Gearbox rebuild - 105 - Alfa Romeo Bulletin Board & Forums
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post #1 of 31 (permalink) Old 08-14-2018, 02:52 AM Thread Starter
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Gearbox rebuild - 105

Hey all,

I will be starting my gearbox rebuild soon and decided to start this thread related to this build.

I did read the numerous threads on here related to the subject and they will surely help during the rebuild process.

Tools I have:
20 Ton Press
Bearing separator for 3" to 4"
Knipex Circlip Pliers
Vice

I have read that I will also need a long metal pipe of about 1.5" diameter, oven and a freezer.


So far I have dis-assembled the gearbox to a bare case and cleaned the case.

What length of pipe do I need ?
What other special tools do I need for this job ?
Should I consider doing the 1st gear fix mod ? Please bare in mind I do not have another gearbox for spares.


Thanks

1971 - 2000 GT Veloce Euro
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post #2 of 31 (permalink) Old 08-14-2018, 03:14 AM
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I’ve got one (two actually) I’d like to do at the same time, so will follow along with interest.
I only have a 6ton press

I want to do the 1st gear mod. Also, perhaps, have some parts drilled/lightened I recall a thread where this was discussed but can’t find it ant the moment.

I also have a spare case. Does anybody know if there are any differences in 105 g’box casings?

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post #3 of 31 (permalink) Old 08-14-2018, 04:17 AM
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I think there were are few differences. The ones I know about is the diameter of the input shaft is larger on the cable operated gearboxes. So that means the bearings are different. The NOS bearings are practically all gone they have various codes allocated to them from the factory and suppliers like RIV, FAG, SKF. I have just had a minor rebuild of a 2L gear box. Currently I have a cable box in pieces, trying to source the last of the bearings in NOS. I am looking at finding NOS syncro rings and syncro sleeves for the cable box.

Last edited by Steve105; 08-14-2018 at 04:20 AM.
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post #4 of 31 (permalink) Old 08-15-2018, 01:06 PM
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Quote:
Originally Posted by Craig_m67 View Post
I also have a spare case. Does anybody know if there are any differences in 105 g’box casings?
I can't say definitively across all years, but I just rebuilt the transmission from my '69 Spider. I also have a gearbox from a Spica 2L with short shifter shafts. I went back and forth trying to get the best starting point for my rebuild.

There are some subtle differences in the two split case castings like some markings, etc but they looked interchangeable to me. Also the internals were VERY close to interchangeable. If I recall, the one thing that kept me from dropping the 2L shafts into the 1750 case was that the rear bearings on both shafts were different. Both races on the 1750 stayed pressed into the rear cover (the shifter tower casting) while the races on the 2L came out with the shafts. I expect the machining in the rear casting is different but I did not measure them. The other bearings fit in the casting but the bearing retention changed from a snap ring to a crimp nut. The two shafts looked to be the same diameter.

In short I feel pretty sure that the split cases in the two transmissions I have are interchangeable (keeping in mind the different shifter shafts) but two rear castings are different to account for the rear bearings. I suspect I could put the late shafts and late rear casting in the early split case, or the early shafts and rear casting on the late split case, as long as I kept the shifter shafts for my bell housing.

Last edited by 61SS; 08-15-2018 at 01:20 PM.
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post #5 of 31 (permalink) Old 08-22-2018, 04:21 PM Thread Starter
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I have proceed to disassemble the gears from the main shaft. It was a piece of cake and the press didn't have much work to do. All gears came out very easily with the worse being the 3rd gear registering around 4 tons on the pressure gauge.

I have inspected the Synchro Rings and Sleeves and to be honest I am not sure what to look for. The rings to me look a little worn whilst the sleeves look OK'ish I guess. Please note I still had the odd 2nd gear grind when I get in my racing mood. No grind when shifting slowly.

I cannot verify if the gearbox was ever rebuild in these last 48 years of its life and I after this rebuild, I doubt it will be rebuilt again (unless broken) and therefore the common sense is to change all rings and sleeves for good.

