TC gears vs diff ring/pinion for regear? (1 Viewer)

[lumbee1]

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.

 

[-Spike-]

I regeared the diffs. No issues, no noise. I even feel pretty good about the strength of the setup, since they were done by Zuk and I have yet to hear about any 80 series R&P failures that weren't attributable to the install. I believe his methods produce a better, tighter result than even the factory setup.

That being said, if I could have gotten the ratios I wanted, I'd have done the tcase instead. Rough estimate of the diff regear cost was about $2k all told. I don't know what tcase gears cost, but expect it's comparable to that if you do it yourself. The install of tcase gears is less invasive, and I'd assume less dependent on installation method for durability.

 

[Cass007]

80 Series Underdrive high range gears and 3:1 low range gears

80 Series 3:1 low range gears

80 Series 4:88's and a whole lot of Terrain Tamer

Looks like OTRAMM has done both. He's not local to you, but maybe he could address some of your questions and then you could use him as your vendor. I will be very likely making the trip to his show when I get my re-gear done hopefully this year.

 

[OTRAMM]

I like the t-case gears for ease of install. They aren't super difficult to do, you'll just need a good assortment of press adapters and a shop press. I usually pull the t-case out of the truck and do them on the bench. It's easier to get the shims to stay in place that way. Grinding the case for clearance on the low range side is a bit time consuming.

 

[Freshmeat]

I've always had the mentality to reduce the axle gears first, as it'll reduce the load on everything forward of that, meaning transmission and transfer case.

With the Samurais a lot of guys do the t-case gears, but many are also blowing up t-cases because it's more load than that little case can handle.

I believe the FJ80 case is going to be stronger, so I wouldn't hesitate to regear the case on this, but I'd still opt for the regear in the axles before doing the transfer case.

Personally, I had intended for my build to be based on 5.29s for 35s, but now knowing that I can do t-case low range as well, I'll likely stick with 4.88 for the axles and do the 3:1 in the transfer case to get the extra crawl when I'm off-road.

 

[shmabs]

I've been contemplating this as well. I'm currently running stock 4.11's on 285s, if I installed the 10% underdrive gears, that would be like having 4.5xx in the axles correct?

 

[Tools R Us]

I like the rubber overdrive of 37"s with 4.1 gears, cruising at 70mph/2100rpm is nice, crawler gears took care of the trail thing. Another consideration is drive-line speed, the faster the drive shafts spin, the more critical balance and correct geometry is, higher chance of vibration, greater wear, etc. By putting the gears in the transfer you retain the solid factory diff gears and don't spin the drive-line as fast.

 

[lumbee1]

I like the rubber overdrive of 37"s with 4.1 gears, cruising at 70mph/2100rpm is nice, crawler gears took care of the trail thing. Another consideration is drive-line speed, the faster the drive shafts spin, the more critical balance and correct geometry is, higher chance of vibration, greater wear, etc. By putting the gears in the transfer you retain the solid factory diff gears and don't spin the drive-line as fast.

That's an excellent point. I need to make some calls to get a quote for dropping the thirds off for regear. A buddy told me he got the regear done for $1323 a few years back from a very reputable shop. After reading the comments, I still like the TC gears over diff gears.

 

[White Stripe]

Lower differential gears = weaker differential since u get less tooth mesh. More tooth mesh = greater strength and longer differential life. I would go tcase regear personally.

 

[nukegoat]

Lower differential gears = weaker differential since u get less tooth mesh. More tooth mesh = greater strength and longer differential life. I would go tcase regear personally.

Not really true, and even if it were, it doesn't make a lot of sense because you're increasing the torque placed on on the output shaft, the drivetrain, and the pinion as well.

 

[White Stripe]

Not really true, and even if it were, it doesn't make a lot of sense because you're increasing the torque placed on on the output shaft, the drivetrain, and the pinion as well.

Sure it is. Lower gears is less pinion teeth. Of course you may have different experiences and a different opinion. But I've known guys to do fine on 4.11s, but when they go to lower gear sets they shred them, even with a tighter mesh. One guy is on his 5th set of 4.88s. He's got a heavy foot and a supercharger, but he never had issue with 4.11s. As far as greater drivetrain stress, I agree, but Toyota's drivetrain are pretty bullet proof. Even guys with 6bts, turbo 1fzs, or high power ls motors don't have any issues that I have seen.

 

[nukegoat]

Sure it is. Lower gears is less pinion teeth. Of course you may have different experiences and a different opinion. But I've known guys to do fine on 4.11s, but when they go to lower gear sets they shred them, even with a tighter mesh. One guy is on his 5th set of 4.88s. He's got a heavy foot and a supercharger, but he never had issue with 4.11s. As far as greater drivetrain stress, I agree, but Toyota's drivetrain are pretty bullet proof. Even guys with 6bts, turbo 1fzs, or high power ls motors don't have any issues that I have seen.

