Rockwell diff - loose pinion nut??????

Gentlemen,
The back diff in the old White RoadBoss has had some pain and suffering in its long life however a bit of driver error seems to have triggered some interesting events - your help is needed!

In December, the nut behind the wheel (me) reversed up an incline; the incline was flat on top and the result was that the back diff dropped as it left the incline and followed the flat while the front diff was still on the incline. The result was the jackshaft got onto such an acute angle the as it turned it snapped off the front of the back diff yoke.

A new jack shaft, a new back diff yoke, all new uni's, new seal. new back diff pinion nut, and all back together for $2,000.00 - and the driver learned a very expensive lesson.

1400km later and oil leak developed from the pinion in the back diff - the pinion nut had come loose. Oil was travelling up the spliones and leaking from between the splines and the nut/washer. So mr fix it (not me, but a guy with all the right tools and a lot younger than me) says "they come loose all the time..." and Loctited the nut back on, rattle gun with maximum pressure, clean down - should be all good.

Now the first weird one is "they come loose all the time" - well I have never had one com e loose and nobody I know has had one come loose !!! Any of you guys heard of it??

Today, only 548km since the last fix, it is loose again - oil leaking and the yoke moving up and down/in and out.

Last time we put on a new nut and loctited it, but that didn't work.
The threads on the pinion are not 100%, they are probably 90% OK with some marks on them from the first failure.

Knowledgeable sirs :- What the hell is going on here?? HELP
cheers,
Bretto
PS : I believe that they are the big version Rockwell/Meritor diffs, with Hendrickson spring suspension in a 1979 White RoadBoss.

TRB Man
FWIW
they do get a bit of wear n tear
my diff man uses wot he calls a speedie seal n thourghly cleans the splines n uses good quality U bute loctite n let it set over night B 4 use so it will go hard (hope n u're the same LOL)

but others may have more knowledge other than fitt n all new bits


Cya
[ch9787]

Hi ya Swishy,
The speedy sleeve is used where the pinion seal has gouged a track on the pinion yoke - I don't have that problem as I got a new pinion yoke when I snapped the other one in December.

Does he really use Loctite on the pinion nut?? I would not have thought that a 3" nut would benefit from Loctite.
Anyway Swish, thanks foir yer input
Bretto

Yep i always use locktite on them .....takes some getting back off at times but haven't had many come loose.

So you have had one come loose???

i believe that its wise to use a new nut when the original is taken off .. i had a gearbox rebuild once and they didnt replace the large nut (external)on the output shaft..less than halfway on my first trip(a 1850km trip to mackay)the nut came loose. . i ended up getting a new nut made at a engineering shop after i nursed the truck that far . . diff pinion bolts seem to come loose as well if you reuse the old nut . . . . probably something to do with the 200+ft/lb of torque when they are put on

Hello,

loose pinion nut will come loose if you have any wear on the shaft,even a micky hair, it works backwards and forward, and undoes the nut or wears the nut, you may be lucky by haveing a washer,
and a rattle gun would have to be the worse thing to use, the pinion will bounce and give false reading, you need a bloody long bar and a big pair of stilsons to lock the pinion flange to the chassis, once they start they never stop, beats me why the dont have a tapered spline,
Rob

Howdy,

The Inter RA57 Diff is a spicer and the nuts come loose from time to time. If not picked up straight away the yoke can wear a little on the spline then it doesnt matter what you you wont stop it coming loose and leaking.
Ive had success with taking yoke off and get it perfectly clean as with the splines. Prime with loctite primer then apply a liberal dose of loctite master gasket to the pinion spline then put super nut lock in a new nut then torque it up real tight. I use a torque multiplier to do it up. You will struggle with a spanner and pipe to get it tight and about all a rattle gun will do is make a heap of noise.
Tight is in the order of 700 - 800 ftlbs.
The problem is with them if the nut is loose it allows the preload collar to rattle around between the bearings and can wear it or the shims to the point when you do retorque it up you can end up with to much preload on the bearings and they will poo their pants shortly after.
If its just a weep its usually salvagable...if its dripping its crook and needs to be checked out properly.

Basil

An update :
Pulled the jack shaft out revealing the back diff pinion nut was at the end of the thread and only finger tight. Removed the yoke, splines are still good as new, as are splines on the pinion. Bad news is the thread has a low section, meaning that the very crests of each thread are just not there - and this is where the locking part of the nut sits.
At this stage, cleaned down everything, used super Loctite shaft lock on the yoke splines, silastic the washer so oil won't seep past, and nut locker Loctite on the nut. To tighten, we used the 3/4 drive rattle gun; then we attached a 3/4 drive power bar, locked it to the ground, and reversed the truck about a foot with the bar locked on the ground which took the nut up about another 1/2 to 3/4 turn over what the rattle gun could do. It is now F$%cking tight!
If it comes loose again, then we must presume that the threads on the pinion are the problem, and will have to pull the diff and probably replace the pinion
cheers all
Bretto

Bretto,

Did you use loctite primer before using the loctite?

As basil mentions in his post using the primer. Also no matter how clean you get metal it isn't REALLY clean enough for loctite to really grab.

I believe if you use primer and loctite for example you wouldn't have any thing come loose! As for getting it apart again? Might need a bit of heat!

If you have troubles have a look at loctite website or contact loctite they are always willing to give ideas on which product and how to use loctite!
au.iloctite.com