Me and my dad have been working on this dozer for the past year and 3 months just fixing it up to get it working properly. Everything now works on it good now besides the oil cooler which had a huge leak. Ive been wondering and thought just to bypass the cooler itself now I've been researching and saw people talking about taking the plunger and spring out of the filter housing if im going to bypass and I just want to make sure here on the acmoc forms that it would be the correct thing to do. Aswell I saw that my shifter boot has dry rotted and is no longer in working order does anyone know how im able to take my boot off and replace it without destroying anything ex. shifter knob. Also does anyone have the part number for the shifter boot.
Down below are some pictures of the filter housing, shifter boot and knob. If anyone can help me solve these problems I would appreciate it.

Straight from Caterpillar service magazine..1956.

The D2s &4s that I have with leaking coolers; I just cut the oil lines and looped a piece of hose into each oil line.

I have looped cooler lines on several Cats with leaking coolers. Also taken out plunger but was unable to find plugs with proper thread to plug ports. 3/4" NPT will force in but not correct.

Plug 2D2182
Gasket 6B3410

This is from OM. Use hydraulic fitting "O-ring Face Seal" plugs size dash10 (1"-14tpi) straight thread.
Remove face seal o-ring.
I also stretched a #116 Viton o-ring over the plug but I'm not sure that is necessary. I used Teflon paste pipe thread sealer.
Plugs are only a couple of $ each.
Plug the oil cooler too for a clean installation.
Remove oil cooler by-pass valve and spring.

That factory letter explained why my dads old RD4 has what I call the "PENCIL THIN " blades on it. I only recently noticed it was different from my 6U. I guess that a real restorer would want the 6 blade fan. I only care about what works best. Grant.

-10 ORB is a 7/8-14 thread,

you can just loop the pipes.
or do what we did.
mount a transmission cooler for a toyota landcruiser in front of the radiator. this is after the factory rad had the tanks removed and the oil cooler core was blanked off using devcon brushable putty the rad tanks were also coated internally with it too as there was some corrosion damage.

I believe your shifter boot should be an 8F8079