Changing gearbox gaskets

[Alex Laidlaw]

I now have the following gaskets sitting in front of me:
Mac's diff cover
Front cover to main case 1340989
Side (top) cover to case 1340991
Main case to 5th gear case 1340992
diff case to 5th gear case 1340993

...and a 340 that seems hell bent to deposit the contents of its gearbox on my drive.

I recently changed the gearbox oil from black sludge to Castrol GTX 10/40 engine oil, unfortunately I think the cleaning properties of this fancy new oil has removed the sludge that was sealing my gearbox. I am certain that the front cover is leaking, partly because when I got the car part of this gasket was dangling out the bottom of the gearbox and has now disappeared and when I park pointing downhill I get a bigger puddle!

With the Haynes manual helpfully advising me to buy a new gearbox I'm a little unsure as to how straight forward it is to replace these gaskets? The front cover definitely needs replacing and Mac's diff cover has nice non-scary instructions so I'll definitely be doing those two the others could probably be left, at least to see if they are actually leaking.

Has anybody done this before is it going to explode into a million pieces when I take it apart? Do I need to apply a sealant to these gaskets and if so what is best?

[Ride_on]

I've separated dIffs several times, look out for the bearing shims and make sure you have the right gasket for this joint as it forms part of the bearing clearance calculation (and is clearly described in my manual) for the shim thickness requirement.

The side I don't remember anything, have not tried the front cover. Never bothered with sealant and certainly not on the critical join between gearbox and diff.

If the shims are wrong or you use the wrong thickness gasket your gearbox will whine on slowing down.

[Alex Laidlaw]

In the end I only decided to change the front cover gasket, nothing scary only took 10 minutes once the 'box was on the bench. It could probably be done in situ by supporting the front with a jack, though keeping everything clean would be much harder.

Undoing the long M8 bolts that hold the gearbox to the front cross member was the biggest faff, because the holes in the back seat floor that appeared to be there to allow access to the bolts were smaller than the 13mm socket required. I managed to pass an extension bar through the hole and get a shallow socket on to it to undo these. Surely they were meant to be allen headed rather than hex headed bolts!









After removing the plastic input shaft cover and the gear linkage connector it is just a case of removing the four bolts and sliding the cover off, there is only one shim on the input shaft.



Bolts torqued to 31 lb/ft as per Haynes manual



The gasket has these unused tags that are exposed at the bottom of the gearbox and will inevitably get pulled off at some point, possibly pulling the gasket down with it, probably a good idea to chop them off.

[filthyjohn]

Cheers for the part numbers! Are they all still readily available from Volvo or did you get them from a 3rd party?

[trabitom99]

Cheers for the part numbers! Are they all still readily available from Volvo or did you get them from a 3rd party?

Hi John!

Many of those should still be available, check out this post:
http://www.volvo300mania.com/forum-uk/v ... 85#p120285

Cheers

Tom

[filthyjohn]

Ah, in that case thanks to you too Tom.