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Any 3-sync geaqrbox experts?

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CMCon98 Avatar
CMCon98 Colin C
Boston, MA, USA   USA
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I'm rebuilding our '64 gearbox and I've run into a snag. Everything is out of the main case except the first motion shaft, laygear, and third motion shaft. The layshaft is out and the laygear is sitting in the bottom of the case in accordance with the factory manual. The next step is to drive out either the first motion shaft or the third motion shaft by using a brass drift to tap out the bearings from the inside of the case. I can't get the first motion shaft bearing to move at all. I can get the steel bearing retainer that holds the third motion shaft bearing to move a tiny bit, but it's impossible to keep it straight because you can only tap on one side of it with the drift and hammer. So it wants to 'cock' in the aluminum case bore rather than come out straight.

Any suggestions?

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and6412 Andrzej Wojcik
Kraków, Poland - Krakow, Poland   POL
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1965 MG MGB "Crisp"
1976 Mercedes-Benz SLC "[SOLD]"
2001 Porsche Boxster S
I'm for sure not an expert as you have asked ;-). However, I did this job recently and can advise you or share some pictures (as I documented every detail).

Let me understand correctly. You have mentioned:

In reply to a post by I can get the steel bearing retainer that holds the third motion shaft bearing to move a tiny bit, but it's impossible to keep it straight because you can only tap on one side of it with the drift and hammer. So it wants to 'cock' in the aluminium case bore rather than come out straight.
Did you remove the rear section of the gearbox case already? There is nothing like "steel bearing retainer" as I remember. As far as I remember the only thing you could call this name was aluminium, however, I'm not sure right now (see picture - already removed a little).

If we are talking about the same element I also had a serious problem to remove it. I just hit it with the hammer through wooded long block until I removed it. And yes, I also hit it from mainly one side only as there is no access to another side. By the way, mark the correct position of this retainer and pay attention to it when reassembling. This is possible to put it in the wrong position and aim the positioning bolt into the oil gallery (and stop oil from flowing) instead of correct position.
Alternatively, you can remove (if you find an easier way) only the 3r Motion Shaft bearing from this retainer as well.

1st motion shaft let go easily by hand in my case.



Edited 1 time(s). Last edit at 2018-03-19 01:00 PM by and6412.


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sweep Avatar
sweep Gold Member Chris W
Gosford, NSW, Australia   AUS
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1966 MG MGB "Basil"
2013 Volkswagen Tiguan
2015 Audi A3
I did a full pull-down and swap around of two 3 Syncro boxes, one with OD and one without and I don't remember any issues like you're describing.

I have some photos in my journal, HERE which may be of some help.

Unfortunately the disassembly process is not described, which tells me that I had no issues as you've described. (or, I was lazy in my documentation)

In reply to # 3699822 by CMCon98 I'm rebuilding our '64 gearbox and I've run into a snag. Everything is out of the main case except the first motion shaft, laygear, and third motion shaft. The layshaft is out and the laygear is sitting in the bottom of the case in accordance with the factory manual. The next step is to drive out either the first motion shaft or the third motion shaft by using a brass drift to tap out the bearings from the inside of the case. I can't get the first motion shaft bearing to move at all. I can get the steel bearing retainer that holds the third motion shaft bearing to move a tiny bit, but it's impossible to keep it straight because you can only tap on one side of it with the drift and hammer. So it wants to 'cock' in the aluminum case bore rather than come out straight.

Any suggestions?



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LannM Avatar
LannM Platinum Member Lann Mauck
Verdigris, OK, USA   USA
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1958 MG Magnette ZB Varitone "The Queen"
1963 MG MGB
1967 MG MGB GT
I would put the driveshaft flange back on the end of the 3rd motion shaft and use a slide hammer to bring it out.

Lann



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and6412 Andrzej Wojcik
Kraków, Poland - Krakow, Poland   POL
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1965 MG MGB "Crisp"
1976 Mercedes-Benz SLC "[SOLD]"
2001 Porsche Boxster S
In reply to # 3700130 by LannM I would put the driveshaft flange back on the end of the 3rd motion shaft and use a slide hammer to bring it out.

Lann

Now I remember. At some stage, I did similarly. I installed a flange, support it somewhere height enough and simply use the weight of the gearbox case as an inertia hammer.

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CMCon98 Avatar
CMCon98 Colin C
Boston, MA, USA   USA
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I ended up reinstalling the driveshaft flange and using the long, heavy distance piece like a slide hammer to tap the shaft and bearing carrier out of the case. Only light tapping was necessary, nothing was beat up or damaged, and it worked like a charm. Then the input shaft tapped out easily with a brass drift inserted into the pilot hole where the needle bearings go. All three ball bearings are being replaced as a precaution, but all three were original 1964 bearings and still smooth and tight.

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Boris67MGB Richard Boris
Kings Park. NY 11754, USA   USA
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1967 MG MGB
The method Colin used is what I used for the my numerous 3 synchro gearbox tear-downs. Note: there are some steps that must be accomplished prior to teardown. 1: must measure laygear end float before removing layer. 2: you must mark the mid bearing housing to the aluminum case so you know where the peg and reverse cut-out are located for reassembly; 3: measure on mainsheet the float between 2nd & 3rd speed gears. On reassembly there are some critical clearances that must be controlled. 1:Laygear end float must be less than 0.003 inch. 2: 2nd to 3rd speed gears clearance must be less than 0.006 inch to assure smooth gear shifting. Also inspect the 3rd motion shaft roller bearing race for wear. This section inserts into the first motion shaft with 18 roller bearings; you should replace them! Note: I have seen many gearbox cases that have too much wear to get correct laygear end float even with largest thrust washer. With that issues; you may need to replace the case. On the 2nd to 3rd speed clearance; I would replace the interconnecting bronze thrust washer with a new one. I very hard to find the largest 3rd speed thrust washer; if needed; contact John Esposito. I would recommend using the steel 2nd speed synchro and associated 2nd gear.

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