Truck Buyers Beware

[Lakepilot]

Originally Posted by malibu

GM went with the 3.08 gears when they came out with the 6 speed trany. The 6 speed shifts through the first three gears quickly so the gearing can be higher or lower depending on how you look at it. The older trucks had 4 speed trany's requiring the 3.73 or 3.42. I have an 06 chevy with the 3.42 and with tow/haul mode its not bad when towing. It all depends on how much weight you are going to tow?

Think snow!

I agree with Malibu. The 4 speed used in Silverado's was a 4L60 and had the following forward gear ratio's

1=3.06
2=1.63
3=1.0
4=.7

The 6 speed that replaced this is the 6L80 and is geared as follows:
1=4.027
2=2.364
3=1.532
4=1.152
5=.852
6=.667

The gears in the axles then determine the final gear ratio i.e. 4.10 or 3.73 etc. Look at the 4L60 ratio of highest gear to lowest gear versus the 6L80. Much wider.

By the way I also have an 05 Silverado with 3.42 gears and occasionally tow a 5,000 trailer (can you say large flat plate front) and used to tow my 21' Four Winns. The truck does it. But it is more optimized for daily driving. I drove to Mcadoo PA and picked up that trailer getting 20 mpg. Pulling it back I got 13 mpg.

This issue comes up all the time on an RV site I frequent. One thing I've noticed from that site, a lot of folks claim you need a 3500 diesel dually to pull a 2000 pound trailer.

[Dave R]

Originally Posted by Lakepilot

I agree with Malibu. The 4 speed used in Silverado's was a 4L60 and had the following forward gear ratio's

1=3.06
2=1.63
3=1.0
4=.7

The 6 speed that replaced this is the 6L80 and is geared as follows:
1=4.027
2=2.364
3=1.532
4=1.152
5=.852
6=.667

The gears in the axles then determine the final gear ratio i.e. 4.10 or 3.73 etc. Look at the 4L60 ratio of highest gear to lowest gear versus the 6L80. Much wider.

Thanks for the info. That's a nice spread of gears and is different than I imagined. I can now see that the overall gearing could be numerically lower and still offer perfectly adequate towing performance.

You typically stay out of overdrive when towing, so the 6 speed is limited to 4 speeds and the 4 speed is limited to 3 speeds. With 3.42 gears, in fourth gear, the 6 speed would have roughly the same drive ratio as the 4 speed in 3rd gear with 3.92 gears.

I'd avoid 3.08 gears, even with the 6 speed. There's no good gear for towing. 3rd is too low (4.71) and 4th is too high (3.54).

[fatlazyless]

After sitting unused for over two years, and taking about two hours to clean and vacuum a large chipmunk or mouse(?) nest built directly on top of the engine last month, I am pleased as punch that my '97 F150 xlt xtracab 2wd w/ 206k miles, a V6 and 5-speed manual starts up and seems to be running real nice. And, all it took was a new Wal-Mart battery for $65 and some new fresh gasoline and a bottle of el cheapo $2 carb-ejector cleaner.

I was stunned!

Have no clue on the rear end gear ratio!

Old Ford pickups never die, they just become neighborhood eyesores!

Could be I should go to VIP-Laconia for a $23 oil change and pour some Restore in with the new oil.....probably a good idea.

[Rattlesnake Guy]

Question for the experts. We have two Ford Expeditions with tow packages. Can someone explain what the overdrive on off function actually does? I know it is supposed to be off when towing and on when driving but does it do more than prevent me from going into the highest gear on the highway? If I am pulling the boat up the launch ramp at 1 mph, does it matter if the switch is on or off?

[lawn psycho]

Originally Posted by Rattlesnake Guy

Question for the experts. We have two Ford Expeditions with tow packages. Can someone explain what the overdrive on off function actually does? I know it is supposed to be off when towing and on when driving but does it do more than prevent me from going into the highest gear on the highway? If I am pulling the boat up the launch ramp at 1 mph, does it matter if the switch is on or off?

It prevents the transmission from shifting into overdrive which is your highest gear. Makes no difference at the ramp unless you are unloading at highway speed

[Dave R]

Originally Posted by Rattlesnake Guy

Question for the experts. We have two Ford Expeditions with tow packages. Can someone explain what the overdrive on off function actually does? I know it is supposed to be off when towing and on when driving but does it do more than prevent me from going into the highest gear on the highway? If I am pulling the boat up the launch ramp at 1 mph, does it matter if the switch is on or off?

It makes no diffference at low speeds and simply locks out overdrive like you think it does.

I was told by a friend that used to own a transmission shop to use the "O/D off" function whenever driving below 50 MPH or when towing. He also said when towing to ALWAYS shift (up or down) on a lifted throttle. This means that if I'm about to climb a hill that I'm reasonably sure will require 2nd gear at some point, I should manually downshift to 2nd before I start the climb. I have followed his advice and it has proven to be great. My 11 year-old Durango has 120,000+ miles with lots of heavy (7400 lbs) towing on the original transmission with no issues. Dodge transmissions have a pretty bad reputation for short lives.

