I was planning on changing my rear end gear from a 3.08 and go to a 3.73, as per most peoples advice on this board, but then I got thinking.
With my 3.08 at 65, I'm turning 1600 RPM in OD and 2300 RPM in 3rd . If I were to put in 3.73's at 65 I'd be at 1900 in OD and
about 2800 RPM in 3rd. The way I see it , I may as well stick in a huge tranny cooler and leave the 3.08 gear in.
With the 3.08 , 2300 RPM in third seems perfect for a 4.6
With the 3.73 , 2800 RPM seems a little high and 1900 in OD seems a little too low.
Aside from the off the line advantage of the 3.73 , I think the 3.08 would be obviously slower to take off but a large tranny cooler should take care of
the tranny.Any input/advice would be greatly appreciated.

 

Why would you choose to disagree with the wisdom of all the engineering/test time that went into Ford's selection of 3.55 and 3.73 for towing?

 

Y2K
I don't disagree.

I do how ever feel that what I had previously outlined makes perfect sense.
Sure a 3.73 or 3.55 will get goin' better than a 3.08
Lets face it a truck with 3.08's slow, a truck with 3.55's is a little "less slow"
and a truck with 3.73's is again a little"less slow"
I'm sure that Ford specs what they do for performance as well as vehicle longevity.
I personally like my 3.08 gear all year long except for that once a year maybe that I have to tow 5K
For my purposes, a 3.08 gear with a HUGE tranny cooler seems logical

 

You gave no indication of the load, wind load, frequency of towing, or terrain.

But, assuming that you tow infrequently and on flat land and with moderate load...

...I can agree with your solution.

You may even find that towing in second gear (with the torque convertor locked) at speeds of 45-55 might be quite acceptable.

You will not be generating any appreciable heat as long as you do not churn the oil by driving with an unlocked convertor.

 

2800 is close to the torque peak, which is where you want to be. Also, I have never been able to get my tranny to lock in 2nd. I've heard it will but mine hasn't yet.

I think you will not be very happy with a truck that can only use 1st and 2nd when towing (specially if you are in Toronto cottage country traffic).

When I went from 3.55 to 4.10, the truck was better to drive all the time, not just when towing.

Ian

 

I went from a 3:08 to 3:73 for the express purpose of towing, even though I will tow only once or twice a year. I believe Ford stuck 3:08 gears in their trucks only for the fuel mileage requirements, its my truck now so out with the old and in with the new. Your reasoning is well thought out and makes sense, however, I felt that driving with the 3:08 and coming to a hill or wanting to pass someone, you put the pedal to the metal and not much happens, except a higher torque is distributed through out the drivetrain, I think this will eventually lead to a shortened life span of one or more components. When you put the pedal to the metal with the 3:73, the torque is transfered to the wheels. I know where you're coming from though, I obsessed for over 6 months before I finally took the plunge and did it... . The daily drive is more fun now too! I vote for the gear change.

 

Enlighten my ignorant self...

How do you keep a torque converter locked?

 

SEADOO
The converter will not lock up in1st or 2nd gear, only in 3rd and 4th. It does this automatcally as load allows.

 

The convertor will lock-up after a pre-determined period of time at throttle position. Quick throttle-position changes will unlock your torque convertor, as will wide-open-throttle operation.

With my setup (11,500 GCW - normal-sized wind load for a full-sized travel trailer), operating in cruise control can result in an up-hill pull where the throttle has not been released long enough for the torque convertor to lockup. Fortunately, I have an ear for it, and de-throttle it to the point where the convertor locks -- then merely don't apply as much throttle as would unlock the convertor.

Any time you touch the brake pedal, your convertor unlocks.

On-off the throttle (as opposed to steady or slowly-changing throttle position changes) will cause your TC to unlock (try this yourself: from 45 mph in OD slowly increase the accelerator -- the TC will stay locked. Next, quickly move the accelerator just a bit -- you will be able to unlock the TC and still stay in OD. The same holds true for 3rd gear at various loads and speeds).

Simply put, you can get yourself into situations during perfectly-acceptable operation (by the Ford towing specifications/requirements) where your transmission can "lessen your satisfaction" (I edited out the phrase "overheat and self-destruct" in favor of the less-libelous phrase: "lessen your satisfaction") due to no fault of yours.