SEcond hand diff leaking at the big nut at the front

[Olivier]

Got a secong hand Diff today, its leaking a bit at the Nuts at the front that hold the triangle that hold the prop. They untied it trying to take it out. Today I took it out to see if the seal was OK, no leak there. Can I just tied it up again ( the nut) and this would stop the leak as there is no gasket apparently on the nut.
Also MB is charging 10 pounds for the single new nut, this is madness. Do you have a part number for it?
Now that I have the second hand Diff in the boot, would anyone recommend me to changed the seals on the side as I have them ( it was for the diff on the car) or I should just leave it the way it is as its not leaking and I won't risk moving things inside as I'm a bit daunted to open it?
Thank you.
Olivier

 

[Number_Cruncher]

You've probably ruined the diff.

Look at;

Êàòàëîã

You'll see there's a spacer - it's collapsible, and it's a use once only part, and it allows the preload on the pinion bearings to be set accurately.

The correct thing to do is to remove the front inner race of the pinion bearing, and slide in a new collapsible spacer.

The more usual bodge is to mark the position of the nut relative to the shaft, and count the number of turns - then, after renewing the seal, count the nut back on, and line the marks up. I expect you've made no marks, and you tightened the nut up as far as you could? If so, you pinion bearings will be crushed, and won't last long at all.

At least this can't be blamed on comedy fuel!

 

[johnsco]

Many diff oil seals show slight weeping.
Unless it's an actual drip, best thing is to leave it alone.

I've never done a MB diff, but the collapsible spacer is similar to the collapsible washer principle used on a number of GM diffs.
Not only does its correct loading set the pre-load on the pinion bearings, which is critical for their life and noise-free operation.
If it acts the same as on the GM diff, then incorrect loading can affect the mesh between the pinion and the crown wheel causing noisy operation and accelerated wear of both gears.

Hope it's not too late to avoid serious damage.

Johnsco.

 

[Olivier]

Is the spacer number 110 and the 2X 113?

You've probably ruined the diff.

Look at;

Êàòàëîã

You'll see there's a spacer - it's collapsible, and it's a use once only part, and it allows the preload on the pinion bearings to be set accurately.

The correct thing to do is to remove the front inner race of the pinion bearing, and slide in a new collapsible spacer.

The more usual bodge is to mark the position of the nut relative to the shaft, and count the number of turns - then, after renewing the seal, count the nut back on, and line the marks up. I expect you've made no marks, and you tightened the nut up as far as you could? If so, you pinion bearings will be crushed, and won't last long at all.

At least this can't be blamed on comedy fuel!

 

[Olivier]

Cheers John. My Diff is leaking and this is one of the reason I want to change it, its clunking too. I have decided to put new seals on the "new" one as its in the boot and aesy to work on it.

Many diff oil seals show slight weeping.
Unless it's an actual drip, best thing is to leave it alone.

I've never done a MB diff, but the collapsible spacer is similar to the collapsible washer principle used on a number of GM diffs.
Not only does its correct loading set the pre-load on the pinion bearings, which is critical for their life and noise-free operation.
If it acts the same as on the GM diff, then incorrect loading can affect the mesh between the pinion and the crown wheel causing noisy operation and accelerated wear of both gears.

Hope it's not too late to avoid serious damage.

Johnsco.

 

[Olivier]

This is for John and NC, Rereading the post, the Diff came like this,with a wee leak coming from the shaft through the nut, how can the spacer been damage when the only part that ( I moved) was 128 on the diagram? The nut was untied though, then perhaps the previous owner did take or move the spacer?
This make me worry about replacing the seals now, at the front and the side, would that be adviced or should I leave the Diff un touched?
Thank you
Olivier

 

[Olivier]

I expect you've made no marks, and you tightened the nut up as far as you could? If so, you pinion bearings will be crushed, and won't last long at all.

The nut is only hand tights, no forcing there, the 128 part as been pushed in with light hammering as it it tight.
I'll take it out again and look properly.
Thank you.
Olivier

 

[Number_Cruncher]

The spacer is designed to collapse, and hence is a use once only part.

The bodge method just about gets away with it (even better if you measure the friction torque before and match it again afterwards), but, if you've over tightened;

a) if you leave it, the bearings will be damaged, and you might also upset the mesh, as per Johnsco's post.

b) if you release the nut a bit, the spacer will not open up again, and so, won't be acting as a spacer any more - you've already crushed it.

The collapsible spacer is 110, and there are 2 thrust washers, 113.

It's remarkably easy to turn a quiet diff into a noisy one when trying to fix pinion oil seal leaks, and I second Johnsco's advice, unless it was truly pouring oil out you would have been much better off leaving well alone.

 

[Number_Cruncher]

The nut is only hand tights, no forcing there, the 128 part as been pushed in with light hammering as it it tight.
I'll take it out again and look properly.
Thank you.
Olivier

If you haven't re-tightened the nut, then, you actually stand a chance of getting away with this.

