Rear axle ratio, need some advice.

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Sep 12, 2014 | 1:34 PM

#31

tamss13

CF Beginner

Joined: Apr 2014

Posts: 6

Likes: 0

Quote:

Originally Posted by SWHouston

The likleyhood of you getting better gas mileage is not likely.
The 4:10 is going to spin the Drive Shaft/RPM about 25% faster at the same speed, causing more motor miles than with the 3.4. The lower gear will make the ride more "powerful' (like for Towing), which I don't think you're interested in...so...

1) Either you misunderstood him...
3) He doesn't know what he's talking about...
3) He's trying to get work that you don't need...

If you're going to replace the gears, I'd stick with the 3.4 or 3.7 at the highest.

Well I went with the 3.7 and used a different Mech.....going to 4.10 just did not seem right and no where on the GREAT WWW could I find anything that would confirm his statement......

Sep 12, 2014 | 3:27 PM

#32

intheburbs

CF Pro Member

Joined: Aug 2013

Posts: 997

Likes: 21

From: SE MI

Quote:

Originally Posted by tamss13

No not doing any of that....my suburban is basically a big old station wagon...kid hauler.....

The mechanic told me I would get better gas mileage going to the bigger rear end...and with so many miles on the truck it would reduce the engine wear....but I can't find that confirm his statement anywhere.

The exact opposite is actually true. The 3.42 rear would be best for your application - it'll keep the revs down on the engine at cruising speed and it will get you better mileage.

Believe me, I know. My 01 Burb has the 4.10 axles. As previously said, it's great for towing my 5000-lb travel trailer, but it never does better than 15 MPG on the highway.

Sep 12, 2014 | 7:41 PM

#33

73shark

Administrator

Joined: Apr 2006

Posts: 11,329

Likes: 193

From: KC, MO area

I know this sounds counterintuitive but when the GMT900 came out in 2007, those with the 4.10 axle were reporting better gas mileage than the ones with the 3.70 axle. It was assumed that the lower axle ratio put the engine closer to it's sweet spot and therefore yielded better mpg.