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Discussion Starter #1
I'm in the process of rebuilding my transmission. It has 1st & 2nd grind and it would pop out of reverse. Reverse was easy to see the problem as the fork has worn away with ~1/8" of clearance.

For the 1st/2nd issues... first looking at the syncros, although the wear shape isn't terrible on a few of them the "blotchy" or broken out areas look bad to me. So I was going to replace all of them. For the dog gears, 1st looks the worse (picture). So the question is... is this a candidate for 1st / 5th positon swap or would you replace.

Your thoughts?

Also... I was thinking of first calling APE for parts but their website wasn't found. Anyone know the story?
 

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The synchros are junk and should be replaced, along with their mating sliders. The synchros and sliders wear together and should be replaced together.

From your photo, it looks like the dog ring teeth have had their pointed tips worn down. The one photographed should be replaced. For the others, even if the teeth look okay, measure the (new) synchro ring diameter installed, ie, on the gear and dog ring with circlip, using a micrometer. There should be a spec for it, and if it's out of spec, that means that the dog ring has worn and should be replaced.

Hope this helps.
 

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The synchros are junk and should be replaced, along with their mating sliders. The synchros and sliders wear together and should be replaced together.

From your photo, it looks like the dog ring teeth have had their pointed tips worn down. The one photographed should be replaced. For the others, even if the teeth look okay, measure the (new) synchro ring diameter installed, ie, on the gear and dog ring with circlip, using a micrometer. There should be a spec for it, and if it's out of spec, that means that the dog ring has worn and should be replaced.

Hope this helps.
There is no doubt that the dog gear is trashed and the matching slider. The synchro must have been worn as shown allowing a lot of gnashing of the teeth as they say. If in doubt, replace. No one likes to do this job twice.

I am curious as to comparing the synchro's new vs old on the dog gear. Could you please elaborate on this more as what you are saying isn't clear to me. I haven't seen any reference to this in the factory manual.
 

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I am curious as to comparing the synchro's new vs old on the dog gear. Could you please elaborate on this more as what you are saying isn't clear to me. I haven't seen any reference to this in the factory manual.
Yes, the Alfa manuals I have do not include a specification. Actually, they have very little information or specification for rebuilding transmissions. Perhaps there's a better manual.

In use, the synchro rings will wear both the inside of the dog ring as well as the sleeve. Unsurprisingly, if the wear is excessive, synchronization won't work particularly well. Porsche used the same type of synchro in their 356 and 911 series cars through 1986. Here's the specification in the 911 workshop manual, demonstrating how to measure as well:

checking.png

I know who to ask for a specification if that would be helpful...
 

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The manual does specify the clearance on the shift fork and sleeve.

Being I don't deal with Porsche, this is the first I have seen measuring a synchro in the gear. I can't speak for others on the BB as to their experience with this particular measurement. From the diagram, measurement looks to be taken at 90 degrees from the opening of the synchro ring.

I would say ask your source for the measurements as we all could benefit.
 

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I plan to inspect a transmission someday soon, I hope someone may forgive me borrowing this thread to pose some basic questions to learn from. What am I looking at in OP? Are those black rings the synchros? Then two gears, the smaller one is the 1st gear dog gear? And the chunks missing from the teeth indicate wear?
 

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I plan to inspect a transmission someday soon, I hope someone may forgive me borrowing this thread to pose some basic questions to learn from. What am I looking at in OP? Are those black rings the synchros? Then two gears, the smaller one is the 1st gear dog gear? And the chunks missing from the teeth indicate wear?
Yes, you are seeing the gear dog that holds the synchro ring with worn edges. they should be nice and pointed.

The synchro's shown are what they look like when they are removed from the gear dog. They should have nice dark sandpaper feel to them without any shiny parts showing. Second gear if it is worn out, the synchro will be shiny.

The dog ring and synchro slider all should have nice points so they will slide in easily. The synchro slows down the gear so the two will mesh. When the synchro is worn, the gear can not slow down and the slider will jamb up against the dog teeth creating a grind you hear.

At least that is the theory as I know it.
 

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Richard Jemison
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Syncros

In your pics of 5 syncros from the left to right #s 3/4/5 are worn out.

Read the sticky and other info on this area of the BB. There`s answers to all your questions without starting another thread.

1st should be replaced with a complete 4th or 5th syncro assembly (2 directional) any with worn teeth should be replaced along with the slider rings that engage those dog teeth.

Measuring installed bands is a waste of time. The wear under the teeth changes the OD. Measure a new syncro band`s thickness at the center. Then you have a reference. the ends at the split wear fast, so you will see that on all of them.
 

