I have the transmission out of my 500 and I have a leak at the shaft seals. I need new axle boots. I can't tell what size shaft seals they are...19mm or 21mm. Its a 1970 Fiat 500F. On the transmission are the numbers 110F-100 4107991. I'm trying to measure the shafts but I'm not sure where to measure from. The shaft center or the splined end. Very hard to measure! Someone out there has to know which ones I have. Any help would greatly be appreciated!




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They are likely to be 19mm but you could measure the inside of the hole on your boot and this should confirm

Mine are original 19 but yours look too good to be original to that car. As a rough guide if you have no measuring tool, I would get a spanner and try the open end over the shaft. See what the smallest that will fit it is. I've always thought you measure the main shaft but maybe the shiny bit where the seal actually rubs?
I have seen 19 and 25mm quoted.

Well now that I measure the opening in the boot, it seems to be 25mm. Maybe that is the point of the shaft where it needs to be measured. I think I need to go buy myself a measuring device.
Are there any other seals besides this boot that need to be changed internally? I just want to be sure this leak stops.
I'm purchasing a transmission gasket set to take care of any leaks that might be coming from that but it seems mostly to be coming from the axle boot. This one was in bad shape.



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I think that you might fix it with new seals which fit in a carrier in the end of the rubber boot but as you're doing it, the boots are cheap anyway. If you get a 25mm measure anywhere on it I don't think it is a 19mm.
There is an "o' ring under the bearing carrier but that doesn't sound like the problem..that could cause a leak more inboard of the boot if faulty. Otherwise you have the top cover, an ungasketed joint of the two halves of the box, the selector shaft o ring and the gasket for that end piece and a seal where the input shaft protrudes; all from memory so might be more, but I think you're on the right track.

This is the dimension you need to measure.

I think the later model Fs and the Rs had the thicker shafts.

Mine were 19mm (mid model range F). When I fitted the 126 transaxle I replaced the longer 126 shafts with 25mm 500R shafts.

Chris

Bambino said:

This is the dimension you need to measure.

I think the later model Fs and the Rs had the thicker shafts.

Mine were 19mm (mid model range F). When I fitted the 126 transaxle I replaced the longer 126 shafts with 25mm 500R shafts.

Chris

Click to expand...

Thanks! Then they are 25mm.

Bambino, I have a small leak in one boot, but I get a thumping sound when I take my foot off the gas or in neutral. I think it comes from the axel. Maybe even the one without the leak. Do you think it could be a bearing or ?

The 1st, and easiest places to check are (a) the sliding coupling---is there wear in the splines. These are often forgotten when lubricating various parts on the steering/transmission and, (b) the metalastic coupling that connects the sliding coupling and the stub-axle.
When it comes to new seals in the gearbox half-shaft boot, I fit "VITON" seals. The specifications of these seals are:---"25mm x 35mm x 7mm SKF--Viton oil seal double-lip R23/TC-with stainless steel spring" I bought mine from:--Lancashire seals (Atherton,manchester, UK M46 9GG) but there may be other sources for these seals. They are not the cheapest, but they are probably the best. These specifications are for 25mm drive shafts.