Twin engine duramax truck...

Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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you guys need better cop friends. One called me on the way back up to flagstaff on a sunday night to make me purposely fuck with another cop buddy of ours. he gave me the mile marker and said "go as fast as you can". done deal. whipped by at some point well north of 100mph (damn 02 gauge cluster lmao), hit the train horn and lights go on his car. i pulled off at the first exit a couple miles up the road and called my buddy that instigated this. apparently he was right by our other friend. he says

"dude that was the funniest shit ever. hes sitting there playing mine craft on his comp, snacking on shit and all of sudden the radar goes crazy. he throws his shit into the pass seat, spills his drink, hits the lights, slams into gear and just as hes going, we hear the train horn. he stops, backs back up and goes 'THAT MOTHER F**CKER!!' i havent laughed that hard in a long time!"

all i was doing was just laughing. he comes in the next day (i was the auto mechanic for them then) juuuust ribbing me about 🤣
 

MarkBroviak

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you guys need better cop friends. One called me on the way back up to flagstaff on a sunday night to make me purposely fuck with another cop buddy of ours. he gave me the mile marker and said "go as fast as you can". done deal. whipped by at some point well north of 100mph (damn 02 gauge cluster lmao), hit the train horn and lights go on his car. i pulled off at the first exit a couple miles up the road and called my buddy that instigated this. apparently he was right by our other friend. he says

"dude that was the funniest shit ever. hes sitting there playing mine craft on his comp, snacking on shit and all of sudden the radar goes crazy. he throws his shit into the pass seat, spills his drink, hits the lights, slams into gear and just as hes going, we hear the train horn. he stops, backs back up and goes 'THAT MOTHER F**CKER!!' i havent laughed that hard in a long time!"

all i was doing was just laughing. he comes in the next day (i was the auto mechanic for them then) juuuust ribbing me about 🤣

Your not wrong but in this area it is hard to know all of them unfortunately. My father was a cop in this town when I was a young kid so when I got my license his buddies would follow me home and wait till we got to the house to turn the lights on just to shoot the shit with him, got to the point that I just ignored them lol. I tuned a few of the police vehicles over the years also as I couldn't have my K9 officer rocking stock shit! He used to borrow our trucks to screw with the county boys at night which was priceless! Was riding shotgun with a customer in his pulling truck the week before Schied's years ago and the officer that pulled us over apologized when he found out I was in the truck with him lol. I was in my late 20's when I got pulled out of my car at gun point by a county who was a bit uptight but the second officer on the scene was the same guy that pulled Larry and I over the night before for doing a 4x4 boosted launch at him in Larry's LLY on the other highway so he thought it was hilarious that I was pulled over again the day later which is probably why I didn't go to jail because the first officer wanted to hang me by my nuts!
 

DAVe3283

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Sep 3, 2009
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I still don't know why they didn't just run two independent ECUs and TCMs. Feed them off the same throttle, run the same tunes. Odds are they'd shift at the same time, but if not, who cares? With the outputs linked it shouldn't be able to have any weird drivability issues.

It appears they're just running both valve bodies off one TCM, so it's only learning one of them. Can't imagine that is going to hold up long term. Though I'm surprised it's working at all, so maybe it'll last fine too?

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juddski88

Freedom Diesel
Jul 1, 2008
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I still don't know why they didn't just run two independent ECUs and TCMs. Feed them off the same throttle, run the same tunes. Odds are they'd shift at the same time, but if not, who cares? With the outputs linked it shouldn't be able to have any weird drivability issues.

It appears they're just running both valve bodies off one TCM, so it's only learning one of them. Can't imagine that is going to hold up long term. Though I'm surprised it's working at all, so maybe it'll last fine too?

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Could've done it a couple of ways, but hopefully with what they did, they increased voltage a little bit before splitting signals...
 

Leadfoot

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Dec 27, 2006
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Just thinking out loud here. While there are many ways to skin a cat, is there a better way he could have done it?

I'm THINKING what they did was probably the safest given current technology. There's no way to ensure both engines would operate 100% identical even if doing the same thing (by running both off of one ECM) and even less chance of both trannies shifting identical (even if built with the same parts side by side by the same builder). Multiple TCM's runs the risk of having one transmission shift before the other (even with the slippage of a converter that's still tough on parts). While both transmissions may not shift 100% identical (one may take a few more milliseconds to complete a 1 to 2 shift), the best chance to prevent a tie-up between the two is shifting them at the same time (via one TCM). Hopefully even if one shifts slightly quicker, the other is in the process of releasing clutches and there is minimal tie-up/wear.

