CRAWLIN' (1 Viewer)

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tewlman

tewlman

Joined
Nov 24, 2003
Threads
33
Messages
343
How low is too low for gear ratios. I am in the planning stages of a new rig, my 76 FJ40, and plan on using an SM420 tranny(7.05:1) mounted to my stock transfer case(1.992:1). I have 4.10:1 pinion gears. Then I decided to get an AA Rock Box, it has a 3.44:1 reduction. My lowest crawl ratio would be 198:1.
Is this too much????? I could use my stock tranny, but i don't know the gear ratios there. Can anyone lead me to the right source for my stock tranny ratios?
 
http://cjford.stormloader.com/Tech/mantransinfo1.htm for tranny ratios

I run 62:1 right now...SM465, 72 t-case, 4.11 axles. Not slow enuf in some cases. Planning a minitruck doubler somday, will give me more options. IMO, 100:1 is "ideal" for the majority of wheelin...

Honestly, ratios depend on where you wheel. you might only need 198:1 4-5 times a year, but REALLY need it. You don't have to shift both t-cases into low, so you have the option of 57.4 with just the stock t-case in low, a near-ideal for most stuff 98:1 with just the rockbox in low, and the 198:1 for anything else.

I love selectivity....do the doubler....
 
you can also use the doubler in 2nd or 3rd ... do the doulber you will never want anything else ... i miss mine and the 4 to 1..... you may only need it 2 or 3 times ... but the look on everyones faces when you do it and they cant BECAUSE of the doubler .. priceless plus every thing is easyer with big low gears
 
both seem like intelligent responses to me. I appreciate the input. Has anyone heard of the new AA FJ40 transfer case? It seems like a good approach also, it is a redesigned case with 4.0:1 low range. You use your shafts and put them in the new case. It is cast iron also! It is not out yet, but expected in the next 3-4 months

You could use the SM420, with 4.10 gears and crawl at 115:1. I think I'm with you guys though, I like the ability to really slow things down if i need it.
 
Sounds like you're talking about the "Orion" from AA. Sounds stout but haven't seen one yet. I'm installing a Rockbox between the stock trans and t-case in Petes 78. Recieved the Rockbox and it really is a sweet part. Can't wait to get it on the trail and go reeeaal sslllooooowwwwww. 8)
 
ratios:

first gear x t-case1 low x t-case2 low x ring/pinion = crawl

6.5 x 2.4 x 2.313 x 4.11 = 148.3:1
(SM465 x minitruck range x 72 FJ40 t-case x stock diffs)
...and yeah, I'm guessing on the mini low...can't recall offhand...

also see the tech links, right column under Misc at the bottom for the calculators link...I think there's something in there for autocalculating..
 
Are you sure about the gear ratio in the transfer case? Mine is a 76 lc, and I thought the ratio was 1.992 in it. ???
 
He's using a 72 (3-spd) t-case number. Yours is a 4 spd case. You can't use a plate adapter with a 4 spd case, so most people switch to an older case to use the shorter adapter and get the slightly lower low range.
If you keep your 4spd case, you'll need a longer spud-shaft type adapter. Not very condusive to using a doubler.
 
I am at 79:1 (420/3spd case/4:88), turn 42" swampers fine, and will be 137 after the Orion.(when we see them).

Do I NEED 137:1? I do not know if I need it, the truck has worked great for ten years with the 420 and stock t-case, but I know that I have been in places where I could have used it. My gearing has not stopped me from going anywhere that I have wanted to.

Post pics of your swap.

Good luck!

-Steve
 
hey poser,
what kind of suspension are you using to run 42" rubber, and do you have issues with it being top heavy?
I really am a newbie to the LC world, I bought this thing in june. It was in rough shape but I had been looking for a while and decided what the heck! I've done enough wheelin to let it get in my blood, but have had to rebuild the tranny and transfer case. then I got a little carried away in a mud hole and blew the engine.

Now I could have saved some time and a lot of money and just bought or rebuilt a 2f, but NO. since the body needed some work and a few other things were bothering me I decided to strip it down to the frame, fix the body, trick out the suspension, drop in a rock box, change to a GM tranny and now have my hands on a stroked 350 with a 400 crank bored .06 over. :cheers: ( did I mention this thing has gotten into my blood and wallet.)

I am a bit confused about the tranny though. I have both an SM420 and SM465 available to me for about the same price. The 420 is in a 65ish 1/2 ton 2wheel dr p/u, with the cast bellhousing. the 465 is out of a 77odd 1 ton truck, 2 wheel dr also, but no bell housing. I have the stock 76 transfer case. which would be the best setup and what would i need to complete the job? ???

Help before I go insane!!!


Thanks,

Steve :beer:
 
If I am not mistaken you will have to change the output shaft (need 4wd output shaft)on the 465 to use it with the cruiser stuff. The 420 will work fine as is.
 
420 has a 10-spline output shaft, and will match the input gear of a 73-older t-case.

465 4wd has a 10-spline output shaft and also matches the 73-older gear.

465 2wd is a longer shaft and more spline (don't recall spline count tho)

I'm unsure what the rocbox matches up to however....I know AA makes a long adapter for the 465 2wd trannies, like 5.5" long.

Spaceghost makes the 3/4" adapter for the 420, I outta have a 465 3/4" plate adapter for the 4wd 465 available in a few weeks...

76-t-case is 16-spline input.

However, with the rocbox, all this may be addressed in that....worth a inquisitive call to AA I think.
 
The rock box is available with 10 or 16 spline. I'm installing one for Pete in his 78 tween stock trans and case. Nice goods.
 
I used the fine splined 2wd 465 in mine (I think 32 splines) with the AA long adapter and am VERY satisfied... I ended up going with the fine splined 465 because a) all the 10 splined 465's I looked at had TERRIBLE wear on the splines and the fine splines looked great & b) thought the fine spline would be stronger & better long-term --
So...
1) I would definitely go with the 465 2) if you can afford the 5" adapter length I would also go with the 2wd SM465 for a good long-term solution :)
 
[quote author=tewlman link=board=12;threadid=8341;start=msg71440#msg71440 date=1070591579]
hey poser,
what kind of suspension are you using to run 42" rubber, and do you have issues with it being top heavy?
Steve :beer:
[/quote]

Bahahahahahahahahah....have you SEEN Steve's rig? It redefines the term top heavy, BUTTTTTTT, he knows how to drive it and the sucka works!

Something as big and heavy as Steve's rig defies the laws of gravity and torque by allowing a 3 speed transfer case to live all of these years :flipoff2:
 
[quote author=tewlman link=board=12;threadid=8341;start=msg71440#msg71440 date=1070591579]
hey poser,
what kind of suspension are you using to run 42" rubber
[/quote]
He's SUA !! Do you believe it? I don't... ;) :D
 
I run the AA Rockbox with an SM420, 72 3sp transfer case, and 410 axle gears. I love the gear options, I use the low low low more than I thought I would. Did I need to be that low in those situations? probably not, but again I love the gearing, and I'm like 230-1. You can use the 465 to the Rockbox to either a 3sp or 4sp Cruiser transfer case AA has both output shafts for it.
 
[quote author=CruisinGA link=board=12;threadid=8341;start=msg73525#msg73525 date=1071017915]
He's SUA !! Do you believe it? I don't... ;) :D
[/quote]

Here ya go...
 
Another....
 
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