So this is to change your gearing, instead of doing both differentials? To save on the price of doing both diff gears & labor x2?
Basically, yes. You MAY still want to regear the diffs down the road, but the transfer case upgrade is a great first step for many folks.
As with many things in the offroad community (owners) and industry (shops and product vendors) we sometimes buy (or sell) the wrong product at the wrong time, often for the wrong reasons.
Yes, the HF2A transfer case modified gears
may eliminate the need to regear your differentials, or the use of these components may help fine-tune your differential, transmission and tire (diameter) decisions based upon your needs.
We are conditioned by forums, friends and vendors to think about tire size, differential gearing and lockers, but t-case gear options not so much, even though the economics make sense.
So what solution sequence you use can improve your results and reduce your total build cost at any point in time. If you start with larger tires for clearance, the perceived power of the vehicle may suffer due to higher overall final drive gear ratio (“ODR”). WHAT? What is that?
The overall final drive ratio of a vehicle from the output shaft of the transmission to the pavement are comprised of the following variables:
• Are you in low range or high range?
• Stock transfer case gears or modified? What ratios in low and high range?
• What gear ratio are the differentials? 3.73, 4.1, 4.88, etc.?
• What diameter are the tires?
Take all that together and you end up with distance traveled per revolution of the transmission output shaft.
Most folks start by increasing their tire size, which has the effect of reducing effective ratio (say from 4.1 to 3.9 for purposes of example) which means you have less “grunt” for towing, crawling, etc. The next step usually to replace the ring/pinion set in the differentials to lower the ratio. Again, for example, you replace the diff gears with 4.88s and your effective ratio (because of the tire diameter) ends up around 4.4. The effect of all that MAY be to give you the low range crawling ability you wanted for offroad, trail, etc. but you have increased your engine revs at highway speed.
An alternative approach (if possible) is to pick the tire size you want and install them, but step two is to regear the transfer case – both high range AND low range.
What options exist for regearing an 80 or 100 Series t-case? Here are the most popular that we offer, all made in Japan by gear grinding experts:
3.1:1 Low Range Crawler Gear Set = 25% lower gear ratio
10% Hi Range Overdrive Gear Set – go from 4.10 to 1 to 3.70 to 1 for lower engine revs on the highway
10% Hi Range Underdrive Gear Set– go from 4.10 to 1 to 4.56 to 1 for higher revs on the highway
If you want to run medium diameter tires and middle of the road diff gear ratios, think abou the overdrive gears in high range and a 3.1 crawler gear set for the low range. The HF2A is a great transfer case and seldom go bad and can accommodate both modified gears, plus if you are going to be in there anyway, why not go ahead and improve the low range crawling capability by 25%?
If you are into really big tires and your rig lugs at low revs on the highway (lots of shifting and loss of power), consider the underdrive gears. The low range gears do not affect the high range operation,. You can also do one or both.
If you run underdrive or overdrive high range gears, the low range gear ratio will be affected.
Once the t-case is upgraded, you can then figure out if you need to regear the differentials and how deep you want to go. If you want, you can even order up a rebuilt transfer case with the gears installed by Georg at Valley Hybrids and he will ship a finished unit on an exchange basis. List price on the OD and UD gears are $505 for the set and the crawler gears are $725. With our sale pricing it is a pretty good deal.
Georg
@orangefj45 would have to quote labor and shipping, but that’s the way I would look at the issue of if, why and what of t-case regear decisions.
