Anything will roll on flat ground <img src="/forums/images/graemlins/lol.gif" alt="" /> I have a 8% grade that will kill anything on 38's including full size V8 trucks!

I don't know if that is totally correct. Gen II monteros have 1.9 low transfer ratios STOCK with 4.2 ratios in the diffs. If you put 3.15 ratios in the transfer and 4.9 in the diffs, that is a huge difference in gearing. Gen II monteros were engineered for 30 inch tires stock, so changing the gearing as mentioned above should allow to spin 38's with about the same 'feel' as it was stock. I know someone on here knows how to calculate ratios into tire changes. according to ratio calculator a tire change from 30 inches to 38 inches with an original ratio of 6.1 (4.2 diff and 1.9 tcase) would need a new ratio of 7.7 to feel the same as it did with 30 inch tires. 3.15 plus 4.9 is over 8 ratio which will give it more power with the 38 inch tires than it had with 30 inch tires with the old ratio of 6.1. I could be messing up on the math, that is why i used the online calculator, but someone on here did it before.

So you are saying that I can drive around in LOW range in my montero with 38's on it? <img src="/forums/images/graemlins/lol.gif" alt="" /> <img src="/forums/images/graemlins/lol.gif" alt="" />

Theoretically if I coudl put 15:1 gears in the axles, IT MIGHT be able to move around, but you're not doing any offroading with 38's and ANY stock engine that came in a montero.

Not to mention breaking axle parts.

And those gears are available for both gen I's and gen II's for both the t case and the diffs. I have them in my SR. I have plenty of power to spin 35-38 inch tires with just 200hp.

ok, so if you calculate high range, your old tire size is 30 and new tire size is 38, old ratio is 4.2, all you need to keep the same 'feel' is a ratio of 5.3 which is a little higher than 4.9 which is what you can put in but it isn't that far off and when it really counts is when you are fourwheeling which you can then use low range and be better off than you were stock.

BTW, when in high range, t case ratio is 1.0 just to clarify my calculation of having an old ratio of 4.2 and a new ratio of 4.9

Cap510 does ok with his 35's and gears. Still I wouldn't want to be in a Montero over 40 mph with 38's on it <img src="/forums/images/graemlins/lol.gif" alt="" />

Interesting math...

To calculate drive ratios don't add the ratios, MULTIPLY the gear ratios: (in gen 1=) 4.652 diff x 1.944 tcase low = 9.04

So from a 35" tire to a 30" tire would cause your torque to be reduced by 30/35= 0.857x. To correct this, the diff would need to be changed to 4.652 / 0.857 = 5.428 diff gears.

For the basic gen1, the 28.5" stock tire swapped to 33's = 28.5/33=0.8636x, which would cause about the same difference as the 30 to 35 tire swap. And hence the popularity of the 5.29 diff gears: they correct the drive ratio back to "normal". CapnCrunch has done this, and he can move pretty good up the hills in Colorado with a 2.6L pushing 33's!

With the 4.3 swap, it works the same way, except that GM put the extra engine torque to good hiway use (in the original Blazer) by using diff gears of ~3.5, much taller than Mitsus. So in the Mitsu, with the 4.652's, I "gain" crawl ratio compared to GM, but at the cost of hiway low rpm cruising. It would have been helpful to swap in a set of say 4.22 Mitsus to help the hiway a bit, or even use 35" tires, as either would help the hiway milage. With the 4.3, 33" tires are a must in the Gen1's.
The loss/gain in torque with any of these diffs/tire combinations would not be an issue for the 4.3, but overall, I prefer the lower final crawl ratio it affords...


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No matter what you say, it's just not dooable, AND have a good running truck. On a Gen 1, It's gonna require a 6-8 inch body lift, OR a at LEAST 8-10 inch suspension lift which does not exhist. I don't know about a Gen 2....\

Then EVEN if you could get gearing low enough(which you can't) then you would not have enough power to do anything except move around the driveway. Here are the problems.

#1 Fitment.. Massive lift, and or body removal required
#2 Gearing.. They do not make 7.13's for our trucks. Even if they did, the power required to get the mass of a 38 inch tire moving, and keep it rolling is stupid large. You ever picked up a 38 inch tire? How about even a 35? I wonder how much a 38 inch swamper weighs?
#3 Power.... If you want to stay mitsu, you'd better rob a Fuso Truck <img src="/forums/images/graemlins/smile.gif" alt="" />
6 cylinder deisel. <img src="/forums/images/graemlins/kewl.gif" alt="" />
#4 Strength of drivetrain. Stock drivetrain can't handle much bugger than a 33 reliably. Sure some people run 35's in their Gen1, but..... well..... those trucks don't run very well, or anymore at all.

THE ONLY EXCEPTION to these rules are if you live in Iceland.

It's Just NOT going to happen unless you do the following.

Get something capable of producing 300-350 Ftlbs....Get Axles capable of handling 38's(D60's/Portal/Rockwell).. Install appropriate gear ratios, and THEN bolt your 38's on.
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