I am toying with the insane idea of doing yet another gear swap.

Not like the 4.10s aren't good enough.. I just want to push this truck to it's max by adding a set of 4.88s.

I just got a question though...

Would it be too much work for the engine to be revving so high on the highway?

I like the fact that there is barely any strain on the engine/tranny... it's funny actually. Truck runs excellent on the 4.10s. From all of the stuff I've hauled and things I've pulled, I've never had a problem with power - ever.

And no... I'm staying with my stock tires thank you.

 

I'm quite happy with my 4.56's but 4.88 on stock tires? I would think that would be a bit much. I have 285/70/17 tires and I think my RPM's are kinda high on the highway. I'm around 2K RPM at 70mph and I've been told that isn't anything to worry about.

I guess it all depends on what size tire you're going up to and how long you will run 4.88's on your stock tires. I plan on going to 35" tires next so maybe I will regret not getting 4.88 cause I do like how my truck is now with the 4.56.

 

If you want to see first hand what it would be like, drive on the highway in 4th (4.88 * 0.8 = 3.90, pretty close to 4.10). Don't forget to check the gas mileage. It would also just about turn 1st into a granny.

 

chris. 2k at 70mph doesnt sound bad. i have stock 3.55 but bigger tire 285/75/16 i thing that turns my gears to lik 3.12 or 3.08. with speedo at 70 i push 2k but im really going 80mph. so i guess at 60mph im pushin around 1700.
dont go 4.88 on stock tires. my f550 tow truck has 4.88 ran through a 5speed. with a granny gear under reverse. sure it pulls real low but cant go over 80 on the freeway

 

Yeah you are right... I was messing around with the gear calcs on this one site, and got what you got.

Doesn't look like a good idea. I think my 4.10s are good enough. The stock 3.55s were like BLAH even for the few months that I had them last year. I could never imagine driving this truck with 3.55s. But Ford put them in there.

That's what I thought.

At 65 I'd be turning 3k rpm.

And no, I'm not planning on buying bigger tires.

 

Funny you post this. I've been going back and forth between 4.10 and 4.56 for my truck. I need new tires and plan on going with a 285. I've had tons of people say this is too much gear for a 285. Several guys that are running this same combination say it is just fine. I tow and haul fairly often and think I would be ok. I've also seen people running 4.10 on stock tires and saying how great it is. One guy had 4.56 on a lightening and said he loved the gears. I agree with you that 4.88 is a little steep for stock tires. Good luck with your decision.
Rich

 

go with 4.56 and sell me your 4.10s for cheap

 

Ya know, I'm quite happy with my 3.55's.

 

My Expedition has 3.31s Atleast that's what the code reads on the inside of the door.

 

Screw that I have 4.56's with 35" Tires and the RPMs are to high for me with this setup. No way would i ever even consider going to a 4.88 with stock diameter tires.

 

hey richard whats the final gear ratio with the 35's. assuming they bring it down to like 4.10-3.90 right. and were did you get your gears

 

I got the work/parts done in Sacramento

 

3.55's were ok for the OBS trucks, glc. I had them in my '99 and I had no issue hauling anything. Everything I threw at it, the truck hauled it without complaining. Personally... if I still had the '99, I would've done a 3.73 swap... and that would've been like overkill to the max for the OBS with the 5 speed.

But since the NBS trucks weigh a lot more, you need a steeper ratio to pull what I pulled with my '99. Kinda sucks if you think about it... but at least there is a way to resolve that issue.

The key is to get an equal balance of torque to weight ratio to the ground. The more torque you can get to the rear wheels, the better the truck will be a hauling.

Since I do nothing but haul, the 4.10s make it perfect. Not to mention my city and highway mileages are excellent. There is minimal clutch and tranny wear, and the engine doesn't bog. It's always in the right range.

Also, I don't know if you guys knew this or not, but... the first gear ratio in the 5 speed standard is 3.91 (M5OD-R2) and the 4 speed automatic (4R70E and 4R75E) have a 2.84 first gear ratio. Thus making the standard allowable to lay down more torque even from the outset. Less torque multiplication off a torque converter, which is some what negligable from what I've read and understood. But it's nice to know there are ways to calculate this stuff to find out what would actually be the best way to go.

I think I'm going to stick with what I've got and be happy with my 4.10s.

 

That's what mine had, and I had the factory tow package.

The swap to 4.10s was great.
I ran stock-ish diameter tires...285/60R18.

 

That's awesome because I'll be picking up 18s soon and was planning on running that same size tire. Gears? Hopefully in the future. But not right now.