I'm ASSuming IF running both engines off one ECM and running both transmissions off of one TCM they would have to be setup in a Master/Slave setup where only one is sending input (engine RPM, output shaft speed, etc), and since they are tied together through a gearbox the +/- from one to another would be minimum. One is controlling and one is being controlled/cloned.

The only thing is I'm assuming you would want to have external monitoring for things like oil temp/pressure as well as tranny temps to be able to keep an eye on both engines/transmissions as only one is sending info to the ECM/TCM...

Thoughts???

Also Cody doesn't seem like a technical wiz (not that I am), so I'm wondering who was hired to do the TCM work?
 

Leadfoot

Needs Bigger Tires!
Dec 27, 2006
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I still don't know why they didn't just run two independent ECUs and TCMs. Feed them off the same throttle, run the same tunes. Odds are they'd shift at the same time, but if not, who cares? With the outputs linked it shouldn't be able to have any weird drivability issues.

It appears they're just running both valve bodies off one TCM, so it's only learning one of them. Can't imagine that is going to hold up long term. Though I'm surprised it's working at all, so maybe it'll last fine too?

Sent from my FlashScan V2 using Tapatalk
I would think that if one transmission is in 3rd and the other is in 4th, it would be a BIG deal especially on a full throttle romp. Some of the best builders have said they have built "identical" transmissions that behave differently. Same year truck, same tune, same tire, same engine mods, etc and one will behave differently than the other. Each Allison 1000 seems to have it's own unique identity.

Making sure they shift at the same time is probably the best way to minimize transmission/driveline damage and one TCM seems like the best way to handle it (given the current tuning and hardware/software limitations), unless there is something I'm missing (an that is VERY possible).
 

DAVe3283

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Sep 3, 2009
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I guess I fundamentally don't see the problem if one engine was in 3rd and the other was in 4th, so long as they had completely independent controls.

Imagine towing a big trailer down a steep hill. That can apply hundreds of HP to the transmission, yet doesn't hurt anything. Each engine would, worst case, see it like a trailer down a hill helping it accelerate.

Now if the engine cranks were hooked together forcing them to spin the same RPM, then that would be bad if they were in different gears. But that doesn't appear to be the case here, since they can start and idle one with the other off.

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Leadfoot

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I guess I fundamentally don't see the problem if one engine was in 3rd and the other was in 4th, so long as they had completely independent controls.

Imagine towing a big trailer down a steep hill. That can apply hundreds of HP to the transmission, yet doesn't hurt anything. Each engine would, worst case, see it like a trailer down a hill helping it accelerate.

Now if the engine cranks were hooked together forcing them to spin the same RPM, then that would be bad if they were in different gears. But that doesn't appear to be the case here, since they can start and idle one with the other off.

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Like I said I could be missing something, but I think in "theory" they are crank to crank (via gears, if you take out the fact that a transmission can act as a hydraulic coupling), and would be an issue if one was in 3rd and the other in 4th, or both in the same gear but one locked the converter and one didn't (again why one TCM makes sense).

Yes one will try to speed up the other (or slow down) and they will fight each other but unlike towing a trailer on a steep hill, there is actually torque being applied vs potential energy. With mismatched speeds either one/both transmission will slip or parts will break. I guess a third option is one engine will stall and the one running will force the other to turn (which is more like the towing scenario where power is only transmitted one way).

In one of the videos he posted (
Source: https://www.youtube.com/watch?v=9wiaZbvAaO0
), just past the 3 minute mark they show a HUGE custom dropbox that connects both engine/trans combos, and transfers the power down to the driveshafts (most likely with gear reduction as well).

While not physically crank to crank, when the transmission are in gear and converters locked, the cranks are forced to spin EXACTLY the same speed or break parts. Maybe there's some sort of clutch or torque limiting coupling to prevent damage but I did not see anything like that in his build videos.

He states one engine/trans is mounted forward and the other is mounted backwards, so I'm willing to bet each input is offset either left to right or up to down with identical tooth count input gears that mesh (because each gear will be turning the opposite direction) and then those drive a gear that powers the HUGE chain down to the driveshaft outputs.

