crawl ratio (1 Viewer)
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yes, but with adapters.. SM465 or SM420. Adapters have been around for forever.
Downside is the chevy trannies make the truck less streetable. SM420 has a lower 1st, SM465 has more synchro'd gears. 4.88s would be my first advice, then look at spending on trannies or even a Toybox.
But cheapest is 4.88s because that's ALL you have to change. H41 might be a wash vs the 2 chevy boxes after you buy adapters and possible driveline length issues.
Downside is the chevy trannies make the truck less streetable. SM420 has a lower 1st, SM465 has more synchro'd gears. 4.88s would be my first advice, then look at spending on trannies or even a Toybox.
But cheapest is 4.88s because that's ALL you have to change. H41 might be a wash vs the 2 chevy boxes after you buy adapters and possible driveline length issues.
Tigerstripe40
SILVER Star
SM420 is really the way to go for cheap gearing while keeping streetability.
I can only speak for myself, but I am runnign an SM420, 'Cruiser '4 speed' t-case and 35" tires. There are VERY few times when I feel I need anything lower than that.
I am into my SM420 conversion about $700 TOTAL using a new old stock transmission, but I admit that I did get a hookup on a few parts. That said, I had to do NO driveshaft modifications, other than swapping the '4 speed' yoke for a '3 speed' yoke on the front drive shaft, and grinding the front output flange and '3 speed' yoke to clear the transmission.
SM420's ist gear is 7.01:1
2nd is 3.54:1 (same as the stock first gear in the H42)
3rd is about 1.71:1
4th is 1:1 (same as the stock 4th gear in the H41/H42/J30)
As far as streetability goes, it's really not that big of a deal. Sure you have fewer gears. But I drove my FJ40 daily for several YEARS with the SM420 and I can't really complain about it's streetability. It is what it is. The ONLY problem I have with the SM420 is that when I am on the freeway climbing a hill, 3rd and 4th is a little wide of a gear spread. BUt when I get on the trail, and slide the gear shifter into first gear and crawl up pretty much ANYTHING I point the truck at, it's MORE than worth it.
Both the SM420 and the SM465 have UN-synchronized first gears. Though, you would NOT want to drop the transmission into first while moving so teh point is moot.
The SM465 has smoother synchro's than then SM420, but again, it's really not that big of a deal.
The SM465 is also a good choice of a transmission as there are more parts mroe widely available for the SM465, as well as more adapter possibilities.
FJBen
SILVER Star
Orion! 
Gives you 58:1 in a bolt on package. Probably around $1,500 and no other mods. Change your tranny later for even more low.
SM420/SM465
Gives you 67:1 You can get the 420's/465's for under $100 adapters are fairly cheap IIRC under $250. Shifting definiltely more clunky but not unbearable. Grind the t-case like was said and you are golden. I daily drive mine and with a 350 and the SM420 I don't see any power gaps, but I don't particularly like the shifting compared to the Toyota tranny's.
You've got some options thats for sure, how much do ya want to spend?
Gives you 58:1 in a bolt on package. Probably around $1,500 and no other mods. Change your tranny later for even more low.
SM420/SM465
Gives you 67:1 You can get the 420's/465's for under $100 adapters are fairly cheap IIRC under $250. Shifting definiltely more clunky but not unbearable. Grind the t-case like was said and you are golden. I daily drive mine and with a 350 and the SM420 I don't see any power gaps, but I don't particularly like the shifting compared to the Toyota tranny's.
You've got some options thats for sure, how much do ya want to spend?
As long as you find the input gear to make it work with the 10 spline output of the 420.
You will also need an adapter to make the transfer case bolt to the rear of the transmission.
You will also need to source a three-speed flywheel housing, unless you already have a Chev engine in your truck.
Can be done, as has been described, as long as you are not paying someone to do the work for you.
rokbox or a toybox whatever you wanna call em
sm420 swap is cheap.
4:88 ring and pinion. it will make it just like it was with stock gearing you keep your highway gears because you now have bigger tires. made my speedo and everything work just like it was with stock gears and tires. however if the next thing your doing is lockers dont do this because you should do the ring and pinion and lockers at the same time to save m0ney setting up the differentials. So. transmission and transfer case. sounds like the 420 has a great low 1st gear. I have a h55f transmission and a 3.05 marks geared transfer and it has good gearing and is a 5 speed. but it was way over 1500$ X2
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How would that allow him to keep his highway gears?
He is going to 35s .. it is a '78...
so to keep a stock ratio, if everything measured exact-
29/35 = 4.11/x
29x = 35*4.11
x = (35*4.11)/29
x = 4.96.. shoot he's taller than stock even
rusty_tlc
Dain Bramaged Member
Not the same thing.
Rockbox = Advanced Adapters
Ratio; 3.44:1, Length - 5"
Toybox = Marlin
Ratios; 2.28:1 or 4.0:1 or 4.70:1, Length - 6.75"
Either one requires substantial modifications, new driveshafts (expensive double cardon in the rear) and is close to the orion alone in cost.
The OP was looking for an inexpensive option.
is their such a thing?
sure you can pick up a tranny for 150 bucks but is that all it costs? i dont think so.
what are his skillz like? is he paying someone, is he capable of doing mods like this?
his question is so vague
tell me what you can do for cheap and ill pay you that price to do it to my rig.
you are driving a landcruiser, you want cheap buy a heep.
mho
orion
I am very curious about the Orion. The PO of my 77 fj40 changed out the diffs for some 3.70's I think. It's great running around town but can't imagine trying to crawl with it. 4low is still pretty fast. Is the Orion an addition to my transfer case or a total replacement? Would it only affect 4 low? Not trying to hijack, just trying to understand the consequences of each choice. Thanks, Slow Poke
I am very curious about the Orion. The PO of my 77 fj40 changed out the diffs for some 3.70's I think. It's great running around town but can't imagine trying to crawl with it. 4low is still pretty fast. Is the Orion an addition to my transfer case or a total replacement? Would it only affect 4 low? Not trying to hijack, just trying to understand the consequences of each choice. Thanks, Slow Poke
FJBen
SILVER Star
Replacement bolt in 4:1 t-case. Either you can build it, OR send it to Poser! Thats my vote. My Fj55 on 35's and stock gearing was AWFUL to crawl with. It actually bogged down badly unless you went crazy on the skinny pedal.
do a search on "orion" and you'll find PLENTY!