I bought a 94 f-250, 4x4, 5 speed ,351, extended cab early this year and was told it had 4.10 gears. I decided to change all the fluids today and found it has 3.55's. I haven't been impressed with it's towing abilities thus far. Has anyone had real world experience with how much of a difference 4.10's would make. I hate to spend the money on gears but if it would wake the truck up it would be worth it. I generally tow in 4th unless going downhill for a long ways. Thanks.

ya, 3.55's are a little tall if you're towing more than 7-8k. You can swap out with anyone with the same axles. there's quite a few that have 4.10's that want 3.55's for mileage.
If you're towing under ten thousand, I'd consider stiffening the shifting and building a little power. You might decide you dont need the gears.

I tow my 4700# rig on a 20 ft. trailer with a generator, welder, air compressor, spares, and other tools. Camper shell on the truck.

4:10s would do WONDERS for that little 351.

My father tows a 28' travel trailer with his 1989 Ford Clubwagon van. It has a 351 in it. Came with 3:55s, then he swapped to 4:10s

HUGE difference!:eek:

That's alot of stuff for 3.55's. If I were you, I'd swap in the 4.10s.
If it's your DD, you might lose 2-4 mpg on the highway. other than that, it'll help your towing greatly
edit: http://motors.shop.ebay.com/_Car-Truck-Parts-Accessories__Ford-4-10-ring-and-pinion_W0QQ_nkwZFordQ204Q2e10Q20ringQ20andQ20pinio nQQ_fxdZ1QQ_trksidZm39
there should be a good set of used gears there every once in a while. might also check ford-trucks.com, they have a good section of classifieds.

i went from a 3.08 single wheel rear to a 4.10 dually rear in my project truck. i towed with it a few times with both the 3.08 and a 4.10, and a very underpowered 305.

i did not feel much of a difference in how it got the load moving,or how much throttle it took to keep it at speed. im sure there was an increase in engine power to the ground, but it was hardly a night and day difference that i could feel.

only thing i noticed was maybe a very slight increase in acceleration off the line with no load,and a higher cruise RPM.

im not saying that you should stay with your 3.55s,i just dont want you to spend the $$ on gears and expect a miracle.

i agree with mr chaos- add some power and make sure the tranny will handle it and youll prolly be alot happier with the results. if not,do the gear swap then.

my 2 cents,for what theyre worth :)

http://www.streetperformance.com/m/cats/197-exhaust/3738-cat-back-exhaust-system.html

http://www.streetperformance.com/part/jet-performance/shift-improver-kit/61908-650211.html

http://www.streetperformance.com/m/cats/193-air-intake/3554-air-filter.html

I'd start with those. The worst thing that could happen is you get a bit better fuel mileage.

Honestly, if it's a Tow truck only, id do these then gears too. but if it's DD, then i'd do these, then think about whether or not you need the gears.

It's pretty much just for towing unless the weather gets bad or I get tired of driving my shitbox work car. Thanks for the links. I already have a K&N FIPK, Dynomax muffler, and tuned up everything. It's a manual tranny. The best gain so far was bumping the timing from 10* to 14* with the little plug out.

I bought a gasser truck 3 years ago, 96' 351w, 4x4 crew, F350. Did OK, Had a 460 in a identical truck, so I was used to more grunt.

The oone with the 351w had 4.10's already, I was pleasantly surprised when I tuned it up and redid the exhuast with headers how much that little motor would pull. Did alright by me pulling my CJ on a open deck.

Never gonna compare to a diesel, but like I said, it did good enough for me.

LT headers and a good 3" single exhuast really did wonders for my 351w. Something to consider.....Edit: Just saw your Dynomax, get a high flow cat and do up some headers with a custom Y pipe, the stock Y is a choker.

It's pretty much just for towing unless the weather gets bad or I get tired of driving my shitbox work car. Thanks for the links. I already have a K&N FIPK, Dynomax muffler, and tuned up everything. It's a manual tranny. The best gain so far was bumping the timing from 10* to 14* with the little plug out.

I noticed your timing adjustment. Did you end up having to go to 89 or 93 octane gas? Did you change your plug gap? Curious.

Does it have the granny low?
with a K&N FIPK I'd check the MAF to make sure it's not bad. oiled filters tend to do that. that would majorly hurt your power output if it were bad.
Next I'd look into ignition modules...
If it's got the granny low, I personally wouldnt swap gears, because normally the gears help with takeoff, and not much else.

it has granny 1st. I don't use it much unless towing.

It does not ping at all on 87 octane even in 5th gear at 40 mph. Haven't changed the plug gap. I thought about getting a better coil and then opening up the plug gap a little.

Does it have the granny low?
with a K&N FIPK I'd check the MAF to make sure it's not bad. oiled filters tend to do that. that would majorly hurt your power output if it were bad.
Next I'd look into ignition modules...
If it's got the granny low, I personally wouldnt swap gears, because normally the gears help with takeoff, and not much else.

Why do oiled filters hurt the map sensor?

Why do oiled filters hurt the map sensor?

Oil coats them, so they don't read properly. My 3.0 had it happen, just needed to be cleaned with brake cleaner....

Also emphasis on MAF not MAP. (Mass Air Flow, not manifold absolute pressure)

Oil coats them, so they don't read properly. My 3.0 had it happen, just needed to be cleaned with brake cleaner....

cleaned, sometimes replaced. find it, unplug it, drive it around, see if there's a difference in power. if there isn't, try cleaning it.

Doesn't have maf. I'll check the readings on the map sensor when it's above 20* outside.

Doesn't have maf. I'll check the readings on the map sensor when it's above 20* outside.

hmm... is the sensor in the air stream, or does it have a hose that comes off the manifold? If it has the hose, then it wont be affected by an oiled filter, unless the hose is plugged.

It has a map sensor with a vacuum hose attached to it. I believe this system was referred to as speed density by Ford.

If you tow in the mountains much, I'd go 4.56. It's not your DD and you have o/d so it wouldn't be bad at all. Especially if your tires are larger than stock.
Travis..