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Gearbox oil

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hamgr Avatar
hamgr Graham Hammond
Littlehampton, SA, Australia   AUS
I have had some pretty bad oil leaks from a fairly recent engine and gearbox rebuild. BN1 with a fourspeed modification.
As both oils were still clean I put it down to rear main seal leaking. I removed the gearbox to get a better look at the rear main area but found the leak was from the gearbox.
I had used Redline V90 in the gearbox and the leaks were coming from the bell housing to gearbox bolts. While the bolts were tight i i could see the oil coming out between bolt head and the spring washer.

i have since heard others having issues with keeping redline oil in the gearbox. So have instead used Penrite GB30. Hopefully this will fix the leaks.

As the gearbox is still out, the throughout bearing for the clutch, looks okay but when do you normally consider replacing? everytime you remove the gearbox, it was second hand to begin with?

Hamgr

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PAN Avatar
PAN Alwyn Keepence
Ipswich, Queensland, Australia   AUS
Graham,
If the chamfer is still visible on the circumference of the carbon thrust, then I believe the throw-out is still OK.
I use Penrite Gearbox Oil 40 in my BN1 gearbox. No leaks inside the bell-housing.
Cheers,
Alwyn

Vintage n Classic Avatar
Vintage n Classic Silver Member Geoff Golding
Nelson, Tasman, New Zealand   NZL
Hi Graham

I use Castrol GTX 20-50 in our 4 speed gearbox.......no leaks. Whilst you have the gearbox on the floor, check the seal on the drive shaft at the bell housing end.......oil is like blood it makes a hell of a mess and goes everywhere i.e. it looks really serious but often the cause is something minor

Cheers
Geoff

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San Jose, California, USA   USA
I rebuilt my BJ8's engine recently. I pulled the clutch housing off the gearbox to send to the rebuilder. On re-installation I spread Hylomar on the paper gasket between the two, and I put copper washers under the bolts between the housing and the gearbox, and put threadlocker on the bolt threads. The engine and gearbox do not leak; unfortunately, I have to pull the gearbox out as it started jumping out of fourth after the overhaul. I've used Redline MT-90 for years in the BJ8; it used to leak before the rebuild, but now all I have is some slight weeping at the gearbox/OD mating surface. Be sure the oil level in the gearbox is correct; I overfilled mine after the rebuild and it peed all over the floor, but that stopped after I got the level right.

I didn't replace the release bearing as it had about a quarter-inch of graphite disk left. It's my habit to put the gearbox in neutral whenever I come to a stop.

DTDuck Avatar
DTDuck Dan Marshall
Redwood City, California, USA   USA
In reply to # 193016 by hamgr I have had some pretty bad oil leaks from a fairly recent engine and gearbox rebuild. BN1 with a fourspeed modification.
As both oils were still clean I put it down to rear main seal leaking. I removed the gearbox to get a better look at the rear main area but found the leak was from the gearbox.
I had used Redline V90 in the gearbox and the leaks were coming from the bell housing to gearbox bolts. While the bolts were tight i i could see the oil coming out between bolt head and the spring washer.

i have since heard others having issues with keeping redline oil in the gearbox. So have instead used Penrite GB30. Hopefully this will fix the leaks.

As the gearbox is still out, the throughout bearing for the clutch, looks okay but when do you normally consider replacing? everytime you remove the gearbox, it was second hand to begin with?

Hamgr
This is the problem with using synthetic oil. These gearboxes were engineered to run on 30w conventional motor oil and so were the seals. Modern cars are engineered with synthetic oil in mind and the seals are designed to hold them. The problem is that the lubricating properties of the synthetic are so good that the seals won't hold them (too slippery if you will). Don't get me wrong I love synthetic oil and regularly used Redline in my old spridget when I was racing but I had the same problem, it was nigh on impossible to keep the leaks down to a manageable amount. So if you are going to try using synthetic you will have to fit modern oil seals to hold it. In the end I gave up and switched back to dino oil and used Valvoline 50w racing oil without further difficulty. Good luck.

Dan M.

100M Avatar
100M mike lewis
harbor island, sc, USA   USA
I have used non detergent 40 weight oil for about 7 years and works great for the overdrive and gearbox.

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