Gearbox oil leak

[mario308]

Hi,
I’ve done a search but it’s not come up with great results so I’ll ask the question here.
I’ve lost a lot of oil from my gearbox and it’s quite wet underneath, I suspect this has been going on for years but my question is apart from the gearbox oil drain / filler plug could the gearbox leak from anywhere else apart from the 2 driveshaft seals?
It’s def gear oil as the engine oil level on the dipstick doesn’t really go down plus it does smell different to engine oil.
My questions are firstly is there a nice picture thread showing you exactly what to do and is there a way of doing this job without separating the drive shafts from the wheel hubs?
I’ve heard you can separate the bottom ball joints and swing the hubs out or is this method daft?
Car is an 87MK1b T-Bar with 148k miles.
Cheers,
Mario.

[IanParkhouse]

Find a 2nd hand box.

Disconnect the passenger side hub from the gearbox support the gear box and engine. undo all but the drivers side engine mount. (i.e passenger side, Front and rear) Jack the car up. the gearbox can now be taken off the engine as it's hanging down at a nice angle.

I didn't touch the suspension but if you do drop the strut you'll have much more space to work with.

[LimeyMk1]

Disconnect the drivers side drive shaft as well.

And the shift linkages and the clutch slave cylinder and the wiring for the reverse switch & startermotor. Thermostat housing, speedo cable, earth strap, starter motor.

I'm sure I've missed some others.

Mario do you have a copy of the Toyota service manual for the Mk1?

1st job though, before you remove anything would be to localise the leak. Clean up the box, go for a drive and re examine to see where it's all coming from. It might be coming from somewhere that can be repaired with the box in situ.

[mario308]

I've got both the Toyota BGB manuals engine /body etc but I really don't want to drop the gearbox, that's way too much work for me with just axle stands etc. Fairly sure it would be the drive shaft seals I don't think it’s coming thr the bell housing main shaft seal /bearing as my clutch works / sounds /smells fine. – (Clutch was changed 11 years and 30k miles ago and still good.)
Doing a general search on Google does suggest that these seals do go from time to time.

Just trying to establish if there are any other areas where a leak could occur?

[IanParkhouse]

Disconnect the drivers side drive shaft as well.

And the shift linkages and the clutch slave cylinder and the wiring for the reverse switch & startermotor. Thermostat housing, speedo cable, earth strap, starter motor.

[LimeyMk1]

Just trying to establish if there are any other areas where a leak could occur?

Driveshaft seals are the primary leaky points. They're not too much of a PITA to change.

Otherwise I can't think of any other leaky spots on the gearbox. The sections of the box are generally well sealed unless there's a crack.

[mario308]

Thx Limeymk1,

I guess I need to take a closer look. I studied the BGB & the Haynes manual & it looks like there are a few nuts & bolts to undo inboard –just outside the G/box - to separate the drive shafts from the G/box. Anyone ever done this? Book suggests once the driveshafts are clear these short shafts then have to be pulled /drifted out which then reveals the oil seals in the G/box housing.
I guess then its;
Prise out seal
Replace seal
Refit shafts

Cheers.

[kaiowas]

That's pretty much it.

Before pulling the halfshafts out of the gearbox it's best to make sure you have drained the gearbox oil (otherwise you'll make a mess when the shafts come out) and before you drain the oil it's worth making sure you can undo the bolt for the oil fill point, it's usually very tight and more than one owner has been left with a rounded off plug, an empty gearbox and had to find alternative means to refill it!

[mario308]

One final ask;

OK so that’s very encouraging, do you think this can be done without disturbing the shafts at the wheel hub ends?
i.e. just work on the inboard bit?

[LimeyMk1]

Yep, if you undo the 6 nuts and seperate the long part of the driveshaft from the stub you can lift the axle up and secure it out of the way.

You may need to remove the muck shield on the short axle side (2 12mm bolts).

When you come to reassemble make sure you line the protrusions on the axle up with the stub (they're between the 2/3 of bolt hole pairs).