Gearbox oil leak from driveshaft

[Stuleslie]

I changed both output oil seals on a NG1 gearbox on my 72TC. N/s seal is ok but I have had the o/s seal off four times in trying to cure the leak. It is not just an odd drop but I estimate I lose 250ml every 50 miles. In the pic. there is a drip on the drain plug and a small pool of oil at the bottom edge of the castellated nut after a rest drive of 10 miles.
1. I have shimmed the drive shaft and there is no play there, the roll pin is very tight.
2. I have added sealer around the o-ring at the base of the gearbox splines
3. I have fitted a 35mm internal diameter seal instead of the nominal 36mm hoping that would seal better.
4. I have checked that the spacer between the inner bearing and the shims/driveshaft that covers the o-ring and makes a seal with the oil seal is not oval, measured to within 0.01mm.

The only thing I have found is that I can move the splined output shaft sideways by a few thou. Is this enough to lose so much oil? Has anyone any idea if there can be any play in the gearbox output bearing?
Any advise would be appreciated as I any going bonkers
Thanks Stuart

[buzzer]

Did you seal the threads on the seal/bearing carrier. I couldnt see the pic. Use a non setting sealant on the thread such as blue hylomar

[Stuleslie]

No I haven't tried that, I'll give it a go, Thanks

Sorry the pic did not download, here are new ones.
It looks like there is no oil coming through the splines. I just can't understand how so much oil can be leaking so quickly.
I checked the air breather thinking there might be pressure in the box but it was ok.
Stuart

[jbcollier]

It's a bit of a bodge up to allow the shafts to be load bearing.

How are you fitting the seals?  They have to be fitted from the inside of the diff nut.

[Stuleslie]

Yes done that JB, several times.
The left side is OK and was treated in the same way.
I wonder if there is movement from the diff when driven. I cannot feel any play at the shims or the U/Js or the wheel bearing.

[jbcollier]

The seal-nuts set the position and preload of the differential.  Any chance it is a bit loose and the diff (and output shafts) able to move around?

[Stuleslie]

I cannot tighten the nut past the mark I made at the beginning of this work but that is not to say it is in the right place. The history of the box is that I only ran it a few hundred miles before I striped the car and then it has sat for the best part of 15 years idle. The problem has only shown itself since I have had the car back on the road. It could mean the leak has always been there. I think it might be time for a strip-down.

[buzzer]

Looking at the pics it looks like the oil is pooling out of the threaded seal holder. It will leak from their if not sealed. And it will pour out I know as when I built my box I didn’t seal the thread.
As long as you put the seal holder back to where it was you should be ok but these seal carriers control the diff bearing clearance and the diff backlash. The manual goes into a lot of details on setting this up and it has to be done with the gearbox out and the bell housing removed to check the backlash.

[Stuleslie]

Took the seal out again today. Checked seal position, checked the inner spacer for roundness. On re-assembly, I sealed under the spacer around the o-ring and the nut threads. Result....just the same!
Buzzer, there is also a pool of oil at the bottom of the seal lip that touches the driveshafts. The leak must be around the turning shaft.
I spoke to Richard at Banks and he said he has another solution which will take a couple of weeks to get hold of, so I’m waiting with bated breath.
I will let you know what happens in a few weeks.
Thanks very much for everyone’s input.
Stuart

[buzzer]

Ok so definately looks like the seal. I think I actually have a leaking seal at the moment, but as I’m just getting it on the road I will bed it in and monitor for other leaks etc and address them later. I also had a leak on the selector seal which on the 365 is low down. I seam to have fixed that but bizarrely I am getting leak above that seal now near the mountings at the rear.
Be interesting on Richards fix. A tighter seal?

[Lotuswins]

No doubt its the plug which has the 5th gear detent ball and spring behind it.  You will need to remove it and seal with silicone if the aluminum sealing washer isn't doing its job.  Its a coarse thread, so needs torque to seal but with the slotted screwdriver its hard to get torque.  I've always sealed with silicone to get it leak free.

Jerry Rude
4005R

[buzzer]

Yes that was my thought but just assembled it with blue  hyloma so May have not sealed it properly. I’ll monitor and confirm.

[Stuleslie]

It was suggested to me that the leakage problem might lie with the o-ring behind the spacer at the bottom of the splines on the output shaft. After measuring I bought an o-ring 21mm id x 29mm od x 4mm thick. this caused the spacer to sit proud of the bearing but when the drive shaft, shims (same number of shims) and roll pin was inserted I think a good fit was made. The result.........no difference!
I then received the 'good' seal from Richard which turned out to be exactly like the Renault original complete with castellated nut. I think he got the nut machined up locally. See picture of new Renault seal with the original (below) I took off in the first instance. You will see it includes a metal shell and felt washer.
The distance the seal is pressed into the nut is critical so that the seal lip rides the flat portion of the inner spacer. I measured everything and concluded that the metal shell of the seal on the new part should be pressed 2.5mm into the nut (from the back, if you know what I mean?). I went to the trouble of making a 2.5mm spacer so that the distance was correct and that the seal was square. All back together and road tested, the result......no difference!
You should see in the other pic. a pool of oil on the threads of the nut but the felt washer is also wet with oil. The amount of leakage I'm experiencing cannot be coming from the thread and must be coming from the seal lip. I can only conclude that there are some forces pulling the shaft laterally, particularly on cornering, to cause the seal to leak. This makes me think there is something wrong inside the Diff. Remember this gearbox has not been run for many miles since bought and could have had this problem from the beginning. Having said that why is the other side not leaking?

[Gmg31]

When you received the banks kit did you ring him to talk you through it?  I can't fully rammer but I'm fairly sure I had to change part of the seal before fitting it which I would not have know if I hadn't rung him.

Sorry that is vague.

[Stuleslie]

Hi Gary, yes I’ve been talking to Richard throughout this episode and he has not mentioned taking the seal apart. The main point is making sure the seal lip is rubbing on the inner spacer. The measurement is a bit tricky as a reference point is difficult to maintain. But there is at least 6mm to play with so I am sure I am putting it in the right place.
The latest line of thought from Richard is that the bearing may not be fully seated and that under stress it might move up/down, front/back and thus open the seal. I feel the amount of oil loss must be due to something causing the seal to move off the inner spacer.
I will be taking the gearbox out and removing the bell housing to check for backlash on the crown gear and check the position of the bearings. Watch this space
Stuart