It might seem kinda brutal to drop into 2nd gear and rev to 4000 RPM to maintain highway speeds up long hills, but it does not hurt the engine at all. It's not any different than the loads a boat engine sees.

[NoBozo]

My current '07 Toyota Tacoma V-6 4x4 (245hp) Access Cab (5 spd) Automatic requires me to be in D4...NOT OD when I TOW. I have a 3,000# trailer/boat. I get 21 MPG on the highway w/o the boat. With the boat I get about 16 MPG in D4. My rear end ratio is 3.73. It is adequate..

My OLD (142,000 miles) 1995 Tacoma V-6 4x4 (190HP) Access Cab STICK (5 Spd) got 27 MPG on the highway W/O the boat and 21 MPG WITH the boat.... going over the mountains from the LR to Rutland, Vt to Lake George.

My new truck is nice because it has all the STUFF that the old truck didn't have..A/C..power windows..etc.

BUT..the old truck was a real working truck...the new one is ...well.. comfortable. NB

[Seeker]

My '04 Avalanche Z71 4x4 w/ tow pkg says to use the Tow/Haul switch and I think it says to drop down 1 gear. Hey, I read the manual 5 years ago. I can't even feel my 12'x101" snowmo trailer w/ 2 4-stroke 2-ups behind me but i sure know when I have a 2,999# boat and trailer behind me. Feels like I'm towing my tractor without a trailer. I don't tow more than a few hundred miles a year so fuel economy isn't an issue.

[Lakepilot]

Originally Posted by Dave R

It makes no diffference at low speeds and simply locks out overdrive like you think it does.

I was told by a friend that used to own a transmission shop to use the "O/D off" function whenever driving below 50 MPH or when towing. He also said when towing to ALWAYS shift (up or down) on a lifted throttle. This means that if I'm about to climb a hill that I'm reasonably sure will require 2nd gear at some point, I should manually downshift to 2nd before I start the climb. I have followed his advice and it has proven to be great. My 11 year-old Durango has 120,000+ miles with lots of heavy (7400 lbs) towing on the original transmission with no issues. Dodge transmissions have a pretty bad reputation for short lives.

It might seem kinda brutal to drop into 2nd gear and rev to 4000 RPM to maintain highway speeds up long hills, but it does not hurt the engine at all. It's not any different than the loads a boat engine sees.

I agree with everything you said. It's the shifting of the tranny at speed that heats it up. If you had a temp gauge on monitoring tranny temp. you'd see a big drop with it in one gear, even loaded, versus constantly shifting. Lot's of rvers have temp. gauges. Cheap way to extend the life of the tranny,

[lawn psycho]

Originally Posted by Lakepilot

Lot's of rvers have temp. gauges. Cheap way to extend the life of the tranny,

I think they are being added standard on a lot of trucks now. I know the F-150s have them although there could be certain models that don't but I think it's standard equipment.

[Coolbreeze]

I think this forum site needs a new topic area. Maybe we'll call it "hot rod shop" or "tech talk" where we can discuss topics like this. I think it will be a huge hit!
The information listed is really useful. Great New Year to all!
-Coolbreeze

[trfour]

Originally Posted by Rattlesnake Guy

Question for the experts. We have two Ford Expeditions with tow packages. Can someone explain what the overdrive on off function actually does? I know it is supposed to be off when towing and on when driving but does it do more than prevent me from going into the highest gear on the highway? If I am pulling the boat up the launch ramp at 1 mph, does it matter if the switch is on or off?

If I am pulling the boat up the launch ramp at 1 mph, does it matter if the switch is on or off?

No, but I would manually shift it into first gear, just in case of any wheel slippage.
Always use low ,or first gear when towing a heavy load up a ramp, or just to get it moving, depending on mud-sand that the trailer tires may be in.

For over the road...

When you tow, be it a utility, boat or travel trailer, with the added weight, never use overdrive as this will overheat and burn the transmission fluid and cause early transmission failure. Repair, ball park ( $2500.00 ).

Also, you need to make sure that the factory 'Tow Package' includes an external transmission cooler, the heavier duty the better.

I've done a lot of towing over the years with many different tow vehicles and combination trailers. I have installed auxiliary coolers and even temperature gauges to monitor transmission temps.

Many may or may not have read my blog out here. My Dad towed a 46' house trailer across this wonderfull Country of ours with a 1949 Buick RoadMaster. The rig weighed 7.5 tons. The dynaflow automatic transmission used 1/2 a pint of automatic transmission fluid after our 4,376 mile trek...

I hope this helps.

Terry