weak front 70s diff

[crushers]

so it has been reported the the reverse pinion front center unit is a weak setup which has got me to thinking what would stop a guy from pulling the reverse high pinon front center unit and repacing it with a normal rear center unit from a Prado?
i have not bothered to check this out yet so this is just an idea that came to mind. i know those rear center units can stand a lot of abuse in the mini trucks so...
why couldn't even the 80 series boys that have a habit of snapping the "weaker" center unit do this? of course then the 80 series guys would have to run 4.9 in the rear diff as well....
cheers

 

[beanz2]

80 series cruisers have a tie rod behind the axle and needs the high pinion to clear it. On a 1990+ cruiser maybe.

Dave

 

[crushers]

good to know, shoots that idea down...
figured there was a reason...
i will check on the 70s and see if this is viable or not...

 

[Jim_Hbar]

Wayne:

I'm sure you know this, but all things being equal (and they usually never are, but that's another story) - the high pinion should be the stronger set-up for the front axle when the L/C is driving forward.

What is the mode of failure? Housing?, Diff?, Gearing? Bearings? I'm curious...

Jim

 

[crushers]

i have never broken one so i am not sure, i have heard it can be the carrier itself and loading the teeth when backing up...
my understanding is the teeth on the reverse pinion are cut at a shallower angle thus reducing the strength...
if i could get my energy back i would wander out to the garage and pull the new front diff out of the box and take a look at it...
the rear center unit of the LJs are suppose to have the same cut as the larger rear diffs giving them a stronger mesh...
i guess this is just chat till i actually pull one apart...
cheers

 

[beanz2]

On reverse, the pinion is pulled into the diff by the cut of the gears. The factory spacer crushes further reducing gear contact, already on the coast side when in reverse. A solid spacer instead of a factory one could prevent this.

The low pinion should fit on a late 70. A minitrucker would pay good money for a high pinion diff.

Dave

 

[Tapage]

Always I thought all of us love a hi pinion setup in both diff for the drive shaft angles .. furthermore clearance issue .. but never think that are a weak point for the simple hi pinion configuration ..

Always I thought is a 8" issue .. vs 9.5"

 

[AlbyOne]

I have broken two 4.88 ring and pinions [driving forward]. True they are weaker in reverse. I am now arranging for a custom housing with a Nissan GQ/GU front centre [high pinion] grafted in leaving the FJ80 axles CV, hubs etc.

 

[bigbrowndog]

I have broken two 4.88 ring and pinions [driving forward]. True they are weaker in reverse. I am now arranging for a custom housing with a Nissan GQ/GU front centre [high pinion] grafted in leaving the FJ80 axles CV, hubs etc.

Way to go. Good idea. A bloke I know wrecked his as he rolled backwards on a slight creek bank and then took off steady forwards. Hard to believe and not cheap.

 

[beanz2]

We have no such option here, no Nissan Patrols imported since the 1960's although we can use a Ford 9" high pinion. But in a 70 series there is no need for a high pinion diff, right?

Dave

 

[Tapage]

I never broke a R&P .. but I have friend that is a expert .. broken 4.88 rear.

this one ..

 

[eurotrash]

I do not know if there are any differences between 70 series, except for spring or coil setup. Most common is the coil version here in Holland, that's also the one I used for the SAS of my '90 4R.
The solid axles with coils all have back steering and a high pinion diff, identical to the HDJ or FJ80.

You can't mount a normal diff in a high pinion axle cause you would hit the backsteering.

I've broken one 4.3 high pinion diff (in reverse, about 5 teeth missing) and some 9-10 rears. OEM, new, used and rebuilt, they all seem to shear of teeth when dumping the clutch at high revs.

 

[Tapage]

but in reverse .. I never pull nothing ( trailer, stuck car etc ) in reverse ..

 

[tlcruiserman]

I would question anyone who says the high pinion diff are weaker than regular ones. I have never broken one and don't hear of any of the my 80 series friends breaking them either. The high pinion is stronger when pulling forward than the regular front diff (stronger pulling in reverse). it is so mounted to give you the better strength (forward side of gear) when pull forward, this is what is needed the majority of the time.

I guess it could be debated that the smaller ring & pinion is not as strong as the larger one, but again I have not read of that being a problem on 80 series or on the minitrucks.

