RZX Posted December 31, 2013 Share Posted December 31, 2013 I have a 1979 R model with the serial number R686ST28431, could anyone tell me the specs on this ?Thanks, RZX Quote Link to comment Share on other sites More sharing options...
umodelnut Posted December 31, 2013 Share Posted December 31, 2013 R means its an R model, the 6 means its an R600, the 86 means it had a 300 Mack motor from the factory, the ST means tandem rear end. Then 28431 means its the 18431st R686ST made. You just subtract the number in the beginning by 1 because Mack began their serial numbers with 1.Someone will correct me if im wrong but I think I got it. Quote Link to comment Share on other sites More sharing options...
39 Baby Mack Posted December 31, 2013 Share Posted December 31, 2013 Pretty close VinnyMack starts their serial numbers at 1000.That make this the 27,431st one made.Everything else is correct.Ron 1 1 Quote Link to comment Share on other sites More sharing options...
umodelnut Posted December 31, 2013 Share Posted December 31, 2013 Oh crap. always screw that up. Thanks Ron! Quote Link to comment Share on other sites More sharing options...
james j neiweem Posted December 31, 2013 Share Posted December 31, 2013 Vinny.Looks like your going to be a Mack expert yet 1 Quote Link to comment Share on other sites More sharing options...
rickykarenpr Posted December 31, 2013 Share Posted December 31, 2013 I like register the serial number of my truck what link register my truck serial number??? Quote Link to comment Share on other sites More sharing options...
staxx Posted December 31, 2013 Share Posted December 31, 2013 . Here's the #1 natural gas truck vin Quote Link to comment Share on other sites More sharing options...
doubleclutchinweasel Posted December 31, 2013 Share Posted December 31, 2013 I have a 1979 R model with the serial number R686ST28431, could anyone tell me the specs on this ?Thanks, RZXA little more info...If I recall correctly, the "86" means the engine was the ENDT 676 Maxidyne, which I THOUGHT was the 285HP version. Of course, I might be looking too far back. Maybe by '79, it was a 300 (EM6-300?).As Vinny stated, the "S" means "tandem" (Six sets of wheels). Also, the "T" means it was originally built as a "Tractor". If originally equipped as a "platform" truck, it would have been an R686S, for instance.Somebody want to add to that engine bit? Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment Share on other sites More sharing options...
RZX Posted December 31, 2013 Author Share Posted December 31, 2013 Thanks for all of the replies, for some reason this R model has a double frame. I don't get this mix up, the serial number doesn't show it. Is this possible ? Thanks again, RZX 1 Quote Link to comment Share on other sites More sharing options...
doubleclutchinweasel Posted December 31, 2013 Share Posted December 31, 2013 The double frame is an option. It wouldn't show up in the serial number. Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment Share on other sites More sharing options...
RZX Posted January 1, 2014 Author Share Posted January 1, 2014 I'm new to this serial number stuff but I thought that a double frame would be indicated by a RD model. I have another question, are 44 rears visible by the cone shaped axle covers ? I'm starting to like this site!!! Quote Link to comment Share on other sites More sharing options...
doubleclutchinweasel Posted January 1, 2014 Share Posted January 1, 2014 I'm new to this serial number stuff but I thought that a double frame would be indicated by a RD model. I have another question, are 44 rears visible by the cone shaped axle covers ? I'm starting to like this site!!!The RD is actually a different model. An R could be ordered single or double framed. I suppose they would do a triple if you wanted! I've seen triple walled B80's.The cone shaped hub is indicative of a double splined axle. This axle shaft is splined on both ends. The hub in not attached to the axle. The hub is splined to mate to the axle. These are great axles.A 44K could be either flat hub (integral) or coned (splined). Some guys say the number of bolts in the hub indicate the size, but I'm not positive.The numbers off the axle housing or build sheet are better indicators. 1 Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment Share on other sites More sharing options...
RZX Posted January 1, 2014 Author Share Posted January 1, 2014 Thanks Bulldog, RZX Quote Link to comment Share on other sites More sharing options...
