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Thanks for that info. I wonder if someone made an air to water intercooler that goes by the pass side battery if it would solve those issues.
it’s like chasing your tail. Then you’re on to the next problem. I’m sure engine efficiency is just not what a 6.7 is and a 6.7 would run cooler even if cooling setups are identical.
in my opinion the biggest downfall is the 4 speed trans, I have a T4 setup which can be argued that it is the most efficient 7.3 turbo setup from an EGT perspective and EGTs can still be problematic between the wide rpm drops between gears. The newer trucks are in the right rpm at the right time regardless of speed. My truck has the power to continue to accelerate up grades but when I shift I drop to much rpm and then lose power/airflow and EGTs become an issue.
a 6/10 speed would solve half the problems.
I cannot agree more with your statement about transmissions. The 6.7 has 10 speeds to work with and that's half the secret to it's towing capacity. If there was any practical way to bolt in a ten speed on my truck it would have been done a decade ago. I can do way more work with 250 hp and ten speeds than 450 and four.
Thanks for that info. I wonder if someone made an air to water intercooler that goes by the pass side battery if it would solve those issues.
it’s like chasing your tail. Then you’re on to the next problem. I’m sure engine efficiency is just not what a 6.7 is and a 6.7 would run cooler even if cooling setups are identical.
in my opinion the biggest downfall is the 4 speed trans, I have a T4 setup which can be argued that it is the most efficient 7.3 turbo setup from an EGT perspective and EGTs can still be problematic between the wide rpm drops between gears. The newer trucks are in the right rpm at the right time regardless of speed. My truck has the power to continue to accelerate up grades but when I shift I drop to much rpm and then lose power/airflow and EGTs become an issue.
a 6/10 speed would solve half the problems.
Could probably mount an air to water IC from a 6.7 where the driver's side battery goes.
I cannot agree more with your statement about transmissions. The 6.7 has 10 speeds to work with and that's half the secret to its towing capacity. If there was any practical way to bolt in a ten speed on my truck it would have been done a decade ago. I can do way more work with 250 hp and ten speeds than 450 and four.
I just looked at a gearing calculator.
I used the rpm band that you want to be in from 2000-3000 rpm. I think anything over 3000 rpm is not doing too much and under 2000 rpm you’re not moving enough air to having EGT issues and not enough air to make power.
Before I get attacked on powerband range, everyone’s powerband is different depending on turbo, injectors, tuning, etc. so for MY truck 2000-3000 rpm is where it wants to be when towing heavy. In an ideal world the ideal rpm range it wants for EGTs and power combo is 2200-2800 rpm. I have 4.88s and my turbo is slightly bigger than it needs to be but 4.88s make up for that. So 2200-2800 rpm is the happy EGT/power spot.
Given that range I compared the 4R100, Allison 1000 6 speed, Ford 6R140 and 10R140.
The 6R140 had some powerband holes below 50 mph. Between 50 and 70 mph you have no holes. You’re in the powerband where power and EGTs are happy. Even if you’re a little low on power at 70 for the grade, the truck can be happy at 60 or 65 mph due to the ratios. A 4 speed would cause you to slow down to 45mph and that’s explained later in this post.
The Allison 1000 had some holes in the 50-70 mph range but between 20 and 45 mph there are no holes. If you’re doing winding switchbacks you probably want the Allison 1000. You can pick your speed for your power on tap.
the 10 speed basically has no holes from 16 mph on up to your max speed. The one hole I found was between 13-16 mph but at that speed is it even an issue? I’d say no because you’re moving so slow the load isn’t great enough to cause issues.
The 4 speed has holes all over. Basically the 4 speed picks your speed for you given the load and grade. What I mean by that is this, let’s say I need 850 lb/ft to move the load up the grade at 65 mph. Let’s say I only make 750 lb/ft and that’s between 2300-2500rpm but I am below that rpm,I slow down, rpm’s go down, EGTs go up. In a 10 speed truck I downshift 1-2 gears, I’m in my peak 750 lb/ft rpm range and I only need 750lb/ft to maintain 60 mph on that grade where 65 required 850. Well I only slowed down 5 mph because I was able to match my speed with rpm and max power relatively easily.
Now, let’s say I take the same example but have 4 gears. I need 850 lb/ft to move the load up the grade at 65 mph. Let’s say I only make 750 lb/ft and that’s between 2300-2500rpm. I am below that rpm, I slow down, rpm’s go down, EGTs go up. As I slow down now only need 750 lb/ft to maintain my new speed at 60 mph well I can make 750 lb/ft but I’m out of that rpm range to make 750 lb/ft. If I downshift I’m at too high of an rpm to continue to accelerate because I am near redline, if I keep the same gear I’ll continue to slow down because I’m capable of making 750 but am not at that rpm So you slow down some more. Now you’re going 50 mph. You only need 500 ft lbs to get up that grade to move the load at 50 mph because of the less drag and load that comes with speed. You can go faster then 50 mph if you had your rpm range you needed but you don’t do your now stuck at 50 mph.
the worse the hills, the worst the cycle gets. It’s a vicious cycle with a 4 speed. Your chances to be over or under your rpm needed to maintain a speed is pretty high, with a 10 speed your chances are low.
