Tow Haul is harder on engine & transmission - Diesel Truck Forum -
Thread Details Posted by eco-rich, this thread has received 5 replies and been viewed 1538 times.

LinkBack Thread Tools Display Modes
post #1 of 6 (permalink) Old 03-16-2014, 03:12 PM Thread Starter
Junior Member
Join Date: Mar 2011
Location: Gig Harbor WA / Cave Creek AZ
Posts: 66
Points: 12,218
Thanks: 12
Thanked 19 Times in 16 Posts
Tow Haul is harder on engine & transmission

My owners manual states that tow haul should be used when towing, hauling heavy loads or when used extensively in stop and go travel.

Accordingly, I've used tow haul when hauling the camper (gvw=14,000 lbs).
And since adding the ScanGuage II it's been easy to monitor transmission, engine and coolant fluid temperatures.

During my recent Mexico trip I quit using tow-haul while driving stop & go traffic through a city.
This resulted in lower temperatures for oil, coolant and transmission fluid temps.

After noticing the improved fluid temps, I continued NOT using tow-haul for most of the trip.
Not using tow-haul resulted in overall lower fluid temps.

The only time that I used tow haul extensively was while crossing the Sierra Madre Occidental mountain range.
Lots of up and down, twisty mountain road where having the lower range gearing was very helpful.

I always thought that achieving lower engine, coolant & trans fluid temps was a good thing.
The question in my mind is, is the owners manual recommendation to use the tow haul mode while hauling or towing. . mistaken?

Has anyone else noticed that cooler fluid temps are achieved by not using tow haul?
Your thoughts?

eco-rich is offline  
Sponsored Links
post #2 of 6 (permalink) Old 03-16-2014, 03:42 PM
Senior Member
harry6.0's Avatar
Join Date: Dec 2008
Location: Spokane WA. area
Posts: 3,051
Points: 142,055
Thanks: 1,507
Thanked 990 Times in 755 Posts
Main thing I've noticed is when towing heavy in hilly areas with tow haul is it tends to keep the turbo spooled up better due to the longer delay in upshifting and results in lower egt's. Turn the tow haul off and it will upshift sooner resulting in lower rpm's and higher egt's. This is only in hilly areas that I use it, on flat or mild grades I leave it off.

The fluid temps can fluctuate dramatically, and depend on rpm and load and ambient temp conditions and heavy winds or not.

What kind of numbers were you seeing in fluid temps for comparison?


Jan 03' built 6.0/F250cc4wd trqsft/SCT-tuned by KEM-Performance/Garrett Powermax vg-turbo/blue spring mod/gauges=egt+boost+fuel+SG2/exhaust/airaid intake/DR 4.5 lift/dual bilsteins/315's/greasable ball joints/powerstop/smittybuilt/kc lights/high idle mod/roll-n-lock/Mobil Delvac1 ESP 5W40 with (Archoil AR9100 in the oil) and (AR6200 in the fuel)

Last edited by harry6.0; 03-16-2014 at 03:45 PM. Reason: added a few words
harry6.0 is offline  
post #3 of 6 (permalink) Old 03-16-2014, 06:26 PM
Junior Member
Join Date: Nov 2009
Posts: 3,533
Points: 70,123
Thanks: 69
Thanked 655 Times in 578 Posts
I have a duramax and in the Alison the transmsion goes into lock up earlier and harsher, the increase in engine RPM is minimal at low power loads but at full power it will go to max RPM.
I hauled a load of top soil, up a hill for about 12 miles the first section is quite steep, in the 8 to 10% range, for about 2 miles. I came to the bottom of the hill at 60 mph in tow haul, and cruise. it slowed to about 52 mph till the engine got up to power and the transmissin went to 4th, and over 3,200 RPM, then it went back to 60 MPH and shifted to 5th to pull the rest of the hill. The temps never went up above normal. There is a free scale at Midway BC it grossed out at 24,552 lbs.
I know from testing that when pulling a hill, and not in tow haul it does get hotter, transmission temp because it stays in torque longer. I take it out of tow haul when on the flatter sections.

