T-case gear swapping to increase crawl ratio?

Does anyone offer a higher ratio gear for the 4low in the transfer case?
I know Marlin has dual kit for 3rd gens but its pricey. Re-gearing the diffs helps a lot for the daily 2wd driving but does a little for crawling 44:1 to 54:1 with 5.29 in the 6mt. Still Jeeps and Broncos are somewhere 100:1

 

I had this same question and I never got a clear answer. It seems like a great way to get a better 4 low ratio with just one gear swap.

 

I think alot off ppl would jump on it.

 

Atlas 2 speed or a 4 speed. With 4 speed you can crazy low crawl ratio.

 

Blow jet was looking into a r161 swap for a 5:1 first gear.

 

If you go to a machinist / gear place I'm sure they can machine up the gears needed.

I think it's very simple. keep stock T-case , no additional doublers or taco box , so no need to rig up shifters or custom driveshafts . Also I don't need 4 different gears for my T case. Just a normal 4H and the 4L can be 1:90 final crawl in 1st and I would be happy. I don't see why more people don't go this route.

 

Marlin no longer makes their tacobox.

 

I would love a lower 1st gear in 4low.

 

Is the Gen 3 T-case old school chain drive with two regular gear set? Seems like not such a big deal...

 

Yes chain drive

 

I spoke with Marlin and Trail-gear and they referred me to Yota Masters in Corona CA. They said they can put together something for me if my pockets are deep enough haha

 

Exactly my thoughts! All I want is 1.5:1 in High and 4:1 in Low

 

You are very wrong and I'll explain why. This whole idea is a good one and one I began exploring last year since I wanted to see why nobody had stepped up to do it and I wanted to understand all the hurdles.

The problem starts with the whole unit being a planetary reduction and not a counter shaft design like the old school Toyota cases. Stock the sun has 53 teeth and the ring has 83. This results in a 2.57:1 reduction. There are only 2 things you can do to reduce the ratio and that is increase the number of teeth on the ring gear or decrease the number on the sun relative to each other.

To increase the number of teeth on the ring gear you must make it larger. But, if you make it larger it no longer fits in the stock case. To work this solution you either need a custom housing or at the least a custom machined front housing section. Also, you can't increase it too much because it begins to interfere with other items in the transfer case. So, this method while theoretically would work, would be a ton of expense for minimal gain.

Reducing the number of teeth on the sun gear is the way to go. When you do this you'd need a custom sun gear and new larger planet gears and planet carrier. In essence, this is the way the Rubicon 4:1 low range planetary gear set works, it has giant planet gears and a very small sun. The issue with this method is the sun gear is integrated into the input shaft and this input shaft is bored on the id so the output shaft fits inside to ride on a support bearing and share oiling ports. Getting to a worthwhile new low range close to 4:1 means the sun gear needs about 28 teeth and at this diameter it's no longer going to have the ID available to mate with the output shaft.

This all means if you go 4:1 you redesign and build new planet gears, planet carrier, input shaft/gear, and output shaft.

If you just go the route of designing and building new planet gears, planet carrier, and input shaft/gear you'll only achieve a small decrease in low range. I don't remember what I figured but I think the limit was below 3.5:1 or something which is a small jump from the stock 2.57:1.

So, while I'm still interested in this, the stock tcase configuration doesn't leave a lot of options to work with. The complexity of the input and output shafts with oiling holes, splines, dogs, odd geometery, gear teeth, and everything else makes it an expensive task. I wish someone would step up and give it a full go, but I understand why they don't. I would definitely buy one if it was available.

 

Wow! That's too bad. Anybody knows why?

 

Nice explanation. Even cutting gears is not simple nor inexpensive, some 20 years ago Marlin marketed crawler gears for the Land Cruisers FJ40 but he gave up eventually since he could not anyone to manufacture the gears strong enough yet affordable. As much as I like my Tacoma, I eventually realized that my 3rd gen Tacoma is good platform for overlanding but if you want rock crawling maybe it's better to somewhere else.

 

hwww.northwestfab.com

 

I can't imagine that working w/o building a whole new transfer case.

 

No , you have to add a crawl box, the stock t-case is what it is...

 

I don't see a solution listed for Taco

 

$2200 for the Tacobox and $300 to have your drivelines shorten/lengthen according to the comments for this video. Imo $2200 is a great deal compared to a $3000+ RTT that most people drive around with. Found this on youtube:

https://www.youtube.com/watch?v=Lweji32Hv7U