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Hi.

I have a 1990 Chev Suburban V1500 4x4 5.7. The door label says the stock tires are 235/75/15, but the truck has 31x10.5x15. I'm planning to buy a travel trailer (maybe 28 footer) and was wondering if I would be better off putting the standard size tires on for better towing performance, or if it will make much of a difference.

Also, I assume it has the stock gear ratio, but how do I check what that is? Is it encoded in the VIN somewhere?

One more thing ... where do I find what the maximum towing capacity is for a truck like this? I have the original manual (last guy left it in the truck), but it didn't seem to clearly list this.

Thanks for your help!

Ross.
 

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Tow cap. should be on inside drivers door. Gears would be in glove box tag, GU5= 3.23, GU6= 3.42, GT4= 3.73 and GT5= 4.10's.
 

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Thanks. That info is very helpful.

Does anyone know about whether it would be better to go down to stock tire size for towing?
 

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Going to a smaller tire with act like you have steeper gears. I would try to see what gears are in the truck before I did anything. Most, but not all 4X4 'Burbs came with trailer towing packages that had the steeper gears.
 

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The trailer towing package I don't think neccisarily meant a steeper gear ratio. My R1500 suburban has the 10K towing package, but came with 3.08 gears. Speaking of 3.08 gears, its RPO code is GU4.
 

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Tow cap. should be on inside drivers door. Gears would be in glove box tag, GU5= 3.23, GU6= 3.42, GT4= 3.73 and GT5= 4.10's.
Could you explain this a bit more? I am kind of curious about swapping gears in my 99' K1500 5.7. What do the numbers mean in terms of power/performance etc? I see a lot of people have Yukon gears in their trucks, whats so special about those?
 

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The gear ratio describes how many rotations of the driveshaft are required to rotate the tires one full rotation. A lower gearing(higher numerical gear ratio) means you have higher torque at the wheel at the cost of top-end wheel speed assuming a constant input RPM. Conversely, a higher gearing(lower numerical gear ratio) means you have less torque at the wheel for a given input power/rpm, but the top-end speed is higher. What this means is that lower gearing is good for towing, and higher gearing is great for high speed and fuel economy. A common towing gear ratio is 4.10s, while vehicles geared for good fuel mileage might have something around a 3.08.

Yukon just happens to be a good quality aftermarket gear manufacturer, and virtually dominates the market. That's why you see people using Yukon gears a lot.

Another thing to be mindful of is that as you go with taller tires, you reduce your effective gear ratio.
 
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