Sterling 10.5 vs 9" hybred axle

[t120r]

I currently have a sterling 10.5 under my EB. Quick measurement shows a 30" long driveshaft where it mounts to my ZF/NP205. A 9" should give me 4 or 5 more inches. Will a 30" long driveshaft cause me issues with vibration? I'm 50/50 building a full float 9" axle with the 10.5 outers. But if I'm wasting my time, I won't. Any opinions?

 

[Broncobowsher]

Length won't cause a vibration. But angle might.

 

[Yeller]

I don’t think it will be an issue unless it is lifted way tall like 5.5”. 3.5” won’t be a problem.

 

[1sicbronconut]

I'm guessing the pinion snout will be lower on the 9" unless you move to a high pinion chunk.

 

[Broncobowsher]

I'm guessing the pinion snout will be lower on the 9" unless you move to a high pinion chunk.

Most axles have the pinion 1-1/8" below the axle centerline. The 9" is odd in that it is double that at 2-1/4" below the centerline.
I was doing an IFS custom job years ago and was searching for different pinion offsets and everything was the same 1-1/8 except the 9".
Now pinion length, that is all over the place.

 

[jamesroney]

I currently have a sterling 10.5 under my EB. Quick measurement shows a 30" long driveshaft where it mounts to my ZF/NP205. A 9" should give me 4 or 5 more inches. Will a 30" long driveshaft cause me issues with vibration? I'm 50/50 building a full float 9" axle with the 10.5 outers. But if I'm wasting my time, I won't. Any opinions?

None of that matters unless you are running a full case Detroit or a Spool.

There are exactly zero traction adding differentials available for a 9 inch that come anywhere close to the brute strength of the Sterling. This is the whole reason for running a the Dana 60 / 14 bolt / AAM / Sterling.

Everybody talks about ring and pinion strength as if that were the thing that failed. But it ISN'T.

The 9 inch is a complete and utter pile of crap as soon as you put a differential in it.

With a spool, or a detroit...it is a respectable, lightweight and strong rear end capable of some amazing things at the racetrack.

With a 2 pinion trac lok, 4 pinion traction lok, wave lok, arb, eaton, truetrac, Zip, you name it...it turns an otherwise robust and desirable rear axle into a giant door stop.

You are wasting your time.

 

[t120r]

Thanks for the replies. I definitely have a habit of overthinking and over complicating things. I only have roughly 2.5" of lift in the back, so I think I should be fine.

 

[nvrstuk]

I currently have a sterling 10.5 under my EB. Quick measurement shows a 30" long driveshaft where it mounts to my ZF/NP205. A 9" should give me 4 or 5 more inches. Will a 30" long driveshaft cause me issues with vibration? I'm 50/50 building a full float 9" axle with the 10.5 outers. But if I'm wasting my time, I won't. Any opinions?

First- I will try to link you to my build list where I built a "914". An aftermarket 9" housing, TruHi9" gears, custom DS (edit: dbl spline) RCV axles, 14 bolt hubs with RCV FF hubs. I had planned on this monster to last forever... yeah, right... 9" won't hold up to that kind of abuse. (edit: blew 2 up) Yeah, a ton of people tell me how they last forever, etc but ask everyone here who has moved to a 14 bolt because of the 9" failures.

Second- 30" long DS is 8 1/2" longer than I ran for 12 yrs wheeling and as a DD. I have a friend from the north who got me into doublers decades ago and he actually ran a slightly shorter DS in his Bronco (different t-case length) and his also has tens of thousands of miles and tons of hard wheeling. NO issues whatsoever for either of us. Not an issue, don't worry.

The Sterling is probably the longest pinion 1 ton rear end that Bronco guys put in their Broncos. The 14's pinion is shorter.

 

[nvrstuk]

Here is a pic of the last 9" I grenaded with an ARB.

The fix for a 9" is to stuff 10" gears in it which is THOU$and$ of extra dollar$. Then the R&P last. The only ARB that will last in that 10" is the Competition model which is always on and needs air to unlock it- that's how it works. I literally twisted a 35 spline ARB carrier in half. The 9" carrier for 35" splines does not have the space to accomadate an ARB that isn't made of exotics to make it strong enough.

This is when I gave up trying to make a 9" strong enough. A stock 14 only weighs a dozen or so more pounds (I have wt differences posted on my build thread), and is multiple times stronger than a 9". The pinion is only slightly longer.

The Sterling has some definite disadvantages over a 14 bolt. Still a super strong rear end. Everyone has pros & cons of course. BOTH are much stronger than a 9".

 

[toddz69]

With a spool, or a detroit...it is a respectable, lightweight and strong rear end capable of some amazing things at the racetrack.

With a 2 pinion trac lok, 4 pinion traction lok, wave lok, arb, eaton, truetrac, Zip, you name it...it turns an otherwise robust and desirable rear axle into a giant door stop.

Why would a 9", for example, with a TrueTrac in it, be a giant door stop, as opposed to a 9" with a Detroit in it?

Todd Z.

 

[jamesroney]

Why would a 9", for example, with a TrueTrac in it, be a giant door stop, as opposed to a 9" with a Detroit in it?

Todd Z.

Because the true trac in a 9 inch is about 20 lbs lighter, and about half as strong as a true trac built for a rear end that doesn't have the third pinion bearing in the way.

So when you start to put the horsepower down, and the 31 spline axles start to candy cane...and the 35 spline shafts show up...the trueTrac carrier starts to grenade.

If you are running a truetrac, you aren't making real power. And then they are just fine.

 

[toddz69]

Because the true trac in a 9 inch is about 20 lbs lighter, and about half as strong as a true trac built for a rear end that doesn't have the third pinion bearing in the way.

