fj40 axles (1 Viewer)

[1978freebornred]

ok im in the process of putting in a 427 bbc that i picked up for 400 dollars and a 1992 nv4500 an stock tcase with 33 in tires an I want to know what the actual strength of the fj40 axles are or at least a good estimate. I looked up the 427 it has a peak torque of 460ft lbs at 3900 roms.?? 350 motors are max torque output of 330ft lbs.??
the gear ratios of the nv4500 are as follows
1st 6.34:1
2nd 3.44:1
3rd 1.71:1
4th 1 :1
5th .73:1
to figure torque output you take 460x trans gear x tcase (1.98)x third member (4.11) and I get 23,733 so youd divide that by 2 to get axle tolerance. 11,866.5ft lbs so I need a axle that will sustain 12,000ftlbs to keep from braking?? what axle would do that?!?!?

are the figures correct?
what is the tolerance of the tcase i want to see if it would even hold up to a 350?

 

[Poser]

You don't need to worry about the axles; the power will not make it out of the transfer case.

 

[whitey45]

Been running a bbc , nv4500 for ten years, no problems ever! But it connects to an np205, dana 60, corporate 14 bolt, 1 ton drivetrain! Poser is correct, your t case and axles will last about a quarter mile on the trail!hth!

 

[1978freebornred]

yeah thats what i was afraid of... so dana 60 is front axle on 1 ton? so how much wider is the 1 ton axles than the stock 40s? how does the front axle line up is it off center? what did you get the parts from? what about a np241?

 

[Gumby]

Dana 60 is the front axle on some 1 tons. Not all by a long shot. They are considerably wider as they came on full size trucks. The front axle can be offset to the ds or ps, but not centered. They put them in fords, dodges and Chevys in the 70s, but you really got to look for them as many came with other options.

The transfer is the weak point. if you build the axles with longfields they are pretty stout.

Sell the 427. Buy a good 350. Leave it stockish. Buy gears. Less weight, easier to get parts for, good useable hp and torque.

 

[1978freebornred]

even with longfields there is a easy possibility of breaking axles... anytime you get one tire in the air or one tire stuck... even if the 350 motor only had 270 lb of toque on the low end instead of the 300. the stock 2f is rated at 200 ftlb and with just a dana 44 ish axle thats just about the most it can take. granted it could be fun as hell on the street with a 350 but still could break stuff offroad.
isnt the d60 on 3/4 ton 4x4 as well? what about the width of those axles? like +5 in on each side or what?
what np205 works with nv4500? 86 and up? 32 spline female? dont you have to have a spacer with that?

 

[Gumby]

even with longfields there is a easy possibility of breaking axles... anytime you get one tire in the air or one tire stuck... even if the 350 motor only had 270 lb of toque on the low end instead of the 300. the stock 2f is rated at 200 ftlb and with just a dana 44 ish axle thats just about the most it can take. granted it could be fun as hell on the street with a 350 but still could break stuff offroad.
isnt the d60 on 3/4 ton 4x4 as well? what about the width of those axles? like +5 in on each side or what?
what np205 works with nv4500? 86 and up? 32 spline female? dont you have to have a spacer with that?

Really? Tell that to the dozens of guys running 350s and stock axles with long inners and birfs. You can break them, but not easily any time you get a tire in the air. In fact, it's damn tough to break them, and they are warrantied if you do. And you said you're running 33" tires? You're not going to break them if your suspension is set up properly. You can snap a pinion off with a 22R if you screw that up enough.

The 350 does have more torque than a 2F, but it weighs 300# less. That's a huge difference on your front axle.

You know all about Land Cruiser axles and what they can take but you can't use google to find out the width of a D60 or what they came in?

 

[1978freebornred]

torque chart

http://www.pirate4x4.com/forum/toyota-truck-4runner/278728-torque-test-new-chromoly-longfields.html

lowest torque 350 with 270lb torque will put out 6965ft lbs of torque so thats more than enough to break old style longfields.

the link above contains said longfield on torque tolerance test and granted it would be a situational one tire gripping when you break an axle, I wasnt familiar with the new ones tolerance but the older ones could break with a 350 especially in the red clay dirt places I wheel near where i live. dana 60 is almost like saying solid axle they came in ford chevy dodge international and jeep. and its estimated that they are 76.5in thats the straightest answer google gives. thats why i asked.

and so others know np205 6 bolt round found in 85 to 92 1 tons with t400 trans, with a short output 32 spline is the way to go, no spacer; spacer with notch with the long stick out on other transmission mated cases. short stick out is about 2.5 in.

thanks whitey for your statement, and cheers poser. and gumby thanks for the advise but i want my 427. 80k original miles cant get better for my investment thus far.

 

[shelfboy1]

you didnt mention where you wheeled ,i ran a 501 caddy with stock axles and 40 " tires for several years and no breakage mostly mud and trail rides .all the guys here are dumping the d 60s and going to rockwells because d 60 parts are getting to expensive.

 

[pb4ugo]

What about the dana 60 frt axle bible in the tech links on Pirate? It probably has more info in there than you need.

 

[Gumby]

If 60s were what you wanted in the first place you could have just said so.

Your math is entirely wrong. Not the figuring, but the application. Have you ever seen a long break?

 

[1978freebornred]

yes i have seen longfields break on a truck with 33 in tires and a 350 motor it was about 10 yrs ago so they were most likely old style longfields. if my math is wrong please show me, it isnt as it would save me alot of work but I doubt it. and even the new longfields will not work for a 427, however they will for a 350 quite well.

stock axles with 501 thats amazing must have never got stuck.

 

[bustanutley]

Your math for understanding the problem is a little bit silly. It comes down to how much traction your tire can produce. From my experience, 30 spline longfields will be very tough in an 33” tire application. But if you want to put dana 60s under it straight away, thats cool.

 

[Gumby]

yes i have seen longfields break on a truck with 33 in tires and a 350 motor it was about 10 yrs ago so they were most likely old style longfields. if my math is wrong please show me, it isnt as it would save me alot of work but I doubt it. and even the new longfields will not work for a 427, however they will for a 350 quite well.

stock axles with 501 thats amazing must have never got stuck.

Big horsepower and torque numbers have very little to do with getting stuck.

Longfeilds will not be your weak link with a 427 either.

The problem with your math is that you're just adding up numbers and ignoring a ton of other variables like weight, tire adhesion, driveline efficiency, suspension geometry and most importantly, the driver ability.