I've tried the search several times, but the words that describe the posts I'm looking for are obviously too common. Any links to similar threads would be appreciated. If not...

What are your opinions on this setup with 38x12.50's?

4.0
TF999
NP231
Ford 9 F/R
31 spl
5.13
Detriots

Are the 38's too much for axles? If not is the gearing enough? I've always been a creeper, and never broken anything axle wise with the same setup on 36's.

i think you would be fine, those axles are easy and cheap to build as well.

i think you would be fine, those axles are easy and cheap to build as well.

Agreed, except I would go 5.38's and 35 spline if the gears and axles aren't already bought. Strength numbers on the 5.38 are much better and not that much different to final drive ratio.

5.13s would be ok as would the 31spline.

An ARB in the front makes it a little easier to steer..................And I hope you are running CTM's and Alloy axles.............

5.13s would be ok as would the 31spline.

From the "Rock Jock vs Pro Rock" (http://pirate4x4.com/forum/showthread.php?t=512789) thread:

Strength factors:

1 5.38 1.1997
2 4.11 1.020
3 4.86 .9968
4 4.57 .9783
5 5.14 .5430


31 spline vs. 35 spline only makes sense if you haven't purchased axles and side gears/carrier yet.

I don't have solid #'s on ARB's, but if you ask around you'll find that the ARB is the weak point of any 9" center section built with Richmond Gears (full diameter pinion neck). Other carriers (detroit or spool) don't have the advantages (selectability) of the ARB, but they are definitely stronger.

Not trying to be argumentative, just want solid info here.

Agreed, except I would go 5.38's and 35 spline if the gears and axles aren't already bought. Strength numbers on the 5.38 are much better and not that much different to final drive ratio.

Gears haven't been purchased yet, I wanted to get all the info I could before I did so! I think I'm going to go with the 5.38's so I can get the extra gearing.

An ARB in the front makes it a little easier to steer..................And I hope you are running CTM's and Alloy axles.............

Yeah, no kidding. With the Detroit in the front it does make it a little tight in some areas that aren't really that tight. A selectable would make it a lot easier, but I haven't heard much of anything positlve from the guys I know who run ARB's. For now I'll probably stick with the Detroit until it explodes.

From the "Rock Jock vs Pro Rock" (http://pirate4x4.com/forum/showthread.php?t=512789) thread:

Strength factors:

1 5.38 1.1997
2 4.11 1.020
3 4.86 .9968
4 4.57 .9783
5 5.14 .5430


31 spline vs. 35 spline only makes sense if you haven't purchased axles and side gears/carrier yet.

I don't have solid #'s on ARB's, but if you ask around you'll find that the ARB is the weak point of any 9" center section built with Richmond Gears (full diameter pinion neck). Other carriers (detroit or spool) don't have the advantages (selectability) of the ARB, but they are definitely stronger.

Not trying to be argumentative, just want solid info here.

Hey guys, thanks for all of the info, it's really helped out a lot. Anyone who's running a similar setup be sure to share your info too.

Thanks guys! :)

For now I'll probably stick with the Detroit until it explodes.




You will have it for a long time then, I run 38X12.50s on my YJ with a ford 9inch rear 31 spline axles and detroit locker, I have 5.38 gears in it it crawls like a beast. I have not had any problem with this set up and have yet to break anything, I am running a D44 front with CRome Moly axles and ctm Ujoints.


http://i141.photobucket.com/albums/r78/angler1979/th_MVI_0565.jpg (http://s141.photobucket.com/albums/r78/angler1979/?action=view&current=MVI_0565.flv)

Awesome rig! What's your suspension setup? Is your front stretched or are those YJ leaf springs? Build Thread?

Seeing that you said it's all 31 spline, I assume the front is based off of D44 outer stuff... I assume yo uare runnign chromoly shafts and good joints since the 31 spline involves custon axles either way.

It'll hold for a while... If it breaks, look at upgrading to 35 spline front and rear and D60 outer junk on the front.

Awesome rig! What's your suspension setup? Is your front stretched or are those YJ leaf springs? Build Thread?

The front is brand new OEM stock YJ springs in stock location, the rear is Brand new OEM stock XJ springs, the rear Axle sits 6 inches back from the original location, giving it a 101inch wheel base. its SOA of course, I used the 7inch anti rap spring perches from blue torch fabs, I made a custom traction bar out of 1 inch DOM and Heim Joints, the shocks are Procomp Nitros for a 8 inch lift. out back are boomerang shackles and in from are 1inch lift heavy duty shackles. I have never paid one cent to have my jeep modded I did every single mod myself.

