View Full Version : Building To break...
06-16-2003, 05:47 PM
Everyone talks about having a "fusible link" in your drivetrain, most use ujoints as that link(or those of us with D20s coming out of our ears, tailshafts)...But normally if you toast a front joint it takes out the shafts, if you pop a dshaft joint you bang up your dshaft or more...
How about a slipjoint fuse similar to a hubfuse, have a slipjoint made with a replacable double splined fuse, that way when it shears it keeps the dshaft together and keeps it from flopping around under your rig... It would be easy to replace and would keep you from exploding other parts, they could be made with differant break ratings to coincide with the differant tcase ratings... that way one for say a d20 would blow before one for a np205 would, etc...
Should I apply for a patent???
06-16-2003, 09:53 PM
if u can figure it out, it would have to be for off road only, as on road the shaft would want to wobble bad if it is slightly worn.
i also has ideas about a fusible link, but my idea was a shear pin in the d shaft, but i would have same problem.
06-17-2003, 01:07 AM
I think the best way to build is not to break. Overbuild everything and you'll be happy with the result. Since I overbuilt my drivetrain I've not broken a single part. Back when I used to run 1310 u-joints and stock driveshafts I would break at least one a ride, sometimes 2 or 3. Also, I used to carry 3 spare rear driveshafts, one front, and about 4 1310 joints. Having a fuseable link sucks because it'll break when you need it (ie really trying to make that one obstacle) and then you have to fix it on the trail which always sucks even for the easiest fixes. I can say though that breaking a d-shaft u-joint isn't a death sentence. I had a shaft last through about 7-8 joints before the ears were too messed up to go on.
06-17-2003, 01:13 AM
Yea I do not think creating more weak links is the answer. Not for me anyhow.
06-17-2003, 04:05 AM
having $7 Ujoints as the fuse is alot better than a $300 shaft... I have not yet blown a shaft or a joint.... so far soo good.... but we will see... ;)
06-17-2003, 05:36 AM
I agree with RockJeep44. Over build with the best you can afford.
There are situations where breaking down could create a very serious situation for passengers and riders. In Ouray last year, there were situations on trails where breaking down could have led to serious injury or death.
Some trails are very narrow and breaking down could stop traffic both ways.
The philosophy of running what you have till it breaks is dangerous to me. If you have to have more power, bigger tires, lift, etc., build it right the first time.
06-17-2003, 08:36 AM
Actually I agree with the build it right the first time... I was just trying to one up warn's hub fuses because when they let go it'll destroy a locker, and the fact that blown joints are bad anytime... I was just saying that if you have a tcase rated at 10000 ft/lb and a fuse rated at 9500 ft/lbs if you built right neither will break, but then again "everything breaks", i'm not wanting to create a weaker link, just trying to keep the tcase from being the weakest link...
06-17-2003, 12:17 PM
Where is the weekest part in a driveline? I would think the U joints first, then shafts? But what part of the shafts, right out of the tcase, or at the diff? I have a 1310/1350 conversion for my 14ff, but my dana 60 I putting in is gonna be 1350 all around, plus a high angle jobber. But coming out of the rear of my tcase I still have 1310. I guess one day I will upgrade that spot. For now, Im just happy to have 1 ton axles! Dennis
06-17-2003, 12:32 PM
KYJ10: its generally where the slip joint is. Thats where I see most shafts break.
06-17-2003, 12:58 PM
Back when I ran stock units I always twisted them right in the middle of the tubing or wherever there was a dent. Ever since I've been running my custom heavy duty shafts I've beat the total living crap outta them with no breakage. Definitely worth the $$$.
06-17-2003, 01:25 PM
my front shaft twisted into 2 shafts, tight in the center of the tube.
I agree with Rockjeep on the shaft issue. If you're breaking stockers left and right, upgrade. Heavy duty shafts are fairly cheap when compared to several stockers and the time it takes to replace while you're strapped to a tree on a 50 degree hill....that is, if there is a tree to strap to.
Relavent anecdote: My buddy has been breaking 44 shafts in his early Bronco ('74) since he bought it in '76. He finally fixed the breakage issue. Found a "steering" Dana 70 from a forklift. Re-tubed it to fit. Dana 70 FRONT! in a short Bronco. To use a technical term; it's neat-o. He needs it though: built Cleveland, SM420, NP203 doubler, Dana 20, 5.38's.
06-17-2003, 03:29 PM
keep in mind that what will break when is not an exact science,and you cant allways predice when something will break before someting else.
usually in a front axle a u joint will fail and take out both shafts. every now and then,tho, a shhaft will break before the joint,or spider gears or a pinion will break before either.
one of the best examlpes i can think of comes from the "great d20 debate" where i recall FSJeeper telling how he twisted a d20 output shaft before breaking the spider gears in a rear 44 "trash loc"(a notorious week link). i broke several rear 44s and the 10 spline outputshaft on my spicer 18 held up to all of them. i didnt start breaking transfer cases till i swapped in my 14 bolt. not too long ago i had a friend with a burb with 40" gumbos break a 205 before breaking anything in his front 10 bolt.
safety should always be considered 1st and foremost. it is not a safety issue for me to run what i got till i have prollems with it,cause my trails loop around so that camp and spareparts are accessible,and breakage does not usually involve a possibility of rolling off a narrow mountian pass.
some other stuff to consider,anyway smile.gif
06-19-2003, 03:19 AM
Scotty, exactly what part broke in your friends NP205? The only thing I have seen go in a NP205 is those crappy 10 spline sleeves they used to use.
I can not imagine breaking a 32 spline all the way NP205.
06-19-2003, 05:15 AM
not sure what he broke,he never took it apart to see,that i know of. it was behind a th350 ,so it was prolly a 28 spline in,and what ever the outputs normally were on one of them. next time i see him ill see if hes found out what happened to it yet
all i can say for sure is that it let go in a "spinning tires suddenly finding traction" situation in a mudhole over at haspin
the breaking power came froma very worn out $100 350 chebby smile.gif so its not like it was behind a 1000+ hp 454 or anything like that
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