I have a 2010 Screw (4X4) with the 6.5' bed and a 5.4, V8. I just had a 2” ReadyLift leveling kit installed. I had the local spring shop install an extra leaf and re-arch rear springs. The factory 265/70r17 Michelins still have some life in them, so it may be a few months before I upgrade the tires; which brings me to the subject of this post.

I am looking replacing the Michelins with some 285/75r17 tires. If I stick with the factory rims, I am comfortable that “fit-ment” will not be much of issue. Although the truck is a 4x4, it seldom leaves the pavement, but I do pull a trailer from time to time. Here are my concerns...

I would like to hear from the guys that are running this combination. How significantly did 34” tires and the 3.55 gears impact performance. How about gas mileage? My truck is mostly a daily driver. I'm and old man and I drive pretty slow, but I need to be able to pull out into traffic and and get on up to speed, when necessary.

What should I expect? Can I get away with 34s with 3.55 gears?

 

I know you are looking for people with 3.55, but I have 3.73 and yes I did notice a change in performance and gas mileage (~1.5mpg loss). However on the performance side my gryphon made up for it. I say go with the tires and get a programmer.

 

I'm running 295/70/18's (roughly 34.5") with 3.73s, and like mdhawkin said, I lost mileage too (probably 1.5-2 mpg). My programmer made up for some of it, but I'm still re-gearing to prolong the life of my transmission. Tires this size have a lot of mass for 3.55s to get rolling.

 

Well not regearing now could mean a new tranny at some point in the future, sooner than it should be. As far as pulling into traffic and such, just depends how fast you want to do it. Anything made today has a lot more power than the 1980s. I myself prefer to womp on it when getting into traffic just so the guy who is now behind me doesn't have to slow down because some rude person jumped out in front of him and is making their way slowly up to speed.

 

i ran 34s (nitto terra grapplers in the same size you mentioned) on my 02 with a 4.6 and 3.55 and honestly it was fine...they are def going to affect your gas mileage a little bit and there is a noticeable power difference, but add a programmer (I highly reccomend a gryphon from PHP) and you will be more than happy. currently my truck has the same 34's (although pretty worn out) and after my 2V 5.4 swap and PHP tuning the truck is fast! The edge says Im doing 0-60 right at 7 sec. Id say get a programmer when you put the tires on, and your truck will look great and probably drive a little better than it already does!

 

i had 3.55's on my last truck. pics in gallery of the setup. i had leveling kit and 33's with 20inch wheels. which is kinda heavy and i could feel it. Hated it. i was fine, but hated it.....had the same deal only 35inch tires on the truck before that it was 3.73 and felt much better to me, but it was also a supercab not a crew..that could have made up for some stuff.

 

I am in the same boat. Screw longbed with 3.55s. I have 285/70/17 and tow a 5000 pound tt. Not sure how big the trailer you tow is, but it definitely gives the truck a workout. When its time for new tires I want to go bigger, but am only going to go up to 295/70/17 without regearing. Like u say, fitment won't be an issue, but the gears are killing me too. 4.10s would be nice.
[IMG][/IMG]

 

I have 3.55s currently on my truck with 35's and I noticed a big difference once I got the wheels put on.. I added a Gryphon CTS and it made a good improvement but still not where I want it so I am planning on upgrading to 4.56s in the near future.. If you dont plan on re-gearing at some point, I would reconsider that size tire..

 

I'm planning on changing the stock Perellis to GY Silent Armor 285/60/20. That's actually a 33.5 tire, so I'm hoping it doesn't kill me. I'm just not sure going from 3.55 to 3.73 is worth a regear (cost and headachges of it not being done right). If I was going any larger, I'd surely want the 3.73.

The larger diameter will be the real test for this 3.55 axle. I'll post my mileage change, once I have enough to make a substantive comment.

 

I'm planning on changing the stock Perellis to Goodyear Silent Armor 285/60/20. I had these on a 2006 FX4 and loved them. I think they are the best looking AT tire. My next choice would be Cooper Zeon LTZs.

The GY 285/60/20 is actually a 33.5 tire, so I'm hoping it doesn't kill me. I'm just not sure going from 3.55 to 3.73 is worth a regear (cost and headachges of it not being done right) on this particular size. If I was going any larger, I'd surely want the 3.73. The larger diameter will be the real test for this 3.55 axle. I'll post my mileage change, once I have enough to make a substantive comment.

Please post your MPG stats, etc if you are running anything larger than stock on a 3.55.