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Being I don't deal with Porsche, this is the first I have seen measuring a synchro in the gear. I can't speak for others on the BB as to their experience with this particular measurement. From the diagram, measurement looks to be taken at 90 degrees from the opening of the synchro ring.

I would say ask your source for the measurements as we all could benefit.
Please let me know the Alfa car model of interest. The fellow whose company makes the synchros and dog rings is more than happy to share the specs he works with, but he asks for the specific model. He tells me they are, at least for the most part, numbers they have reverse engineered from existing parts.

Yes, I measure at 90 and 270 degrees from the gap in the synchro ring. That seems to give the best numbers, that is, numbers that with a new dog ring and synchro are closest to nominal. It will vary a little if you measure at a different point on the circumference. Cheers,
 

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The response from the maker of synchro rings and dog teeth was as follows:

The ones we make fit '68-'94 Trans. (not 164). These use moly coated synchro rings.

3.008" (76.4 mm) installed major diameter is the spec. we use for new dog rings with new synchros. +/- .002" is probably OK. Don't have any info on wear limits. These synchros are very similar to early 911 but they are wider.​

Hope this helps.
 

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That dog tooth is toast and syncros are cheap to replace. Used dog tooths are available in good shape from some people on this forum. AS mentioned earlier, they should have sharp points.
I think there is a post from Vintre called "gearbox rebuild for dummies" or something similar on here somewhere that will show more detail than you ever wanted to know about a rebuild. Check it out.
Check the reverse idler gear and the reverse gear itself and also the rod for the shift fork to make sure you dont have more troubles with reverse. I have seen all damaged and the rod bent slightly causing the gears not to engage fully.
 

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Richard Jemison
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Syncros

NOTE!:
The response from the maker of synchro rings and dog teeth was as follows:

The ones we make fit '68-'94 Trans. (not 164). These use moly coated synchro rings.

3.008" (76.4 mm) installed major diameter is the spec. we use for new dog rings with new synchros. +/- .002" is probably OK. Don't have any info on wear limits. These synchros are very similar to early 911 but they are wider.
Hope this helps.
Problems with aftermarket syncros is the inability to engage gears.
Tightness between the dog assembly and the snap ring interfere with compression. As well the aftermarket syncro bands are thicker at the crown of the bands making the compression for the slider to "ride" over the crown and engage the teeth of the dog assembly impossible.
Spruell`s "suggestion" to grind away the excess was just another attempt to shrug off his responsibility for selling bad parts.

I`ll not ever again use aftermarket syncro parts on any transmission I build.

Now for your information. Long has lived the rumor that non moly (pre 1963) syncros are incompatible with modern "Moly type components.
In my race boxes, both those of Transmissions and Transaxles, I have used late Moly type dog assemblies and Slider rings (both small ID 105/115 and larger ID 116/119 type which are better(harder) alloy, fitted with the harder alloy "non-moly" syncro bands.

This pairing gives much longer service than the fast wearing "Moly" bands.

Be aware that the "brake bands'' under the syncro bands are not all the same width. If installing the snap rings over the aftermarket syncros is "difficult to impossible" measure both the width of the brake bands as well as their length which can make compression of the wider & thicker aftermarket syncros an issue.

The length of the bands used when "converting" the 1st gear 'one directional" syncro is critical. Do not use any part of it's internal assembly. Use only the "lock, bands, and engagement slider" of 2nd through 5th gear assemblies.
 

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Discussion Starter #15
Hi All,

I thought I'd give an update. So I ended up getting a dog gear (with straps & segments for first gear fix), syncros slider, and 5th gear fork from APE. For syncros, it's a hard call now a days hearing about the current supply of syncros and their dimensioning problems. In the end I went with a set from Alfaholocs hoping they got it right. Interesting in cross section height they were ~0.1mm shorter than the best worn one I had. But the ID was a few tenth of a mm larger bring the OD to about the same place?

Putting stuff back together I put my "new" dog gear at 1st, swapped by 5th for 2nd, and the best syncros slider between 1/2. Hopefully putting the best parts in-between the most used 1/2.

For the popping out of reverse I'm a little nervous that I didn't find a reason for the fork to be so worn. ...oh well. Everthing is back together and is working great.

Thanks to folks who have ever posted about transmissions as all the info helped me rebuild mine.

PS I bought a 10 pack of viton o-rings for the shifter rods. Leaves 7... PM me if you want a set, free ;-)
 

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Reverse forks bend. Especially if backed up steep hills a lot.
 

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Discussion Starter #17
That would make sense as I bought the car from someone in the Bay area and they had a steep driveway. Hard to get a straight edge on the wear surface to verify. Works now so hopefully the replace fork will hold out.
 
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