Whats the correct diff ratio??
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
ok, side thought. from the engine to the trans. although they list the final drive ratio's, is there any loss in revs in the trans, with the likes of the torque converter, etc??
I dont know - it just doesnt make sense - the engine certainly doesnt want to rev over 32/3400 rpm on the dash tacho, the manual count of the rear diff comes up at 3.5(ish), any all the maths ive done, all the input from you guys, all doesnt add up in the proven maths.
I dont know - it just doesnt make sense - the engine certainly doesnt want to rev over 32/3400 rpm on the dash tacho, the manual count of the rear diff comes up at 3.5(ish), any all the maths ive done, all the input from you guys, all doesnt add up in the proven maths.
The engine CANNOT exceed ~3400 RPM, as that is where the mechanical governor shuts it down. It may sound like it's wound tight as all get out, but it can actually live at that RPM all day long.
Swapping to the E4OD transmission will do 2 things. 1.) Adds an OD gear, which will lower RPM at cruise speeds. 2.) Adds a locking torque convertor, which stops the minor RPM loss caused by the C6 non-locking convertor.
However, these transmissions are not cheap, and require a controller in order to work.
If you really want to lower the highway RPM, you can increase the rear gear ratio. A 3.08 would be about as tall as you would really want to go. Any higher, and it would most likely kill both the power and MPG.
Back when the 6.9L was installed in F250/F350 trucks, they offered 3.08, 3.55, and 4.10 rear gears, and used tires in 33" tall range. The 4.10 trucks had the best towing/pulling capacity, and the 3.08 trucks had the highest top speed and unloaded MPG. The 3.55 trucks were a happy medium, giving decent MPG and pulling power.
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
One thing I forgot to mention. This engine is known to be rather loud, so Ford added a lot more sound deadening on the trucks that had it factory installed.
Just the sound of the engine's air intake is rather loud by itself. Add the diesel rattle, and it quickly gets noisy under the hood, even at 1000-1500 RPM.
Just the sound of the engine's air intake is rather loud by itself. Add the diesel rattle, and it quickly gets noisy under the hood, even at 1000-1500 RPM.
Moderator
Joined: Jan 2001
Posts: 57,005
Likes: 2,750
From: Virginia
I am not good at geography, but New Zealand is a island correct? What are you doing that you need to drive so fast? I figure on a island, you would not need to do anything but putt around at a lower speed.
My truck originaly had the diesel, the c6, and 4.10's. It was excellant for running around town and smaller roads. It just wasn't cut out for the high speed interstates though.
My truck originaly had the diesel, the c6, and 4.10's. It was excellant for running around town and smaller roads. It just wasn't cut out for the high speed interstates though.
Thread Starter
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Freshman User
Joined: Nov 2010
Posts: 38
Likes: 0
From: Inglewood, Taranaki
LOL... Thats a cheap shot at New Zealand!! LOL.. Yeah, we are a 2 big islands, and a few little ones. I live in a Place called Taranaki.
Its about 4 hours drive to our countries biggest city, Auckland, and 3 and a half hours to our capital city, wellington.
it not a hick country, with goat track roads, and 1 mile from coast to coast. Yes, we can get into top gear, and stay there long enough.
Hey, let's be honest, our south island beaches were long enough for Burt Munroe many yeah ago to perfect his 1920's indian Motorbike, before coming over to your salt flats and laying down some long standing land speed records!!!!
LOL.
Really, the point of the thread was to find out what normal revs are for the Navistar, what cruising revs should be, and why the maths of working out the diff ratio wasnt working for me! Ive come to the conclusion that i have to get the tacho checked. see if the RPM's that im working on are actually correct.
The good news from the thread, is that it looks like a regular poster in it, looks like he if from NZ, and as there arent many of these trucks around here, it is always good to know some who has one... LOL
Its about 4 hours drive to our countries biggest city, Auckland, and 3 and a half hours to our capital city, wellington.
it not a hick country, with goat track roads, and 1 mile from coast to coast. Yes, we can get into top gear, and stay there long enough.
Hey, let's be honest, our south island beaches were long enough for Burt Munroe many yeah ago to perfect his 1920's indian Motorbike, before coming over to your salt flats and laying down some long standing land speed records!!!!
LOL.
Really, the point of the thread was to find out what normal revs are for the Navistar, what cruising revs should be, and why the maths of working out the diff ratio wasnt working for me! Ive come to the conclusion that i have to get the tacho checked. see if the RPM's that im working on are actually correct.
The good news from the thread, is that it looks like a regular poster in it, looks like he if from NZ, and as there arent many of these trucks around here, it is always good to know some who has one... LOL
Elder User
Joined: Jan 2009
Posts: 774
Likes: 1
From: East Tennessee
My truck does 2400-2500RPM @ 60mph. 31x10.50 15", NP435 with 1:1 4th gear (C6 3rd gear is 1:1). I have 3.50 gearing. Don't worry, if you are correct on your axle being 3.50 or 3.55, then 60mph isn't 3000+ RPM.
Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
The C6 is a three-speed. It sounds like you aren't getting out of second gear. How many shifts is it making?
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Freshman User
Joined: Nov 2010
Posts: 38
Likes: 0
From: Inglewood, Taranaki
Nah, im leaning towards getting the rev counter check - ie see if its reading correct before digging around too much more!!!
Moderator
Joined: Jan 2001
Posts: 57,005
Likes: 2,750
From: Virginia
Check the wires for the tach(rev counter). On the front of the engine, on top of a rounded housing, there should be a sensor threaded in with two wires coming off of it. This is the sensor for the tach, it reads the gear teeth inside the housing that powers the injection pump. These wires are known to get a bad connection where they go into the sensor. Also I believe you said this engine was a swap. The diesel takes a different tach, with different wires. The gas engine tach won't work.
Thread Starter
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Freshman User
Joined: Nov 2010
Posts: 38
Likes: 0
From: Inglewood, Taranaki
Check the wires for the tach(rev counter). On the front of the engine, on top of a rounded housing, there should be a sensor threaded in with two wires coming off of it. This is the sensor for the tach, it reads the gear teeth inside the housing that powers the injection pump. These wires are known to get a bad connection where they go into the sensor. Also I believe you said this engine was a swap. The diesel takes a different tach, with different wires. The gas engine tach won't work.
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