More MPG, Cooler Engine while Towing

BlackLibertyCRD · **Posted:** Thu Jun 25, 2009 11:22 pm

I again was towing a 3,000 lb enclosed trailer across country hitting mountain passes and head wind ands getting poor mileage and engine running up to 3/4 on the temp gauge. I decided to try something different. I slowed down to 62 MPH and locked to cruise to 1,975 RPMs. That kept the transmission in forth gear even going down hill and stayed in forth except streep grades. On steep grades I hit the overdrive cancel button and the RPM in third would be 2,675 RPM until I reach the top of the grade and turn overdrive back on.

The results, more MPG and cooling running engine towing in forth even on flatland. Towing through the mountain passes I got up to 20 MPG :shock:

and on flatland 22 mpg :shock:

Engine stayed cool at the 1/2 mark on the temp gauge. I made it from Deer Lodge, MT to Ritzville, WA on 19 gallons. I made it from Ritzville, WA to Camano Island with more then 1/4 left on the fuel gauge.

Yes the trailer was loaded with heavy load and this result is better then I even had with an empty trailer. I can't wait for the trip back with a light load to see if the results is better.

onthehunt · **Posted:** Fri Jun 26, 2009 1:58 am

You mean 5th gear with unlocked converter?? 5th gear is @50 mph. Converter locks at 62 mph. Maybe I have it all wrong.

flash7210 · **Posted:** Fri Jun 26, 2009 8:44 am

Actually the shifts go like this...
OD on:
1 - 2 - 3 - 4 - 4+lock - 5+lock

OD off:
1 - 2 - 3 - 3+lock

I was confused too for a long time.
4+lock occurs at ~50mph
5+lock occurs at ~60mph or ~2000 rpm

So when he said he was pulling 1975rpm in 4+lock, he was right on the
edge of shifting into 5+lock.

Its hard to say exactly what speed these shifts occur. Every ones speedo
reads a little different depending on calibration and tire size.

CATCRD · **Posted:** Fri Jun 26, 2009 10:45 am

flash7210 wrote:

Actually the shifts go like this...
OD on:
1 - 2 - 3 - 4 - 4+lock - 5+lock

OD off:
1 - 2 - 3 - 3+lock

Flash has it right.

dieseldoesit · **Posted:** Fri Jun 26, 2009 11:04 am

Is there anyway to hold it in 4+ lock? I wish this transmission was one of those manumatics or whatever that the subi's and vw's have. It would be nice to control the shifting more.

WolverineFW · **Posted:** Fri Jun 26, 2009 12:47 pm

dieseldoesit wrote:

Is there anyway to hold it in 4+ lock? I wish this transmission was one of those manumatics or whatever that the subi's and vw's have. It would be nice to control the shifting more.

Cruise control if you have it.

BlackLibertyCRD · **Posted:** Fri Jun 26, 2009 1:46 pm

I use the cruise control to keep in 4th tc lockup and 1,975 and 62 mph to prevent it from shifting to 5th lockup. That would have the engine lugging too much for the weight I was pulling.

DOC4444 · **Posted:** Fri Jun 26, 2009 2:34 pm

So to hold in 4+ Lock, engage the "OD off" button and engage the cruise control at your desired road speed?

Thanks,

DOC

BCool · **Posted:** Fri Jun 26, 2009 2:51 pm

This is what I do, I tow often (2500-3500 lbs once a month) and this works best until you hit the big hills.

I towed 6000 lbs plus from vegas to sacramento a couple years ago, through the steeps (tehachapi) I slowed way and could keep 4rth or 3rd. But all through the valley I found that I was doing best if I could keep it just below 5th gear in 4rth, about 61mph (this is all with my 235x85 tires, spedo is off). On any kind of decent it would jump to 5th though, kind of a pain.

CATCRD · **Posted:** Fri Jun 26, 2009 3:53 pm

DOC4444 wrote:

So to hold in 4+ Lock, engage the "OD off" button and engage the cruise control at your desired road speed?

Thanks,

DOC

No, if you hit the O/D off button you will be limited to 3rd gear with lockup and doing close to 3000 rpm at 60 mph.

Leave O/D on, accelerate up to about 1900 rpm and set the cruise, and the tranny will never go into 5th. You'll be doing about 60mph depending on what software you have. Accelerate above that though, and it will go into fifth.

Gears FOUR AND FIVE are overdrives in this transmission, so if you turn them off you are limited to 3.

BlackLibertyCRD · **Posted:** Fri Jun 26, 2009 8:02 pm

BCool wrote:

This is what I do, I tow often (2500-3500 lbs once a month) and this works best until you hit the big hills.

I towed 6000 lbs plus from vegas to sacramento a couple years ago, through the steeps (tehachapi) I slowed way and could keep 4rth or 3rd. But all through the valley I found that I was doing best if I could keep it just below 5th gear in 4rth, about 61mph (this is all with my 235x85 tires, spedo is off). On any kind of decent it would jump to 5th though, kind of a pain.

