8" vs. 8.4" diff

Why do the Off Road models use a smaller rear differential? It seems like you'd want a larger/stronger one for the abuse they see. From what I understand, the Off Road is the only one with the small 8". So what gives?

 

The 8.4 still has a 8 inch ring gear it just has a stud girdle that increases strength. The 8 inch locking diff is plenty strong for what it is bring used for.

 

What is a stud girdle and why doesn't the OR diff have one?

 

It ties both carrier bearing caps together for less deflection. My guess the reason is because the 8.4 was not out when the elocker was designed, not really sure. The difference in strength is probably marginal.

 

Not sure, but I think 8.4 " is the ring gear diameter where as the 8 " has an 8" ring gear diameter. I also think that All Pro and others have used it as opposed to the 8" for strength in their builds and add lockers like the Detroit Locker fro way more durability. I think, and have read.

 

http://www.pirate4x4.com/forum/toyota-truck-4runner/228681-myth-settled-8-4-v6-4cyl-all-8-a.html

The "8.4" does have some better features but a larger ring gear it does not.

 

I thought wrong.

 

How can you tell which one you have? Is it only the OR package trucks that have thr 8"?

 

The "8" inch comes with the TRD e-locker rear end.

 

Ok, thanx

 

every time i hear someone reference whats strong than another. Remember... the stresses typically seen by the open diff (dont kid yourself about the mechanical lsd) on the "8.4" are going to be much less than what is possible on the 8in locking diff when its locked, simply due to the nature of being locked.

Yes if both tires are on pavement and you gun it in either config they will see the same stress obviously. But where you see failures is on the trail, and the failures you see are typically with the stock elocker (8in) on a truck that is modded with bigger tires in obviously a pretty crazy situation to need a locker. You dont hear of the failures on the 8.4in because they simply arnt put into the situations to do so because with the open diff the truck cant get there!

 

Mostly but not entirely true. What about shock loads on a LSD or open diff. Those loads would potentially be higher than a locked diff not slipping.

 

They're both weak. D70 FTW.

 

70 HD.\/ \/

 

Lol Dana 80 ftmfw

 

This is true i guess. If the person is hopping up and down yeah the loads could be higher. But like stated the stock e lockers that you typically see fail are on rigs with bigger tires in some pretty gnarly situations w/ the locker engaged and a heavy foot. If the 8.4 could have gotten to that same spot it would have broken as well.

Unless you are doing serious crawling on 35's the stock diff both 8 and 8.4 are pretty darn good.

 

There's guys running elockers on 6k lbs rigs on 42s. The failure point is going to be the shafts first then more than likely the ring and pinion.

 

There are plenty of photos of failed ring gears on the 8.0.

The 8.4, even though it is truly the same size gear, has 12 bolts vs the 10 bolts in the 8.0.

It has been said, but again without some kind of slow motion of the failure, that the girdle will keep the bearings aligned and support the outward stress on the ring and carrier. The 8.0 without the girdle, flexes the internals, then the gear slips and breaks.

FWIW, my 2010 DCLB TRD Sport has been swapped to remove the open diff and now runs a TrueTrac. If anything, the stupid electronics cause the most grief to sort out how best to over ride them with the button when off road.

PK

 

Who's running 42s with 6k # rigs? Only rigs I can think of are new 4 runners and tacos that weight that much.

Well you didn't say elocker Toyota axle... But I'm assuming you are, and talking about the 8" lol

 

Nobody on here have seen a few on pirate. Probably a little high on the weight guess. The way some toy guys are going now are 9.5 hybrid axles.