SavageTitan Posted April 2 Share Posted April 2 Hi I'm new got a couple of questions. My questions are purely for my own edification. Many years ago I drove a double stick daycab straight truck. Said vehicle was long had a 3 PC driveshaft, walking beam suspension, a steering damper shock, it had a 4k gallon water tank with a trash pump to siphon load when top loading wasn't possible. I remember the engine was a Thermodyne 600, it was big and either teal or turquoise color to it. The trans being a 2 stick had a 5 speed main, the other stick was kind if a menu: high or low forward or reverse - I think it was called a Brownie? I never got that to split between high and low no matter what I did. I simply took off in one range or the other. Top speed was about 54 mph. Now the interior, hoola hoop steering wheel PTO throttle lock placed where your right knee was, every bump you couldn't see in advance - got you cracking your left hands knuckles on the wing window's handle, but the A/C worked! My questions: how big was this engine, how much HP did it make, and how the hell were you supposed to shift that trans??? Truck was a beast 3 point turns for just about every turn, it had super single steers, the hood was too heavy for one person to lift it off - this coming from someone with enough backside to pull off extended hood Pete's with no problem. The walking beam suspension was very cool helped support all that weight in turns off-road. All in the truck was big, capable, uncomfortable, and had balls for days. I believe truck to be a 1973 or slightly older, it was older than myself, hood and fenders all one piece steel with the bulldog for you to dangle from. I would literally not fit inside that truck nowadays, at least not behind the wheel. Any help with my questions I give you a thanks. Quote Link to comment https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/ Share on other sites More sharing options...
Mark T Posted April 2 Share Posted April 2 Sounds like the truck had a six speed in it. You don't "split" shift them. With the 3 position lever in HI you'd shift the other 5 position lever as a 5 speed. The "low" position was for crawl'n around in soft stuff with the 5 position lever in first. When the 3 position lever was in "reverse" That was reverse and the 5 position lever allowed you to chose the speed you wanted to go backwards in. Very unlikely that truck had a Thermodyne in it. Maybe a 237 or 300 ??? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/#findComment-572674 Share on other sites More sharing options...
JoeH Posted April 3 Share Posted April 3 The trans was 6 speeds forward, 5 speeds backwards. Left stick is gears 1-5, right stick direct low reverse, like you said. Low just sets all the gears down one notch. 2nd becomes equivalent of 1st, 3rd equivalent to 2nd, etc. Its just to give you a crawler gear. You only use low range for 1st gear when you need to crawl. Now the 5 speeds reverse... Fantastic feature. You can put it in 3rd reverse and cruise over soft ground before the ground even knows you're on it. Engine is probably a 283hp, with the engine mounted charge air cooler. Quote Link to comment https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/#findComment-572705 Share on other sites More sharing options...
Joseph Cummings Posted April 3 Share Posted April 3 33 minutes ago, JoeH said: The trans was 6 speeds forward, 5 speeds backwards. Left stick is gears 1-5, right stick direct low reverse, like you said. Low just sets all the gears down one notch. 2nd becomes equivalent of 1st, 3rd equivalent to 2nd, etc. Its just to give you a crawler gear. You only use low range for 1st gear when you need to crawl. Now the 5 speeds reverse... Fantastic feature. You can put it in 3rd reverse and cruise over soft ground before the ground even knows you're on it. Engine is probably a 283hp, with the engine mounted charge air cooler. 5 PTO speeds too 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/#findComment-572706 Share on other sites More sharing options...
tjc transport Posted April 3 Share Posted April 3 and reverse top speed was almost equal to forward top speed too in 5th. 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 https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/#findComment-572707 Share on other sites More sharing options...
Vladislav Posted April 3 Share Posted April 3 Did the truck have an off-set cab? I honestly can't imagine a full one part hood made of steel. DM or DMM or RD800 could have steel nose but the engine gets accessed through a baterfly hood shells. Unified fiberglass nose is a different story. And with super singles at the front it was the most probably DM or DMM model. But all this just my guesses. 2 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/#findComment-572736 Share on other sites More sharing options...
JoeH Posted April 4 Share Posted April 4 12 hours ago, tjc transport said: and reverse top speed was almost equal to forward top speed too in 5th. I won't ask you how you know that! 4th is the most I ever had opportunity to try 🤣🤣 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/#findComment-572777 Share on other sites More sharing options...
JoeH Posted April 4 Share Posted April 4 5 hours ago, Vladislav said: Did the truck have an off-set cab? I honestly can't imagine a full one part hood made of steel. DM or DMM or RD800 could have steel nose but the engine gets accessed through a baterfly hood shells. Unified fiberglass nose is a different story. And with super singles at the front it was the most probably DM or DMM model. But all this just my guesses. I bet it was a DM. The wing window sits notoriously close to the steering wheel, I know I clipped my pinky on ours a few times. Don't think I ever had that issue on our R models. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/#findComment-572778 Share on other sites More sharing options...
Vladislav Posted April 4 Share Posted April 4 7 hours ago, JoeH said: I bet it was a DM. The wing window sits notoriously close to the steering wheel, I know I clipped my pinky on ours a few times. Don't think I ever had that issue on our R models. Strange. I'm pretty sure the steering column fitment to the cab dash support plank is almost similar (the same) in DM and R-model cabs. And the door position too. Driver seat is the same mounting either so I can't imagine the distane between the wheel and the vent window differs anyhow. If only the offset cab allows better look to the left side for anything nice or desirable so the driver leans against that bad spoken piece of glass. 1 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/#findComment-572789 Share on other sites More sharing options...
Popular Post JoeH Posted April 5 Popular Post Share Posted April 5 On 4/4/2025 at 4:27 AM, Vladislav said: Strange. I'm pretty sure the steering column fitment to the cab dash support plank is almost similar (the same) in DM and R-model cabs. And the door position too. Driver seat is the same mounting either so I can't imagine the distane between the wheel and the vent window differs anyhow. If only the offset cab allows better look to the left side for anything nice or desirable so the driver leans against that bad spoken piece of glass. There's enough of a difference that you hurt your pinky if that wing window is open. Floor boards are different to accommodate different shifter positions, accelerator/brake pedals are different positions. Just a couple minor driver position differences, really. We have a 1980 DM686SX that is my reference, compared to a 1979 R686ST that we have as well. Same steering wheels, just that minor positional difference. 3 Quote Link to comment https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/#findComment-572956 Share on other sites More sharing options...
Vladislav Posted April 6 Share Posted April 6 20 hours ago, JoeH said: There's enough of a difference that you hurt your pinky if that wing window is open. Floor boards are different to accommodate different shifter positions, accelerator/brake pedals are different positions. Just a couple minor driver position differences, really. We have a 1980 DM686SX that is my reference, compared to a 1979 R686ST that we have as well. Same steering wheels, just that minor positional difference. Ok, I don't see hard matters to disagree. And I didn't have painful pinky but you had. 1 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/75364-trying-to-get-rough-performance-specs-on-an-engine-from-description-alone/#findComment-573010 Share on other sites More sharing options...
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