Technical Seriously, no gearbox fluid leaks?

[nzbobc]

So, a few posters have mentioned that they don't have any leaks after rebuilds. Tell me how?!?

I've replaced all the gaskets, O-rings, and boots on the transmission but there's still fluid coming out in two places:

One is where the gear change linkage passes thru. Damon had mentioned that it may be due to the end housing being worn if there's still leakage past a new O-ring. He also mentioned using a 126 boot on the linkage since it buts up against the transmission and would catch fluid escaping but this would seem to be a stop gap measure. Is there no other way of stopping the leak other than having to shell out for a new housing?

And, what about those those rubber boots on the half shafts? They have what look to be splines that would seem to promote leakage.

It's a little frustrating having these after taking the time to replace them all...

 

[Franko500]

With regards to the drive shaft boots, the grooves allow oil to lubricate the shafts where they rotate in the plastic sleeve. But you will also notice they have a oil seal at the front edge. If they leak renew them, if they still leak then check the drive shafts, the area where the seal sits needs to be very smooth. If they have worn you will feel it as you run your fingers over it. Chances are the seal is not seating properly on the shaft so you may be looking at new shafts.

 

[Damon500]

So, a few posters have mentioned that they don't have any leaks after rebuilds. Tell me how?!?

I've replaced all the gaskets, O-rings, and boots on the transmission but there's still fluid coming out in two places:

One is where the gear change linkage passes thru. Damon had mentioned that it may be due to the end housing being worn if there's still leakage past a new O-ring. He also mentioned using a 126 boot on the linkage since it buts up against the transmission and would catch fluid escaping but this would seem to be a stop gap measure. Is there no other way of stopping the leak other than having to shell out for a new housing?

And, what about those those rubber boots on the half shafts? They have what look to be splines that would seem to promote leakage.

It's a little frustrating having these after taking the time to replace them all...

Hi Bob,


Yes it is possible... It is important to have minimal play between the selector rod and housing - often there is wear in both but mostly in the housing. Back (in the day) when I was working on 500's in NZ (before we had heard of the internet) we used to have the selector housing sleeved but the new 126 housings are cheaper than most machinists would charge to do this.
The axle boots are fine - there are two types of sleeve, plastic or steel. The plastic types are usually cheaper but work fine. The grooves help the oil drain back from the seal and are correct.
As per previous post make sure that the shafts are not scored or corrosion pitted in the seal area and use plenty of grease on the axle splines to prevent cutting the seal surface when installing.
Keep going with it- the other thing that helps is regular use!

 

[nzbobc]

I can't seem to solve this one. I've just replaced the half shafts and the drive shaft boots and after just a week of driving, I've got a leaks from both boots.

The shafts are nice and smooth, the boots look to be in great shape, and I took care not to do any damage when putting them on. It feels like a nice close fit between the shafts and the seals.

Is it possible that fluid is leaking around the outside of the seal? It does seem to be a pretty snug fit between the rubber of the boots and the seals. But, as I want to stem the flows, I'm giving some thought to putting a bead of silicone between the outer edge of the seals and the boots. Any thoughts?

FYI, fluid level in the box is up to the bottom of the filler hole.

TIA,

-bob

 

[F123C]

x2 what Damon500 says

Also would suggest you try wrapping the splines and unmachined areas or the driveshafts with pvc tape plus oiling/greasing same before fitting new seals. Even the slightest nick on the delicate seal lip can result in a leak!!!
You could certainly use a smear of sealer around the outside of the oil seal when fitting it into the seal carrier if you wish.

You mentioned an 'O' ring on the gear selector shaft? I thought it was an oil seal with a lip? (my memory could be faulty!). If the shaft is free from damage/wear, you could try a new seal gently on the shaft and check if the lip is a good fit. I.e. oil the shaft and see if the oil seal scrapes away the oil when it is slid on. Again I'd favour using pvc tape and oil/grease when installing a new seal to prevent damage to the seal lip. Iirc, this seal can be changed in-situ without removing the end casing.

