Hello folks,  I'm looking for plugs to wash steering clutch cases D4. Is there any common plug to use, or are they caterpillar components?

Hi, Jimmy977.
I think I've seen somewhere that they are 2 1/4" pipe thread. No doubt, if I am wrong, somebody will be along to tell me so.

Just my 0.02.

For one of the drain plugs on my D4 I machined a 2”- 12 tpi parallel thread tap to clean out threads as the plug would get tight just as the copper gasket would start to experience some compression.

They could be different on the steering clutch or different on different production ranges, but that’s what I used in mine.

On my D4, I borrowed a couple of final drive fill plugs from a D2 parts machine and they worked just fine. If you cover the final drive fill, you could probably use the ones from your own machine for your washing. Grant.

The 9u D6's use a pipe plug. I want to say 1 inch, but could be a 3/4 or 1 1/4. If you are working on newer with wet clutches I have no idea. If they are typical Cat plug with copper washer with a female hex that is not a pipe thread.

EDIT TO THIS POST  THE D4 uses the same plug as the filler holes, keep reading more information in latter posts. IT IS NOT A PIPE PLUG 

they are npt thread go to a plumbing supply and buy some normal threaded bungs. remember pipe is nominal bore size not outside dia. if memory serves they should be 1 1/4 npt

For my ‘49 D4 7U, I bought these. Unfortunately price has doubled since I bought them. Perfect fit.

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The steering clutch housing uses the same recessed hex plug that is used in many compartments in the D4.

It most certainly is not a pipe thread, these plugs use a copper gasket for sealing, pipe threads use a tapered thread for sealing.

The OD of the thread on these plugs is 2.00”

If this was straight pipe thread 1 1/2 NPS has a 1.875” OD, 2” NPS has a 2.351” OD.

Then again I guess if you jam a 11 1/2 TPI plug into a 12 TPI hole.

Here is the description of that plug from the Cat NPR, it must have been late on a Friday afternoon or something when it was written.

 

The cast OD of the flanged portion is approximately 2 1/2”