3rd Gear Synchro

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RattleTrap

3rd Gear Synchro

Post by RattleTrap »

I've spent the last 3 or 4 days taking my transmission out because I needed to replace my rear main seal. Since the transmission's out, I want to replace a little 3rd gear grind I have when shifting. I'm pretty confident it's a problem with the synchro…what other parts would might I need for this job? Is there anything I should know before I try taking things apart? I've never done any transmission work before, so any help will be appreciated. Thanks!
BEEK
Posts: 1833
Joined: Wed Mar 24, 2010 10:45 pm
Your car is a: 1975 Spider
Location: clermont fl

Re: 3rd Gear Synchro

Post by BEEK »

replace the shift sleeve and check the fork for wear. I would also check and replace the syncros on the other 3 gears, you can flip 5th gear syncro if that has not been done already
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider
, 6 Lancia Scorpions, 2018 Abarth Spider, 500X wifes, 500L 3 82 Zagatos. 82 spider 34k original miles, 83 pininfarina, 8 fiat spider parts cars
son has 78 spider
vandor
Posts: 3996
Joined: Sat May 23, 2009 1:23 pm
Your car is a: 1971 124 Spider
Location: Texas, USA

Re: 3rd Gear Synchro

Post by vandor »

You will need a gasket/seal set. I would also replace the synchro springs, they do break every now and then. When it happens the synchro can't work at all. Replace shift forks if they show any wear. Check and replace if necessary all gears and sliders.
Csaba
'71 124 Spider, much modified
'17 124 Abarth, silver
http://italiancarclub.com/csaba/
Co-owner of the best dang Fiat parts place in town
RattleTrap

Re: 3rd Gear Synchro

Post by RattleTrap »

Image

Image

Now that I've got the synchros out, I can see why 3rd gear was grinding I think. I assume it's because its inner teeth are bent out like they are. In the second picture I put the 3rd synchro ring on the right and one of the other three on the left.

My question is: how did this happen? Is it just normal wear? I'm not too excited about spending more money on parts, but if there's something in there that could damage the new one like this, I might as well replace it.
BEEK
Posts: 1833
Joined: Wed Mar 24, 2010 10:45 pm
Your car is a: 1975 Spider
Location: clermont fl

Re: 3rd Gear Synchro

Post by BEEK »

take a picture of the 3rd gear where the sycro goes, i want to look at the condition of the teeth, also the shift hub, and the same mating teeth
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider
, 6 Lancia Scorpions, 2018 Abarth Spider, 500X wifes, 500L 3 82 Zagatos. 82 spider 34k original miles, 83 pininfarina, 8 fiat spider parts cars
son has 78 spider
RattleTrap

Re: 3rd Gear Synchro

Post by RattleTrap »

Image
New synchro already installed.

Image

So that's what the grinding was doing….
BEEK
Posts: 1833
Joined: Wed Mar 24, 2010 10:45 pm
Your car is a: 1975 Spider
Location: clermont fl

Re: 3rd Gear Synchro

Post by BEEK »

by the picture, i would probably reuse the 3rd gear, and definatly replace the shift slider (hub).

this is not normal wear to have caused the syncro to look the way it does. i have seen that a time or 2 before but i cannot say how that happened. i would speculate that the syncro damage was from forcing the transmission into gear
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider
, 6 Lancia Scorpions, 2018 Abarth Spider, 500X wifes, 500L 3 82 Zagatos. 82 spider 34k original miles, 83 pininfarina, 8 fiat spider parts cars
son has 78 spider
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