Can someone give me some power increase tips for towing with a 2000 Expedition?...I'm about maxed out with 8500 lbs (30ft camper)...I've checked into new tow vehicles, but can't afford this route....My Exp. is a 4x4 with the 5.4 and 3.53 rears......Thanks for any help you can give me.....

 

I think the best route to take is get a higher ratio rear end. i had a 5.4 with a 3.73 and it did pretty well with everything I wanted to pull. Other than that, the usual intake and exhaust changes, maybe a chip or programmer, but your biggest gain would come from the diff setup.

 

Thanks for the response....Any guess as the best way to change the rear?...Would the entire rear be replaced or only the gears?....Thanks..

 

It would be just a gear swap, but don't forget with 4x4 you'd have to do the front as well. You might check some local 4x4 shops as they pull 3.73 out quite often to put in higher for guys running big tires and lifts.

 

He would need LOWER ratio axle gearing not HIGHER.
Try to score 4.10's

 

DORF -

You can alter your vehicle's performance by changing the ring and pinion gear inside your rear end, which multiplies the power coming through the driveshaft. If you have a ring and pinion gear with a "high numerical ratio" (e.g., 4.11:1), that's what's typically referred to as a low, or steep, gear. If it has a "low numerical ratio" (e.g., 2.73:1), that's a high, or highway, gear. Low gears are designed to provide quick acceleration from a dead stop, but they increase the rpm at which your engine spins on the highway. High gears are often called highway gears because they do just the opposite, making your engine spin more slowly at highway speeds, which prolongs engine life.

Mike had it right.

Steve

 

Steina,
Keithp asked how to get more performance while towing, he didn't ask about lower rpms or longer engine life.
Therefore, a lower ratio axle will give better performance than a higher ratio, always has, always will. That's why they list the ratios in the towing guides. An F305 Tow Boss has a 4.30 ratio and is rated to tow a lot more than the same truck with a 4.10. Same with the difference between a 3.73 and a 4.10.
A 3.73 is lower than a 3.53 for the mere fact that the ring gear is going to rotate 3.73 revolutions to one revolution of the pinion. The lower ratio allows the engine to deliver more of it's power to the rear wheels than a higher ratio and will make climbing grades easier

Maybe your detailed explaination is useful for the uneducated here but I didn't just fall off the turnip truck yesterday. You're right that people get confused that a higher number means a lower ratio but I'm not one of them and I stand behind what I said earlier.

Bigger tires would call for a lower ratio too since the diameter of the tires can increase the effective ratio. Like Mike says they are probably pulling 3.73's but that's to put in 4.10 or lower to make up for the size of the tires.

Keithp, you should look into an underdrive spliter that will give you a lower ratio for towing but maintain the 3.53 for daily driving. Try US Gear or Gearvenders.

 

DORF -

Glad to hear you didn't fall off the turnip truck yesterday, but the bottom line is:

Higher ratios mean more engine rpm (lower gearing) per mile for increased towing capacity; lower ratios mean less engine rpm for better gas mileage. Therefore Keith needs a higher ratio rear end, not lower as you stated in Post 5.

A lot of uneducated people confuse low ratios with low gearing, but I'm not one of them; you're the one who tried to correct Mike.

Steve

 

Well high or low which ever way it is looked at putting 3.73s or 4.10 in place of the 3.53s would definately increase the towing performance.

 

Mike -

Yeah, 4.10's would probably be the way to go with Keith's TT and the cost is probably the same as 3.73's.

Steve

 

Agreed, I was thinking many people take out the 3.73s when installing larger tires that he might find some good used ones cheaper.

 

Mike -

Good point, but most of the cost is gonna be labor. If Keith goes the swap route, he's gotta decide if 3.73 is enough and it might not be much of a difference with the weight of his TT. 'Course, dragging 4.10's around when not towing won't be doing his gas mileage any good.........decisions, decisions!

Steve

 

Any drag racer knows better, but then it must be different on the west coast...
Also, I asked some of the guys here and they agree with me without a doubt.
It sounds like we agree on the ratios but disagree on what to call them. I've known it my way from the 1950's. This is the first time that I've ever heard it any different.

Oh well, next subject!!!

 

DORF -

I wasn't aware AZ was on the West Coast; you must have a different Atlas than the rest of the U.S.

Glad to hear your friends in Dixie agree with your "He would need LOWER ratio axle gearing not HIGHER" comment; I'm sure that means you MUST be right.

I've also known from the '50's that numerically higher rear end gear ratios mean just that - a 4.11 is higher than a 2.93, and equates to better off-the-line acceleration. That's why I ran 4.11's in the '53 Chevy with a '55 Olds V-8 I used to drag race back in PA.

Steve

 

Well, I've only known it from the 00's that "HIGHER numerical ratio" equals "LOWER gearing". It's quite simple. The pinion gear, which is smaller, has to turn several times to turn the ring gear (which is much larger) once. However, the ratio is often calculated by counting the teeth on the ring gear (more since it is larger) and dividing by the pinion tooth count (smaller).

Watch a large truck take off sometime. You'll see the driveshaft turn several times before the wheels turn even once--because of LOW (numerically HIGH) gearing.

LOW in this case is probably just an old reference to gear number, i.e., 1st is LOW gear, or, have you heard "put it in HIGH gear", meaning "go faster"? That's talking about the transmission gear sequence.

Jason

P.S. Dorf, I think you just mis-typed in your first post. You said, "He needs LOWER ratio axle gearing, not higher." I think you meant "LOWER axle gearing..."