Whats the weakness in the dana 30?

[Hank Scorpio]

is it the ring and pinnon? Spider gears? any ideas?

I figure atleast the locker deletes the spiders', should help some. But be intresting to know.

 

[blkaplan]

no clue but sounds like a good question for a 4x4 forum

 

[DerSnart]

My friends with Cherokee's always talk about spline count, my friend with a 4.7 stroker is upgrading to a 35 spline on the back and a 33 in the front.... so based on what they always talk about I would say it might be the axle shafts (Ive seen a dana 35 axle that twisted itself appart, which is why the cherokee guys upgrade I guess). Ill ask around and see what they say on the matter.

Did you break a rear end or somethin?

 

[volvorsport]

its the physical diameter ie like upgrading to a 7 inch or a 9 inch rear from a mustang or whatever

 

[Hank Scorpio]

Haven't broken anything yet Just kinda curious.

So the axle's OD (hence spline count) is to small?

 

[gecko]

Haven't broken anything yet Just kinda curious.

So the axle's OD (hence spline count) is to small?

the jeep guys usually go from the 30's to the 60's in the rear and sometimes even in the front. i'm not sure what the actual weakness of the rear itself is....but the 30 is very strong for what it is.

 

[mikep]

The Jeeps have the 30 in front but not in the rear.
The axles look very thick to me.
I would say that case spread leading to improper mesh in high torque apps.
In any rear with slop, it's impact damage. The slop can be in the diff or the ring and pinion or the bearings.
Also, street gears are hard for good wear properties, race gears are soft for impact strength.
Same thing with axles. Race axles twist, street axles are induction case hardened.

 

[DerSnart]

The cherokee has a D30 in front, and a D35 in the rear (D44 for tow package, very rare). They upgrade to a larger axle... hence the increase in spline count. I talked to one of my friends whose all about XJ's and he filled me on on the subject. The upgrades are done not necessarily for the actual physical size of the axle, but for the increased diameter of the shaft, to accommodate the stresses of wheelin or lots of power. That?s what I was told... this guy owns some mean rigs so I trust his word.

 

[DerSnart]

its the physical diameter ie like upgrading to a 7 inch or a 9 inch rear from a mustang or whatever

You are refering to the diameter of the ring, which has little effect on strength in the Dana's world (it has some effect, but enough to merit much praise). Whereas upgrading the size of the actual axle shaft does a great deal to strengthen a rear end as a whole.

As an example, DSM's have a very very small rear end.... but yet they hold tons of power (mainly due a to a very solid design, but the CV's are fairly beefy too).

 

[DerSnart]

I would say that case spread leading to improper mesh in high torque apps.
In any rear with slop, it's impact damage.

Very true.

 

[Greg Wong]

Doug, from what I have read, and what I have experienced myself, with a 1031 open diff, the weak point is definitely the spider gears. Once you have upgraded to a strong diff, then probably either the axles or the pinion shaft may be the next weak link. But it seems like it is fairly difficult on a 240 with street rubber to get enough traction to hit that next weak link. Also, if you upgrade to a carbon fiber driveshaft, it will absorb a lot of shock and will help your rear end last longer.

Just my impressions, hope they help.

Greg

 

[boostdemon]

i think the next one after the diff is the axle splines... i've heard of more axles going then pinion gears

 

[Hank Scorpio]

Ya. See the powertrax does away with the spider gears which is good I guess strength wise... the next question would be whats next Seems to me splines?

We'll see how she lives up to slicks lol

Greg, thanks for the advice on the CF driveshaft

 

[DerSnart]

Best of luck with the slicks, it'd be cool to see your car in the 12's!

 

[ElPiloto]

In a high torque situation, the pinion gear tries to push the ring gear sideways. When this happens, the weakest link breaks. Usually the carrier/spider gears.

Tires act as a "circuit breaker" and prevent breakage by slipping. Put some sticky slicks on and the weakest link in the drivetrain will break, whatever that is.

 

[Hank Scorpio]

Best of luck with the slicks, it'd be cool to see your car in the 12's!

Oh I know it'll do that on street tires Slicks are for the 11.999 dreams

 

[opeterson]

How is a CF driveshaft going to absorb shock? CF is very strong, and very brittle, and won't deform or store much energy.

 

[Bishop]

Splines, twisting, breaking, etc...

Somewhere in my mountain of car mags I had a couple of articles that mentioned Dyna diffs, one was purely about diffs, the other was some hot stuff turbo that was breaking it's Dyna 30, both articles mentioned the splines as the weak point.

I think there may have also been another article about using Dyna diffs in rotary cars as an alternative to bigger more expensive options for high performance etc, can't be sure about that one though, it's been a while since I went through my old mags, and I lost a fair few last time I moved house.

 

[JohnLane]

If you do not have dead bearings (lots of warning about impending failure!!) you will NEVER break Volvo rear end gears inless you manage to feed them a busted up spider gear. I fed 500 horses through 4.10 gears and the gears and housing never failed. However...... I broke LOTS of limited slips. The spider gears break.....the clutches strip their splines off....The clutches strip off the teeth that nestle with the diff carrier. The spider gears strip the splines off where they meet the axle. The Detroit True-track lasted longer then the clutch-type differentials but left a LOT more debris in the housing when it shattered into a LOT of small bits.......We all know that noise......The ice is in the blender for the Margaritas and you push the 'Frappe' button.....Yeah.....That one. Sometimes to the added tune of rear tires that no longer want to turn.....Gulp. In the end the only thing that lived for any period of time was the stock carrier in which I welded the spider gears to the carrier. Hmmmmm......Where is the next fuse? You guessed it!! The wheel studs!! I have broken all five of 'em off a few times. Never did find one of those wheels. I have also broken several axles off where the splines meet the diff carrier. This makes for handling that the driver does not find to be amusing as the axle that ALWAYS breaks is on the outside (loaded) and it breaks as weight shifts onto it due to application of a LOT of torque. This will not be an issue if you have less then 400lb/ft at the wheels.
The Volvo rear end is said to have less parasitic loss then a Ford 9" thing. What I know for damned sure is that the Ford 9" is a LOT heavier then the Volvo rear end. Unsprung weight is NOT our friend.
My 9" Ford is due for repairs and will be done with an aluminum center section to reduce unsprung weight. I'm also going to change my final drive ratio to 3.0 for more top speed and quieter freeway runs.
Have fun!!
John Lane

 

[knucklehead]

my car eats spider gears, but i haven't broken anything else yet.