Military D7 sn question

That would be equivalent to the D7F 94N1 to 5191. 180 hp with D333cT engine.
Your 61G0351 would be 1970 vintage.
That is before the change to the beefed up transmission at s/n 94N5660 (formerly used the D6C transmission) so operate accordingly.

This unit (of which I don't own yet) has 648 original hours. Looks like brand new other than heavily faded green paint. I might make an offer on it. Did those early transmissions have any good luck or did they all fail eventually? Also could they be updated at all to last longer?

Nothing wrong with the D6C transmission, just proved to be a little light for the D7 application. Unless it is seeing severe service I doubt that it would be a problem. Yes they could be upgraded to the later transmission.

OM has the D7F transmission designs confused. The early D7F transmission is a physically large, low speed, high torque transmission - which was quite a troublesome and high maintenance transmission, simply due to it being a high torque transmission.
The planetary housings, shafts, gears and needle rollers in these transmissions had a short working life, due to the high torque they were subjected to.

The later model transmission, used from 94N5660-up is the D6C transmission. The transmission is virtually unchanged from the D6C.

This later model transmission is a physically smaller transmission than the earlier transmission - but it runs at much higher rotational speeds, and therefore lower torque levels, than the early transmission.

The later model D7F transmission has different transfer gearing on the rear of it, to enable the transmission to run at higher rotational speeds.

I owned 3 x D7F's, with both transmissions. These tractors all did at least 13,000 hrs before I traded them - and they were worked hard.

The early D7F transmissions kept me poor, but the later transmission is an exceptionally reliable, long-life transmission.

I reckon I could rebuild the early D7F transmission in my sleep, such is the number of times I had them apart for major repairs.

It's not possible to update to the later model transmission from the early transmission, the changes were just too many and widespread, it was a major redesign on the part of Cat.

Nothing wrong with the D6C transmission, just proved to be a little light for the D7 application. Unless it is seeing severe service I doubt that it would be a problem. Yes they could be upgraded to the later transmission.

Yup, sorry about that, I did get it backwards.

Drew - That's a pretty sweet-looking tractor, but here's my take on it.

1. It has a massive push block welded to the ripper - that means only one thing. It's been tandem-ripping some murderously hard rock, and being pushed by another tractor. That's about as hard a type of work as you can get.

2. Be careful of military "hour meter readings". They are untrustworthy, because the military swap components like you and I swap out dirty shirts for clean shirts. They will pull an entire component and replace it with another entire component.
So if an engine develops a major oil leak, they don't fix the leak, they just haul the engine out and drop in another - complete with another hour meter.

3. The tractor does look reasonably low hour. However, if it has had a full rebuild, including new undercarriage, you wouldn't know if it has done 600 hours, 6000 hrs or 16,000 hours.
I can rebuild any tractor to make it look like it's low hour. All it takes is plenty of money.

4. The undercarriage sports extreme-service track shoes. ES shoes are designed for hard work in exceptionally abrasive conditions - such as very hard, very abrasive rock.

5. The military tractors rarely suffer from being worked to death - they suffer from neglect, being left out in the elements, and long periods of lack of use. Not the best way to treat valuable, complex machinery. Look for corrosion on the top of dipsticks, this is an indicator of more corrosion inside the major component - caused by sitting around unused for long periods.
Oil drains off surfaces it's meant to protect after as little as 2-3 months - and corrosion then sets in. I'd rather buy an expensive tractor that's been used regularly, rather than one that has sat unloved for multiple months, and even years.

https://www.machinerytrader.com/listings/construction-equipment/for-sale/24901529/cat-d7

Regards, Ron.

94N1-up to 5191 is a 73 year and with the 5192 they put in a 3306 engine according to my book. catskinner

This unit (of which I don't own yet) has 648 original hours. Looks like brand new other than heavily faded green paint. I might make an offer on it. Did those early transmissions have any good luck or did they all fail eventually? Also could they be updated at all to last longer?