Was looking at 4.56 gears and noticed they also make the 4.88. The 4.88 are a better price. Is there THAT much of a difference between these two?? Thanks.

 

Thanks. That's a start. Appreciate the info.

 

Cant really answer about the 4.56 but Im running 4.88s with 35s and it runs great. Especially in the sand, it doesnt bog down like before.

 

Thanks. I think for the difference in price. The gear ratio might end up better. I'll look closer to the 4.88.

 

Is this going to be a daily driver or a weekend truck to haul the toys around with?

How many RPM's are you turning at 70 mph?

I have a 4.6 V8 and manual transmission, 4.56 with 35" tires I turn 25-2600RPM at 70 mph (This is from using a GPS and not my speedometer.) I don't regret puttin in 4.56 gears, but if I was to do it over again I would go with 4.30. I wish I was turning 2600RPM going closer to 80mph. If I try going 80 I turn 3000 rpm. The truck seems to be screaming and I can watch the gas gauge steadily drop.

I just went on a 100 mile trip (one way) this weekend and put the cruise control on 70 mph and got 14mpg. I just wish I could get 14mpg going 75-80. Everyone is passing you going 70.

However, I do have the power to pull my ski boat much much better. When I was running 35" tires and the stock 3.55 gears I had to ride the clutch until next week and heaven for bid if I stopped on a hill.

When I put it in 4-lo, I could move a mountain. The truck almost crawls in gear with out giving it any gas.

 

4.56s = 35s

4.88s = 37s

 

I recently added a set of Yukon 4.56's to my truck. The biggest difference i noticed is going up hills there's no more gear searching. We took a trip this past weekend and went up a very large hill (for Hawaii standards) and my truck took if very smoothly. I actually told my wife to listen to the truck because the last time we took that same hill you could hear my truck constantly shifting, I even broke out a video of the previous trip and she noticed it right away. Also I am pretty much back to the same RPM's I saw when the truck was stock. At about 70-71 I'm pushing right at 2000 RPM's. I'm pretty happy with my decision.

 

I'm thinking the reason I'm turning such a high RPM is because I have a manual. I asked whether or not this mattered before making the gear change and got conflicting answers. Oh well, live and learn.

 

4.88 will only be 7% higher RPM than 4.56 at the same speed - amounts to an extra 140 rpm at 2000 over the 4.56. If the price is that good, suggest it would take a long time to save the additional cost of the 4.56 in fuel economy.

And, if you're running a truck that really needs these types of ratios, is fuel economy really a big concern?

 

The truck is not a daily driver. I travel for my work and use the truck to tow my wifes car on an 18 foot trailer 2-3 thousand miles every 3-4 months. the truck feels underpowered as it is and would like to pep-it-up a bit hoping that better gearing will help deliver torque needed to move the truck in sand, snow, mud and going up hills. I don't expect a Hummer H1 performance. I have the 3.73 LS right now and didn't really know that 4.56 may be that much of a difference. I saw a website where the 4.88 were at 258.00 and the 4.56 were at 271. Not much difference. I take it that the 4.56 will get better gas mileage. I just don't want to regret my purchase either way. Of course with gas above 3.50 a gallon I also have to look at being able to feed the beast.