By Tony K
You may hear a lot about having a really low crawl ratio and while this sounds great there is more to it than just numbers. So just how do you determine the crawl ratio in your rig, multiply 1st gear x low range x diff gears. This gives you a crawl or final drive ratio. And what exactly does this mean? It will tell you how slow or fast you can go at a given engine rpm. You can do the math yourself or use the gear ratio calculator here on the website, it can be a lot of fun to mess with but be careful as some of the numbers are incorrect, but it will get you close.
To save you some time though I have put the most common ratios you might end up with in a mostly stock rig as well as what is in my diesel and Erics rig too. Threw in a couple of possibilities as well just for comparison.
H42, 2.27 low, 3.70 diff gears 30:1
Without a doubt the most common wagon on the road. Works well but could use some improvement.
H41, 2.27 low, 3.70 diff gears 40:1
Here is a great idea for a cheap way to get a good ratio while still keeping your road manners. A 25% improvement just by swapping out the tranny.
H41, 2.27 low, 4.11 diff gears 46:1
Currently the set up in Eric’s rig but I do believe he wants more (or should I say less) Worked great all the way through Rubicon while pulling a trailer. Need I say more?
H55, 2.29 low, 4.88 diff gears 54:1
My diesel rig set up works great. I cannot say I have ever felt the need for a lower gear to get over something. Do I frequently wish for more on the highway, absolutely.
H42, 4.0 low, 3.70 diff gears 52:1
New gears for the t-case just might be an option to consider. Plenty of low range grunt while maintaining highway manners.
H55, 4.0 low, 4.88 diff gears 95:1
If you really feel the need, you can get carried away…
What’s it all mean? There is a lot to think about and more options than you might think when it comes to improving the crawl ratio of your rig. Everything is a compromise. Improving one area will generally effect another.
-Tranny-
I think the biggest thing I have learned by messing with all these numbers is that the most important factor for crawling is first gear in the tranny. Lowering this gear has the biggest effect on your crawl ratio for the lowest amount of dollars and the least amount of modifications that need to be made to your drivetrain. And if you think about it, on Land Cruisers it is the easiest and cheapest thing to change. There are some good options for reasonable prices.
-Diff Gears-
Traditionally thought of first when it comes to lowering a crawl ratio but not always the best option. A low gear set in the diff’s handicaps you on the highway when it’s time to get home, at least for a non trailered rig. Not to say that it isn’t a good thing to change the gears but never as the first option. It should be tied to other changes. Not cheap to do either.
-Tire Choice-
Not really thought of very often when it comes to changing the crawl ratio but tire size can have a drastic effect on the final drive ratio that the numbers don’t show. This additional number is important and is the last part of the equation. While taller tires have long been considered “rubber overdrive” people tend to forget that the reverse is also true. A smaller tire will work as an underdrive thereby improving your crawl ratio. Consider running the smallest tire possible that will still get you over obstacles. (33’s are the shortest I would consider)
And here is some food for thought. If you have the same tranny and tcase gears in two rigs but put 37″s and 4.88 diff gears in one, you can almost match the final numbers with 31’s and 3.70 diff gears….
-T-case gear change-
For years the mini truck guys have had the option of lowering the ratio in the t-case just by swapping out a gear. This is also an option for a split t-case that just may make sense on your wagon but there are a few things to consider. It’s expensive on our wagons as you have to change multiple gears and the t-case may have to be modified to clear the gears. And from what I am starting to hear is that the 4.0 low gears are loud. Lots of noise coming from the t-case when you are on the road.
-Doubling up the T-case-
Another choice that presents all kinds of options. Lots of gears to select from but I think in reality it’s like a 24 speed mountain bike, you only will use a few chosen gears and lots of them will never be used. Probably the most expensive option as it also involves modifications to the driveshafts and additional mounts for all the extra weight. But hey, you can get the gearing so low even your brakes couldn’t slow it down in low range.
-Toybox-
Another option for super low gears. Toybox’s are reduction boxes design to double the number of gears available in your t-case. It fits between your tranny and t-case and requires a few mods that make me a bit hesitant. Driveshafts have to be cut and the one that makes me nervous would be having to cut off the output shaft of my tranny. Not something I would be eager to do. Pretty expensive as well.
How low is too low and what is a good all around ratio for wheeling and the road? I don’t know if there is such a thing as too low and in reality it all comes down to how you want to wheel your rig. Maybe think in terms of low enough to get you where you want to go. For the type of wheeling I do a crawl ratio somewhere between 45 and 54:1 works great, doesn’t have too much effect on the highway and is easily within reach financially for most people. Been some amazing places and haven’t found the need for lower gears so far.
A simple swap of the tranny may give you all you need and is the least expensive option. For myself a combo of tranny swap and diff gear change worked out quite well. But I have to admit the possibility of a t-case gear change or a toybox sounds like they would be a lot of fun….
And don’t forget to factor in the other variables (Tires, including size, pressure and tread pattern as well as lockers) which will all effect how well that drive train puts your crawl ratio to use.
