[jrthomas15]

I have a 2006 xlt 4x4 with 35's.my question is what do you guys think about changing gears. Is it worth it to change. I have 3.55s ls

[JackandJanet]

Originally Posted by jrthomas15

I have a 2006 xlt 4x4 with 35's.my question is what do you guys think about changing gears. Is it worth it to change. I have 3.55s ls

Well, those gears with those tires make for a pretty slow accelerating truck (at any speed). If you want more acceleration, a higher gear ratio is certainly the way to get it. AND, if you tow much, I'd say you are badly undergeared, which probably puts more strain on your transmission.

BUT, you have a 4x4, which means you need to regear both the front and the rear. This is not cheap, but I don't have any figures to quote you. It would be less expensive to return to your OEM tire size, I think.

What were your OEM tires? We could use the gear ratio calculator to figure out a suitable replacement gearing to get you back to what you had at stock. And, the next size up from that would give even better pulling power probably.

- Jack

[88Racing]

With the 35's I'd suggest 4.56 gears.
Here's a good site to get them from.
Auto Parts - Differentials. AMC,Chrysler,Dana Spicer,Ford,GM,Suzuki,Toyota,

Go with the Yukon brand.
You'll also have to an install kit for each differential.
Also contact a local drive line/gear shop to see how much they would charge for parts and labor or just labor.
Changing gears isn't for the amatures or novice weekend wrench turners.

[jrthomas15]

I'm pretty sure my stock tires were 275/70/18

would putting in 4.56s help out with gas mileage

[88Racing]

Originally Posted by jrthomas15

I'm pretty sure my stock tires were 275/70/18

would putting in 4.56s help out with gas mileage

Regearing is always a good option.
It definately will help get the truck going.
Be better for your tranny.
But at highway speeds you may or may not see improvements.

[907DAVE]

On my old truck (F-150) I went up to a 4.56 from 3.55 when I put the 35's on. It was a night and day difference, truck was much more enjoyable and had all the power back. I used my truck for about everything, towing, DD, highway, ETC, and would not change my decision on gearing a bit.

Also since you are most likely going to be changing the carrier in the rear (to make room for the larger pinion) you might consider adding a locker or some type of limited slip. IIRC you can use the stock front carrier, but you will have to have to buy a special "notched" center pin if you go with the 4.56's or larger.

[jmt0645]

i'm currently running 33's and just swapped from 3.55LS to 4.56LS and the difference is night and day. acceleration is amazing and city milage i gain 1-2 mpg as i'm not having to put my foot in it as much, hwy (65-70) stayed the same, but anything over that speed it drops off. check ebay for the parts, i got mine from AZRACEPLACE for 215 shipped (2wd), they have 4wd sets for around 450. labor to install at my local shop was only 375 and took 2-3 hours

[JackandJanet]

Originally Posted by jmt0645

i'm currently running 33's and just swapped from 3.55LS to 4.56LS and the difference is night and day. acceleration is amazing and city milage i gain 1-2 mpg as i'm not having to put my foot in it as much, hwy (65-70) stayed the same, but anything over that speed it drops off. check ebay for the parts, i got mine from AZRACEPLACE for 215 shipped (2wd), they have 4wd sets for around 450. labor to install at my local shop was only 375 and took 2-3 hours

That's great information, jmt. I kind of suspected there would be a dropoff in mpg at higher speeds, but it makes sense that you could get an improvement in stop and go driving, since you get 0 mpg when you're not moving and the lower gear ratio keeps you at or near that condition longer.

And, as I said, the higher gear ratio has to reduce strain on the transmission.

[jmt0645]

Originally Posted by JackandJanet

the higher gear ratio has to reduce strain on the transmission.

my trans temp avg 170 cruising before, now its closer to 145. CHT has gone from ~205 to ~190 also

[JackandJanet]

Sounds reasonable, especially for the transmission. I suspect the engine is operating at a reduced "load" too, so that would account for the lower CHT. I keep a fairly close eye on my CHT and TFT and as soon as I start climbing even a gentle slope (more engine load) the CHT goes up a bit. On downhill stretches, even if not coasting, because some gas is needed to overcome wind resistance and maintain speed, the CHT will go down.

I'm a bit surprised at the reduction in your CHT though.

All these conversations almost make me want to regear my truck, since I tow with it. (You'd think though, that the factory tow package would have included optimized gearing.)

- Jack