skydawg Posted March 17, 2022 Share Posted March 17, 2022 (edited) What sort of mileage could I hope to get w/ a light spec 1961 B61,S/A,END 673,Duplex direct,4.66 dual reduction rear axle,11x22.5 tires,bobtail only.I also could use an explanation of "Dual Reduction",as per the rear axle. Thank You. Edited March 17, 2022 by skydawg Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/ Share on other sites More sharing options...
Popular Post doubleclutchinweasel Posted March 17, 2022 Popular Post Share Posted March 17, 2022 (edited) The double reduction rear uses 2 sets of reduction gears. This eliminates common issues found with deep reductions through only one set of gears, namely the huge difference is size between the 2 gears. The smaller gear is always weaker. By using 2 sets of reduction gears in series, you get 2 stronger pairs of gears. in a typical 4:1 pair, for instance, you might have 10 teeth on the input and 40 on the output (just easy numbers, not real numbers). The 10-tooth will be weaker then the 40. But, if you do a 2:1 and then feed that output into another 2:1, you have 2 sets of gears that are closer in size to each other, and therefore stronger. Most of the S/A units I have seen have the first reduction set in front of the axle. But, I have seen a few with it on top, like the tandem versions. You can see the cross shaft cover on the side. Here is a little graphic for reference. The first reduction is similar to a regular spiral/bevel setup, and the second is more like a helical spur gear setup. Edited March 17, 2022 by doubleclutchinweasel 3 Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492467 Share on other sites More sharing options...
skydawg Posted March 17, 2022 Author Share Posted March 17, 2022 Wow,great explanation,thanks,Weasel! Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492469 Share on other sites More sharing options...
mowerman Posted March 17, 2022 Share Posted March 17, 2022 Generally anything back then got around 7 miles per gallon bobtail at .least that’s what I heard I have never done much Bob tailing…. Bob Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492471 Share on other sites More sharing options...
doubleclutchinweasel Posted March 17, 2022 Share Posted March 17, 2022 57 minutes ago, skydawg said: Wow,great explanation,thanks,Weasel! You are quite welcome. BTW, my '70 R600 with 1:1 high gear, 4.17 rears, and an ENDT-673C got about 10 MPG bobtailing, as long as I kept it down to 50-55 or so. If I tried to go 60, it dropped to about 8 pretty quickly. Of course, I was babying it. Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492476 Share on other sites More sharing options...
mowerman Posted March 17, 2022 Share Posted March 17, 2022 i hadda 1970 chevy 4by 4 in the 70s mileage was terrible 350 2 barrel...7 mpg.lol.bob Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492483 Share on other sites More sharing options...
67RModel Posted March 17, 2022 Share Posted March 17, 2022 12 minutes ago, mowerman said: i hadda 1970 chevy 4by 4 in the 70s mileage was terrible 350 2 barrel...7 mpg.lol.bob Gas was probably like 25 cents per gallon prior too the "energy crisis" during that time Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492487 Share on other sites More sharing options...
mowerman Posted March 17, 2022 Share Posted March 17, 2022 Yes sir in fact I drove that very truck all the way from Massachusetts to Southern California I think it cost me 250 bucks. Bob Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492489 Share on other sites More sharing options...
mowerman Posted March 17, 2022 Share Posted March 17, 2022 That was in 1978 Think it was around $.65 I am not sure if it was certainly a lot cheaper than it is now… bob Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492491 Share on other sites More sharing options...
Popular Post doubleclutchinweasel Posted March 17, 2022 Popular Post Share Posted March 17, 2022 I still remember how we drove fuel prices down after the first "shortage". We started pumping oil out of the ground here, and all of a sudden, there was plenty of foreign oil at reasonable prices. Time to do it again! Sorry. I try to avoid the political commentary. I won't do that again. Promise! 3 1 Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492496 Share on other sites More sharing options...
HarryS Posted March 17, 2022 Share Posted March 17, 2022 I get just over 12 mpg with '60 B-61 S/A, 673 N/A, duplex od, 4:25 axle and 10:00x20 tires. Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492497 Share on other sites More sharing options...
mowerman Posted March 17, 2022 Share Posted March 17, 2022 (edited) Kind of hard to keep your mouth shut when nobody was doing anything about it. Bob Edited March 17, 2022 by mowerman Misspell Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492500 Share on other sites More sharing options...
mowerman Posted March 17, 2022 Share Posted March 17, 2022 High paying Private sector jobs paying taxes win win situation Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492501 Share on other sites More sharing options...
mowerman Posted March 17, 2022 Share Posted March 17, 2022 Kind of funny how some of these treads turn into something completely different but then again he was concerned about his mileage… bob 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492502 Share on other sites More sharing options...
mowerman Posted March 17, 2022 Share Posted March 17, 2022 As I mentioned I don’t use much of it and it doesn’t affect me but I am concerned about my fellow man… bob Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492503 Share on other sites More sharing options...
High Binder Posted March 17, 2022 Share Posted March 17, 2022 I've been around a while but when I was a kid, my friend and his brother had a Cushman scooter with a gallon tank on it. We would pool our pennies and buy 10 cents worth of gas, which would almost fill the tank, and we would ride around town all day. The garage mechanic, who also pumped the gas, would get so mad because he would have to stop working on a vehicle and pump 10 cents worth of gas. Gas was around 14 cents a gallon. I would love to have that scooter now. It would be worth more than my car. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492509 Share on other sites More sharing options...
mowerman Posted March 17, 2022 Share Posted March 17, 2022 A buddy of mine has one for sale it’s in San Diego 40 something Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492510 Share on other sites More sharing options...
mowerman Posted March 17, 2022 Share Posted March 17, 2022 (edited) I have a snapshot of it and a video clip can’t figure out how to get either one of them on here sorry… bob Edited March 17, 2022 by mowerman Missing word Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492511 Share on other sites More sharing options...
Mike Harbison Posted March 20, 2022 Share Posted March 20, 2022 I would get 10 to 10.5 mpg with my 65 twin screw ,711 with a 18 speed Quad and 5:73 rears,going to Walcott pulling my empty 46 LaCrosse lowboy and i did bobtail it to the ATHS convention in Milwaukee. I thought that was pretty good considering i had my foot on the floor most of the time,2000 to 2150 all the time. Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492741 Share on other sites More sharing options...
63BMack Posted March 20, 2022 Share Posted March 20, 2022 Going to Walcott I got 11mpg B61, 300+, 13 speed Overdrive roadranger, 3,87 rears, twin scew. Put a trailer on it and drops down considerably. Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492763 Share on other sites More sharing options...
hicrop10 Posted March 20, 2022 Share Posted March 20, 2022 My 64 B87 with a 335 Cummins would only get 3-5 miles per gallon.We would pull the lowboy with D8’s or D9’s from Philadelphia to Allentown which was no more then 200 miles and we would have to fuel up when we got back to Philadelphia.That was running loaded one way. Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492787 Share on other sites More sharing options...
mechohaulic Posted March 21, 2022 Share Posted March 21, 2022 On 3/17/2022 at 1:04 PM, doubleclutchinweasel said: I still remember how we drove fuel prices down after the first "shortage". We started pumping oil out of the ground here, and all of a sudden, there was plenty of foreign oil at reasonable prices. Time to do it again! Sorry. I try to avoid the political commentary. I won't do that again. Promise! don't know if I would call it a political comment ; more like speaking the truth and we all know politicians don't do that. and to stay on topic;; more oil means better mileage. I know = best i can do 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492811 Share on other sites More sharing options...
Freightrain Posted March 21, 2022 Share Posted March 21, 2022 My 673, 4.64 triplex would get 9 bobtail. Around 8 with my 14k trailer. This is right up at 2100 rpm. I did have the pump rolled up a couple flats. I had it really up and got 4 mpg! Once fuel hit $4/gal about 10 yrs ago I moved it back to get better mileage again. My 237, 4.10 gets similar mileage pulling my trailer. Just doesn't slow down on the hills like the 673 did. I do run it at 1800 rpm at 65 mph. 1 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/69395-b61-mpg/#findComment-492847 Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.