View Full Version : D4 large diamter front idlers

06-07-2012, 08:46 PM
HI gents,

i have a d4 6u on the mend with a 7u i am using for spares.
the 7u has the large diamteter solid idlers while the 6u has the older smaller diameter cast iron spoked type.

can someone explain if the larger diameter idlers are worth using, and why cat went to them.


06-08-2012, 01:36 AM
The smaller spoked idlers are for towing where most of the machine weight goes to about 75% of the length of the tracks starting from the rear, the larger solid idlers are used on dozers to carry the blade to reduce 'nose diving' and give a longer, more stable length of tracck to make dozing easier. Changing over might not be straightforward, there will be more links (longer tracks) used with the larger idler.

12-11-2012, 06:45 PM
hi catsilver thanks for the reply

i rebuilt the large idler internals and put them on the D4. they were in much better nick then the original spoked items.
one thing that i would like to point out to others that are thinking of doing this
is that the two arms coming back from the idlers to the track tension adjuster nut are very slightly different,
and if you are doing the change over you will need these as well.
i have a set of 32 link chains that are like new but i thought i would get the last out of the 31 link chains
that were already on the dozer first.
quite funny really as now the track adjustment is waaay back, to the naked eye you would assume the pins and bushings are perfect.
well, from about 30ft anyway : )

so far this old girl has had the following done to her

rebuilt RHS final drive
New recoil shafts
Large diameter solid idlers with rebuilt internals
grousers removed and track chains put the right way round
rebuilt diff
rebuilt gearbox
rebuilt clutch including new plate and facing pressure plates plates
rebuilt pony
rebuilt injector pump
disassembled and cleaned radiator
rebuilt starter pinion
put starter motor and alternator on.
rebuilt water pump
hard faced sprockets
turned down and adapted pinion from a later d4
stripped two other d4's for parts.
rebuilt rams
made a submersed rotary jig driven by a windscreen wiper motor to build up track rollers while not wrecking seals.
unseized about 600,000 bolts.
3 sets of E sized oxy and 2 acetylene bottles worth of heat put into it, and the two other dozers stripping parts.

if i did it again there would be so many things i would change.
i aquired another two d4s towards the end of the rebuilding process so i could have saved allot of time there. hindsights always 20/20 though isnt it.
all this is between working 6 days a week as an engineer, house renno's fixing tractors and cars.
will be good so see it all back together and sitting pretty in the shed with a nice polish on the blade. : )

D4C Charlie
12-11-2012, 07:33 PM
Thanks for the post callan. Thats the kind of stuff I like. Charlie

12-11-2012, 08:41 PM
Callan, you must be my twin located in a paralell universe.

I can't believe our similarities...eg., working full time, buying two spare D4s late in the piece, rebuilding this that and the other...just about everything you have mentioned, I have done or will need to do.

PS what is the wiper motor device actually used for and how does it work?

12-11-2012, 08:45 PM
...sorry, think I have worked that out now, from your picture I presume you are welding up the idlers using a wiper motor to power a mechanism to rotate them etc:)

Deas Plant.
12-11-2012, 09:56 PM
Hi, Callan.
It sounds as if you have put in a few hours, maybe even days, of work on this jigger. What would you throw at me and how hard would you throw it if I said that you had got out of it lightly? LOL.

Great job, M8. I admire your perseverance. But I think I'll stick to herding photos and data and playing with the machines at the various shows that I attend and help put together. Yer cain't take a D4 - or a D9G dozer - along with you when you are travelling around in a trailer home pulled by a 4X4 pickup, which is my retirement plan.

Thanks for sharing.

Just my 0.02.

Rome K/G
12-11-2012, 10:05 PM
Good job!!!! you did allot of work there. You will be glad you did when you go to work it and it runs and works as it should without a bunch of trouble and you know what you've got now. Thats the way i like to do things, go all through it and and make sure everything is up to spec. Have fun with that tractor and even make some money on the side doing custom work. be safe.

12-11-2012, 11:26 PM
thanks for the kind words fellas, means allot to me.

inter, the jig i made was as you guessed it .
the windscreen wiper motor rotates one roller which in turn rotates the track roller very slowly.
what you cant see is that i tack welded a bracket onto the end of the roller that the magnetic earth
clamp attached to. i was all worried at the start in regards to needing a rotary earth clamp designed
for the task but a 15 dollar one did the job no worries.
the wiper motor was powered by a 12v battery charger that I converted some years ago into a variable power supply.
dont ask me how i knew to turn the charger into a variable power supply as its slipped my mind....
seems after a while your brain can only fit so much in, and as you cram something in one ear, a little
bit of something else falls out the other side: )

will keep you posted with pics as the final pieces come together.
none of this would have eventuated without the help from the fellas
on this board that have helped me over the last year or so.
so thankyou very much.
your help has been greatly appreciated.

12-12-2012, 07:20 AM

Nice job, I like your track roller.

When you start operating your tractor, pay attention to those worn track chains. If the tractor has a rough ride, this may be due to the sprockets climbing up on the bushings. This is due to the track having too much length between each track pin. Might not be a problem, just something to watch for when you start using the tractor.

12-13-2012, 04:40 PM
Read your post on rebuilding track components,and myself do not believe one should hard surface [your sprockets] any metal which are in contact
with each other,have not seen any satisfactory results. In my view this will accelerate wear on the joining part.

12-13-2012, 05:11 PM
Did you use a water bath on the roller to keep it cool when welding it? I couldn't tell from the pics.

12-13-2012, 08:28 PM
yeah mate the rollers were in a water bath.
took a good 5 hours to get everything set up perfect to get a nice flat bead.
i have two spare UC's now so it was a waste of time but a learning excersise none the less.
as for the hardfacing, the welding game is a bit of a fickle one that i try not to stir up to much excitement on as it seems to be a hotly debated topic.
i will soon find out if what i did worked, and if it didnt, no big deal as i have the spares there to replace the worn gear.
and in reality , for what i am using it for, i dare say it will do about the same as its operator and plod along just nicely : )