the perfect jeep drivetrain!

I want to expose a theory of mine to the light of scrutiny..(peer review).

It is my humble (most of the time) opinion that if you are building a drivetrain the strongest part needs to be only stronger than the amount of friction you can put to the ground under ideal circumstances..(not counting stupid attacks like 5 grand,sidestepping the clutch in 4 lo trying to bunny hop a 3400lb jeep.)
Anyway what I am saying is.. if all the parts in the drivetrain are strong enough to withstand 500 ft lbs from the engine and the tires are spinning at 300 ft lbs.. nothing should break (unless it's worn out) or you shock load it as above..

or on the other side if the weakest link in the drivetrain is say .. a front axle u-joint that snaps at 2500 psi.. putting in a warn hub fuse that strips at something slightly less and you should have a "break proof trail rig?

Funny, but I think Jeep knew what they were doing 60 years ago.

The Go-Devil 4 cyl wasn't strong enough to break anything, or strong enough to move the Jeep out of it's own way on the road. But, with the combination of a 3 spd and 5.38 gears, it didn't matter that it had a Dana 25 front axle and Dana 41 rear. It went wherever it was pointed.

My Dad had one of the best "stock" drivetrains that I've ever seen. It's was a Forest (DEP), it was ordered with a 4 spd and limited slips front and rear. So the 4 cyl, T-98 4spd, D18 x-fer case, and 5.38s with limited slips front and rear.

Personally, if you want a little more power, but not enough to break, then it's the Buick V-6 or the 4.0L

Just my opinions. I'm not a Jeep V-8 guy. Heck, a Buick V-6 with V-8 powered can be dropped into some Jeeps without changing the motor mounts. Can you GNX in a Jeep? There a was a article about a Commando with one in it a few years ago. Who needs a V-8?


Erik

I think I may run two of these to protect my 44's
http://www.pirate4x4.com/forum/showt...iveshaft+shear



Jeff

It might work if you have a tendency to get a little rough on the skinny pedal.

I've been running a 44 rear for years with 35, 36, and now 37" tires. Worst I've done is slightly twist the splines on one axle shaft (it has a full Detroit). I did manage to blow the u-joints out of the Dana 30 pretty regularly. I carried an extra set, and could swap a shaft in under 30 minutes on the trail. Haven't broken a front since I went to a 44 with internal hubs. I do have a Dana 60-2 (1.5", 35 spline semi floater with 5 on 5.5" pattern) that I will eventually swap in just to make it more bulletproof.

I've always been pretty easy on the gas, and let gearing and lockers do the work. I've got a T-18 (6.32), with a Scout Dana 300 and 4.27 gears in the diff for about a 72:1 low-low. I have 4.88s for when the 60 gets built, which will put me at about 82:1.

Bob
tufcj

i have changed my opinion a few time over the years. for now i think the bulletproof dt would be a indy al block amc variant, 700r4 with mods, stak 3 spd t-case, d80 front thats been spooled and 300m shafted, and a 14bolt spooled and 300m shafted.

fairly affordable, fairly light for its strengh. oneday, i'll have it or change my mind again. :roll:

Well I kind of agree that jeep had it right 60 years ago..and truly the 225 v-6 (aside from idling like a coffe can full of rocks) was a pretty good match for a cj.. and the fuel inected 4.0.. perfect..(I do have a 304 powered cj-5 but in truth it is much more fun on the street than the trail..) but I don't mud bog (on purpose anyway). I just four wheel with some guys that have overbuilt thier rig to the point of absurdity. Big Cams Bigger Carbs and literally tens of thousands of dollars..and I usually go get them with my J-10 with 4" of lift and 33"s and 360..(ok it does have limited slip in the rear) but the drivetrain is all stock with a T-176 np 208 and other than breaking a shift tower one day being an idiot while drag racing some guy and powershifting second.. (ok your friends will laugh when the shifter comes out of the trans in your hand. ) I havent broken much

I just wonder how much of the current high dollar stuff is driven by the magazines and thier "Blow stuff up it's cool !" mentality :-|

I agree with the concept of a fusible link in your drivetrain. I have a Jeep Wagoneer that I use for offroad. I have a stock 401, bored .030 over by PO, oiling mod and soon to be Edelbrock MPFI. Behind that is a T400, shift kit and heavy duty planetary (Sun gear with 8 planetary gears, 3:1 first gear), shift kit and a shortened 32 spline output shaft from a chevy truck. Behind that is a 4.3:1 Atlas transfer case with 32 spline input/outputs. This drives Dana 60 FF axles F&R with 4.10 gears, a Detroit out back and an ARB up front. I also have the warn HD lockout hubs up front.

My fusible link is the 1310 drive shaft u-joints all around. Why...they are easy to replace on the trail if I get crazy with the go pedal. And more importantly to me, they will bust before I start to mangle the high dollar parts. I believe my warn hubs are the second weakest. If I bust these, I would put drive flanges before stepping up to the next strongest u-joint, a 1350.

Another thing. Blown 7 I saw your engine build posts here and on PBB and must say you have an awesome motor. :lo1l:

You have a good point in that your off-the-curve HP and torque numbers will probably kill your 44's and I suspect you will be upgrading these soon (welcome to jeep ownership) Not sure what tranny you have, but if its a 400, it should be fine. I went with the 4.10 gears in my 60 and not to steeper gears because they have the largest contact patch (aka stronger) than a steeper gear. I don't have the numbers for the 1310, 1350 and 1410 u-joints, but there is a size/strength tradeoff here. I think the u-joint stregth numbers can be had over on PBB in the tech section. I think this route (making the drive shaft u-joints your weak link) serves the same purpose as the torque limiter device (I am guessing that is a high dollar part).
Good luck with your build.