Basically you can have the power to take the grade at the speed you want to take it at but you don’t have the rpm range to do it. That’s not an issue with the 10 speed.
A 7.3 needs more tools and tricks, it needs a VGT turbo to widen the rpm band to make up for the 4 speed.
a 6.7 can probably get away with a 4 speed better then a 7.3 because it has better technology to make up for the crappy 4 speed.
now pair old motor, old technology, old trans vs. new motor, new technology, new trans, the gap is greater then ever. If the 7.3 had a new trans I bet the gap would be significantly less in performance, it would still be there but significantly less. Same with a 6.7 getting a 4 speed and comparing it to the 7.3. The 6.7 would be a much bigger turd with a 4 speed compared to what it has now, the 10 speed.
if I am off base with my torque and speed thought process please chime in. I don’t like to put out bad info but that’s how it’s working in my brain.
The ZF6 is really no better. It’s got a granny low to get moving. That’s now a 5 speed in my opinion.
you may have a little less issue at slow speeds but it’s not much different then the 4r100
4.30 gears (285/75 tires) offer up a pretty good middle ground with the trade-off of higher RPMs. Running 68-70mph around 24-2500rpm in 4th it keeps it right in the sweet spot and can drag it down to 2100rpm (under full throttle) before it downshifts. When it does downshift into 3rd I have to back off to around 28-2900rpm (58mph or so) and it wont lose anymore speed.
I have been toying with doing my zf6 swap and dropping from 4.3 gears to 3.55, that way I can drop a gear and still have similar final drive ratio as the next gear with 4.30.
I almost bought a 07 classic duramax cclb srw with 141k miles the other day, but then I saw the carfax lol
With our breed of trucks we have two choices when it comes to transmissions. Deal with what we have or pay A LOT of money to swap in a transmission that was not designed to fit under the truck or buy a different truck. When I bought my ZF6 truck almost 10 years ago to be a tow pig, I 100% did not want a 4R100. I wanted the ability to control the shift points, control my speed going down a grade with the transmission and didn't want to deal with the tuning issues that seem to plague some.
After many cross country trips and 70,000 miles of towing heavy I am still very pleased with the 3.73/ZF6 combination under the truck. Others prefer different gearing or transmissions and I encourage them to seek out what will make them happy while towing, driving or on a daily basis. Just yesterday I was walking up my driveway and said to myself as I looked at my truck, "I am done upgrading as it does great as a tow pig". If we need to replace the injectors, I will. Same goes for other parts. Although, I am not naïve enough to think it will be around for the next 23 years due to gubment regulation, unavailable parts or some jackass that is playing FaceBook on his phone runs into it. At that point, we will either get a 6.7L of one flavor or the other or a motorhome and sell the 5th wheel.
1st world problems are great problems to have and I am grateful everyday for them.
Another version of what ESwift posted above is below. This is from my personal archives of endless PDF's, images and links.
Saying the ZF6 is a 5 speed because it has L gear which is just a granny is silly. It's nearly the same ratio as reverse, which everyone complains about being too fast, so is L/granny also too fast?
Even the auto's first and reverse gear ratios are nearly identical like the L/R on a ZF6, does that mean the auto's are only a 3 speed in your mentality as well?
Or since the auto's first gear is between the ZF6's 1st and second gear does that mean the auto only has 3.5 gears?
I used the rpm band that you want to be in from 2000-3000 rpm. I think anything over 3000 rpm is not doing too much and under 2000 rpm you’re not moving enough air to having EGT issues and not enough air to make power.
I've always wished for a transmission that has enough ratios to provide a 300 rpm drop if I shifted at 2800. 2500-2800 is the sweet spot on my engine. Above 3000, it starts to drop of significantly and I could probably move the power band up a bit if I get a bigger exhaust housing, but then I lose low end torque and my truck is a tow pig. Don't want to do that.
I don’t tow Heavy like you folks so maybe my experience is different.
I have no issues with 1st or 2nd gear. It tows everything I need well there. If need to slow down slightly at that point to hit the sweet spot of rpm then it’s not a big deal.
My issues lie with 3rd & 4th of the 4R100. The jump from 1:1 to 0.71:1 creates a big difference in rpm. 4th isn’t enough rpm, 3rd is more than needed. The ZF6 suffers the same fate at the top 2 gears.
Saying the ZF6 is a 5 speed because it has L gear which is just a granny is silly. It's nearly the same ratio as reverse, which everyone complains about being too fast, so is L/granny also too fast?
Even the auto's first and reverse gear ratios are nearly identical like the L/R on a ZF6, does that mean the auto's are only a 3 speed in your mentality as well?
Or since the auto's first gear is between the ZF6's 1st and second gear does that mean the auto only has 3.5 gears?
it takes 1 gear to get up to 23 mph in a 4r100
it takes 2 to do similar speeds in a ZF6.
is it nice to move extremely heavy loads? Yes, but I’m less concerned about having gear options below 20 mph then I am in the 30-70 mph range
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