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.

 

[White Stripe]

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.

From what I've seen I disagree, but it's the internet. So everyone has a opinion. Not out to squash anyone's reasoning, just tossing in my opinion as well.

 

[nukegoat]

From what I've seen I disagree, but it's the internet. So everyone has a opinion. Not out to squash anyone's reasoning, just tossing in my opinion as well.

Yeah except my opinion is rooted in math and engineering

 

[baldilocks]

By reading the OP’s opening post, it’s very clear that he has already convinced himself that re-gearing the transfer case is the way to go. And for him (or her which ever the case) that may be true based on the way he (or she which ever the case) decides to use the vehicle.

In my case, I didn’t buy an 80 to depend on for anything except draining my wallet and recreational use. Therefor, I built it with off road use, mostly rocks, in mind with little care about daily driving even though we recently went on a 4000 mile road trip which included a lot of wheeling along the way.

So, I run 37’s-4.88-3.1 transfer case gears. It works for me. If I had it to do over again now knowing I would end up on 37’s, I would go with 5.29’s only because I own an 80 with off road use as its main reason for taking up space in my driveway.

The crawler gears are 3.1:1, the factory R&P ratio is 4.1:1 so there isn’t much validity in the theory that the tranny and T-case would be over stressed unless the axle ratio is reduced.

Anything can break on any given day especially when the driver is a fool. I’ve seen the unsinkable sink and I’ve seen guys run 37’s on a Dana 30 under and XJ with success, at least for while.

I think that, for you, doing the t-case first is a great starting point for the reasons you stated in the first post. If, later, you feel the need for more you can do the axle gears.

 

[lumbee1]

By reading the OP’s opening post, it’s very clear that he has already convinced himself that re-gearing the transfer case is the way to go. And for him (or her which ever the case) that may be true based on the way he (or she which ever the case) decides to use the vehicle.

In my case, I didn’t buy an 80 to depend on for anything except draining my wallet and recreational use. Therefor, I built it with off road use, mostly rocks, in mind with little care about daily driving even though we recently went on a 4000 mile road trip which included a lot of wheeling along the way.

So, I run 37’s-4.88-3.1 transfer case gears. It works for me. If I had it to do over again now knowing I would end up on 37’s, I would go with 5.29’s only because I own an 80 with off road use as its main reason for taking up space in my driveway.

The crawler gears are 3.1:1, the factory R&P ratio is 4.1:1 so there isn’t much validity in the theory that the tranny and T-case would be over stressed unless the axle ratio is reduced.

Anything can break on any given day especially when the driver is a fool. I’ve seen the unsinkable sink and I’ve seen guys run 37’s on a Dana 30 under and XJ with success, at least for while.

I think that, for you, doing the t-case first is a great starting point for the reasons you stated in the first post. If, later, you feel the need for more you can do the axle gears.

I prefer the ambiguous term them or they.

My Cruiser is built for everything from daily driving (if necessary), rock crawling, overlanding, etc.. We took it from North Carolina to the Grand Canyon last year. At sea level, stock gears are fine most of the time but at altitude the need for gears becomes more noticeable. I don't plan on selling my Cruiser anytime soon and therefore want to invest in the right solution (for now) to make driving it anywhere more comfortable.

 

[baldilocks]

You used the term rock crawling. Then you should be geared as low as possible with little to zero regard for grocery store duty.

What I learned during our recent road trip through mostly high elevations is that the 1fz, even mine with 281k, is perfectly suited to spinning at 3500 or even 4000 rpm all day if need be in order to access the 212hp it produces. And the job gets done.

I find it amusing when posters refer to the 1fz as under powered or gutless. It was cutting edge at the time it was designed putting out very similar numbers to the American V8’s of the time but more smoothly. Fuel economy is the same story.

I still think doing transfer case gears first is a good idea if you are not sure whether or not you will need or want even lower gearing in the future.

 

[just differentials]

We have both of your considered options available at JustDifferentials.com

Nitro Gear & Axle Landcruiser 80 Series Transfer Case Low Range Gear Set: MCTC-1131
Nitro Gear & Axle Landcruiser 80 Series Gear Package Kit: Toyota Land Cruiser 70 80 Series Gear Packages

 

[nukegoat]

I find it amusing when posters refer to the 1fz as under powered or gutless because it was cutting edge at the time it was designed putting out very similar numbers to the American V8’s of the time but more smoothly. Fuel economy is the same story.

That's a good point. But I've become a man of distinguished tastes

 

[baldilocks]

That's a good point. But I've become a man of distinguished tastes

And you have proven that nuke.