New to me D8H

I just signed the papers on a 1971 D8H today. Has completely new undercarrige, including pads, papers on a Cat engine rebuild less than 200 hours ago, papers on one rebuilt final drive, service records for that past few years, has a cab w/ A/C, 3 shank parralell ripper, and a 14' Balderson U blade.

Looking for any tips and tricks that will help make this a long-lived reliable farm Cat. Any known weak areas to keep an eye on? Anything to do or not to do to it?

I will be using the ripper a little in the spring and it currently has one tooth. Any reason not to get one or two more? I have heard these vintage of cats break or work loose the transmission mounts when heavy ripping - any truth to this? If so, one tooth will do just fine...

Find a straight blade and lose the U blade. Too much weight for what you need. Look for cracks in the frame. Transmissions do work loose for a number of reasons. Check yours to make sure it's tight. If you're ripping clay, no problem. If rock, you won't be using 3 shanks. Check all the transmission screens for debris. Change the transmission filters. Pull the final fill plugs and see if any oil comes out to verify pinion seals are not leaking. Check the final filters for debris. Test the coolant. Are there guards on the hydraulic hoses going to the blade cylinders. There's an update for the cross tube that helps prevent an oil fire if you break a hose. The hose guards are a part of the update. Keep the belly pans clean. Grease the u-joint between the T/C and transmission. If you're working in the hills, run the transmission 5 gallons overfull. Never allow the engine to overheat. Obtain a manual and learn how to grease the water pump and idler sparingly. That should get you started in no particular order.

If you don't have an Operation & Maintenance Manual, get one. The best investment you are ever likely to make.
They can be downloaded from Cat for less than $50.

Its true alright , one on a farm next door broke its rear housing ripping , ruin your whole day doing that .

Daniel Davis said:

I just signed the papers on a 1971 D8H today. Has completely new undercarrige, including pads, papers on a Cat engine rebuild less than 200 hours ago, papers on one rebuilt final drive, service records for that past few years, has a cab w/ A/C, 3 shank parralell ripper, and a 14' Balderson U blade.

Looking for any tips and tricks that will help make this a long-lived reliable farm Cat. Any known weak areas to keep an eye on? Anything to do or not to do to it?

I will be using the ripper a little in the spring and it currently has one tooth. Any reason not to get one or two more? I have heard these vintage of cats break or work loose the transmission mounts when heavy ripping - any truth to this? If so, one tooth will do just fine...

Click to expand...

Check Break said:

Find a straight blade and lose the U blade. Too much weight for what you need. Look for cracks in the frame. Transmissions do work loose for a number of reasons. Check yours to make sure it's tight. If you're ripping clay, no problem. If rock, you won't be using 3 shanks. Check all the transmission screens for debris. Change the transmission filters. Pull the final fill plugs and see if any oil comes out to verify pinion seals are not leaking. Check the final filters for debris. Test the coolant. Are there guards on the hydraulic hoses going to the blade cylinders. There's an update for the cross tube that helps prevent an oil fire if you break a hose. The hose guards are a part of the update. Keep the belly pans clean. Grease the u-joint between the T/C and transmission. If you're working in the hills, run the transmission 5 gallons overfull. Never allow the engine to overheat. Obtain a manual and learn how to grease the water pump and idler sparingly. That should get you started in no particular order.

Click to expand...

Lots of good stuff here. Any particular area to look for cracks?

How many transmission screens are there? Can they be checked with oil in transmission or do I need to drain it first?

The lift hoses do not have guards, but a friend that works at Cat told me about them and thought Cat will do the upgrade for free. We will see.

Why is the U-balde too heavy? What little I have driven it the Cat seems to have good balance and the U-blade will be great for one of our irrigation projects.

Nige said:

If you don't have an Operation & Maintenance Manual, get one. The best investment you are ever likely to make.
They can be downloaded from Cat for less than $50.

Click to expand...

