My truck (64k miles)was riding on 37's and they were worn down.
I decided to replace with 325/70/17 (35 inch) for several reasons.
First of all cost. Got an awesome deal on these nitto's and paid $155 a piece brand spanking new. (shipping was extra but no biggie for someone who is a freight broker haha)
So while that was being done we noticed play on the right side.
The bearing was toast (lots of metal shavings too ) so that got replaced.
After that still play and the pitman and Idler will need replacement. The tierods are good.
So yes the 37 inchers were trying to there best to wear everything out under there.
2nd reason I went for 35's is the gearing ratio's. With some headwind or going up a hill, it would easily drop out of 4th gear to 3rd. With the 35's that goes a lot better.
3rd. Mileage. I think I improved my mileage with at least 10%

Down side? I liked the looks of the 37's better but the driveability and cost are much better with the 35's.

Oh I forgot to mention. The old tires were cupped pretty bad and I never knew how much noise they were making until I had put the new ones on.
I just hear the wind now (plus some engine noise of course.

Also just found out I have a massive air leak somewhere and they suspect the intake manifold gasket to be the problem.
Wife is not happy with all the credit card receipts I have been giving her.

 

Ouch! Sorry to hear about your woes... I was really considering 37's but am happy with the 35's as well. I spoke to someone at a 4x4 store and he mentioned that the pitman arm was a problem child. Curious to hear the cost there... Another point is that I honestly didn't consider the gear shifting - interesting. Are you going to replace the intake manifold gasket yourself? Probably isn't too difficult nut time consuming to do. I remember a few years age when I took my wheel off my Jeep and the hub bearing damn near fell off on my hand. Obviously I didn't plan on it and ~ $300 later learned my lesson.

 

Those are all common wear items (except the intake manifold). Anytime you put more weight on the tire/wheel assembly you are going to accelerate wear on the hub/idlar/pitman/brakes and also affect the gearing. common issues on any vehicle with large rims or tires.

 

Cost of pitman and idler are around 320 dollars.

I tested the intake manifold at coldstart by spraying some carburator fluid around it but it did not suck any of it in as far as I could tell. Engine rpm's did not change. so maybe it is not the gasket.

 

Problem was the intake manifold gasket. The stupid thing is made out of pastic and once the weather gets cold they shrinksomewhat and allow air to be sucked inside, messing with the air fuel ratio thus throwing a cell. Once the engine is warmed up it will expand and seal itself.
You can test this on a coldstart by spraying some carburator fluid around the intake. If the engine rpms change you will know it is the problem.

 

Sorry to hear this..

 

I put 35s on mine AT's from MT's and what a difference. I did purchase my hummer used with MT's. It did some damage to the front end allignment. 35's only look good with a good width. Gettem extra wide.

 

In 35 inch the widest available is 325. Only 2 brands carry these. I have the nitto's. Bunch of variety in 315 width though

 

Yes the stock 315's are weak looking due to the proportion of the big vehicle. Any other car would look massive. Although I did purchase some 315's because the tire shop showed me the product compared to the weak 315 spare I had. This aftermarket 315 had probably 2 inches more width than my stock 315 bicycle tire, spare. They were much cheaper than the 325's. Although I will be getting 325's next time around. They just match the body better. Any pics?

 

You can also go with a 35x12.50r17. they are very close to stock but wider and slightly taller.