Just my 2 cents

 

[Behemoth60]

I would question anyone who says the high pinion diff are weaker than regular ones.

OK...

I've seen two broken, and I almost NEVER wheel with small gear trucks. Jeff Zepp on the 75 pick-up at Moab 2001, and Drexx's 80 at Pismo 2002.

I don't know the failure mode on the 80, but the 75 failed due to the carrier breaking. The stock carrier on the open diff has only four small points in the casting that transfer the torque from the ring gear to the spider gears and axle shafts. These casting points broke, and precipiitated the rest of the failure.

Word is that installing an ARB air-locker is the solution to strong front ends in these trucks. The carrier casting is solid with no gaps at all. Mucho stronger.

I would also suggest that a reverse spiral high pinion is exactly the wrong design for a front axle. The reverse spiral is strongest when going forward. Weakest in reverse. When in reverse, the vehicle loads up the front axle and applies the highest torque on the gears while they are in thier weakest configuration. A standard diff on the front is weaker going forward, strongest in reverse, so that when you have the highest torque on your front axle, you have the greatest strength. For the record, the two failures I directly know about happenend while the vehicles were going forwards when they should have been strongest.

I know it's not meaningful, but of all the wheeling I've done, I've never seen a broken front diff on a full size standard spiral cruiser diff.

Peter Straub

 

[crushers]

broken front diff carrier or broken front diff?
broken front diff is broken axle (birfield most common)?,
broken pinion?
broken teeth off the crown gear?
broken teeth off the pinion?
what exactly are you saying?
i have seen all of the above on full size front axles
(granted most if not all due to abuse or neglect)
cheers

 

[Tapage]

I never seen a front standar ( low pinion ) front axle broke R&P or something inside 3rd member. For sure a lots of bierfilds ..

Sometimes 2 or 3 times I seen rear pinion broke .. with 350 V8 engines in 40 models .. with huge tires and all sover the pinion splines .. ( 4.88 in all cases )

I thought and agrees with the most strong setup are low pinion front and rear .. but I thought for regular use hi pinion 8" are enough strong ..

 

[Behemoth60]

broken front diff carrier or broken front diff?
broken front diff is broken axle (birfield most common)?,
broken pinion?
broken teeth off the crown gear?
broken teeth off the pinion?
what exactly are you saying?
i have seen all of the above on full size front axles
(granted most if not all due to abuse or neglect)
cheers

For the sake of this discussion, I would assume that 'Diff' is an assembly of the carrier (Which is itself an assembly of spider gears, shafts, and some sort of structure which may or may not include a locking mechanism), ring gear, pinion gear, and the pinion and carrier bearings. I would NOT assume that 'Diff' includes axle shafts or birfields.

I would define 'broken diff' as any individual part of the differential assembly becoming broken and ceasing the transmission of torque from the driveshaft to the axle shafts.

Peter Straub

 

[tlcruiserman]

In all my wheeling I have only broken a rear pinion and that was do to driveshaft sliping out and catching the frame. I have been wheeling 80 series cruisers since 97 and have never broken a front axle carrier. I will say that all the 80's I have wheeled did have factory front e-lockers. If I recall I though drex broke the ring & pinion not the carrier housing?

Michael

OK...

I've seen two broken, and I almost NEVER wheel with small gear trucks. Jeff Zepp on the 75 pick-up at Moab 2001, and Drexx's 80 at Pismo 2002.

I don't know the failure mode on the 80, but the 75 failed due to the carrier breaking. The stock carrier on the open diff has only four small points in the casting that transfer the torque from the ring gear to the spider gears and axle shafts. These casting points broke, and precipiitated the rest of the failure.

Word is that installing an ARB air-locker is the solution to strong front ends in these trucks. The carrier casting is solid with no gaps at all. Mucho stronger.

I would also suggest that a reverse spiral high pinion is exactly the wrong design for a front axle. The reverse spiral is strongest when going forward. Weakest in reverse. When in reverse, the vehicle loads up the front axle and applies the highest torque on the gears while they are in thier weakest configuration. A standard diff on the front is weaker going forward, strongest in reverse, so that when you have the highest torque on your front axle, you have the greatest strength. For the record, the two failures I directly know about happenend while the vehicles were going forwards when they should have been strongest.

I know it's not meaningful, but of all the wheeling I've done, I've never seen a broken front diff on a full size standard spiral cruiser diff.

Peter Straub