The owner supposedly has a full set of books that come with it.

epirbalex said:

Its true alright , one on a farm next door broke its rear housing ripping , ruin your whole day doing that .

Click to expand...

Hmm, I think I will just stick with one tooth. Same me $3K a piece anyways.

When you get it, check all the fluid levels and then just go run it. Any problems will shake out and you can fix them as they occur.

frame rails were prone to cracking just in front of the hard bar crossmember. when crossing dirt ridges, etc. don't let the front end slam down- ease it down

Any particular area to look for cracks?
Check the outside of the frame from the back of the hard nose to the ripper. On another note, if CAT did the engine rebuild, they should have built up the frame under the rear engine mounts where it naturally wears. It would be a good idea to look to see that the mounts are sitting on the top of the frame and not down in a hole worn into the frame. This affects alignment with the transmission.

How many transmission screens are there? Can they be checked with oil in transmission or do I need to drain it first?
The H-s had three screens. One under the seat, one next to the filter body and one up front next to the cooler. A better design than the K if you ask me which only had two. When the H transitioned into the K, the third screen got lost in the upgrade. I believe the screen upgrade was made later than 1971 but don't remember and don't have reference material at my location.

The lift hoses do not have guards, but a friend that works at Cat told me about them and thought Cat will do the upgrade for free. We will see.
CAT used to do this upgrade for free as it's cheaper than relitigating the matter. I wouldn't take no for an answer. Your problem is going to be finding someone in the shop who is old enough to know what you're talking about.

Why is the U-balde too heavy? What little I have driven it the Cat seems to have good balance and the U-blade will be great for one of our irrigation projects.
Perhaps it's just personal preference. The U blade works well pushing gravel in a quarry. If your irrigation project includes a dam, it will hog out a lot of dirt. If you're going to be driving around ripping flat ground, that's a lot of weight to be hanging off the hard nose all day long. A 14' blade requires permits and pilot cars to move. You can take the corner bits off a straight blade and stay under 12'. Back to personal preference. If that U blade has been hanging there for 50 years and the frame, cross tube and hard nose don't have any cracks, and you like it, then there's no reason to waste money changing it out.

Hmm, I think I will just stick with one tooth. Same me $3K a piece anyways.
Two will add more balance and it's a great way to move weight from the seat (your pocket) to the rear of the tractor.

Check Break said:

Any particular area to look for cracks?
Check the outside of the frame from the back of the hard nose to the ripper. On another note, if CAT did the engine rebuild, they should have built up the frame under the rear engine mounts where it naturally wears. It would be a good idea to look to see that the mounts are sitting on the top of the frame and not down in a hole worn into the frame. This affects alignment with the transmission.

How many transmission screens are there? Can they be checked with oil in transmission or do I need to drain it first?
The H-s had three screens. One under the seat, one next to the filter body and one up front next to the cooler. A better design than the K if you ask me which only had two. When the H transitioned into the K, the third screen got lost in the upgrade. I believe the screen upgrade was made later than 1971 but don't remember and don't have reference material at my location.


Why is the U-balde too heavy? What little I have driven it the Cat seems to have good balance and the U-blade will be great for one of our irrigation projects.
Perhaps it's just personal preference. The U blade works well pushing gravel in a quarry. If your irrigation project includes a dam, it will hog out a lot of dirt. If you're going to be driving around ripping flat ground, that's a lot of weight to be hanging off the hard nose all day long. A 14' blade requires permits and pilot cars to move. You can take the corner bits off a straight blade and stay under 12'. Back to personal preference. If that U blade has been hanging there for 50 years and the frame, cross tube and hard nose don't have any cracks, and you like it, then there's no reason to waste money changing it out.

Click to expand...

Cat did not do the rebuild. It was done by the owners in their shop with Cat parts. Same with the undercarriage and final drive. They run a couple D9's and D10's and do all their own work so I think they know their way around Cats. This was their last flat track Cat and they let it go because they bought another D10.

