC 15 has a single plate over-center type with hand lever.

[Blake Malkamaki]

The DD clutch is a double plate spring type with foot pedal, the OC 15 has a single plate over-center type with hand lever.

I didn't know the over-center clutches were single disc. I have not been into one yet.

The foot clutches all the way down to the E are double disc. Not sure about the older models.

[Robert Barbour]

On the D the double clutches are 11 inches in diameter, the single on the OC 15 is 14 inches.  The OC 18 has a double over center type with 14 inche disc.  Generally the over center type have a higher clamping force than the spring type.

[Blake Malkamaki]

Does anyone know what year the over-center clutches came out? Were they offered on the letter models? I know it was an option on some models.

Blake

[Robert Barbour]

The only models I know for sure that used them were the OC 15 and 18 and optional on the OC 12.  With the higher clamping force they were usually used on high horsepower applications.  They may have been used on the FD or 80 models but I don't have any information one that.  I think they go back to the thirties, will have to do the research on that.

[John Schwiebert]

The first OC-12 models did not have the over center clutch. After a certain serial number they have the over center cluch. Later OC-18 models have a ceramic disk to improve the life of the clutch. I used to have a service bulletin on that. A friend of mine has an early (one of first 50) OC-12, it does not have the overcenter clutch. Adjustment of both is covered in the operators manual I have.

[Robert Barbour]

Well John I guess "optional" was a poor choice for words.  What I meant was that both types of clutches were used on the OC 12.  Anyway I have a parts book dated May 1959 and it raises as many questions as it answers!  The foot clutch was used up untill serial number 2JX960 except for 47 units the first being 2JX434.  But they list a coupling change(for the foot clutch) that was made at serial number 3JX198!!!!  Also I have unit 3JX574 and it has the foot clutch!!!!  On to the ceramic clutch!!  That is what I think I have in my OC 15.  The picture in the parts book showes a disc with a set of round ceramic "pucks" on the disc.  Mine looks like a standard disc except the facing is a very hard ceramic material.  It is in good condition so I guess they last very well.

[John Schwiebert]

Well I got my OC-12 home a month ago. If I looked right the serial number (and it was early this morning not the best light yet) is 3JX018. I am sure of all the numbers except the 0. It has the over center clutch. I have a dealer friend who has some not all sales prices books. I will be seeing him in the next couple of weeks. I will see what I can find out. I do not have an OC-15 parts book but have 2 OC 12 books. Other than that what is new with you? John

[Robert Barbour]

By the book all 3JX's should have the overcenter clutch.  Mine has a dozer and rear winch.  The winch controls are on the left, so my thinking was that the foot clutch was used because is is easier to operate the winch that way than with the overcenter clutch with it's controls on the left as well.  On the ceramic clutch, I have a OC 12 gas service manual and it has a picture of the over enter clutch disc and it is similar to the OC 15.  The diesel book does not have the same picture.  This year not much is gettng done on the tractors as I am building my new shop and at 30 X 50 that is quite a job!  I have a bunch of service bulletins, will look throu them and see if there is anything of interest there.

[John Schwiebert]

Robert: Check your P M box. You and I need to compare notes. John