If this doesn't cure the problem, you might be able to fit a felt (don't know if there's a modern equivalent) seal/washer behind the oil seal to assist it.

Check also that the gearbox breather is clear. Iirc it's a press-fit in the top of the gearbox, possibly the bellhousing part and looks like a cap about 12mm in diameter. This cap should be free to rotate. Underneath there's a tube with 1 or 2 holes. If this breather is blocked, pressure will build up in the gearbox as it heats up and oil will then find any weak points in seals/gaskets.

Hope this helps
Al.

 

[fiat500]

I always think that seals against oil are very mysterious and potentially temperamental things. All of the possible reasons for leakage seem to have been suggested and NZBob has pre-empted them all. I am sure that oil wouldn't seep past the perimeter of the seal in most circumstances, but inside a plastic carrier it is possible. You could try replacing the seals with new ones and put some bearing-fit around the edges.
I saved the metal inserts from my original gaiters just in case of this sort of problem.
I can't remember if there is any sort of return drain hole inside the driveshaft housing, but if there is such a thing, it might be possible to locate it in the wrong place. Very frustrating.

 

[nzbobc]

Thanks guys for the thoughts.

Peter, the seals on the half shafts are the metal ones. Or, I should say, the seals have metal frames to them. I've tried 4 boots, with some of the seals having plastic frames. I have another set I can try but I'll also look to see if there are any high quality ones out there. There's no drain as far as I can tell, other than the grooves mentioned earlier in the thread.

Al, good thought on the gearbox breather. I really thought that was going to be it but I looked and it was clear of any build up of gunk or obstructions.

As for the leak at the gear selector shaft, I did cure that one by following Damon's recommendation and replacing the end housing with a new 126 one. My old 500 housing had no oil seal, only the O-ring on the selector shaft. The new 126 housing does have an oil seal on the end. The 126 housing is the one on the left in the photo below. So, thankfully, that's one less leak. Actually, I've stemmed all the leaks except for the drive shaft boot ones. Must be something I'm doing since no one else is having this problem. Need to inspect things a bit more...

 

[Damon500]

Glad you are nearing the nirvana of an oil tight 500, they are generally pretty good if you take care with assembly and use them regularly.
A little weeping from the boots around the driveshafts is nothing much to worry about and will often reduce with regular use- usually if it leaks significantly after boot and seal replacement it will be due to wear or corrosion pitting on the seal surface of the driveshafts.
If you decide to have another look then check to make sure there are no grooves or pits in the area the seal runs on and you can try linishing the shaft with some fine sandpaper (around 400 grit should work) and replacing the seals (you can replace them separately if the boots are ok)
One other trick is if you jack the car up enough on each side (or the rear) you can do the job without having to refill the gearbox. Make sure you use appropriate stands underneath for safety though!

 

[Luxe]

Yesterday I found out that the bell housing where the linkage passes through is worn ovular on my car. I am having a machinist refit a replacement bushing in the housing. I will let you know how well this works!

 

[nzbobc]

Lux,

I lucked out as that was one of the few places I wasn't leaking oil... It's on the end near the clutch, correct? There's a bush there and a seal.

I've been somewhat successful in plugging a couple more leaks. I found that fluid was leaking around the outside of the seals in the rubber boots. After taking them apart, the outside of the seals (the metal bit) showed signs of wear as they turned in unison with the half shafts. So much for a tight fit between the seals and their plastic holders. I have 4 new boots and with all them, I can easily spin and remove the seal from the plastic holder.

Following the advice of a couple of folks, I put a bead of RTV in the plastic piece that holds the seal and another one in the rubber boot that holds the plastic piece.

As my luck would have it, now one side is nice and dry and the other side has started leaking again. The seals were mint as are the half shafts where the seals rub against.

