Rear Gearbox Leak

cdnp6

cdnp6

Member
I had my series 1 manual TC up on the lift yesterday to refit the bushings of my
gear shift top mount bolts.
While under the car, I noticed I have some oil leakage at the rear of
the gearbox, and the selector shafts were dripping a bit.
This looks like the most probable cause of the leak. I check the
gearbox level often, and its always good.
So not too worried about volume lost, but wondering about what I need
to do to correct this leak.
I may be mistaken, but I think I read in one of the forums that the seals for the shafts
can be replaced with the gearbox in situ. Anyone done this and can provide instructions?
Roy
 
You can't replace the selector shaft seals without removing the gearbox, and then taking off the top cover and rear housing. I don't know if the seals are still available. They don't tend to leak so the breather hole may be blocked, but I doubt that you could clean that out without removing the box either. You can replace the tailshaft seal, and the rear housing gasket in-situ but that's about it.
 
Does anyone have a good photo of the series 1 4 cyl manual gearbox so I can see where the breather hole is?
I have checked the level of gearbox oil again and there has been no change.
Could I lose oil from the rear of the gearbox if the restoration shop overfilled the box?
Thanks.
 
The breather is just a small hole drilled through the top cover, which I doubt you'll be able to get at with the box in-situ.
 
I still seem to be losing oil through the rear top of the box.
Every time I check the fluid level, it's fine.
I am still thinking that the box must have been overfilled.
I may drain the gear box and refill it to be sure the level is right.
Any recommendations on the type of oil I should be using? Are there any additives I should try?
Roy
 
If you're checking the level and it's correct, draining and refilling won't make any difference other than renewing the oil. I can't see how you could overfill it unless the car was jacked up high on the filler plug side. Use 20/50 engine oil, and don't use any additives.
 
The book basically says that you should fill the 'box until the oil spills from the filler hole (or that's my interpretation). There's no confusion there it would seem as you can only fill it to the level of the hole (& I'm sure you didn't have the side of the car jacked up when you did it) so draining & refilling can only bring you back to square one. I think you're just putting off the inevitable which would seem to be removal of the gearbox for inspection. Hassle I know, but probably necessary unless the oil is travelling down from the engine to the 'box & dripping off of it which seems possible if the gearbox oil level isn't dropping.
 
I'm inclined to agree with the possibility of the engine as a source of the oil. I seem to recall that the 4 cyl has a small O ring towards the back of the head gasket. If this is damaged or miss-aligned that will cause small quantities of oil to escape right at the back of the head block joint and then run down onto the top of the gearbox? Anyone able to confirm this?

Your engine is newly rebuilt as I recall, so if it was this cause I'd want to find it soon and get the shop to put it right!

Chris
 
The "O" ring at the back of the head gasket normally runs down and looks like a rear main leak, but it's possible that it could be making it's way as far as the back of the gearbox. If the oil you are seeing is black then it's engine oil, gearbox oil doesn't go black in use, so if it's clear then it's from the box.
 
Thanks for the insight guys.
I will get under the car to look for evidence of an engine leak.
One thing I have noticed, is that the gearbox oil is fairly dark, so first off, I will be changing the gearbox oil.
So, it looks like I will have to start thinking about pulling the engine and gearbox.
Are there gasket sets available for this gearbox, or do I need to start looking around for a replacement...
Roy
 
Gasket sets are readily available, as are rear seals. I'm not sure if selector shaft seals are, but they rarely give problems, and if they do need changing things get a bit more complicated as you have to remove the selector arms from the selector rods, which means setting them up correctly when you refit them.
 
Well, good news and bad news.
Good news is, after mopping up some of the caked on grime, I had a better look at the box.
The front of the box is dry, and the oil is definitely leaking at the back.
It looks like it is the rear main seal.



I think it was mentioned that this could be replaced on the car without having to remove the box. :)
Please feel free to post the procedure if you have done this. :D
In trying to change the gearbox oil, the plug was securely fastened and all I can do is round the edges, so unable to do this at this time. :x
Roy
 

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The rear seal can be done in-situ. You'll probably need to remove an exhaust section to get the prop out, although that can be done without if you're lucky, then remove the rear flange, prise out the seal, install the new one and RITRORP.
 
As luck would have it, I just happen to have a replacement exhaust system I need to install...
I was supposed to have the exhaust done on Wednesday. I told the shop to cancel my spot, and we would do both jobs at the same time.
I ordered the seal this morning.
 
I was told that the 4 speed transmission rear oil seal is the same as the differential seals.
Is this right?
They have different parts numbers, are they interchangeable?
 
I don't know if they are the same. Do they mean the diff output shaft seals, or the pinion seal? I can see that it might possibly be the same as a pinion seal as that has the same type of flange, the output shaft seals I'm even less certain about.
 
I'm sorry Harvey, I didn't think to ask that.
I have to phone again for some small bits. I'll see what I can find out.
 
Finally got all my parts together and had the rear transmission seal replaced.
Here's a shot of how the prop shaft was throwing the oil all over the tunnel.


The rear seal was replaced in situ after disconnecting the prop shaft. The support cross member hardware was looking pretty sad so I supplied a new spring and rubber cushions.
The snub rubber was checked and left in place. I drove the car for about half an hour afterward and so far there has been no new oil splattering. I'll have to keep an eye on this.


I also had most of my 2 can exhaust replaced with a 3 can mild steel system that was supplied with the car. The new rear silencer section had been installed by the previous owner and is still in good shape. After running for a half hour or so, The exhaust started sounding loud at one of the rear joins, kind of the same sound as when there's a hole in a silencer, but only with acceleration. I guess I need to go back and have the flanges tightened. Is this better to do when the pipes are cool or hot?
Roy
 

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Sounds like your car is really getting there! Just that respray to go and you'll have a daily driver to be proud of!

Chris
 
Those rear engine mounting and support bars are missing various rubbers and spacers, they don't bolt directly to the brackets on the tunnel like that. They should have Nylocs, or at the very least spring washers, too.
 
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