Samurai 4:1 Rock Lobster Reviews

I've noticed that quite a few people here have Rocklobster boxes on vehicles that are on & off road driven.
I'm guessing they're the 4.1:1 or 4.9:1. Either way about 20% reduction in High Range.
Why get them & what are they like ? I've heard stories of even the prebuilt boxes being noisy after about 100 miles.
I not really interested in boxes where you've installed the gears yourself as it's something I'd never do & it's not what I've been offered.
If it's to correct for bigger tyres why not go for a never opened SJ410 case with the 20% hi range reduction as factory cases never seem to go wrong if looked after.
I can't see the reason for low range crawler gears in UK mud where there are no rocks & you need high rpm to clear the clogged tyre treads.
Opinions please.

As far as the rocklobster boxes, I think the noise issue is mostly from the builds using existing gears from the SJ410 and SJ413 transfer cases. Using the Trailgear or Sumo reduction kits should probably eliminate or significantly reduce that issue, especially the 4.9 and 6.4 kits that have all new gears. I haven’t received my 4.16 kit yet, which does use one existing gear. With the lockdown, i couldn’t confirm the gear noise yet anyway. Martin might be the first to give feedback.

Most people use the reduction gear kits due to a desire to gain a lower low range. Since you have neither interest nor plans to rebuild a transfer case, I will focus on the question of using a stock SJ410. If you are satisfied with stock low range, as you seem to indicate, using the transfer case from the SJ410, along with slightly larger tires should give satisfactory results. If you haven’t already invested in parts, you could also achieve similar results with a diff re-gear.

A "rock lobster" box is a general term for combining the gearsets from a 410 and 413 transfer box to make a lower geared "crawler" box.

The other way to correct gearing of course is to change the "final drive ratio", i.e. the dufferentials, in my buggy build I've swapped the old 3.9:1 diffs for later 4.3:1 diffs, this regears sufficiently for me to run 29" tyres...

There's also the option for replacing the gearbox and transfer box as well as the differential ratios...

HTH

Not quite sure but I think the term "rock lobster" was first used by a US company. Later by others and this makes it a bit unprecise for my liking.

I have built, made and sold or traded 7 of the 4.16:1 low range SJ410/413 transfer boxes. I used my colleagues experience to machine and weld the gear wheels at high precision. Only one of the boxes had a slight noise with singing gears.
Done right with a high degree of skill there should be no noise difference from the 410 box before or after the conversion. In high range it is just the same.
Done bad there will be misalignment, shrinkage from welding and faulty play and clearance, and in the worst case cracks, scaling and scuffing at the gears with lacking or faulty heat treatment.
For my 2005 jimny transfer case I bought a gear kit. but here the noise from the aftermarket chain wheels are horrible. The 17% lower high range comes with a loud price..
On my 2005 car with 235's a 4.16:1 SJ transfer would not be possible due to the total ratio.

Thanks guys.
I was trying to keep the reviews towards on road experience as that's where this vehicle will live most of the time as a commuter car doing 90 mile daily round trips once or twice a week.
It already has a stock Samurai box running 235/75-15 under 2" suspension & 2" body lift
But of course I want to go taller tyres (don't we all)
Diffs. I did think about them but don't want to cut the axle. Did think about a complete axle swap.
I was offered the RW built rock lobster book for £300 so took it as it seemed like a great deal but now thinking it may be too low geared.