Our irrigation project requires hogging out about 50K yards of material out of the lakeshore to get down to the low water mark, installing 400 feet of concrete pipe into a pair of 40' tall 12' diameter concrete sumps, and then backfilling the 40' cut. I think the U-blade will be preferred for this work. As for hauling, farmers in Montana can get away with just about anything. We can be up to 16' wide with "farm equipment" without even having a permit.

We will look for cracks and check all the screens for sure.

I was last through your area in 2004 when my FIL passed. Sounds like Californication has not reached you yet. 16' Friendly and No WOTUS.

Check Break said:

I was last through your area in 2004 when my FIL passed. Sounds like Californication has not reached you yet. 16' Friendly and No WOTUS.

Click to expand...

We are lucky that it's not worse than it is for sure. We have been working on the irrigation project for almost 4 years now doing a full blown Enviornmental Assesment, but we are making progress.

I prefer the U blade. Just my opinion

A U blade works great when you have a four barrel ripper with two shanks on the back. A straight blade works great when pioneering road or working a lot of hard rock and has something like a winch on the back. Each has its place.

Got it in the shop to give it a once over. Drained the final oil, it looked good. A little silver on one side, but no chunks. I have heard that I may need to bleed the pump and filters when I refill with oil. Is this true? If so, how do I go about doing it?

Also, the Serial number on the rear of the tractor is 46A25696. Just out of curiosity, what year does this decode to?

Second, there is a number stamped on the lower left rear of the block that is 17375. Is this the engine serial number? The reason I ask is that by the tractor serial number I thought it should have the later scroll injection pump but this tractor has the older pump. Maybe an engine swap at some point? Just wondering for future reference in case I need to order parts.

My info shows the machine is a model year 1971. If the engine number holds per regular machine numbers it is a model year 1968. Generally if all you have done is drain the final drive oil and refilled it, the final drive pump will not have lost a prime. I've only worried about priming when I rebuild a final or installed a new pump.

Got the oil analysis back for the right final drive (which is the new one). Everything was good except silicon, which was at 111 PPM. obviously getting some dirt in it from somewhere. For some reason the left final analysis hasn't come back yet (sent in at the same time) but I am really worried about it now. I cut the filter open from both sides and found a little shiny in the right filter as I would expect on a rebuilt gearbox but the left final filter looked like it had fine sands in the pleats.

Where should I look for dirt getting into the finals? Just the air vents? Should I replace the vents? The finals have no leaks...

The right final could have had a little contamination at time of rebuild. Better to drain and replace filter and sample it again after 200 hours. The left final filter may be decades old. Is there a date on it. The stuff you see in the filter could have come from the final drive covers. Unless the sample shows she's coming apart, service and resample in 200 hours.

Daniel Davis said:

Got the oil analysis back for the right final drive (which is the new one). Everything was good except silicon, which was at 111 PPM. obviously getting some dirt in it from somewhere. For some reason the left final analysis hasn't come back yet (sent in at the same time) but I am really worried about it now. I cut the filter open from both sides and found a little shiny in the right filter as I would expect on a rebuilt gearbox but the left final filter looked like it had fine sands in the pleats.

Where should I look for dirt getting into the finals? Just the air vents? Should I replace the vents? The finals have no leaks...

Click to expand...

If you have any doubts whatsoever, replace the breathers for the final drive cases. The Part Number was 8S-5820, but now 9G-5127 will also fit. IIRC they're not particularly expensive, about $10 or so each.

The SOS numbers for that final drive allow up to 50ppm silicon @ 1000 oil hours before it goes into the "Action Required" category. This particular compartment is inherently "dirty", just bear that in mind.

The left final came back at 40 PPM on the silicon and everything else was good.

Thanks for the breather part numbers, will order them tomorrow. Might not need them, but a few dollars just to be sure is worth it in my opinion.

"normal" silicon at 1000 hours on the oil is 0-40 ppm. Monitor compartment 40-50, Action Required above 50.
So even the other side was right at the top end of the normal range.