So when you start to put the horsepower down, and the 31 spline axles start to candy cane...and the 35 spline shafts show up...the trueTrac carrier starts to grenade.

If you are running a truetrac, you aren't making real power. And then they are just fine.

So I'll be fine with my well-worn 5.0 and old farmer-like driving habits. Thanks.

Todd Z.

 

[nvrstuk]

So I'll be fine with my well-worn 5.0 and old farmer-like driving habits. Thanks.

Todd Z.

No stroker for TZ !! lol

We can "fix" that ya know!

 

[ntsqd]

I seriously considered putting a TruTrac in Snowball's rear D60. It got the OX instead only because I wanted to try one out.

If Todd even muttered something about putting a stroker in he'd have some house guests as I would demand that Lars stop in Santa Paula on his way to PHX long enough for me to climb in his RV7 with a bag full of tools and some clean underwear.

 

[nvrstuk]

He'd be stopping by here first to pick me and I could parachute out at Todd's since I'm sure Lars wouldn't want us sharing a seat!

 

[1969miller]

None of that matters unless you are running a full case Detroit or a Spool.

There are exactly zero traction adding differentials available for a 9 inch that come anywhere close to the brute strength of the Sterling. This is the whole reason for running a the Dana 60 / 14 bolt / AAM / Sterling.

Everybody talks about ring and pinion strength as if that were the thing that failed. But it ISN'T.

The 9 inch is a complete and utter pile of crap as soon as you put a differential in it.

With a spool, or a detroit...it is a respectable, lightweight and strong rear end capable of some amazing things at the racetrack.

With a 2 pinion trac lok, 4 pinion traction lok, wave lok, arb, eaton, truetrac, Zip, you name it...it turns an otherwise robust and desirable rear axle into a giant door stop.

You are wasting your time.

I assume this is the same for a front 9in? Was considering building a 60/9in front and this post discouraged me a little. Looking for more info or options.

 

[Yeller]

Same on the front. Now, I’ve built a bunch of 609’s, they are are great combination with a spool or Yukon Grizzly. Their only advantage is packaging in the vehicle, their size does make them package easier than a Dana 60. IMO packaging is the only reason to consider it, weight is not enough to matter.

 

[nvrstuk]

As I was typing this response, my screen showed that someone else had posted a reply... it was Steve who later in this post I recommended 1969Miller ask for a recommendation- so he's all over it! thanks

IMO and with my ability as a "unsponsored product tester" I would avoid the TruHi9 products. I'm sure there are hundreds out there that have used their TruHi9 diffs w/o issue. I however have not. I grenaded two of them and not having a $pon$or well, the pocket didn't like that. I was running them in the rear not the front. I liked everything about the idea for running them up front but with my luck and since the guys at TruHi9 weren't giving me free replacment parts I made the EASY decision to go with a HP D60 up front. Narrow it down and you have a R&P that is multiple times stronger.

I will try to find my pic of a 9" r&p and a D60 r&p side by side and you will see that if you're looking for beef that the D60 is a hands down winner.

That's my experience. If Yeller or others that have designed, built, and run dozens of these front ends can share what they have found over the decades.

 

[nvrstuk]

Here's the page link to a D60 & 9" side by side

https://classicbroncos.com/forums/threads/why-dana-60.319526/page-4#post-3486261

 

[jamesroney]

Same on the front. Now, I’ve built a bunch of 609’s, they are are great combination with a spool or Yukon Grizzly. Their only advantage is packaging in the vehicle, their size does make them package easier than a Dana 60. IMO packaging is the only reason to consider it, weight is not enough to matter.

From a durability perspective, this is mostly true...but it's tricky up front.

It's important to remember what ACTUALLY breaks. Most applications don't have a problem up front, because there are so many other things up front that will grenade first...that the 9 inch APPEARS to be adequate, but in reality it is a mirage.

Consider that most people drive aggressively in the forward direction... when you ride your dirtbike aggressively in the forward direction...what happens to the front wheel? The answer is that the front wheel is basically airborne, and just along for the ride. Same thing when you are WOT with traction off road. So you think your front axle is plenty stout. But 90% of the time, it isn't doing anything.

Now once you get in the rocks, or you start to steer...your speed is usually much slower. The front axle u-joint strength is inversely proportional to steering angle. So if your wheels are pointed fully left or right...the axle shaft / u-joint / hub will twist off long before your 35 spline ARB starts to slip. So you upgrade your shafts, add drive slugs, and RCV joints. Then you add traction to half of the front tires, and you add maximum thrust (the skinny pedal) and then add a little sand or mud to allow the rear axle to slip a little...and suddenly the front axle has to do some actual work. (this is the @nvrstuk use case...)

The vast majority of use cases do not ever actually exercise the front axle. But when you need it most, the selectable 9 inch carrier will always disappoint. The ARB 9 inch Comp locker would not exist if the standard locker was adequate. It didn't help that ARB was in develpoment for the 9 inch forever, and in denial about the shortcomings for a season or two. Never forget that in the front axle, the standard 9 inch is pulling on the pinion, and contact is on the coast side of the tooth. So usually, just about the time the comp locker starts to come unglued, the carrier deflects, and the ring gear strips. (But at least the pinion support doesn't puke itself out of the case.)

I think that you could build a fairly robust tru-hi 9 up front with their ring gear thrust plug, and run a full case detroit / grizzly / spool and it would be pretty good at twisting 35 spline chromo's in the forward direction. Just don't back up, or try to steer and you will be fine.

Or you can get a junkyard 60 and a 14 bolt. It's your wallet.