Popular Post dayradebaugh Posted June 1, 2019 Popular Post Share Posted June 1, 2019 Truck pictured is a B81SX that I repowered w/237. Has a quad box. Just getting it back on the road after couple of years storage. She's low-geared; have forgotten the final ratio, but the best she'll do is about 45 mph, 5th gear HI range. Question: Can I drive this thing using just using 5-speed main box, with compound in LO or Direct safely, that is, without putting too much torque on the tranny-clutch during shifts, or should I split? Thanks Day Radebaugh 4 Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/ Share on other sites More sharing options...
dayradebaugh Posted June 1, 2019 Author Share Posted June 1, 2019 Thanks very much. Original engine was, as I recall, ENDT 673 turbocharged. When I did engine switch (it's been about 10 yrs) there was talk about the 237 supplying more torque at lower RPM than the original, and that I ought to be especially careful not to lug it down. Going to teach my son-in-law to drive it, and wanted to start him out on just main box. Truck normally not loaded, and I fully agree with your suggestion. Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424174 Share on other sites More sharing options...
dayradebaugh Posted June 1, 2019 Author Share Posted June 1, 2019 I appreciate the suggestion. I'm in Kansas, and this unit came from the East Coast somewhere. Pulling an end dump I imagine, since at one time it had a 5th wheel, I'm told. Has triple frame, outer layer of which was rotted, so I replaced that, rewired, new paint, had cab redone, new brakes and tires, then installed the Holmes 750. Wouldn't mind having a higher top end, setting aside the fact that I'd hate to have to stop the truck at those speeds, but so it goes. What would I look for to replace the pumpkins? Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424181 Share on other sites More sharing options...
Freightrain Posted June 1, 2019 Share Posted June 1, 2019 With said slow gearing, skipping gears is fine. With mine I try to keep it above about 1400 on a hard pull(with my trailer). Below that the old triplex starts complaining! You'll feel it start to thump and that's tough on these single countershaft boxes. Bet you can start in 3rd low, 4 lo, then split it up a few. I only need 2 lo when starting with my trailer. I have 4.10 gears out back. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424186 Share on other sites More sharing options...
JoeH Posted June 2, 2019 Share Posted June 2, 2019 We call them pumpkins. Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424188 Share on other sites More sharing options...
dayradebaugh Posted June 2, 2019 Author Share Posted June 2, 2019 Many thanks, guys. This thing is so low-geared that it certainly makes sense to just shift the main box, or even skip gears. There is a very good truck boneyard and parts warehouse out west of Wichita called Southwest Truck Parts, and I'm betting they'll either have it, or know someone else who does. I'll shoot a pic of the differential housings tomorrow and put it up. Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424202 Share on other sites More sharing options...
JoeH Posted June 2, 2019 Share Posted June 2, 2019 Our dm686sx used to top out at 47, dad ran it for 15 years that way then it dropped a bearing in one of the differentials so I made him buy a junk yard pair that'd do 60+. Was much better to drive after that, except for the 20k steer axle that felt like you were riding a brick down the road... There's only two highways around us that we drive on and they're both 55mph. We don't need more than 65. Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424214 Share on other sites More sharing options...
dayradebaugh Posted June 2, 2019 Author Share Posted June 2, 2019 Sorry for the quality of these pix, but it's dark under there. 1. Looking at front diff from ahead of axle rear diff, sho 2. Going into rear diff 3. Looking up at rear diff carrier cover from below The immediate problem I see is getting these chunks in and out without taking the bed off. Many thanks. Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424271 Share on other sites More sharing options...
dayradebaugh Posted June 2, 2019 Author Share Posted June 2, 2019 If I had X-ray vision, I'd guess that the bogies look like this, also from BMT website. This tells me right away how I would do the switch. Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424272 Share on other sites More sharing options...
dayradebaugh Posted June 3, 2019 Author Share Posted June 3, 2019 This is getting interesting. I'll get those numbers off the rear diff housing tomorrow. 8.27:1 rings a bell from long ago. This truck must have done the real heavy lifting. I was a much younger man when I spent a summer mounting and drilling the holes in the new 3rd frame member from the inside out with a 1/2" Makita drill. I certainly know the cribbing routine; I had the Holmes 750 all cribbed up as I restored that monster, see below. I live in oil field territory in Kansas, and the local oil field guy brought his big old tandem out to lift the bed onto the truck. On the left of the picture, I'm getting the Mack positioned to drive under the bed after the crane on the tandem hooks up and lifts it up. That was exciting. Here's another of the finished truck. Only thing left to do is hook up the 750 to the Mack PTO. Here's the inside: Truck had been sitting for 2 yrs. unused. Went out Friday and, after charging the batteries, she fired right off. Had to give it just a little snort of ether, but after that she primed up and got going. Thanks much. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424281 Share on other sites More sharing options...
dayradebaugh Posted June 3, 2019 Author Share Posted June 3, 2019 It was a lot of fun. All my buds came down and helped out. Measured that bed and where it would sit on the Mack about a thousand times. Notice the fender skirts and flares we installed. Replaced those rubber flares with stuff that wasn't floppy, and turned out very well. The stripes on the back end were all hand done by the painter, a young kid. I was pretty impressed. Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424294 Share on other sites More sharing options...
dayradebaugh Posted June 3, 2019 Author Share Posted June 3, 2019 Here's my rig up truck: Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424295 Share on other sites More sharing options...
mowerman Posted June 3, 2019 Share Posted June 3, 2019 Wow nice looking ride thanks for sharing always liked those steel nose B models as a kid in the 60 s there was allot of them..in construction...bobSent from my iPhone using Tapatalk Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424300 Share on other sites More sharing options...
dayradebaugh Posted June 3, 2019 Author Share Posted June 3, 2019 That old deuce, pound for pound, is the hardest working truck I've got. You're right; you don't need that winch or gin poles every day, but when you do it does the job. Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424311 Share on other sites More sharing options...
dayradebaugh Posted June 3, 2019 Author Share Posted June 3, 2019 Rob: Numbers off the rear diff housing are: IQFA5477 SWD 592 Thanks Day Below I'm loading up my '35 Diamond T 211 on my '80 Autocar rollback. A'nd the '21 Seagrave firetruck up there too. AC14 Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424373 Share on other sites More sharing options...
dayradebaugh Posted June 4, 2019 Author Share Posted June 4, 2019 Rob: What options would I have to change out the carriers? What should be on my shopping list? Would this website be a good way to look for them? Thanks Day Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424387 Share on other sites More sharing options...
dayradebaugh Posted June 4, 2019 Author Share Posted June 4, 2019 Rob: Transmission, right side: 4KB 5122A Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424450 Share on other sites More sharing options...
dayradebaugh Posted June 4, 2019 Author Share Posted June 4, 2019 Sorry Right side 4KB 5122A LFC 4 24 66 Left side rear Part no 281KB531 Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424451 Share on other sites More sharing options...
Rob Posted June 4, 2019 Share Posted June 4, 2019 Hi Day; I'm looking for a number such as TRQ7220 or just Q7220 or something along those lines. The 4 24 66 I believe means the transmission case was either cast, (if raised), or manufactured, (if stamped) on that date. Either way it appears to be a replacement transmission. Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424453 Share on other sites More sharing options...
dayradebaugh Posted June 4, 2019 Author Share Posted June 4, 2019 I'll try again tomorrow. Where should I expect to see these numbers? Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424459 Share on other sites More sharing options...
Rob Posted June 4, 2019 Share Posted June 4, 2019 Should be on the left side of the main case. About centered. The numbers will be hand stamped; not cast into the case. Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424461 Share on other sites More sharing options...
dayradebaugh Posted June 4, 2019 Author Share Posted June 4, 2019 Many thanks. Tranny is pretty clean, and does not appear to leak much. I'll scrub it up and find them. Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424462 Share on other sites More sharing options...
Rob Posted June 5, 2019 Share Posted June 5, 2019 (edited) What size are the tires? Look to be 11X24 from the photos earlier. Edited June 5, 2019 by Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424472 Share on other sites More sharing options...
terry Posted June 5, 2019 Share Posted June 5, 2019 1 hour ago, Rob said: Should be on the left side of the main case. About centered. The numbers will be hand stamped; not cast into the case. Should be right behind the fill plug. terry Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424475 Share on other sites More sharing options...
dayradebaugh Posted June 5, 2019 Author Share Posted June 5, 2019 Many thanks for the suggestions, guys, otherwise I wouldn't have found the numbers. They are: TR 7220 3K610 11KBA3648 AP51 Quote Link to comment https://www.bigmacktrucks.com/topic/57459-63-b81sx/#findComment-424556 Share on other sites More sharing options...
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