My tires are 245x70r16 so your speedo must be much slower. I would go by the tach. and set to 1,975 RPM and will stay out of 5th, at 2,000 RPM it will shift into 5th on decent not what I wanted. I figure with my tires and speedo error I must be doing more like 60 MPH. Your tires would read the speedo more correct than mine if you have a 2006 like I do.

Silverdiesel · **Posted:** Sat Jun 27, 2009 2:02 am

That OD "off" -1975 RPM- 62 MPH is great and I agree but places like I10 in West Texas is 80 MPH speed limit and 62 MPH cruise gets you rear ended so to speak.
I am all for getting that coolant temp down but I think that gauge is working with fuzzy math from the ECU.

findings:
If the temps really do get dangerously hot the engine will go to limp mode any way and,
A good after market gauge set up is in order to see real temps.

One of my must do future mods is an array of four aftermarket gauges:
Coolant temp, EGT, Boost pressure and Trans fluid temp.

When I get these four gauges put in I will be a happy camper!

Roland

PhoenixCRD · **Posted:** Sat Jun 27, 2009 12:45 pm

Silverdiesel wrote:

One of my must do future mods is an array of four aftermarket gauges:
Coolant temp, EGT, Boost pressure and Trans fluid temp.

When I get these four gauges put in I will be a happy camper!

Roland

Sounds like an Arizona Wrench Day is coming again to the greater Phoenix area

I'd like a set of gauges, too.

Gary

BlackLibertyCRD · **Posted:** Sat Jun 27, 2009 11:07 pm

Silverdiesel wrote:

That OD "off" -1975 RPM- 62 MPH is great and I agree but places like I10 in West Texas is 80 MPH speed limit and 62 MPH cruise gets you rear ended so to speak.
Roland

That is with OD engaged so you have 4th, not 3rd. Towing over 60 MPH is not recommended by most trailer makers.

retmil46 · **Posted:** Sun Jun 28, 2009 8:19 pm

If you have the 05/pre-F37 shift points, 5th lockup happens at 58 mph.

BlackLibertyCRD · **Posted:** Sun Jun 28, 2009 10:58 pm

retmil46 wrote:

If you have the 05/pre-F37 shift points, 5th lockup happens at 58 mph.

Finally, something good to say about 06/post-F37 shift points. I know if mine was in 5th and I was slowing down, it downshifts to 4th at 58 MPH and upshifts about 63 MPH when speed resume.

nursecosmo · **Posted:** Mon Jun 29, 2009 12:18 am

BlackLibertyCRD wrote:

retmil46 wrote:

If you have the 05/pre-F37 shift points, 5th lockup happens at 58 mph.

Finally, something good to say about 06/post-F37 shift points. I know if mine was in 5th and I was slowing down, it downshifts to 4th at 58 MPH and upshifts about 63 MPH when speed resume.

What's good about it? The higher RPM lockup points suck.

BlackLibertyCRD · **Posted:** Mon Jun 29, 2009 1:07 am

nursecosmo wrote:

BlackLibertyCRD wrote:

retmil46 wrote:

If you have the 05/pre-F37 shift points, 5th lockup happens at 58 mph.

Finally, something good to say about 06/post-F37 shift points. I know if mine was in 5th and I was slowing down, it downshifts to 4th at 58 MPH and upshifts about 63 MPH when speed resume.

What's good about it? The higher RPM lockup points suck.

The point of this topic is not to lug the motor when towing is what 58 MPH 1500? RPM will be doing. It will use more fuel, cause engine to run hotter and make towing unpleasent. I remember saying to my wife many times that I wished I had a stick so I could leave the darn thing in 4th gear. Seem to my experiance that 1,975 works more effiecent than trying to maintain lower rpm.

nursecosmo · **Posted:** Mon Jun 29, 2009 1:21 am

BlackLibertyCRD wrote:

nursecosmo wrote:

BlackLibertyCRD wrote:

retmil46 wrote:

If you have the 05/pre-F37 shift points, 5th lockup happens at 58 mph.

Finally, something good to say about 06/post-F37 shift points. I know if mine was in 5th and I was slowing down, it downshifts to 4th at 58 MPH and upshifts about 63 MPH when speed resume.

What's good about it? The higher RPM lockup points suck.

The point of this topic is not to lug the motor when towing is what 58 MPH 1500? RPM will be doing. It will use more fuel, cause engine to run hotter and make towing unpleasent. I remember saying to my wife many times that I wished I had a stick so I could leave the darn thing in 4th gear. Seem to my experiance that 1,975 works more effiecent than trying to maintain lower rpm.

So true. for towing 4th gear is better on grades. For normal driving it sucks though.

butcher_block · **Posted:** Mon Jun 29, 2009 10:22 am

so what RPM would be best for light load cruising (most roads round me are 40mph but i can get away with 50)
i see the highway bout once a month

at what point is the motor bogging

this is all about me hunting the right rear gears and 5/6speed man trans for my most used speeds

More MPG, Cooler Engine while Towing

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