Rear End Gear Ratios

[DaveDurling]

I am new to this forum and RVing, so please help.  I am looking at buying a Yukon XL 2500, probably 8.1 motor.  I already own a 30 foot Travel Trailer, about 7000# fully loaded.  The Yukon XL  is available with a 3.73 or 4.10 rear end.  What are the advantages or disadvantages given the size of my trailer

 

[Gary RV_Wizard]

The 4.10 rear axle will give you better pulling power, e.g. better acceleration from a stand still or passing, better hill climbing, etc. This comes at the expense of some fuel economy when you are not towing, though probably not much.

There should be separate capacity rating figures available for each of the rear axle ratios. If you can't find it in a brochure, ask the dealer to look it up for you.  Ask about GVWR and GCWR as well as the generic "tow rating".

You definitely want the 8.1L to tow trailers in that size range. A big block engine is a better hauler overall. You might even consider a Duromax diesel if it is offered in the Yukon.

 

[Chet18013]

You will probably be looking at a 2 mpg penilty if you get the 4.10. Of course, there's always the GearVendors. If you get the 4.1 and a GV, you will have the advantage of the 4.10 and be able to get the mpg of the 3.73. That's what I did with my Dodge diesel. See: www.gearvendors.com.

Chet18013

 

[Gary RV_Wizard]

I don't think the 4.10 will have much, if any, mpg penalty when towing.  The 4.10 gearing basically enables the tow vehicle to spend more time in overdrive compared to the 3.73 and buys back whatever "penalty" there may have been otherwise., But when NOT towing, 2 mpg could well be the right ballpark.

What transmission comes with the Yukon + 8.1L?  Is it a 4 speed 5 speed or a 5 speed?