In his truck it seems as if when the transmissions are in gear (and especially when converters are locked), they essentially are connected. What's nice is when the TCM commands Park or Neutral, the engines can be started/stopped independently without worrying about one engine trying to affect the other (beats having to start both at the same time), as the transmission becomes a disconnected hydraulic coupling.

Again, I am NO expert and have not put my hands on this truck personally to see what has or hasn't been done, but I've followed the build for quite a while now as I was interested in how it was done and the dual transmission control was one of the aspects I've been most curious about as to how they were going to overcome the issues associated with that.
 

Leadfoot

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Dropbox.jpg This is a CRUDE drawing of what I believe is in the truck or at least the concept. The outputs of the transmissions are tied together in the dropbox (middle top) which means the cranks are tied together when the transmissions are in gear. The inputs are offset due to the transmissions turning opposite directions, The chains (dotted lines) can be different lengths as long as drive sprockets are the same size/tooth count, and the driven sprockets are the same size/tooth count. The difference in the drive vs driven sprockets will give you gear reduction if there is any (which I'm assuming there is). Basically the ouputs and inputs are always tied together unless the chains break.
 

Bdsankey

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They're running two separate ECMs hence why they can start them individually.


I don't see an issue with them not being in the same gear (for a short period of time) as long as they were smart enough to disable lockup. The torque converter will allow for enough slip/rpm difference, in my opinion, that it "should" be ok. Also being unlocked buys them some margin for error in shift timing as well.
 
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Bdsankey

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View attachment 112957 This is a CRUDE drawing of what I believe is in the truck or at least the concept. The outputs of the transmissions are tied together in the dropbox (middle top) which means the cranks are tied together when the transmissions are in gear. The inputs are offset due to the transmissions turning opposite directions, The chains (dotted lines) can be different lengths as long as drive sprockets are the same size/tooth count, and the driven sprockets are the same size/tooth count. The difference in the drive vs driven sprockets will give you gear reduction if there is any (which I'm assuming there is). Basically the ouputs and inputs are always tied together unless the chains break.
How are the cranks tied together? Using that logic then I should not be able to put my truck into park with the engine running or I shouldn't be able to stop the truck in drive/reverse with the engine running.

You're forgetting the absolute biggest key here in an automatic transmission, the torque converter.


As for the drop box/combiner, you're mostly correct. They do actually have a video about it on his YouTube channel ages ago if you go dig for it. Being that the engines are facing opposite ways the rearward engine has to actually make a direction change to spin the output shaft of the dropbox/transfercase the proper direction.
 
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shakenfake

Moron
Sep 15, 2022
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No f-cks given. Moron making us all look bad.
I disagree with this one slightly. The guy that makes diesel guys look bad in Westin with the cummins mustang. Thing just billows smoke, literally named it the smokestang. At least this is supposed to obviously be just a monster truck off roader. If it was driven on the road or something sure but I don't know.


He did not disclose the guy who did his trans work I watched the video a couple of times cause I was curious too lol
 

Bdsankey

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I disagree with this one slightly. The guy that makes diesel guys look bad in Westin with the cummins mustang. Thing just billows smoke, literally named it the smokestang. At least this is supposed to obviously be just a monster truck off roader. If it was driven on the road or something sure but I don't know.


He did not disclose the guy who did his trans work I watched the video a couple of times cause I was curious too lol
He used to drive that truck on the road all the time doing dumb shit like rolling smoke everywhere etc before it became literally too large for a road.

He's a smart guy in the sense that he's found a way to win the YouTube algorithm but he's also a dipshit making us all look bad. Taking his big diesel truck into the oceans etc.
 

shakenfake

Moron
Sep 15, 2022
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Shlumpt, TX
No bullshit ever since he got shot in the head his whole persona changed. After he flew down to Cali and started buying the R8 and what not he turned full retard. Divorced his wife and all sorts of dumb stuff. Kinda sucks cause I thought he was great for a while but now he puts on this "I'm too cool but also a moron" act.
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@Bdsankey I agree but I was specifically talking about now. It has been years since he has had monstermax on the road lol The ocean thing was awesome though let's be real.
 
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gmduramax

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Jun 12, 2008
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I see no reason the engines and trans need to be run in sync. If both converters are locked and one trans shifts to 5th before the other one motor will just be at a different rpm. If one is at 4000rpm and one is at 2700rpm both motors are still accelerating. Now as long as that doesn’t cause one to smack the rpm limit. Nothing would ever break. It’s no different from your converter locking on the track it just drags down your rpm.
 
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