truck behavior while towing 10k+
Tuned
Joined: Dec 2008
Posts: 373
Likes: 5
From: Evergreen Colorado
Im (basically) running the same setup as you but towing a 13,000 tow behind.
Your speed and boost are normal. You are pulling some serious grades at altitude.
Your EGTs sound great to me. Don't think you have a boost leak. I have to let off the throttle on most climbs to keep my EGTs under 1200.
I like the look of my 35's and will be regearing to get my towing power back.
When I tow at sea level its like Im driving a different truck.
Your speed and boost are normal. You are pulling some serious grades at altitude.
Your EGTs sound great to me. Don't think you have a boost leak. I have to let off the throttle on most climbs to keep my EGTs under 1200.
I like the look of my 35's and will be regearing to get my towing power back.
When I tow at sea level its like Im driving a different truck.
Thread Starter
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Elder User
Joined: Jul 2010
Posts: 534
Likes: 0
From: Kremmling, Colorado
Im (basically) running the same setup as you but towing a 13,000 tow behind.
Your speed and boost are normal. You are pulling some serious grades at altitude.
Your EGTs sound great to me. Don't think you have a boost leak. I have to let off the throttle on most climbs to keep my EGTs under 1200.
I like the look of my 35's and will be regearing to get my towing power back.
When I tow at sea level its like Im driving a different truck.
Your speed and boost are normal. You are pulling some serious grades at altitude.
Your EGTs sound great to me. Don't think you have a boost leak. I have to let off the throttle on most climbs to keep my EGTs under 1200.
I like the look of my 35's and will be regearing to get my towing power back.
When I tow at sea level its like Im driving a different truck.
Tuned
Joined: Dec 2008
Posts: 373
Likes: 5
From: Evergreen Colorado
Cant decide.
I would like to keep my highway speed in the mid range of the RPM and keep MPG under control. 4.10 like someone stated before would get me close to stock with 35s.
Im sure she would be a towing beast with 4.30 gears. Lower EGTs and the ability to do close to the speed limit over the passes.
She is used 50/50 towing/weekend driver and am considering going with a 4.30 but don't want to be red lining the motor at 80-85mph or killing my MPG.
I would like to keep my highway speed in the mid range of the RPM and keep MPG under control. 4.10 like someone stated before would get me close to stock with 35s.
Im sure she would be a towing beast with 4.30 gears. Lower EGTs and the ability to do close to the speed limit over the passes.
She is used 50/50 towing/weekend driver and am considering going with a 4.30 but don't want to be red lining the motor at 80-85mph or killing my MPG.
More Turbo
Joined: Jan 2006
Posts: 687
Likes: 15
From: Lake Charles, LA
Lead Driver
Joined: Mar 2013
Posts: 7,460
Likes: 85
From: Kent Station, WA
I pulled this from another thread on similar topics. For the diesel stick with the 4.10 gears.
https://www.ford-trucks.com/forums/1...l#post14906049
https://www.ford-trucks.com/forums/1...l#post14906049
I agree with Brent and learned an expensive lesson many MANY years ago.
There is a ridiculously easy formula you should use:
(New tire Diameter/Old tire Diameter) x Current Gear Ratio = New gear ratio
In your case:
(34.6/31.7) x 3.73 = 4.10 gears
You want to end up with an effective gear ratio of 3.73. If you go too numerically high with 4.30 or 4.56 gears, your RPMs will rev too high and the truck will run out of steam at the top.
Given that you're ending up with a 35 inch tire when everything is said and done, 4.10 gears should be your gear of choice, especially if you tow.
This all comes from first hand experience and making an expensive mistake.
It starts at post #54: https://www.ford-trucks.com/forums/6...y-caved-4.html
On page 5 at post #77, I had it right and should've trusted myself and my gut.
Post #102 is where the hard lesson was learned.
There is a ridiculously easy formula you should use:
(New tire Diameter/Old tire Diameter) x Current Gear Ratio = New gear ratio
In your case:
(34.6/31.7) x 3.73 = 4.10 gears
You want to end up with an effective gear ratio of 3.73. If you go too numerically high with 4.30 or 4.56 gears, your RPMs will rev too high and the truck will run out of steam at the top.
Given that you're ending up with a 35 inch tire when everything is said and done, 4.10 gears should be your gear of choice, especially if you tow.
This all comes from first hand experience and making an expensive mistake.
It starts at post #54: https://www.ford-trucks.com/forums/6...y-caved-4.html
On page 5 at post #77, I had it right and should've trusted myself and my gut.
Post #102 is where the hard lesson was learned.
Cargo Master
Joined: Nov 2010
Posts: 2,797
Likes: 10
In regards to your post I feel your numbers are all fine. If you had a boost up pipe leak your egts would be out of control in my opinion.
The biggest killer is the tires and gear combo you are running. I run 4:10s and 285/75 with a manual trans and towing 15-18k behind me over those exact passes am lucky to hold 60-55mph. A lot of people do not realize that towing heavy at altitude is an entirely different ball game than towing anything at low elevation... The positive side of the mountain passes and thin air.... you will know if something is not running properly or leaking on your rig!
I noticed my EGTs were 125-150 degrees cooler when towing 6% grades at 2-3000 feet in elevation vs Taylor Pass that is around 11,200. ITS NIGHT AND DAY DIFFERENCE
I have to laugh when driving up I70 when its littered with out of state trucks and campers all with EGT/overheating yada yada ya issues... even the tractors have major issues up there too.
The biggest killer is the tires and gear combo you are running. I run 4:10s and 285/75 with a manual trans and towing 15-18k behind me over those exact passes am lucky to hold 60-55mph. A lot of people do not realize that towing heavy at altitude is an entirely different ball game than towing anything at low elevation... The positive side of the mountain passes and thin air.... you will know if something is not running properly or leaking on your rig!
I noticed my EGTs were 125-150 degrees cooler when towing 6% grades at 2-3000 feet in elevation vs Taylor Pass that is around 11,200. ITS NIGHT AND DAY DIFFERENCE
I have to laugh when driving up I70 when its littered with out of state trucks and campers all with EGT/overheating yada yada ya issues... even the tractors have major issues up there too.
Senior User
Joined: Mar 2015
Posts: 320
Likes: 1
I am 19,360 lbs gross combined (total truck and trailer) and 285/75/16 tires with 3.73 gears. I can pull the silverthorne to eisenhower tunnel grade with my slowest speed of about 60mph. I would say your numbers sound decent. My EGTs hit 1300F sustained, cooling temps in control.
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Elder User
Joined: Dec 2002
Posts: 797
Likes: 1
From: UT
I have a similar setup as you PJ. I've noticed even running down the freeway pulling my camper, a mild hill will kick it out of OD alot. The locking/unlocking of OD all the time drives me nuts. I don't ever plan on going back to 265's (mine actually came with 235's) and will continue to buy 315's. That said I have bought 4.10 gears to have mine replaced. I went with G2 gear for the rear. For the front, will probably be Dana Spicer since G2 didn't offer it.
Cargo Master
Joined: Mar 2006
Posts: 2,502
Likes: 2
From: Bend Oregon
Just kidding, but it will keep you in the power and in OD.
Elder User
Joined: Dec 2002
Posts: 797
Likes: 1
From: UT
Gear sets will run you $250+ ea. I have the tools to do it myself, but having never done a set I don't have the confidence to do it right. I expect to pay $800-1000 labor to have them installed.
Haha, ya I tried varying from 55 to 75 didn't seem to make much difference.
Haha, ya I tried varying from 55 to 75 didn't seem to make much difference.
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