Questions on inspecting Cat dozers (D6C/D/E, D7E/F/G, etc.)

LCA078 · Jan 17, 2021

I've gained a LOT of insight from this forum on ensuring I don't buy a yellow money pit. I passed on a couple dozers that looked good in pics but didn't look good up close. I've gotten good at measuring rails and rollers but haven't quite figured out a few things.

-When measuring sprocket life, is there an easy way to do it with calipers or good rulers? I can't figure out (or find) how to do it without using the special tool. Or this just a 'trained eye' thing?

-I can pull the final drive filler plugs (between the sprocket and body) to check the fluid but I don't know how to get a magnet in there to fish for shavings (I think that was mentioned something to a few times in other posts). Enlighten me on this.

-Pulling the magnetic screen for the transmission: The first dozer I looked I already made up my mind not to buy it after seeing the leaky finals and worn out u/c so I didn't bother looking for that screen. The last dozer i looked at had a really thick rubber floor mat and I couldn't pull any floor panels get to the screen. That owner wasn't keen on me doing it anyway as he was worried about folks wrenching on it before they bought it. Anyway, does any one have pics of what this screen looks like before it's removed from transmission and/or what it looks like after I pull it?

Thanks

John C. · Jan 17, 2021

The sprocket teeth on these old dogs use a plastic tool that looks like a deformed nut. There are numbers that tell you the amount of wear when you set the nut in the valley between the teeth. I've had them in a kit and never used one. Go look at a new sprocket to get the feel for how much steel shows on the tip of the teeth. The sprocket is 100% or more worn when the tooth tip is sharp.

You will never do yourself any good with a magnet in the final drive. The steel is heavy and sinks to the bottom anyway. If it is a big concern, take an oil sample. Problem with them is they will all show high iron.

The suction screen for the transmissions can be anywhere depending on the model and series of a machine. They usually have lots of trash an them from the brake bands and all that steel in motion. Again, if it is that much of an issue, take an oil sample for analysis.

I inspect machines for a living and even I wouldn't pull an suction strainer apart to check it. Anything that the machine does after words would be blamed on me. I do run the machine and look and feel for indicators of problems. If I suspect something, I'll take a sample and note what I felt. At that point it is up to the seller to prove me wrong if he wants to make a sale.

LCA078 · Jan 19, 2021

John C. said:
The sprocket is 100% or more worn when the tooth tip is sharp.

Thanks- I've seen the plastic gages but figured the calibrated eye ball was best. I'm guessing most folks change their rails and sprockets together so there "should" be some correlation between the two but verifying is good.

John C. said:
You will never do yourself any good with a magnet in the final drive. The steel is heavy and sinks to the bottom anyway. If it is a big concern, take an oil sample. Problem with them is they will all show high iron.

That makes sense as I couldn't figure out how to get a magnet down there. I tried to use my extendable mag pick-up but ended up just giving it a good oiling for when it sits in my tool bag. How to fish in the drive had me puzzled.

As for oil samples, I'm sure an oil sample would only have the possibility of scaring me since I wouldn't have a oil trend with that machine (I doubt I'd be able to get service records for a 40+ year old machine!). Yes- high iron and silicon (dirt?) will be typical I bet. When I check oil, I ensure it's 1) near the full mark, 2) not milky, 3) not smelly like fuel or burnt. My granddad used to taste oil but I don't think I'll go that far.

John C. said:
I inspect machines for a living and even I wouldn't pull an suction strainer apart to check it..

Understand and appreciate the feedback. I know sump strainers and such accumulate garbage over 40 years or so but since it was posted multiple times as suggestion, I figured it was a 'must do'. Without experience in these machines, I wouldn't know which materials in a strainer I should be worried about and which is typical so I fully understand not even pulling it then (kinda like pulling an oil sample with no history). I guess a different question for you, John, is if you were buying it for yourself, would you pull the strainer?

Dave Neubert · Jan 19, 2021

Normally if the sprockets are wore they will come to a point they should be blunt

John C. · Jan 19, 2021

By the time that they become blunt the sprocket has turned into a wheel.

John C. · Jan 19, 2021

On old machines, I'm going to assume that there is a lot of junk in the strainer. I would use my expectations of what an old machine is going to be like and work from that. If the transmission hesitates to go into gear or slams into gear real hard, if it slips while doing stall tests, if the temperature heats up real fast and then takes a long time to go down when doing a stall test would all be signs of problems. Steering issues are another often overlooked issue on old machines. If any of those issues showed up I might talk to the owner about hooking up some gauges if I had to have the machine for some reason. I can't really dream up any reasons though of why I would want any machine with those types of problems.

dozer777 · Jan 19, 2021

John C. said:
Sur les vieilles machines, je vais supposer qu’il y a beaucoup de ferraille dans la passoire. J’utiliserais mes attentes de ce qu’est une vieille machine va être comme et de travailler à partir de cela. Si la transmission hésite à passer à la vitesse ou claque dans la vitesse vraiment dur, si elle glisse tout en faisant des essais de décrochage, si la température se réchauffe très rapidement et prend ensuite beaucoup de temps à descendre lors d’un test de décrochage serait tout ce qui est des signes de problèmes. Les problèmes de direction sont une autre question souvent négligée sur les vieilles machines. Si l’un de ces problèmes s’est présenté, je pourrais parler au propriétaire de brancher quelques jauges si je devais avoir la machine pour une raison quelconque. Je ne peux pas vraiment rêver de raisons pour lesquelles je voudrais n’importe quelle machine avec ce genre de problèmes. [/CITATION]

Dave Neubert · Jan 19, 2021

John C. said:
By the time that they become blunt the sprocket has turned into a wheel.

I was talking about the tips of the sprocket

John C. · Jan 19, 2021

I didn't know I wrote in French so well.

wkp774 · Jan 19, 2021

A tip i have told guys like you, if the seller says you can take a link out get in your truck and go home.

56wrench · Jan 20, 2021

or haggle him down the price of a new undercarriage

LCA078 · Jan 25, 2021

56wrench said:
or haggle him down the price of a new undercarriage

The last machine I looked at was at a local auction yard that I passed by on the way to see my parents over the holidays. No haggling at auctions unfortunately.

That machine was described as Fair. In fact, everything on the dozer was described as Fair in the writeup. Only issue noted was that it did not start even when jumped (wouldn't turn over or even make a sound, period). As I walked up I saw the sprockets had some wear but were not yet sharp. I looked up under the shoes to look at bushings and saw the pins...literally. So much for the statement: Running Gear- Fair condition.

I guess I don't know what Fair means...

Dave Neubert · Jan 25, 2021

Know how to tell if a sales men is lieing

Know how to tell if a sales men is lying .... If his mouth is moving

Questions on inspecting Cat dozers (D6C/D/E, D7E/F/G, etc.)

LCA078

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John C.

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LCA078

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Dave Neubert

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John C.

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John C.

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dozer777

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Dave Neubert

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John C.

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wkp774

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56wrench

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LCA078

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Dave Neubert

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