And, this time around, the drain plug on the gearbox is leaking. That's a first for me...

I've come to realize that this is the path that has been chosen for me: I'm now leaning towards Buddhism and mindfulness as I work towards Zen and the art of plugging Fiat 500 leaks....

 

[Luxe]

Lux,



I lucked out as that was one of the few places I wasn't leaking oil... It's on the end near the clutch, correct? There's a bush there and a seal.



I've been somewhat successful in plugging a couple more leaks. I found that fluid was leaking around the outside of the seals in the rubber boots. After taking them apart, the outside of the seals (the metal bit) showed signs of wear as they turned in unison with the half shafts. So much for a tight fit between the seals and their plastic holders. I have 4 new boots and with all them, I can easily spin and remove the seal from the plastic holder.



Following the advice of a couple of folks, I put a bead of RTV in the plastic piece that holds the seal and another one in the rubber boot that holds the plastic piece.



As my luck would have it, now one side is nice and dry and the other side has started leaking again. The seals were mint as are the half shafts where the seals rub against.



And, this time around, the drain plug on the gearbox is leaking. That's a first for me...



I've come to realize that this is the path that has been chosen for me: I'm now leaning towards Buddhism and mindfulness as I work towards Zen and the art of plugging Fiat 500 leaks....

That is exactly where the end of the gear box is worn. The shaft slops around quite a bit as the aluminum of the gearbox and a bit of the shaft are worn. Van der laan in the Netherlands sells a replacement end for 46 euro, so I am going that route vs machining a bushing.

 

[Labman]

Thanks guys for the thoughts.

Peter, the seals on the half shafts are the metal ones. Or, I should say, the seals have metal frames to them. I've tried 4 boots, with some of the seals having plastic frames. I have another set I can try but I'll also look to see if there are any high quality ones out there. There's no drain as far as I can tell, other than the grooves mentioned earlier in the thread.

Al, good thought on the gearbox breather. I really thought that was going to be it but I looked and it was clear of any build up of gunk or obstructions.

As for the leak at the gear selector shaft, I did cure that one by following Damon's recommendation and replacing the end housing with a new 126 one. My old 500 housing had no oil seal, only the O-ring on the selector shaft. The new 126 housing does have an oil seal on the end. The 126 housing is the one on the left in the photo below. So, thankfully, that's one less leak. Actually, I've stemmed all the leaks except for the drive shaft boot ones. Must be something I'm doing since no one else is having this problem. Need to inspect things a bit more...

I have bit of a leak at the gear selector shaft as well. It's something I should have tackled when I had the transmission/engine out. Can I remove this housing while it's still in the car? My transmission gasket kit had the O ring in it. I was afraid to remove that housing as I didn't know what I was getting myself into. Stupid me.

 

[Luxe]

Sorry for answering this so late. I thought someone already had. Yes you can take it off while under the car, but it is not recommended as gear oil will spill out and you will have to fill it up under the car. You don't have to take the engine out to get the transmission out, but if you are going to take out the trans, why not the engine too! When taking the transmission end cap off it is best to take a look at the nuts and split pins on the end of the gear shafts to see if they are tight and present. Mine where a bit loose and sloppy so they made for improper gear fit and a bit of gear crunch when shifting.

 

[nzbobc]

Labman,

As Luxe said, when I pulled the end housing off, gear oil will leak out even tho I had drained the transmission previously.

Removal of the housing is really straightforward as their are only 5 nuts to remove. You'll have to remove the speedometer drive, unbolt the clutch cable, and the gear shift linkage first. There is a paper gasket for the speedo drive and another between the transmission body and the end housing which should have come in your transmission gasket set.

The only unnerving part is that the gear selector shaft (see photo above) falls out when the end housing is removed and one is left wondering what it connects to. The photo below shows the transmission with the end housing removed and the flattened end of the gear selector shaft fits in U-shaped ends of the selector rods (See red arrow).

