good day. My question is if I change my diff gears on my 2000 f150 4wd off road 4.6 v8 with. automatic 3 speed w/od from the 355 H9 code gears to either 373 or 410s in the rear diff do I have to change the front differential gears to match? If so will I have to sell a Kidney to pay for front and rear gears? How many shop hours or dollars is it approximately?
Any info on this will be greatly appreciated.
Thank you in advance.
Mike.

 

Yes, you have to change both. If you are towing heavy, I'd get 4.56's. 3.73's won't make enough of a difference to make it worth the money, 4.10's, maybe.

Parts and labor are about $1600 and figure another $400 for a programmer and tunes.

So - sell what you have to in order to come up with 2 grand.

 

Thank you very much for your prompt response and info.
Would you happen to know how much of an rpm change on the highway 456’s will make?
I get lousy gas mileage as it is and would like to know how much it will change?
Is the front ring and pinion much more difficult than the rear to change?

 

http://4lo.com/calc/gearratio.php

Assuming 32" tires (gotta start somewhere) and 70 mph in OD:

3.55: 1825 rpm
4.10: 2100 rpm
4.56: 2350 rpm

Changing the ring and pinion in either axle takes experience and tools, if it's not done right you will eat up the new gears.

Gas mileage probably won't change much.

 

How much weight are you wanting to tow?
Maybe you have the wrong idea.
The truck is rated for close to 11,600 gross combined weight.
At this total weight it won't be a Diesel tower no matter what you do..
Good luck.

 

My travel trailer full is is between 8 and 9,000 lbs. tires measured 32-33” tall.
gears are 355 and I’m considering 410-456.
thanks!

 

Well here ya go!
Page 164 in your user manual lists your gross weight at 11,000 pounds max for 4.6/3:55 and 16 inch stock tire size.,
If your tires are larger you just made it worse for towing.
Your truck weighs about 5500 lbs plus 9000 = 14,500 pounds worst case so far.
14,500 minus 11,000= 3500 lbs over limit. That is a lot.
You cannot make up for this legally or otherwise by changing gears.
You don't have enough transmission reliability over the long term with a stock 4R70 and other considerations.
For example, you 'grunt' the load up a steep hill to many times, expect possible converter Ballooning. Then your in for a full rebuild and have it happen again doing the same thing all over again.
Ask me how I know!
Just offering reality to help you know what your trying to do.
You need an F250 Diesel to tow like you want in your part of the world otherwise you will never be happy with what you have for towing...
Good luck.

 

Well, you are overweight no matter what you do with that size trailer.. I was overweight with my 97 F150 5.4 with a #5000 TT.. It towed okay, but was still over weight...

Hell, my Dad towed an #8000 GVWR TT with a 1999 Dodge 2500 with the Cummins in it and you knew it was back there..

I wouldn't tow that much trailer with my 13 F150, so more power to ya!

Good luck!

Mitch

 

I double checked the trailer vin tag. It weighs 7100 lbs. sorry my mistake.

 

4.6 (in any year F150) + #7000 TT is gonna = "dog-up-hill".. In my case, a #5000 TT with the 5.4, 3.55 gears and 265-75-16 tires = 2nd gear, 3500+ rpms to go around 55 mph up a 5% grade with not much pedal left..

4.56 gears will help you get going off the line easier than the 3.55's... But, once you are up and going, you will still need rpms to stay in your engines power range, which is 3500 rpms + so not really sure how gears alone is gonna help?

Good luck!

Mitch

 

Thank you.

 

Towing that heavy, either get a bigger truck or put 4.56's and a programmer in it. You really do have too much trailer for that truck.

 

I installed a weight distribution hitch that makes it stay completely level and handles very well no bounce nothing. The only problem is up the hills. So until I can get a new truck the 456 gears and programmer is probably my best option for now.

 

Your investing in things that may be discarded later except for the leveling assembly.
You cannot make up for a truck that is lacking in power, larger brake area, larger rear, suspension,
higher capacity transmission etc.
Your loaded trailer weighs more than your truck.
Better not to do all this than have the truck break down and have nothing to run as a later result.
If you have money to spend now, better to consider that money with the truck and trade in for one that will do the job while your truck is still running.
Good luck.

 

on my 2000 f150 4x4 4.6 Auto trans 355 gears, Can I change 355 to 456’s in the rear and drive it without using 4wd until I can afford to do the front gears? It would be 355 in front and 456 in rear not using 4x4.