My delimma is if I need changing the Dog Ring of 2nd gear. After reading various threads on this subject, many have successfully changed the 2nd dog ring with 5th gear and since I will be doing the 1st gear mod, I would still need to purchase a new one. Since these are considerably expensive, I was considering to purchase one and use it for the 2nd gear, the old 2nd gear ring will be used for 5th gear and the old 5th gear will be used for 1st gear. Does this make sense ??
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post #6 of 31 (permalink) Old 08-22-2018, 04:27 PM Thread Starter
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2nd Gear Dog ring
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post #7 of 31 (permalink) Old 09-01-2018, 02:47 PM Thread Starter
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Some new shiny parts arrived. Still waiting for two Dog Rings, 5th fork and a magnetized drain plug.
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Last edited by eas; 09-01-2018 at 02:49 PM.
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post #8 of 31 (permalink) Old 09-01-2018, 02:56 PM Thread Starter
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I have checked the axial play between the fork and the new sleeves. Manual says they should be between 0.15mm and 0.34mm and found mine to be around 0.28mm and 0.30mm.

I shall check the 5th gear fork when it arrives.

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post #9 of 31 (permalink) Old 09-01-2018, 03:08 PM
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Hey eas

Thanks for sharing your progress - I can't tell from your picture but I am curious, did your 2nd gear dog ring look noticeably different to the other ones?

Learning, learning..
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post #10 of 31 (permalink) Old 09-01-2018, 03:24 PM Thread Starter
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Hey eas

Thanks for sharing your progress - I can't tell from your picture but I am curious, did your 2nd gear dog ring look noticeably different to the other ones?
Hey Alessandro,

Yes it was different. It was all chewed up
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post #11 of 31 (permalink) Old 09-01-2018, 04:04 PM
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Oh crap that looks well used ;-), thanks for the detailed shot - are you going to replace it as well or still use it for the 5th gear?

Learning, learning..
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post #12 of 31 (permalink) Old 09-01-2018, 06:13 PM
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Hey Alessandro,

Yes it was different. It was all chewed up
While its all apart why not lighten the gears you can take a pound out of the rotating mass between 1,2,3, true up reverse, and fully synchro first....I had it done a while back by a friend... (ony does it for a few friends ) I am sure someone on ABB can help you....with redline gear oil ,it is a dream to change gears...(I also lightened the flywheel)....Balanced and indexed the PP and Flywheel... Even if you do not lighten the gears, ,I would recomend balancing the PP and Flywheel....$100 well spent, others may disagree...
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Last edited by Tom Frasca; 09-01-2018 at 06:20 PM.
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post #13 of 31 (permalink) Old 09-02-2018, 02:54 AM Thread Starter
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Originally Posted by Tom Frasca View Post
While its all apart why not lighten the gears you can take a pound out of the rotating mass between 1,2,3, true up reverse, and fully synchro first....I had it done a while back by a friend... (ony does it for a few friends ) I am sure someone on ABB can help you....with redline gear oil ,it is a dream to change gears...(I also lightened the flywheel)....Balanced and indexed the PP and Flywheel... Even if you do not lighten the gears, ,I would recomend balancing the PP and Flywheel....$100 well spent, others may disagree...
Hi Tom,

I thought about it many times but I did not manage to find the details how should it be done to do them locally at an engineering shop. It would be not worth the expense to ship them over to the States to get them lightened and ship them back to me.

I will be converting 1st gear to fully synchro.

I do have a slightly lightened steel flywheel (16pounds) which was balanced together with the crank, PP and clutch.

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post #14 of 31 (permalink) Old 09-02-2018, 03:01 AM Thread Starter
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Oh crap that looks well used ;-), thanks for the detailed shot - are you going to replace it as well or still use it for the 5th gear?
It will go straight in the bin. I bought two new ones which will be used for 2nd and 3rd gear.

The old 3rd gear dog ring will be used to replace the 1st dog ring, and swapping the 4th and 5th dog ring.

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post #15 of 31 (permalink) Old 09-02-2018, 04:03 AM
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@eas, I failed to mention I changed every other PP spring to GTA, a bit more clamping pressure.
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