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Old 06-08-2017   #1
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Gearbox Rebuild 2nd Gear Synchro Unit

Greetings All, I'm having a tad of a problem with the proper assembly of the 2nd gear synchro unit Having stripped the box, cleaned, inspected and started the re-assembly I found a circlip with the synchro unit As you all can see the first pic shows said circlip in what I think is the correct position, but, now the housing where the 2nd gearshift fork fits will not move (slide) along the unit due to the circlip fouling (second Pic) the unit Does Anyone have a pic or assembly schematic that shows how the circlip is located please?
I have found out that the 'circlip' is in actual fact the 'Synchro Spring' but I still need to know how it fits please???????
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Last edited by Bleeding Knuckles; 06-08-2017 at 16:08.
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Old 06-08-2017   #2
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

It's a long time since I worked on one of these gearboxes, so my memory may be suspect, but....

I think that spring goes inside the 3 metal plates that the synchro sleeve fits over, i.e. to push the 3 plates/blocks (can't remember what they're called, possibly blocker plates?) outwards. It might even be possible to wind the spring into position from it's current position and then tuck the bent end under one of the blocks?

Idk if this is any help,

Al.
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Old 07-08-2017   #3
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

Quote Originally Posted by F123C View Post
It's a long time since I worked on one of these gearboxes, so my memory may be suspect, but....

I think that spring goes inside the 3 metal plates that the synchro sleeve fits over, i.e. to push the 3 plates/blocks (can't remember what they're called, possibly blocker plates?) outwards. It might even be possible to wind the spring into position from it's current position and then tuck the bent end under one of the blocks?

Idk if this is any help,

Al.
Al, Thank you, Thank you, It was doing me ed in When I next have a moment I'll do what you suggest I think that this is one lesson well learnt - apart from the excuse "It came off in me hand Sgt Major" One must take more care, and it would have been a bit of a laugh (not) had I finished the rebuild and found the spring afterwards

Ian.
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Old 07-08-2017   #4
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

That is a tricky little part and from memory you need to assemble the spring so that the up stands line up with the grooves in the sliding sleeve. I assume that there is an up stand at both ends. The steel syncro sliding keys do get filled with crud on the inside and are worth cleaning out if you want everything clean inside. I have stripped a couple of boxes in the past where that spring ended up mangled in the bottom of the gearbox but if you check that the gears change OK on assembly I am sure it will be fine.
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Old 11-08-2017   #5
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

Quote Originally Posted by Toshi 975 View Post
That is a tricky little part and from memory you need to assemble the spring so that the up stands line up with the grooves in the sliding sleeve. I assume that there is an up stand at both ends. The steel syncro sliding keys do get filled with crud on the inside and are worth cleaning out if you want everything clean inside. I have stripped a couple of boxes in the past where that spring ended up mangled in the bottom of the gearbox but if you check that the gears change OK on assembly I am sure it will be fine.
Al, Dave, Thanks for the input - appreciated. After a lengthy fiddle getting the spring into place - result But I must say what a faff it is with lining up the second gear selector rod too. You need an extra hand.I am confident that the synchro is assembled ok and I will give it a good selection run with lots of oil Thanks again chaps.

Ian.
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Old 14-08-2017   #6
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

Just a quick note for anyone rebuilding a 126 BIS gearbox with the higher ratio Diff and Pinion. All of the gasket kits I have seen only supply two oil seals for the gear selector shaft and the clutch actuating arm (small rubber O rings) Please note that the BIS gearbox gear selector shaft requires TWO you will need to find an extra O ring for the rebuild

Ian.
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Old 14-08-2017   #7
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

These all came from 126 gearboxes. Some later gearboxes have a small lip seal, some one or two o-rings.
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Old 30-09-2017   #8
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

Update on the BIS box conversion - well, I got ALL of the gears and bits together in the correct order New seals all round, new drive shafts (25mm) and the THIRD 126 bell housing fitted a treat Or so I thought Because when I finished the assembly of the bearing retainers and tightened up the nuts the differential locked up tight - AGAIN All I can think of is that the BIS gearbox casing is not compatible with a 126 bell housing. I've tried three different bell housings and the last one was a great fit in the critical area between the casing and bell housing for the bearing retainer, but no, the BIS box has very slightly narrow external sides on the casing and this causes mis-alignment when the bearing retainers are up tight. So Decision time - take it all apart and use the 9/39 pinion/crownwheel in my existing box luckily I only need to rescue the pinion as the diff is complete with new drive shafts, but it will mean another strip and rebuild - deep joy just think - all those bearings, gears, synchro units, shims and things to mess around with - engineering bliss !!!!!! In the end I'll have a complete disassembled gearbox of spares

Ian.
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Old 09-10-2017   #9
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

Finally got my box out of the car, and apart from being somewhat mucky - oil leak from selector shaft everything seems to be in order - even all the rubber parts are good to go we shall see what the internal situation is when I get the time to inspect!!! I did notice that the driveshaft couplings were well and truly shot The pic shows the internal face with the rubber oozing out (it's been cleaned off too) the rubber mess is semi liquid and awful to remove, fitting the correct socket is difficult as the coupling rubber centre has contaminated the nut area too preventing a good purchase on the nut I'll have a think about removing more mess before attacking the nut when time allows I didn't have any indication of wear in the couplings either?????

Ian.
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Old 09-10-2017   #10
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

Looks like someone was a little over enthusiastic about lubricating the splines on the drive shaft. Seen that before and not a pretty sight. I use some really heavy duty graphite grease that stays where you put it. If you are going to put a lot of power through those couplings it might be worth fitting the tripod mechanical ones.
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Old 09-10-2017   #11
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

Quote Originally Posted by Toshi 975 View Post
Looks like someone was a little over enthusiastic about lubricating the splines on the drive shaft. Seen that before and not a pretty sight. I use some really heavy duty graphite grease that stays where you put it. If you are going to put a lot of power through those couplings it might be worth fitting the tripod mechanical ones.
Hi Dave, Yes the 'Tripod' would be the answer, but where to purchase ??? Cannot seem to get an answer from the makers and prices are very high elsewhere, I guess I'll have to be 'kind' when I drive

Ian.
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Old 09-10-2017   #12
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

I've fitted the tripod "cv" joints - cost 230....is that dear??? I know that they will handle my rough treatment better than the fragile originals.
This tuning malarkey is expensive - even on a tiny car
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Old 10-10-2017   #13
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

Quote Originally Posted by AndrewHarvey View Post
I've fitted the tripod "cv" joints - cost 230....is that dear??? I know that they will handle my rough treatment better than the fragile originals.
This tuning malarkey is expensive - even on a tiny car
Hi Andrew, yes a malarkey it certainly is The last quote noted for the full CV kit on the 'MOTOMAX' web site is 138.00 but the kit has been unavailable for while now. So, where to get a full kit for the least wedge - Anyone know of the cheapest supplier

Ian.
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Old 10-10-2017   #14
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

MOTOMAX made a set for me at that price I recall....they now sell at 230 on eBay!
Search fiat 126 and they pop up
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Old 10-10-2017   #15
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Re: Gearbox Rebuild 2nd Gear Synchro Unit

R Proietti (fiat500.cc) do them for 70 a side
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