308 GT4 Gearbox / Transaxle Oil Change

I'm planning to change the gear oil in my 308 GT4 at the next service. I'm familiar with the while process but there seems to be various thoughts on adding additional oil to the gearbox above the overflow plug level.

The manual just calls for it to be filled until it overflows from the overflow plug then you're at the correct level. Others mention adding 'just a bit more' to help with 5th gear oil starvation and Birdman 308 mentions adding and "an extra pint or so gearbox oil" on his website.

What's the consensus here? Is the extra oil warranted or needed? An additional "pint or so" seems like a lot extra to me...

 

I think a bit of overfill will not harm the internals, but you might find more leaks at the differential seals.

 

Just did the gearbox oil on my GT4. By the book, filling to the overflow, and it works a treat with no problem getting any of the gears. I used the Redline MTL fully synthetic as recommended widely on this forum.

 

I think you can cause other issues by overfilling it.

Besides, it's sensible once in a while to pull the fill plug out & make sure there is no excess oil in there....If there is then your shift shaft seal is on the way oil & engine oil in there is much more of a concern.

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Can't recall that being an oft reported trouble area (nor see how an additional pint would make any difference for "starvation" based on the oil level shown in the gearbox cross-section figure on page D14 of the 308GT4 WSM (and the proximity of the 2nd gear set next to the 5th gear set). Can you post a link giving a technical description of the issue?

 

Agree - unless there is a subsequent factory bulletin stating otherwise, there is no reason to overfill a gearbox.

 

the diff is over the oil level in any case, so it's useless to add more oil: it's a waste and nothing more. The car must be driven sometimes (at speed) to preserve the diff.

Insted of adding more oil than the correct quantity, maybe better changing it more often

Ciao

 

I believe the wsm asks for approx 5 oz in addition

 

Please indicate what page this appears in the 308GT4 WSM. The OMs typically have a statement to introduce a minimum small amount of the new gearbox oil into the transfer gear fill hole (to ensure that that area is also filled with new oil), but this is not an "overfill" instruction.

 

It must be in the Owners manual. IIRC .19 Liters? It was a little under 6oz IIrc

 

Here, I found this in Birdman website, Step #16
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So overfill for "anticipating leaks" and for "something I heard hearsay about 5th gear being the highest" (which makes no sense to me because the large 2nd gear half rotating next to it will always bring up oil from a very low oil level)? Doesn't convince me...

 

So the 1 pint addition is for in case there’s a leaks but he didn’t say if you found out there’s no leaks to remove the extra pint of gear oil.

 

Intentionally overfilling a gearbox? I do not recall hearing anything as stupid.

Ever seen the inside of a spinning transmission? It looks like a blender. There isn't a square nanometer not covered in oil.


Thanks for the laugh. This place never disappoints.

 

If it’s leaking it’s only going to get worse .Get it fixed , use a experienced F guy , a specialist F shop .
Fill all levels as per correct spec .In this case to the level hole and wait for it to stop poring out before plugging it up .

Over filling tends to increase pressure on seals and just worsens the weeps into leeks , so you end up in a perpetual cycle of overfilling in “ anticipation “.

Fix the leaks stay with OEM levels .

Edit Rifledriver beat me to it .

 

Fantastic… sounds like I’ll be going by the book and just filling to the overflow point. No extra required. Thank you all for your input.

 

308s discovered on Mars .

I,ll get my coat !

 

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Overfill by 1 pint ...in case of leaks ...the hell?

 

Wait until you replace your diff seals, doing everything meticulously, and find you still get weeps/ leaks. The new diff collars where the cv joint bolts on to are no longer available, and the old ones will likely be grooved by the seals from use. You can roughen lighty with emery paper to create a good sealing surface, and try to install the seals marginally different from the original to create a new wear area. And still these darn things weep, and fling some gear oil on the headers.

So I can see why some overfill in anticipation of leaks. Not so simple to fix these leaks.

Let me know who makes a double lip seal that fits, and works. Or who makes a repair sleeve for the diff collars, like there is for some other makes of cars for crank seal leak repairs.

 

Can someone show me a pic of these diff collars that are not available. I would like to try myself to procure a set for the future , just in case.

Thank you

 

I guess you have never heard of Speedy Sleeves. Been fixing oil leaks for 70 or so years.

 

No I had not! Have you sucessfully used these before on the diff flanges? I don't recall any Fchat thread ever mentioning these.

 

I was thinking the same, and was only able to find one, it may well be the last one on a shelf out there for my Mondial 3.2.

The Speedy Sleeves noted may be a great solution. The job was quite time consuming for me to do the seals, and I am not happy that things didn't perfectly seal despite doing everything meticulously. It is not a job one wants to redo.

When one searhces threads on these seals, there seem to be many who still have leaks. I am surprised the Speedy Sleeves are not in more routine use. Or maybe there is some problems with the quality of the seals being sold out there.



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