Build Thread?


http://www.floridajeepers.net/viewtopic.php?t=31300&postdays=0&postorder=asc&start=0

The front is brand new OEM stock YJ springs in stock location, the rear is Brand new OEM stock XJ springs, the rear Axle sits 6 inches back from the original location, giving it a 101inch wheel base. its SOA of course, I used the 7inch anti rap spring perches from blue torch fabs, I made a custom traction bar out of 1 inch DOM and Heim Joints, the shocks are Procomp Nitros for a 8 inch lift. out back are boomerang shackles and in from are 1inch lift heavy duty shackles. I have never paid one cent to have my jeep modded I did every single mod myself.

http://www.floridajeepers.net/viewtopic.php?t=31300&postdays=0&postorder=asc&start=0

Awesome thanks. That's exactly what I needed to see.

How tall is your rig going to be on 38's? A wheelbase stretch could be a good thing IMO.

How tall is your rig going to be on 38's? A wheelbase stretch could be a good thing IMO.

It's already pretty tall. I'm not going to have to lift it to fit 38's because I'm comp cutting the rear for the stretch and moving the front axle an inch forward or so, it's already flat fendered. I have wheels with better backspacing and some wheel spacers to throw on too, so overall it should have a solid stance.

It looks big in my avatar because it's sitting on 33's while I'm building it up.

My buddy snaped a 9" 31 spline axle shaft with 35" MTRs. He probably couldn't do it again if he tried, but it did happen.

FWIW, it was a full bodied CJ with a 351w/T18/D300 and a stock WB.

The 31 spline Detroit was not damaged.



If you don't drive like a sponsored XRRA driver, I'ld say it'll hold.

I run a 2.5 4 banger with a 31 spline 9". it has 5:38 gears and a full detroit. I run 35" tires and have never had a problem until last week.


last friday-sun I was at Attica and was climbing a stairstep ledge and busted the third member in half. I would of thought the 1310 u-joint would of snapped first. I hope it was just a fluke

I hope a nodular third and a antiwrap bar will fix this in the future.
http://img.photobucket.com/albums/v669/Grape_Ape/attica5.jpg
http://img.photobucket.com/albums/v669/Grape_Ape/attica6.jpg



after I fixed it I tried it again. and made it up without any carnage
http://www.midwestjeepthing.com/jeep/member/images/PapaSmurf/100_0107.jpg

I run a 2.5 4 banger with a 31 spline 9". it has 5:38 gears and a full detroit. I run 35" tires and have never had a problem until last week.


last friday-sun I was at Attica and was climbing a stairstep ledge and busted the third member in half. I would of thought the 1310 u-joint would of snapped first. I hope it was just a fluke

I hope a nodular third and a antiwrap bar will fix this in the future.
http://img.photobucket.com/albums/v669/Grape_Ape/attica5.jpg
http://img.photobucket.com/albums/v669/Grape_Ape/attica6.jpg



after I fixed it I tried it again. and made it up without any carnage
http://www.midwestjeepthing.com/jeep/member/images/PapaSmurf/100_0107.jpg


wow :eek: i have never seen a 9" fail in that way.

My guess is it was cracked prior...probably from an impact on the pinion support.

351M, C6, 38x15.50R15's... In a 79 Bronco. I never had an issue and I was always on the go pedal. Wasn't much rocks to climb where I was at the time.

wow :eek: i have never seen a 9" fail in that way.

That's a fairly common failure in a non-nodular OE gear case. The pinion support breaks, rolls in between the R&P and Snap, Bang, Crunch......

I don't have solid #'s on ARB's, but if you ask around you'll find that the ARB is the weak point of any 9" center section built with Richmond Gears (full diameter pinion neck). Other carriers (detroit or spool) don't have the advantages (selectability) of the ARB, but they are definitely stronger.

Where are you getting any info on that? The only guys hurting the 9" ARB seem to be the comp guys (and they run 40" tires with lead shot inside them) and that's from banging them in before they have stopped and I've seen just as many broken Detroits at the comps as ARBs. The nice thing about the ARB is its repairable, the other you just need to buy a new one.

How well would it hold up to 38's with a 5.9l in a tj. I have a 9 inch now but I could also get a dana 60 ff in the rear instead. It would have a spool in it

How well would it hold up to 38's with a 5.9l in a tj. I have a 9 inch now but I could also get a dana 60 ff in the rear instead. It would have a spool in it


How much HP from the 5.9?

It'll depend on your power and your driving style, but as long as you go 35 spline, you should be OK.

I'd upgrade the case right away. I have seen the stock case come apart in dramatic fashion with only 35's. The stock pinion support area is pretty weak. I've taken bone stock axles apart where this area was already comprimised. Anyway for under 250.00 an aftermarket case is a worthwhile investment. 31 spline shafts are marginal in my opinion. FWIW, i run a 35 spline 9 inch with a Strange case. It has taken hideous abuse. I run a 39 inch tire.

I've seen welded 31 spline shafts take quite a beating without breaking running 38's but I decided to play it safe nodular iron case and 40spline... just hope I get to drive it soon :shaking: