Mark T Posted February 2 Share Posted February 2 Just now, Joseph Cummings said: Trying to remember what I had in the diamond reo with the cummins. It was the 900 fp rated 15 speed with the deep reduction on the dash. Normally you drove it like a 10 speed It's easy to forget. Back then trucks had lot slower axles. Like a truck with a 15 over might have had a 4.6 axle and usually you didn't use deep reduction as often as when axles got faster and around the time they became the norm, the knobs with the blue button were around and it was simple to start out in deep reduction. Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568429 Share on other sites More sharing options...
Joseph Cummings Posted February 2 Share Posted February 2 (edited) 15 minutes ago, Mark T said: It's easy to forget. Back then trucks had lot slower axles. Like a truck with a 15 over might have had a 4.6 axle and usually you didn't use deep reduction as often as when axles got faster and around the time they became the norm, the knobs with the blue button were around and it was simple to start out in deep reduction. I can't remember if that was an RTO9515, or an RT9515. But I do know the exporters were hot for them back in the day. Edited February 2 by Joseph Cummings 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568431 Share on other sites More sharing options...
Geoff Weeks Posted February 2 Share Posted February 2 18 minutes ago, Mark T said: A 15 over is a highway transmission. Couple lower than a ten, and at the time a realistic overgear to make in a lever shift. If you were geared between 3.5 and 4.3 usually 1 2 3 and four in deep reduction, you could go to 4th in regular low range. A direct 15 was quite a bit lower than an RTO 13 and made sense if you had a faster geared truck back then. Your losing me, I thought we were talking on hiway and O/D 15's? RTO 12515 has it's lowest starting gear (deep reduction) of 10.93, compare that to a RTO12513 which has 12.5, the 13 has lower starting and closer steps, it has less of an O/D which mean less power lost to heat in the top gears. Front trans is in direct, back box in O/D 13 has between 19 and 15% steps the 15 has between 27 and 30% steps. I know which I would choose! The 15 provides neither lower starting nor closer steps. Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568434 Share on other sites More sharing options...
Mark T Posted February 2 Share Posted February 2 7 minutes ago, Geoff Weeks said: Your losing me, I thought we were talking on hiway and O/D 15's? RTO 12515 has it's lowest starting gear (deep reduction) of 10.93, compare that to a RTO12513 which has 12.5, the 13 has lower starting and closer steps, it has less of an O/D which mean less power lost to heat in the top gears. Front trans is in direct, back box in O/D 13 has between 19 and 15% steps the 15 has between 27 and 30% steps. I know which I would choose! The 15 provides neither lower starting nor closer steps. You could get a 15 in a direct or overdrive. The overdrive version had a much higher lowest gear than a direct 15. I would have to agree, in a truck made to go down the highway, an RTO 13 was better suited to a Cummins of that period. Fifteen was friendlier to different set ups. Like 10s and 15s of that time really worked on Cats. I can speak from experience, a 15 over behind a Maxidyne with a 4.17 axle....pretty sweet. Little less than ideal for crawl'n around , but on the blacktop it works better than comes to mind with a Maxidyne. Larry already has 4.10s in the truck. That's why I mentioned it. His Triplex with 4.10s ??? it'll be pretty much like having an RTO 13 speed if he does away with the 4 way. Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568438 Share on other sites More sharing options...
Joseph Cummings Posted February 2 Share Posted February 2 I always stayed within 100ish air miles. So I never worried about fuel efficiency in high gear. Fuel efficiency wasn't ever going to make or break me. I never wanted to sleep in a sleeper and have to compete with OTR guys. Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568439 Share on other sites More sharing options...
Mark T Posted February 2 Share Posted February 2 6 minutes ago, Joseph Cummings said: I always stayed within 100ish air miles. So I never worried about fuel efficiency in high gear. Fuel efficiency wasn't ever going to make or break me. I never wanted to sleep in a sleeper and have to compete with OTR guys. Lot more ways to skin the cat back then. Now ? 8LL 10 13 or 18 and they all got one foot in the grave and the other on a bananna peel. Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568441 Share on other sites More sharing options...
Geoff Weeks Posted February 2 Share Posted February 2 (edited) 30 minutes ago, Mark T said: You could get a 15 in a direct or overdrive. The overdrive version had a much higher lowest gear than a direct 15. I would have to agree, in a truck made to go down the highway, an RTO 13 was better suited to a Cummins of that period. Fifteen was friendlier to different set ups. Like 10s and 15s of that time really worked on Cats. I can speak from experience, a 15 over behind a Maxidyne with a 4.17 axle....pretty sweet. Little less than ideal for crawl'n around , but on the blacktop it works better than comes to mind with a Maxidyne. Larry already has 4.10s in the truck. That's why I mentioned it. His Triplex with 4.10s ??? it'll be pretty much like having an RTO 13 speed if he does away with the 4 way. 12515 had a lowest ratio of 13.87, but now you are comparing apples to oranges, you loose any O/D so top end is off. Any way you cut it, a 13 has more to offer than a 12 (15). The 13 spds had bigger jumps in low range, where it is less important, and smaller jumps in high range where it really helps. The RT12513 has an U/D splitter The RTO12513 has an O/D splitter, the main box is the same. The RT12515 is direct main the RTO 12515 is an OD main. I will agree that a Cat can handle a slightly bigger jump in ratios but it doesn't loose anything with smaller jumps. Edited February 2 by Geoff Weeks Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568444 Share on other sites More sharing options...
