Just drive the H2 home after having 4.56 gears put in. Have to take it easy for the first 500 miles and no towing. But before I changed the gears I took notes of my rpm's, which gear I was in, and how fast I was going. Then I did some calculations (4.56/3.73) to see what my rpm's would be w/ the new gears. And it turns out my calculations weren't too far off; my rpm's are just a little lower than I had calculated.

I will report back later with more information, but right now it gets through the gears real quick and at 70mph in 6th gear I'm at 2000 rpms which is much better than the 1600 I was at. Below 2000 rpm's this pig doesn't do anything but downshift on the slightest hill or even headwind.

Stay tuned.

 

Good report, i'm regearing mine too soon with 4.88 that needed with 38" tires. I'm going with Yukon ring and pinion, which one did you installed?

 

I went to the same shop that did my gears in my Excursion a couple years ago and both times they used G2. From what I read they all come from the same place in Korea...who knows.

You'll need 4.88's w/ 38's for sure. I'm a little worried about teeth size on 4.56's....wish you the best.

 

If you were ever curious the difference in size between the gears of and Excursion and H2:


The H2's are equal sized and the Excursion front is smaller than and the rear is larger than the H2's.

 

A little update, just went through the 1st tank of gas with the 4.56 gears. With all city driving it averaged 11.6mpg! Before the gears we could never get above 10mpg, 9.8mpg was the norm. I'm pretty sure if my wife (lead-foot) didn't drive it, it could easily get 12mpg in the city. This surprised me b/c I figured the mpg would go down.

Next week will be 500 miles on the gears and the gear oil will be changed and we can tow with it. I'm looking forward to that test.

 

Just to consolidate info:

1. Gears: 3.73 -> 4.56
2. Tires: 325/60r20 (35.5" x 12.8" r20)
3. 18% MPG increase (9.8 mpg to 11.6 mpg) in city

Thanks for all of the info.
Can you post your highway MPG, old vs new?

 

Thanks for summarizing the info. The only highway miles this H2 does is pulling a camper. So presently it averages about 8.5mpg on the highway. I'm not expecting that to change much. My goal for the lower gears was to give me more gears to choose from while towing up hills. I will get the towing mpg up here shortly.

 

No problem.
I'm just curious. I usually see people only talk about upping the gear ratio when moving to 37s/38s or more. I rarely see guys talk about only towing with what equates to stock size tires, even if it's just in this context. If you ever do some highway driving, post some numbers.

I'm glad it's worked out so far. You think 4.88 gears would have been too much for your needs?

 

I just drove on the highway for 40 miles round trip to get the gear oil changed. At 70mph the mpg 14.3. I don't remember what it was before the gears, so I don't know if that was an improvement. I'll have to search my other posts to see if I listed the non-towing highway mpg.

 

[sorry for the long post. Here's the summary: 4.56 gears all around improve mpg and drive-ability. Read on for details.]

This morning I had the chance to do my towing test w/ my 4000lbs camper. It's a 70 mile round trip route that is a gentle climb with a steep climb at the end. It's out and back. I filled up the tank right when I began the test.

This is the first time I did this test w/ the new 4.56 gears. It worked out better than I expected. The h2 no longer down shifts all the time to maintain speed. and I have plenty of power between 65-70mph in 5th gear going up the gently climb. In fact on the way back I spent most of the time in 6th gear which is a first. If you read my earlier posts, 6th gear was completely out of the question while towing. Best of all when the steep climb at the end I could hold 65mph in 4th gear which happens at about 3200rpm's which seems about right for short stints (5-8 miles)

In the end the mpg blew my mind. Our 7.3l diesel Excursion (the h2 replaced) did the same test at 9.6mpg and the H2 did it at 8.5mpg with the original 3.73 gears. This test w/ the 4.56 gears matched the Excursion at 9.6mpg. I actually didn't believe it. So I filled the tank back up when I returned and only 7 gallons were put back in for the 70 mile test. Yes, that's 10mpg while towing. But since I've always uses the dash display, I'm going with 9.6mpg.

I couldn't be happier w/ the 4.56 choice. The H2 no longer constantly down shifts and has power at the mph I like to tow at.

There was a question about 4.88's. My only concern with those would be the gear strength i.e. smaller pinion and ring gear teeth. But if I only had to choose between 4.10's and 4.88's, I'd go w/ 4.88's.