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1971 Dm600 With 13 Speed Roadranger


Olivetroad
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I am a farmer in Missouri and I have a 1971 DM600 that I use for a log hauling truck. That is one tough truck! The engine started knocking today and I need to rebuild or get a replacement engine. The plate on the door reads that it is a model DM607S and the serial number is 6712. The truck has a 13 speed Roadranger transmission which looks newer. The build sheet for the truck reads that the engine is a END673E Thermodyne. But the engine has a turbo and my book reads that the END673 was non-turbo. The engine has rebuild plates on the side with depot numbers so I think the truck started out in life as a military truck (the olive green paint helps as well). The plate reads that the engine serial number is 4K4485. There are raised letters on the block which read: 288GB5320A. There is also a plate on the drivers side firewall inside the engine compartment that reads: U-24688. My questions are: What model engine is this so I can find a replacement? Also, is the transmission original? If not, will a replacement engine bolt up to it or did they have to modify things to use that transmission? Does anyone have a good used engine? Thanks in advance for your help! Check out the photo that I included of the Mack hauling some pallet logs - can you find the white cat on top of the load?

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I am a farmer in Missouri and I have a 1971 DM600 that I use for a log hauling truck. That is one tough truck! The engine started knocking today and I need to rebuild or get a replacement engine. The plate on the door reads that it is a model DM607S and the serial number is 6712. The truck has a 13 speed Roadranger transmission which looks newer. The build sheet for the truck reads that the engine is a END673E Thermodyne. But the engine has a turbo and my book reads that the END673 was non-turbo. The engine has rebuild plates on the side with depot numbers so I think the truck started out in life as a military truck (the olive green paint helps as well). The plate reads that the engine serial number is 4K4485. There are raised letters on the block which read: 288GB5320A. There is also a plate on the drivers side firewall inside the engine compartment that reads: U-24688. My questions are: What model engine is this so I can find a replacement? Also, is the transmission original? If not, will a replacement engine bolt up to it or did they have to modify things to use that transmission? Does anyone have a good used engine? Thanks in advance for your help! Check out the photo that I included of the Mack hauling some pallet logs - can you find the white cat on top of the load?

Sounds like it's been converted to a ENDT673. If I remember correctly the number you see on your block is only the casting number. Try looking on the right (passenger) side of the engine just behind the fuel pump for an engine data tag. That tag should have a number starting with 11GB. That will be the engine assembly number. Another tag should be on the fuel pump. This tag will give the fuel pump part number and it should be possible to find what engine that pump is for.

"Mebbe I'm too ugly and stupid to give up!"

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Might be pretty hard to find an exact replacement, you need to find a good 237 or also called a T675 engine, will fit right in there. Terry

I found a used 1981 EM6 237 engine. Will they bolt in to my truck or does it take a lot of work to make them fit? Just to look at it, the only real thing I see different is that the 237 has the turbo lower on the side of the engine instead of on top on the 673. The EM6 also was in a firetruck with a Allison automatic. Will that be the same bolt pattern as my Roadranger 13 speed has?

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Can't tell you for sure on the front mount, you should be able to compare them to see if they interchange, as for the flywheel housing, if the automatic one is different the one on the old engine MIGHT fit, if not it should not be to difficult to find one that will. Terry

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I would find the source of the knock, then decide what to do.

What is the destination of that load of logs?

FW

I am a farmer but I also own a tree and crane service and we used to just pile up and burn or let rot all the junk logs we bring home. But we found a couple of sawmills not too far away in a Amish community that will buy ANY logs for pallets and blocking. I never in my life thought that someone would buy elm, box elder, locust, hackberry, or any other junk wood! What used to be a waste is now a good deal. We haul a couple loads a week to them and while they do not pay a lot (24 cents a board foot), it is a nice extra check each week. The load in the photo was 2992 board feet but I have had on as much as 4100 feet on a load with some good straight 40 inch diameter logs. The more you load that old Mack, the better it drives and pulls.

I started the Mack yesterday and it ran without any knock I could hear, but it vibrates like it is missing on one cylinder. I did a temperature check on the exhaust manifold and the exhaust for the #1 cylinder never warmed up like the other five did. I pulled the oil pan and there are not any large chunks of metal but there are some small flakes like bearing wear. We turned the engine over and there is compression coming into the bottom of the engine from the #1 cylinder. I took off the valve cover and everything there checked out okay. I think a ring broke on the #1 cylinder and got on top of the piston. This morning I am going to pull the bearings on the #1 cylinder and see what damage I find. I think I am going to pull the engine and replace it with a used 237 I found. I just wonder if it will bolt in place. I called a Mack dealer and he said it would as long as it does not have an aluminum front cover on the engine. This one does not so I hope it fits.

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