1988 ford van fresh overhaul, 1991 nissan pick-up 1993 Caprice 2000 GMC S10 Blaser 2007 nbs 3500 GMC 4x4 crew-cab long box 17 inch single wheels Duramax Alison. BW turnover Ball. Furakawa FL35 loader. Retired, HD mechanic, worked on engines all my life. Fabricator welder. electrician. in the process of finishing my new shop. Live in Rock Creek B.C. Wife has a fruit stand.
Johnp3 is offline  
The Following User Says Thank You to Johnp3 For this addition to TDG:
harry6.0 (03-17-2014)
post #4 of 6 (permalink) Old 03-16-2014, 08:13 PM Thread Starter
Junior Member
Join Date: Mar 2011
Location: Gig Harbor WA / Cave Creek AZ
Posts: 66
Points: 12,218
Thanks: 12
Thanked 19 Times in 16 Posts
Originally Posted by harry6.0 View Post

What kind of numbers were you seeing in fluid temps for comparison?

Outside ambient temps were often in the upper 80's driving at highway speed.
Oil temps mostly stayed below 220 and rarely made 230

In town traffic is where tow-haul keeps the engine in lower gear and builds heat in both oil and trans temps.
Keeping the truck out of tow-haul in town traffic kept tranny temps in the 160's compared to it normally going into the 170's

None of the Mexico driving that was anything that I've repeated.

A good comparison will be when I leave the Phoenix area going up Hwy 17 grade to Flagstaff - a trip that I've done before and will normally see EOT go to 240 very easily in outside temps of 80+ degrees.
This year I will keep out of tow-haul and see how it compares (next month).

eco-rich is offline  
The Following User Says Thank You to eco-rich For this addition to TDG:
harry6.0 (03-17-2014)
post #5 of 6 (permalink) Old 04-12-2014, 12:03 AM
Junior Member
nitrogen's Avatar
Join Date: Feb 2009
Location: Alberta
Posts: 274
Points: 48,743
Thanks: 1
Thanked 34 Times in 31 Posts
I've noticed the same, higher trans temp when in tow/haul. what I'm not sure of, is the max normal trans temp. as long as it doesn't cause it to exceed that, I don't see a problem. There definitely will be more torque load on the T/C lockup clutch when pulling heavy not in tow/haul, which could result in slippage. I'm with Harry not using it when towing hills etc probably will increase EGT.

Canadian Club #31
nitrogen is offline  
The Following User Says Thank You to nitrogen For this addition to TDG:
harry6.0 (04-12-2014)
post #6 of 6 (permalink) Old 04-19-2014, 12:46 AM
Pursuit Interceptor
HeavyAssault's Avatar
Join Date: Dec 2008
Location: Middle, VA
Posts: 735
Points: 60,451
Thanks: 15
Thanked 25 Times in 24 Posts
Images: 5
Tow/Haul does exactly what is supposed to do. It holds the trans shifting till it's a higher in the RPMs. Hence why you see the higher temps. Worth noting for sure, everyday use won't hurt anything. I for one find the shift points just a tad higher over what I would prefer while using Tow/Haul. Now if I'm towing Tow/Haul will be used.

Officially The Biggest Midget In The Game
HeavyAssault is offline  

Quick Reply

Register Now

In order to be able to post messages on the Diesel Truck Forum - forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Similar Threads
Thread Thread Starter Forum Replies Last Post
Tow haul GAM 2008-2010 6.4L Engine Tuner Forum 0 03-25-2011 11:32 PM
Engine & transmission questions JTS51 Medium and Heavy Duty 4 12-08-2009 05:17 PM
tow/haul. why? SSpeeDEMONSS 2003-2007 6.0L Power Stroke 10 11-05-2007 12:37 AM
Tow Haul 68Dodge 2003-2007 6.0L Power Stroke 10 09-24-2006 06:56 AM
To tow/haul or not to tow/haul that is the question! LargeCar The Parking Lot 7 03-29-2006 04:28 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome