Technical Gearbox seals..

[vascrats]

Funny thing about these little cars as you get one and start cleaning it up...You get to a certain point but it is always 'while I got all this off, might as well.....'.

How this translates to this thread is this..I have the old motor out awaiting the body work and 650 motor. With the motor out I am still getting regular oil drips on the oil pan which I would imagine has to be the gearbox (which is what everyone is calling the transmission I believe). When I placed my last parts order I got a gasket kit for the 126 gearbox (starter to R-hand side). I am not sure as of yet where exactly the drips are coming from as I have not had a good time to wipe it down and check yet but I will get to that this long holiday weekend.

What I preemptively wanted to know is if replacing gaskets and seals would be the same or very similar to the 500 gearbox as might be shown in the haynes manual. Secondly, is this something a novice can do or are there specific tolerances or adjustments that are very tricky I could mess up while 'simply trying to replace leaky seals or gaskets'? Lastly, any gearbox build threads that may be handy on this forum or other?

Thanks in advance!
Phil

 

[Bambino]

Phil,
The gearboxes leak in all of the usual places - but particularly past the oil boots on each half axle and between the bellhousing and the main casing. I haven't had to rebuild a gearbox yet but have changed the half axles when I installed a 126 box/diff in my 500.
If I ever strip and rebuild a gearbox, I'll post some photos. Otherwise, the manuals look to be full of good information.
Chris

 

[vascrats]

O.K, I did look under the gearbox last night and it looks like the leaks are at the bottoms of both boots. I originally thought those boots were just dust boots or something but with Bambino's post I realized I assumed wrong.

Looking at Mr.Fiat's prices on the boots, they are cheap so I will get new ones. Question is, would I need the 25mm ones or the 19mm ones? I would be leaning towards the 25mm ones based on the description but I read some places that say the 126 gearbox had to use the 500 shafts to work in the 500 so that puts the little question mark there. How do I know for sure which boots to get?

In my researching I see there is also a large (relatively) o-rings that seals the bearing housings for the axle shafts to the gearbox. Is this a possible leak point that would be worth putting new o-rings on since they came in the gasket kit I incorrectly preemptively ordered?

Maybe I should have just ordered a replacement fiat 500 from Mr. Fiat.

Thanks as always!
Phil

P.S. Here was the link I used for some interesting pics on the gearbox though I am missing the text...

http://www.flickr.com/photos/ricambifiat500/sets/72157615692546231/

 

[vascrats]

From what I can tell, it looks like I would need the 25mm ones (so I ordered them) but can anyone confirm this so I can sleep at night.

Or I guess I could get off (or I should say on) my lazy butt and try to measure the diameter of what I have.

 

[Bambino]

The later model 500s and 126s had the larger diameter 25mm halfshafts.

The 126 ones are longer (wider rear track) so need to be changed for the shorter 500 series shafts when fitting a 126 gearbox to a 500. Someone has already done this bit for you.

So, yes - you need the 25mm boots etc.

Off to bed now Phil and sweet dreams, you've nothing to worry about (yet)

Chris

 

[vascrats]

Thanks Chris!

I guess I was being a bit of a drama queen with the whole sleep thing. Trust me, the rust I found under the rubber undercoating (on the inside of the car mind you) is enough to cause restless nights. Of course the previous owner called it a rust free car. He was right...he did not charge extra for it.

I did end up wrapping a piece of paper around the axle and marking it before jumping in the car for work this morning. Once at work I measured it out to roughly 78mm. I used the PI (mmmm pie:yum formula to translate that to diameter and got 24.828mm. I used a wide sharpie to mark the paper so I knew it was not a precision measurement but close enough.

Now if that 650 motor will get here by Christmas (just to have, long way from putting it in)

Thanks again!
Phil

 

[oopsadaisy]

Of course the previous owner called it a rust free car. He was right...he did not charge extra for it.
Phil

Love it!

 

[vascrats]

O.K., life has finally allowed me to continue on...I have the new motor from Mr. Fiat ....but I really need to get the transmission leak free before I feel like poppin the motor in. I got new oil boots in from Mr. Fiat as well. NOW....I do have the crappy copy of the Haynes manual but can anyone who has had experience outline the process of replacing just the boots?. I want to be sure I only take apart just what is necessary to get the boots on. I do have new dust boots for the other end of the shafts as well.....

Thanks in advance!!!
Phil

 

[Damon500]

Hi Phil,
Gearbox boots are easy and exactly same procedure as for a 500- best to jack the back of the car up so the wheels can turn, undo the 4 13mm bolts holding the axle flange to drive coupling. Once this is off then remove the circlip and spacing spring and the flange will pull off. Place a bucket under the gearbox (small is ok there is only 1.1l of oil) If you jack the car up on the side you are doing then you won't lose too much anyway.
Then undo the 4 10mm bolts on the inner boot securing ring and you can then pull off the boot and ring. You will probably find the bearing lock ring will come out too with the boot- remove from the boot and push it back into place in the bearing carrier. Then grease the seal surface, fit the new boot and then the retaining ring, flange, circlip etc.
Make sure that you put plenty of grease on the axle splines when you assemble it and once you have completed top up the gear oil - this is a 1/2" square plug on RH side of the gearbox bell housing between the axle and engine. It is probably best to top up after the engine is refitted because the gearbox (and car) should be level when checking the level.
Hope this helps! it will be very easy to do if the engine is out.
Regards
Damon

 

[vascrats]

Thanks Damon!! ...and great detail!

My only questions at this point are what kind of grease (newbie here) do you recommend for the splines and seal (which I take is the outer part of the boot that rides on the smoothed surface of the axel) ? and do you need to use anything to seal the boot to the case or will that be fine since it is rubber?

Thanks again!!!
Phil

 

[Damon500]

Hi Phil,
The factory used a White lead based grease- it isn't too critical, you can use lithium or graphite greases- the most important thing is to regularly grease the splines. It is a good idea to regularly squirt some grease in the outer dust boots when you are lubricating the kingpins.

 

[JakeF]

Hi,

I stripped yesterday my gearbox for checking. Everything looked as new, exept the gaskets .
Any tips how to remove the oil seal from this part (price axle housing)
http://www.fiat500ricambi.com/fiat500/Gear+box/VB1032#

I changed the o-ring and tapped the bronze part out (or what it's called) and behind this is the oil seal. It's a real tight fit? When I mount the new one should I give some heat to the metal for easier fitting?
I also changed the oil boots to new ones and the big o-rings.
My gasket set has 3 oil seals, the smallest is for this clutch shaft but the two other biggers? Are they crank seal? Should I use seal with metal(yellow) outside, this ones are all black?

 

[Damon500]

Hi again- good to see you are making progress! The input shaft seal is not easy to replace- basically the easiest way to remove it is to collapse the steel outer ring of the seal with a punch and tap it out- you can then install the new seal with an appropriate sized socket to press it into the housing.
The other seals in your kit will be axle seals- these will fit into the axle boot seal carriers if you still have the 500F axles- if you have 500R or 126 axles they will be of no use to you. In any case if you have replaced the boots including seals and carriers you should be fine.