pinion gear failure

[dougburdick]

My diff started roaring the other day. When I pulled the cover off the back, I found two broken teeth from the pinion gear. The rearend is a '79. It had the right amount of fluid. I havent had this car very long and don't know how many miles it had on it. Has anyone else seen this? Also, I have a leaking rear seal on the tranny. Has anyone ever change this seal on their car ? How hard is it to get the nut off the rear of the output shaft?

[vandor]

Hi,

Those diffs are failure prone. Fiat upgraded it twice in 4 years, making it stronger each time. The easiest thing is to find a good used replacement. We likely have gears for it if you decide to go the rebuild route.

As far as replacing the tranny seal, it's not too hard, it's a bit of a hassle, you have to pull off a pressed on ring that retains a spring before you can get to the nut. I usually use 2 large screwdrivers to get this off, but that is with the tranny out of the car. With it in the car space will be very limited. Maybe a small puller would work.
Once you have that off you will need a deep 32mm socket to get the nut off. Some non-deep ones may work too, just depends how deep they are.

[dougburdick]

So, youve actually heard of them shearing teeth before? I've owned spiders for years and this is the first time I've had this happen. Of coarse, I know nothing of the history of this particular rearend, and it is over thirty years old! I have a good spare from a 81 that I'll be installing. i once tried to get the rear nut off a spider tranny years ago and the thing acted like it was welded on. My 3/4 electric impact wrench wouldnt budge it! Maybe it was the exception to the rule?

Hi,

Those diffs are failure prone. Fiat upgraded it twice in 4 years, making it stronger each time. The easiest thing is to find a good used replacement. We likely have gears for it if you decide to go the rebuild route.

As far as replacing the tranny seal, it's not too hard, it's a bit of a hassle, you have to pull off a pressed on ring that retains a spring before you can get to the nut. I usually use 2 large screwdrivers to get this off, but that is with the tranny out of the car. With it in the car space will be very limited. Maybe a small puller would work.
Once you have that off you will need a deep 32mm socket to get the nut off. Some non-deep ones may work too, just depends how deep they are.

[vandor]

>So, youve actually heard of them shearing teeth before?

Yes, many times.

> i once tried to get the rear nut off a spider tranny years ago and the thing acted like it was welded on.

They are on tight, but my cheap impact always breaks them free, so likely yes, that was an exception.

[dougburdick]

Thanks for the info. By the way, the new head gasket I got from you for my lancia is working great! Thanks,Doug

>So, youve actually heard of them shearing teeth before?

Yes, many times.

> i once tried to get the rear nut off a spider tranny years ago and the thing acted like it was welded on.

They are on tight, but my cheap impact always breaks them free, so likely yes, that was an exception.

[dmg36054]

Doug, I just finished replacing the rear end in my 1981 spider. The pinion gear was missing half it's teeth. Apparently it is fairly common. The replacement process went pretty smoothly, but took a little longer than I planned because I had to swap a few things over to the replacement rear end off the old one. Also, the shop manual said I had to pretty much disassemble the calipers. I found out that that is not necessary. I also disconnected my rear brake lines, then later noticed later that it would have been possible to keep them intact too. If you have any questions, let me know, and I'll tell you what all I did. It may save you some time.

[dougburdick]

Thanks Dennis, I have a complete rear end of that year that I'm swapping out right now.

Doug, I just finished replacing the rear end in my 1981 spider. The pinion gear was missing half it's teeth. Apparently it is fairly common. The replacement process went pretty smoothly, but took a little longer than I planned because I had to swap a few things over to the replacement rear end off the old one. Also, the shop manual said I had to pretty much disassemble the calipers. I found out that that is not necessary. I also disconnected my rear brake lines, then later noticed later that it would have been possible to keep them intact too. If you have any questions, let me know, and I'll tell you what all I did. It may save you some time.