TC gears vs diff ring/pinion for regear?

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nukegoat said:
Yeah except my opinion is rooted in math and engineering
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Im not a differential builder on a regular basis at the shop Im at, other guys here at work are though. I only do differentials from time to time. Im just basing my opinion on what I have seen come in and out of the shop doors in regards to the toyota 8" differentials that are built here. Some were probably lower quality metallurgically compared to a 1990s oem toyota ring and pinion set, but some too were name brand gears too which I would assume rivaled the metallurgy of 1990s toyota gear metallurgy. :beer:
 
lumbee1 said:
I'm planning on regearing my Cruiser this year. I can either regear by replacing both the high and low gears in the transfer case or do the more traditional method and replace the ring and pinion in each of the diffs.

The TC gears is a 10% underdrive which from my calculations with 315's is perfect. The TC gears can be done at home with proper tools and very little down time. The diff gears on the other hand with 4.88's put the ratios a bit over the factory ratios (speedo at 62, traveling at 60). The diff gears would address both high and low at the same time but the 3rd's need to be removed and taken to a professional for proper gear pattern and backlash. I've also read that diff gears can be a little louder than the 4.10 ring and pinion set.

The cost is very close with both high and low gears for the TC costing more. The high gear could be replaced by itself to reduce the cost but that puts the low ranger very similar to the high range. I would want a crawler low range since I would have a more effective high range. The diff gears on the other hand even with labor will cost less.

Obviously there are a lot of threads out there on regearing with the diff gears but there's not a lot of information on replacing the TC gears and much less comparing the pro's and con's of each. As of right now, I'm leaning towards the TC gears for ease of installation and the perfect ratio for 315's.
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While the transfer case reduction gears are great for slow crawling, hill decents, and steep climbs in offroad, the benefit is limited to low-range only. I look at these as Icing on the cake, as a compliment to proper diff gearing. Not as a substitute. If you are running 33” + on stock gearing you can and WILL benefit from changing the diff gears in High and low range. Running larger tires has the same effect as gearing higher, by reducing RPMs below the ideal operating range. What this does is cause overdrive to become less useful as the vehicle is often down shafting, trying to stay at proper RPM’s, thus running even higher RPMS. This is bad for economy, performance, acceleration, wear & tear etc. So regearing your diffs gets you where you should be in Low & High Range, for offroad and Highway use, the transfercase only benefits for offroad and lowrange. Long story short, if you can afford to, do both. If not, do Diff gears. As for the debate on strength between different ratios, while there is theoretically some compromise, the benefits of the proper gearing far offset them. Additionally a new diff with 4.88 setup properly is going to hold up better than a 4.10 diff with 250k on it.
 
For those interested in underdrive high range and crawler low range, Cruiser Brothers has both.
HF2AOD-CB Overdrive Gear Set
I contacted them via DM to confirm that they have underdrive gears.
 
lumbee1 said:
Do you have the underdrive gears for high range as well?
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Yes, diff gears :)
But no, no underdrive high range for the TCase
 
I may be way off track here but, perhaps the underdrive gears were originally intend for use in diesel powered units to reduce highway rpm’s after low ratio ring and pinions were installed to improve off road performance.
 
For more information on overdrive and underdrive.
Transfer case re-gearing

For 315's with a stock drivetrain, the 1.1 underdrive gears will be very close to the factory setup with 31" tires.
 
@lumbee1 - I'm now looking at the same options with 35's being the limit. Leaning towards transfer gears for the simple fact they're made in Japan. Still checking if japanese 4:56 (diesel) are available. If so, I'll re-gear both. But otherwise prefer to stay OEM in the diffs for reasons @White Stripe posted - metallurgy
 
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moab cj5 said:
Right, but the guy posting said that company has the underdrive kit too.
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Mmmmm hmmmmmm. Made by Taiyo Kiko aka SeaMaster in Japan. Same manufacture we've used for gears and shafts for many years. Great quality.

IMG_3569.JPG


That set is long gone but we can get more and/or may have a set there. I'm going to bed. 38 hours of Cruiser talk in the last two days is enough :D

Discussion here: YWST: Low Range T-Case Gear Sets for the 1980-2007 Cruisers
 
I stumbled upon the previous TC gear thread but never read the whole thing. I like numbers and here is what I've found.

The TC gears can go 1.1 ratio underdrive for gassers with 35's or 0.9 overdrive for diesels. With stock 4.11 gears, we can multiply 1.1 by the stock ratio to get an approximation of the final gear ratio. 4.11 * 1.1 = 4.521

Diff gears come in two two popular flavors, 4.88 and 4.56. Most say that the 4.56 is very identical to stock but really not worth the cost. 4.88 is the most popular option to put the Cruiser deeper into the power band, read higher rpms, and helps with the weight of the tires. The drawback is the speedo is off and high speed pushes the rpms up.