When you take out your old diff, rig up a pulley on the front of the pinion nose, and wrap some string round. On the end of the string, put some weight - vary the weight until there's just enough to turn the shaft. This establishes the friction torque you'll aim to set the new diff up to match.

Transfer this pulley assembly to your "new" diff. You should find that with the pinion nut still only hand tight, the weight will drop quickly.

Little by little, tighten up the pinion nut until the weight just begins to drop slowly. Then you'll have matched the friction torques, which in your situation is the very best you can do.

Don't hammer at part 128 - the load will pass straight to the gear mesh, and can be damaging.

In most garages, they don't and won't work on back axles, they send them away to specialists because it's so easy to make one become noisy. If they do work on them, it's usually work which is reserved for the foreman or more experienced mechanics.

 

[Olivier]

Just looking at it now. The seal is not leaking, again as I said, its from the axle, this might be as the nut was not tight.
I'll leave it all the way it is and put it in replacement of the other.
Thanks John for the pulley thingy.
How do you out back 128 withi=out tapping on it, its really tight...
All the best.
Olivier

 

[Number_Cruncher]

You use a 3 legged puller to remove it, and pull it back in using the threads on the pinion shaft.

 

[johnsco]

You need to pull it with some sort of 3-leg puller - Like you might use to pull a bearing off a shaft.

The string-and weight method is how I used to set diff pre-loads.

On some GM diffs, it was also necessary to set the differential side-bearing pre-load by adding and subtracting shims.
A similar method was used using a string and weight to set the bearing pre-load.

Johnsco

 

[johnsco]

SNAP !!
I got diverted half-way through my post.

 

[Olivier]

You use a 3 legged puller to remove it, and pull it back in using the threads on the pinion shaft.

Oh... Well, this is the bad part of it as there were no puller used...
Just hammering it in rotation to pull it strait...
Lets hope it did stand the hammer to pull it out. If not its bye bye Diff...
After all it look OK, better then the one on the car at the moment.
Cheers.
Olivier

 

[johnsco]

Good Luck.
I'm off home now.
Johnsco

 

[lynall]

Ive done a few pinion nose seals on mainly landrovers and trucks and its basically undo nut, beat or and pull flange off, fit new seal the beat the flange home and refit and tighten the nut never had any comeback.

Think truck ones are shimmed so not a problem but pretty sure landrover ones were also crushable spacer and as said never had any bother and i did a lot of miles in my discoveries.

Lynall

 

[Number_Cruncher]

>>landrovers and trucks

There is one significant difference though - on a Land Rover or truck, no-one is going to mind or even notice a little diff whine.

I'm sure you'll get away with gentle hammering, but, the safest way is simply not to go near the diff with a hammer.

As you say truck crown wheel and pinions are near universally shimmed - it creates a much stonger and stiffer bearing set-up than the collapsible spacers which are more common on cars.

When you're working with a fully shimmed pinion, then, you can be quite bold in re-tightening the pinion nut - the torque specified is usually quite high, wheras with a collapsible spacer pinion you generally won't find a torque specified, and there'll be some indirect method involving friction torque specified.

The rear axles of older Merc trucks had the nice feature of having a pair of threaded adjusters [a miniature version of this was also fitted to some Ford Escort back axles], which moved and pre-loaded the crown wheel. These were much easier to setup than the Leyand back axles which were fully shimmed, and you needed to lift out the crown wheel to make a change in either preload or position.

 

[alexander patie]

interesting read this. i was going to post the first reply, but lost the will to get involved! number cruncher has it right again. the "usual bodge" he describes is exactly how i change the seal. i use a puller to get the spigot or drive flange off and always put the nut back to where it came from, and it is usually a very high torque to get it back there, showing the bearings are nicely supported on the pinion/input shaft. also we always use the top man to do this work, hello

 

[Olivier]

After all the hint/ thoughts/ on what to do, I just put back the diff at the position it ""might"" have been in. Looking at the bolt dent and the position of the front seal protecting plate.
So far its as been few hours now, the diff is inclined and no leak. Bone Dry. I did turn in the nut one milimiter too far away though. An easy thing to do. But one millimeter is not that much ( I am not talking deep, I'm talking screwing right side).
The problem as always been the oil coming out from the centre ( axle) as the nut as been moved as well as the triangular prop holder.
I also fought the filling plug as it was completly sealed with rust, but managed to take it out, in case a leak occurr, I could always top it up now.
The Diff will go the way it is hopefully next week.
Thank you all. Olivier

 

[lynall]

None of my disco diffs whined ever, very fussy me i would have had to do something if they did.

As for the trucks 1" nut gun to remove and fit nut.

I think torque is something stupid like 1200nm.



Lynall