Freightrain Posted February 2 Author Share Posted February 2 1 hour ago, Mark T said: No doubt. I think it's cool seeing some of these upgrades and referbs guys are doing now. Lots of them have been done in the past, but now things that are available that didn't exist years back ??? new twist on things. I think it's interesting. I will be doing a hood scoop of sorts to get some air under the hood by the turbine air cleaner. Ron has a Super duty Ford hood scoop on his B model. People think they are gold now so maybe an aluminum scoop from something car related. I will come up with something even if I have to make it. Today's project....triplex assembly. 1 1 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568445 Share on other sites More sharing options...
Popular Post Geoff Weeks Posted February 2 Popular Post Share Posted February 2 6 minutes ago, Freightrain said: I will be doing a hood scoop of sorts to get some air under the hood by the turbine air cleaner. Ron has a Super duty Ford hood scoop on his B model. People think they are gold now so maybe an aluminum scoop from something car related. I will come up with something even if I have to make it. Today's project....triplex assembly. There is a reason you don't see the air to air mounted behind the radiator! I'd do whatever it took to get outside air to the tip turbine. 4 Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568447 Share on other sites More sharing options...
Lmackattack Posted February 2 Share Posted February 2 2 hours ago, Freightrain said: I will be doing a hood scoop of sorts to get some air under the hood by the turbine air cleaner. Ron has a Super duty Ford hood scoop on his B model. People think they are gold now so maybe an aluminum scoop from something car related. I will come up with something even if I have to make it. Today's project....triplex assembly. Larry My Blue B model has a driver side Air filter added to supply outside air to the tip turbine. Its also a B75 long hood so 4 more Inches to work with under the hood and near the cowl. just an idea 2 Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568463 Share on other sites More sharing options...
Mark T Posted February 2 Share Posted February 2 8 minutes ago, Lmackattack said: Larry My Blue B model has a driver side Air filter added to supply outside air to the tip turbine. Its also a B75 long hood so 4 more Inches to work with under the hood and near the cowl. just an idea 😏 that might require it's own thread so we could examine the details wink wink 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568465 Share on other sites More sharing options...
Popular Post Lmackattack Posted February 2 Popular Post Share Posted February 2 3 minutes ago, Mark T said: 😏 that might require it's own thread so we could examine the details wink wink I bought the truck with The tip turbine already installed. But still kinda cool to see how they fabbed it up 3 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568467 Share on other sites More sharing options...
Mark T Posted February 3 Share Posted February 3 Nice truck 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568479 Share on other sites More sharing options...
Freightrain Posted February 3 Author Share Posted February 3 I've been want to get paper filters for the truck, so if I could find a nice pair of smaller diameter housings then I could see putting twins on it. It limits the passenger door so bad I don't want to make the same issue on the driver's side. 1 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568502 Share on other sites More sharing options...
davehummell Posted February 3 Share Posted February 3 Larry when I upgraded the engine in my B I splurged and bought the dry type air cleaner from Watt's it fit were the oil bath filter fit and it looks just like the oil bath one. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568508 Share on other sites More sharing options...
terry Posted February 3 Share Posted February 3 3 hours ago, Freightrain said: I've been want to get paper filters for the truck, so if I could find a nice pair of smaller diameter housings then I could see putting twins on it. It limits the passenger door so bad I don't want to make the same issue on the driver's side. Can't you use a filter that came with the tip turbine engines, it has two separate filters in one housing, one for engine and one for the tip turbine.. it is a bigger housing, but it's all on the passenger side. terry 2 Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568514 Share on other sites More sharing options...
mowerman Posted February 3 Share Posted February 3 Ingenious Terri hats off to you lol Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568516 Share on other sites More sharing options...
Freightrain Posted February 3 Author Share Posted February 3 1 hour ago, terry said: Can't you use a filter that came with the tip turbine engines, it has two separate filters in one housing, one for engine and one for the tip turbine.. it is a bigger housing, but it's all on the passenger side. terry No, i don't want to try and get both hoses out the passenger side. I could notch the hood, but not my first choice. I would get two smaller, matching housings and do like Trent's truck. If all else fails, a KN cone on the turbine would get me by along with a hood scoop. 2 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568520 Share on other sites More sharing options...
Mark T Posted February 3 Share Posted February 3 Mack had the strata tube with the scoop on the hood . Quote Link to comment https://www.bigmacktrucks.com/topic/75053-latest-find/page/4/#findComment-568524 Share on other sites More sharing options...
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