Strutter Posted January 3, 2012 Share Posted January 3, 2012 New to the trucking world, but I'm looking at buying a tandem Mack dump 18 yd. Truck. It has 190,000 original miles. They are asking 22,500. It is in very good condition and it has a 350 hp e7 engine, with a 9 speed trans. Beside hauling dirt, it will primarily be used to haul a 650j dozer and possibly a 160lc John Deere excavator, the excavator being the heaviest(35,000-38,000). My question is would this be a good buy and do you think it would pull the excavator fine with the tag trailer..? Thanks for ya'lls help. All opinions are appreciated Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/ Share on other sites More sharing options...
mowerman Posted January 3, 2012 Share Posted January 3, 2012 ya thats a fare price,maybe a little high,in good shape,and yes thats a good strong engine...good luck.bob 1 Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96617 Share on other sites More sharing options...
David Posted January 3, 2012 Share Posted January 3, 2012 Welcome. In country as flat as Louisana, you could pull both the dozer and the excavator at the same time with the 350. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96619 Share on other sites More sharing options...
Strutter Posted January 3, 2012 Author Share Posted January 3, 2012 ya thats a fare price,maybe a little high,in good shape,and yes thats a good strong engine...good luck.bob Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96622 Share on other sites More sharing options...
cgallamore Posted January 3, 2012 Share Posted January 3, 2012 If it's been maintained properly, you couldn't find any thing better for the application you described 1 Quote http://www.bigmacktrucks.com/uploads/1272400769/gallery_4852_794_314995.jpg Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96628 Share on other sites More sharing options...
Strutter Posted January 3, 2012 Author Share Posted January 3, 2012 Thanks guys, Here's the website for the truck, if y'all would like to take a look. I may have been off a few on the mileage, but this is it, you can tell they gave her a little paint job too. http://m.mnltrucksales.com/List/Trucks/ForSale/3239543 Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96634 Share on other sites More sharing options...
cgallamore Posted January 4, 2012 Share Posted January 4, 2012 Very good looking truckThings I notice from pictures, not trying to nock the truck Apears to be converted tracterGears may be wrong for dump truck, especially with 9spd overdrive trans373 gears with that trans and tall rubber will be a posWheel base a bit short, to much tail hangover, will have to load on cabshield and nothing against tailgate to get enough on steer to be leagleSorry but I'm not a big fan of putting a dump bed on a road tractor Quote http://www.bigmacktrucks.com/uploads/1272400769/gallery_4852_794_314995.jpg Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96661 Share on other sites More sharing options...
convoyduel Posted January 6, 2012 Share Posted January 6, 2012 A "690" would have come from the factory with a 300hp engine or under, unless the engine had to go through a special engineering review. I custom ordered a 355/380 Maxi-Cruise in my '02 RD and it came out as a 690 instead of a 688 as a result. Should have never sold that truck. Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96862 Share on other sites More sharing options...
Strutter Posted January 6, 2012 Author Share Posted January 6, 2012 A "690" would have come from the factory with a 300hp engine or under, unless the engine had to go through a special engineering review. I custom ordered a 355/380 Maxi-Cruise in my '02 RD and it came out as a 690 instead of a 688 as a result. Should have never sold that truck. If you don't mind convoy, take a look at the link at tell me what you think about it. Thanks man. Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96926 Share on other sites More sharing options...
Lmackattack Posted January 6, 2012 Share Posted January 6, 2012 Like mentioned the only issue I see is that the gearing for the mud is not perfect. the 9 speed is more of an on road transmission. I have driven many in the dirt and they will go in and out just fine but if you are stopped and have to start in the think muck first gear is a little fast and is hard ont the clutch. it also lacks a selection of reverse gears but you can get over that....If you do alot of highway it will be fine. Alot of guys put in a 8LL for dump truck and highway. as far as the rest of the truck the double frame is good unless you run in alot of salt. rears and front axel are bullit proof . engine is good and a simple truck to work around if you have basic tools. Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96928 Share on other sites More sharing options...
Superdog Posted January 7, 2012 Share Posted January 7, 2012 A "690" would have come from the factory with a 300hp engine or under, unless the engine had to go through a special engineering review. I custom ordered a 355/380 Maxi-Cruise in my '02 RD and it came out as a 690 instead of a 688 as a result. Should have never sold that truck.The way it was explained to me,under the new,modern & "improved" numbering system,a "690" was a Maxidyne engine,and a "688" was an Econodyne engine.Evidently the Maxi-Cruise engines are in the Maxidyne family. Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96941 Share on other sites More sharing options...
convoyduel Posted January 7, 2012 Share Posted January 7, 2012 It doesn't look bad, but i agree that converted tractors rarely make good dump trucks. There are so many reasonably priced used dump trucks that I wouldn't pay good money for a road tractor conversion, even if it is a Mack. When you order one from scratch, it becomes apparent in just how different a properly spec'd dump truck is from a road tractor. Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96953 Share on other sites More sharing options...
slpwlker Posted January 7, 2012 Share Posted January 7, 2012 I agree on the tractors after watching the yo-yo's in miami. But La,Ms,and Tx got funky weight laws. I don't think that truck would ever get a work out until it pulls the excavator. Probably only gross 43 to 54k Alot of those roads in Ms they got 58k and change weight limits on 5 axle. Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-96970 Share on other sites More sharing options...
randyp Posted January 9, 2012 Share Posted January 9, 2012 Fellow Mackanians, please enlighten or correct me if Im wrong. but is it possible to tell by model or VIN number if a truck is a converted road tractor or a dedicated original dump truck? Is there something bout the last 2 letters? For example R688ST or R688S? Im just curious. My 86 is a R686ST, and am looking at buying another that is also a ST. Input greatly appreciated,,,thanks,,,randyp Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-97223 Share on other sites More sharing options...
David Posted January 9, 2012 Share Posted January 9, 2012 Randy, I don't know about the letters, but I would be looking to see if the frame has been streched, is it a factory double, and any hole without bolts? Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-97251 Share on other sites More sharing options...
convoyduel Posted January 9, 2012 Share Posted January 9, 2012 S means dual drive. T means tractor, but it can be applied to a straight truck with a tractor protection valve package. There will be obvious remnants for a tractor application, including the bolt holes for the 5th wheel mount, possibly a TPV behind the cab at the lower rear cab wall, a tapered end of frame and an electrical plug somewhere near the rear of the cab. A cab and chassis shipped from the factory will also have an "incomplete vehicle" sticker in the door jamb near the other federal stickers. May be gone over the years, but it would have been there if shipped without a 5th wheel. Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-97259 Share on other sites More sharing options...
randyp Posted January 9, 2012 Share Posted January 9, 2012 Okay, many thanks gentlemens,,,,randyp Quote Link to comment https://www.bigmacktrucks.com/topic/22455-1992-rd690s/#findComment-97263 Share on other sites More sharing options...
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