I have a 2000 4.6L F150 with towing package (w/ transmission cooler) and 3.55 LS diff to pull a 23 foot trailer (3600 lbs). just had 265/75/R16 tires put on (maybe a mistake for towing but they ride great) and I am worried about loss of towing power/torque with the new tires. I have had trouble with this trailer when using OD. I read the other threads and will disable OD or tow in D. can I get a 3.73 differential? will it help? and can I put on a better exhaust and/or manifold? don't want it to loud. Gibson claims their side sweep is good for towing and not loud inside cab. other suggestions I've gotten are intake and programming. just want to tow reasonably. I'm new to this stuff but from what I hear 3.73 differential will help alot and then maybe exhaust after that.
what does a diff. upgrade run? and where is the best place to go?
should/can I have new ring and pinion installed or replace the whole differential.
all suggestions appreciated
thanks in advance

 

I went from a 3.08 to 3.73 rear end,big difference. I don't really think you'll notice that big a change going from3.55 to 3.73. I would go with a K&N filter, superchips programmer or flip chip, an aftermarket tranny cooler,larger than the oem. With the R type tires you might have an issue with sway, LT tires would have been nice and cut down on body roll. I'd get a rear sway bar, the f-150 is bad about body roll anyway. These are the cheapest mods I'd recomend,$500-$600. After this I would go with a new exhaust sys. & FPIK. Do you have a weight distribution sys for your hitch, a must have.

 

It is not worth the money to go from 3.55 to 3.73 gears. That is only 5% improvment in gearing. If you have 2wd, then rear gears are about $250 parts, and another $250 for labor. 4wd, is more like $1500.

The first thing I would do is intake and engine re-tune. Those will get you the best improvement under all conditions, and get better fuel economy as well. The pair will run about $500, depending on what tune option you want. I recommend the Microtuner 9100, but that is another $100.

Or, if you have a return policy on those tires, get a smaller size.

 

I have been thinking of changing my gears from 3:08 to 4:10's.. Is this a job that's all that difficult? Is there shimming involved? Neighbor of mine says it's not a hard job, everyone one else I talk to says dont try it yourself

 

Yes there is shimming involved with the pinion and carrier. You need to get the mesh pattern as close as possible to reccommended. You will also need a press to get the carrier bearings on, and you will need things like a dial indicator to measure backlash. This isn't just slapping on a new ring and pinion and bolting it all back together. There is more to this than alot of people thing, and if everything isn't shimmed correctly then your gears will eat themselves up. Unless you've done this before I would have a good gear shop do it.

 

http://www.angelfire.com/theforce/5o...5ohtech001.htm

That is instructions for a 8.8" out of a Mustang but it will give you an idea of what it takes to put a gearset in. Most rear axles pretty much follow his setup instructions with the exceptions of an axle that has a removable center chunk, such as a Ford 9", and it depends on the gearset manufacturer. Some gearsets have a specified pinion depth and backlash they are lapped at which are physically printed on the ring and pinion themselves.

http://www.drivetraindirect.com/html...allguide2.html

 

3.55 is not bad for towing and you're lucky to have the LS already.....Have a ring and pinion installed; you don't need a WHOLE new rear end. I'm with APT, up to 3.73 from 3.55 is a waste of time....I prefer 4.10s for towing. Even more good advice from APT, start with a chip/tuner.

 

Thanks for the advice guys, not what I wanted to hear but will certainly follow it.

Am I being hurt as much as I think with that 3:08 compared to a auto with a 3:55?? I have a manual tranny & my buddy has a auto in a 97 4.6 & at 60 mph he is running 200 more rpm then me both in 4th gear,& he has the 3:55 rear end, guess that's because the manual is geared lower then the automatic..

 

uinthas

I cannot imagine what 3.08 must feel like, as both my F-150's have had 3.73 gears with the 5.4L, but automatics.

How many RPM is the engine turning at your highway speeds, say 70mph or 80mph? On a 4.6L, you probably want to keep that in the 2200-2500rpm range. Much less, and you'll be lugging a little and get worse fuel economy.

3.08 to 4.11 a huge 33% increase in torque! If you were to change gears and keep near stock tire size, 3.55 seems about right to me, still a large 15% increase. That would make your truck feel like it gained 60hp.

 

@ 60mph in 4th gear I am turning 2350 rpm & my buddy turns 2500.. I'd love to have those 4:10's just dont know that $1500 is worth it?? I am looking for a trailer around 19' - 21" that weighs no more then 3000lb dry, then I have a 600lb ATV that I'll be hauling also..

currently I have a 16' trailer that weighs 2500lbs, & also tow the ATV, it seams to do okay with that.. I bought the microtuner, got a little bit more with that, guess I might just have to live with it.. I have thought about selling it & getting a new one, but I really like this truck & it will be paid for this summer with only 78000 miles.. For the life of me I dont understand why ford put a 3:08 in a 4wd truck