I just called my local offroad shop. If I drop off the thirds, 4.56 or 4.88 gears will cost $1435 for parts and labor. The price for the TC gears is higher than that since I will need both the high and low range gear sets.
 
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Both sets installed is awesome! Imo. Low range gears are definitely easier to install.
 
SHREDwagon said:
@lumbee1 - I'm now looking at the same options with 35's being the limit. Leaning towards transfer gears for the simple fact they're made in Japan. Still checking if japanese 4:56 (diesel) are available. If so, I'll re-gear both. But otherwise prefer to stay OEM in the diffs for reasons @White Stripe posted - metallurgy
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There are plenty of us wheeling a lot harder than the overland crowd running Korean gears that work just fine. I'm running a trail gear High pinion front 5.29 and it's holding up just fine. Let's be honest the average 80 owner on this site is OCD and over thinks simple problems. To exclude gears because they aren't made in Japan is ludicrous. Does that mean you don't buy RCV axles because they are made in America?
 
nukegoat said:
Anecdotes are anecdotes. I'm pretty sure @Malleus can chime in here, but the whole myth about numerically lower gearsets being weaker is garbage. First, the cross section at the pinion splines is smaller than the area where the tooth engages. Secondly, since only one tooth pair is really carrying the load (it's not a bunch of teeth simultaneously, in spite of them looking as if they're in mesh) then all that really matters is the contact patch between the teeth under load. Thirdly, there are farrrr more variables at play for gearset life than ratio. You can get gearsets in 50:1 ratios that have "fewer teeth" that
Super-Reduction Hypoid Gears : Gear Technology August 2011

It may be more likely in your case that poorly heat treated or manufactured (or setup) gears are weaker than Toyota OEM, but I don't think you can conclude that there's somehting inherently weaker about lower gears.
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@nukegoat is correct. But don't take my word for it. I've only designed and built several thousand heavy duty axles.

Talk to a gear engineer at an OEM (or second tier) manufacturer, if you want an opinion that you can count on. Internet opinions are worth what you pay for them. "Name brand" gearsets are exactly that, a box with a picture on it. The quality components and professional, knowledgeable setup and installation are what determines life expectancy, as long as the the use is within design parameters.
 
Malleus said:
@nukegoat is correct. But don't take my word for it. I've only designed and built several thousand heavy duty axles.

Talk to a gear engineer at an OEM (or second tier) manufacturer, if you want an opinion that you can count on. Internet opinions are worth what you pay for them. "Name brand" gearsets are exactly that, a box with a picture on it. The quality components and professional, knowledgeable setup and installation are what determines life expectancy, as long as the the use is within design parameters.
Click to expand...
Are Nitro gears any good?
 
lumbee1 said:
I stumbled upon the previous TC gear thread but never read the whole thing. I like numbers and here is what I've found.

The TC gears can go 1.1 ratio underdrive for gassers with 35's or 0.9 overdrive for diesels. With stock 4.11 gears, we can multiply 1.1 by the stock ratio to get an approximation of the final gear ratio. 4.11 * 1.1 = 4.521

Diff gears come in two two popular flavors, 4.88 and 4.56. Most say that the 4.56 is very identical to stock but really not worth the cost. 4.88 is the most popular option to put the Cruiser deeper into the power band, read higher rpms, and helps with the weight of the tires. The drawback is the speedo is off and high speed pushes the rpms up.

I just called my local offroad shop. If I drop off the thirds, 4.56 or 4.88 gears will cost $1435 for parts and labor. The price for the TC gears is higher than that since I will need both the high and low range gear sets.
Click to expand...

Final T-Case Gearing Chart with different options, with any change to the high-range ratio, you are proportionally changing the low range ratio as well. Obviously not a big change but as you calculate your final ratio's it will extrapolate a fair bit. Perhaps I'll add 4.10, 4.56, 4.88 & 5.29 gearing into the chart as well but that becomes a bunch of options :D

Gear Chart pic.JPG
 
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lumbee1 said:
I just called my local offroad shop. If I drop off the thirds, 4.56 or 4.88 gears will cost $1435 for parts and labor. The price for the TC gears is higher than that since I will need both the high and low range gear sets.
Click to expand...

A couple of things to note with that

1. You have to remove the thirds which is going to be a more labor intensive process then a transfer case
2. Don't forget to factor in the front axle rebuild since you have to extract the shafts to get the 3rds out (add an extra $200 to the cost you quoted) now we are in the range of TC gears.
3. While you will get a low range reduction by re-gearing the diffs, you will get more reduction by re-gearing the low range side of the TC.
 
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