Maddog13407 Posted January 1, 2014 Share Posted January 1, 2014 cones on the axles were 38's an up. they were called ''full floating axles'' because the axle was splined on both ends. the 38's and up also had 58 inches bolts holding the cone on while most but not all of the 34's had smaller bolts. never really god the RD and R letters. the older heavy steel nose R models used to be RD's but when they went to the ugly slant nose hood in the earl 90's they called that an RD also. used to be years ago S means straight truck, X meanssingle axle heavy duty, SX meant tandem heavy duty, ST was six wheel tractor or Short tractor. I have seen S and ST's with double frames or single frames also. Quote Link to comment Share on other sites More sharing options...
doubleclutchinweasel Posted January 1, 2014 Share Posted January 1, 2014 Not to put too fine a point on it, but, technically, a "full floating" axle is any axle where the wheel hub is retained solely by the bearings, and not the axle.And, Mack's nomenclature for a straight truck was "platform", and was designated by the letter "P". This was very common on B models. But it wasn't used that much on the R. I do recall P designations on several R400 series trucks though...like an R401P, below. Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment Share on other sites More sharing options...
hicrop10 Posted January 2, 2014 Share Posted January 2, 2014 RZX,I have a 79 r model also.My serial # is 33171.My father brought 20 of them.Serial # starting with 33165-33184.I still have the orignal order sheet.It has 169wb,ENT676-300 series Maxidyne 285 hp.This is the last one we have left.This truck has only 72,000 orignal miles.I willpost a picture of it when I get home.We used them all for pullingdump trailers.I can remember crossing the bridge over into NJ weighing 113,000 taking a load to the landfill.The price we paid for each one was $44,904 that was with us supplying the tires.They gave us a tire credit of $1896 on each truck. 1 Quote Link to comment Share on other sites More sharing options...
hicrop10 Posted January 2, 2014 Share Posted January 2, 2014 Here is my 79 r model 1 Quote Link to comment Share on other sites More sharing options...
rickykarenpr Posted January 2, 2014 Share Posted January 2, 2014 I check tomorrow the serial number in my truck is recorded in the chassis Quote Link to comment Share on other sites More sharing options...
JTB7000 Posted August 6, 2022 Share Posted August 6, 2022 I found an old Mack truck with the serial number U659ST1081 ....any idea what model this might be? Quote Link to comment Share on other sites More sharing options...
tjc transport Posted August 7, 2022 Share Posted August 7, 2022 "U" model 1 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment Share on other sites More sharing options...
mechohaulic Posted August 8, 2022 Share Posted August 8, 2022 any pictures? i got the U-Umodel; got the 6-600 series; got the ST -twinscrew; 1081- vin with only 80 same made before it. what is a 59(659)? what yr? 1 Quote Link to comment Share on other sites More sharing options...
Popular Post 85snowdog Posted August 9, 2022 Popular Post Share Posted August 9, 2022 On 8/7/2022 at 10:28 PM, mechohaulic said: any pictures? i got the U-Umodel; got the 6-600 series; got the ST -twinscrew; 1081- vin with only 80 same made before it. what is a 59(659)? what yr? I see the poster that asked this question never came back . But I wanted to help shed a little more light on it for you . The first number 6 you got right . The 59 is the engine code . From my list from BMT , its a Cummins NHRS6B/320 . I honestly don't know what that is ,lol . Hopefully you can help in that department . You got everything else right , as far as I know . The ST at the end of the number means a little more than twin screw . The "S" means twin screw . The "T" means it was built to be a tractor . 4 Quote Keith Link to comment Share on other sites More sharing options...
Joey Mack Posted August 10, 2022 Share Posted August 10, 2022 (edited) It happens,,, and then 3- 24 months later,,,, You did your part.. always good to see you post.. jojo Edited August 11, 2022 by Joey Mack 2 Quote Link to comment Share on other sites More sharing options...
85snowdog Posted August 10, 2022 Share Posted August 10, 2022 A little more digging ......... If its a true " U659 " there was only 501 built in 1979 only . Thats it . So it could be pretty rare . 1 Quote Keith Link to comment Share on other sites More sharing options...
85snowdog Posted August 10, 2022 Share Posted August 10, 2022 1 minute ago, Joey Mack said: It happens,,, and the 3- 24 months later,,,, You did your part.. always good to see you post.. jojo Thanks Jojo , I don't stop in very often this time of year. I see your busy helping people . BMT is lucky to have you . I still wish you could come north , lol . I don't have a good Mack mechanic . Wish I did 😀 1 Quote Keith Link to comment Share on other sites More sharing options...
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