My 97 cc 3500 automatic has 4.10 gears and the stock 215/85/16 tires. Everything on the truck is completely stock, and I never tow anything. I'm at 45,000 miles now.

If I go up to 285/75/16 tires, with a spacer in the rear, will I cause any damage to my tranny or other components?

Also, will it make my rpms drop at cruising speeds? I'm at around 2200 for 60-65 mph.

It's just geared so low and I love the look of the big tires, but not willing to sacrifice anything else by doing damage.

Thanks all, I used the search but didn't find anything specific to duallies

 

This should probably be in the "24V engine and drivetrain" section for more answers.

You aren't going to hurt the trans with that insignificant amount of tire diameter increase.
Remember these trucks came with 3.55's also. You would need an awful tall tire to get to that ratio thru the 4.10 rear end in your truck.
Also, your speedo will be a little off with taller tires so check it with a gps so you don't have any trouble there.

 

Is it a 4x4 or 4X2 ? Take a look at 255-85-16 tires hard to find but for a dually thay look great. Also 235-85-16

 

Something to look at, just remember the optimum rpms on this chart are for a gasser and is for a 1:1 gear (4th?).

http://www.4lo.com/calc/geartable.htm

 

Thanks for all the replies guys

The truck is a 4x4. I've considered the 235/85/16 but just really like the look of the 285/75/16 on the duallies

Never knew about the 255's, actually found some on tire direct but a little pricey, I'l definitely keep them on the list though.

Thanks for the chart too, looks like my setup now is for nothing but towing power, which I really don't do. Just have to start saving more now, I always forget it's 6 tires now instead of 4!

Thanks guys

 

With the 285 tires, you will need a spacer. I run 285s with 3.55 gearing on my 98 (SRW), and I have no problem towing 10K pounds.

With your gear ratio, you could easily run 35s and be good to go. If you don't tow much, 37s would work too. Wheels would kill your budget though.

 

I went to 235 85 16 with 4.10's on my 99 3500 and lowered my cruise rpm, now it's 2,000 @ 65 mph, just what I'd hoped for.

 

Every situation is a little different as are your eventual goals. I have 3.55's/6 spd manual/currently 32.4" tall tires (285-75-R16 frnt/ 33x15.50 rear)

They are a little taller than the stock tires that came with the truck. The stock tires were the best ratio. 1600 rpm, @ 55 mph in 6th. The current ratio is a bit taller.
Enter the next step. I have a buddy that has a set of 4.10's for my D-60/D-80. I'll have those installed. Next, do some body work (clearancing) on the front fenders with 1/8" rolled plate, widening the opening up and back to the door and giving the rig that "Old Power Wagon" look. I know an armourer (an armor upfitter for military HumVee's) who has the technology for this. Next, have 10" wide x 16" wheels with the right off-set and back spacing for a powered front axle made by Stockton Wheel (down the street from me). I have 12"Wx16" on the rear already.

Buy Mickey Thompson Baja MTZ Radials: 36x15.50R16's for all four corners. 3750 capacity. rim recommendation: 10-13". O.D.: 35.4". I did the math and the net result will be a very similar rpm by changing to lower diff gears and taller tires. It's about a wash. Now, why stay with 16's you ask? Better floatation when you go down on the pressure. There is more sidewall to flex and more cubic volume of air to float the tread on.

Well, this is the direction of travel anyway.
regards, as always, jefe