--breaking a ford 9--

[west747]

after reading a few posts on another fourm ( i know, i know...lol) i got the feeling that for the bigger meats 40 inch and up a 9 inch just wont cut it. the majority of these guys are running 14 bolt ff axles. massive axles i know.

my question is can i safly run 39.5 inch swampers on my ford 9 inch which is spooled without any major damage? the axles are 31 spline and are massive compared to the dana 35 axle shafts, however it is the 3rd member that i am worried about. has anyone ever broken a ford 9inch and if so what part of it is most likely to give under big torque loads? any input, advise or comments would be greatly appreciated!

 

[fourtrail]

run it. a buddy of mine runs 38.5x11x15 boggers in his buggy powered by a 460 and we do burn outs :lol: all the time and haven't hurt it. it is the prefered axle for drag racing and they put a lot more hp to them that your 6 will. the only downside is the low pinion input. the 3rd members are plenty heavy and very cheap so if for some reason you do break one it will be easy to replace.

 

[Junkpile]

A healthy 258 Jeep can wring an axle just as fast as a drag car......once the low range is engaged. The 9" is a close call on tires bigger than 38s. It needs some serious trussing. With aftermarket parts, a Ford 9 can be built to be stronger than a D60. If weight is an issue and money isn't, then the 9" can be the way to go with big tires if quick acceleration is in the plans. For hardcore fourwheeling, it wouldn't be my first choice. Also, the low pinion only amplifies the rear driveshaft troubles that come with YJs.

If you've already got the 9", then go ahead and run it and don't worry about it. I've got a buddy that ran one in the back of his 78 F-150 on 44" Boggers. He never had any troubles.


258 I6 Jeep-- 210lbs-ft torque * 4.03 first gear * 2.62 low range * 4.56:1 rear gear = 10,111 lbs-ft/2 = 5,056 lbs-ft torque going to rear axle shafts

350 V8 drag car-- 500lbs-ft * 1.72 first(powerglide) * 4.56: rear gear = 3922 lbs-ft going to rear axle shafts

http://www.moserengineering.com/moser_interior/axletech.htm

 

[MerkL]

I'd say go with it. My dad has a hot rod, with a 454, running pro-street tires, on his 9" Rear. I think you could do it.

 

[Snitty]

do it... and if you feel insecure... you can weld trusses on there... i personally wouldn't worry about it

 

[jps4jeep]

what color? HELP!

I would not think that the third member would be the issue. If installed properly and geared correctly, there should be no issue. with 39's the issue lies in the axles. a 9" has pretty stout axles and are plenty heavey duty. I would also suggest that the axle tubes be fully welded, and possibly a truss the connect the two tubes together be fabed up to reduce the chance of tube flex and possible axle binding.

 

[redrooster]

The pinion bearings are the source of weakness on the 9". Read up on them, there are plenty of articles. That is why Currie and Strange MFG new center dections with an extra pinion support bearing.
I wouldn't say excessive use of the skinny pedal would hurt it. It is shock loading such as binding the tire between rocks or bouncing it that's going to get you. Run it till you break it.
BTW... All you 14 bolt haters I used to be where you are. Don't knock it till you try it. It's one of the best bargains out there. Cheap lockers, easy setup, lots available, and bombproof. All it needs is a little grinder love.

 

[Snitty]

the 14 bolt is a GREAT axle... but everyone has their preference... and remember... the pinion bearing can be affected a lot with axle wrap.. it puts vertical pressure on the bearing... the better stabilized the axle is, the better it is for its components