The first time around, I replaced the O-ring gasket on the gear selector shaft but I still had a leak. Damon posted that leaks can still happen with a lot of wear in the end housing tunnel that the gear selector shaft goes thru. So, the second time around, I replaced the end housing.

Another option is fitting a 126 dust boot.https://www.fiatforum.com/500-classic/354225-gearbox-leak.html

 

[Damon500]

You can in fact remove the front gearbox housing in situ without draining and refilling the gearbox- if you have a tall enough jack or two legs of a 2 post hoist you can lift up the front of the car so the gearbox oil goes to the rear of the gearbox and then remove the housing. Make sure you place stands underneath for safety though!

 

[fiat500]

I think that maybe fighting leaks is likely to be an ongoing battle
I was just topping up the gearbox because I had noticed a minor leak. I can see that the selector shaft on mine is the culprit. Incidentally, one of the driveshaft boot seals, which have been proven to be of poor quality, is also leaking a bit now it's topped up.

 

[Labman]

Oh how I wish I would have done this when the engine/transmissions was already out. :bang:
That dust boot sounds like a good solution but I guess in time that will fill up and lead as well. It's not a terrible leak so maybe I will just deal with an occasional wipe from time to time.

 

[fiat500]

My gearbox seems to have sychronized with yours and the driveshaft leak, at least, needs dealing with. I can't remember which side I already changed last summer, so I really hope its not the same one again. One of the boots at the driven end of the shaft is already in tatters. These modern parts are rubbish. I now have brand new spares bought from England and from Holland at wildly different prices...they ARE identical!
I wonder if putting a thicker "O" ring on the selector shaft would help against that leak. The 126 style gearbox ends with a proper seal are quite expensive.
PT1_1377 by Peter Thompson, on Flickr

 

[nzbobc]

Peter,

These boots have been problematic for me. If it isn't the boot twisting with the shaft and eventually shredding, it's the seal spinning inside its housing. I had one boot stamped "Made in Italy" and it was no better than any of the others. All four of the new boots, sourced from different vendors, look identical.

I've just put another set in. Through my trials, the seals looked to be in perfect shape before and after some use, so they probably weren't the source of the leaks. But the seals were a loose fit in their plastic housings and rotated with the shafts. I'm thinking this poor fit between the seal and the housing allowed them to leak.

I tried using RTV instead of cement a few months back. In no time, one boot leaked. This time around, I cemented the seals into their housings and the housings into the boots.

Also this time around, I put engine assembly lube on the shaft. Hopefully, this will cut down on resistance between the seal and the shaft for a while and there will be less torque on the rubber boot and it won't shred so quickly (I've also checked for burrs and lightly sanded the wear surface on the new half shafts).

I just received my latest parts order and will be putting the engine back together (had another issue) and should have it on the road shortly. Will report back on how these boots work.

As for the "O" ring on the selector shaft, I had thought of putting a thicker one on, too. I opted for the new housing as I was ordering stuff from Gerstl (And, you know how easily all kinds of stuff gets added to the shopping cart). I like how it has a seal at the end of the housing for the selector shaft. This seal makes for a nice and tight fit around the selector shaft.

 

[fiat500]

Bob, that twisting is why I changed the previous boot....not a leak. I have some vintage boots in my collection of parts that came with my other "car" which seem thicker, shinier and are still useable....just that they fit the bigger shafts. I think I still have the metal seal carrier inserts from the original 19mm boots on my car and I might try to fit a seal into one of them and then insert it into a new boot; I'll feedback on that if I do it.
With some other makes of vehicle, owners' clubs or individuals have come up with solutions to common problems like this. This has involved remanufacturing of small runs of parts. I'm shy of trying this myself but it's worth a thought for some types of badly reproduced 500 parts.
I suppose I

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can partly blame myself as I am really pushing the limits using a 47 year old car as an almost daily driver.