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Old 03-16-2016, 06:42 AM   #1
Chris Wilson
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Default M90 3rd gear synchro welding photos??

I am tryin to find photos of the synchro ring welding mod discussed, but with no links to photos, in the article composition section. I asked there but i am not sure if it is the appropriate place, so asking here too. This was my post:

Are there any photos of what this welding of the third gear synchro in an M90 s all about on here still? In the first part of this thread the photos are no longer there. I can't get my head around what this mod is exactly, I suspect the term synchro ring is perhaps ambiguous and something else is welded? Thanks
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Old 03-16-2016, 07:04 AM   #2
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M90gearboxFix by crogthomas, on Flickr

This is the original photo from the thread. As you suspected, not actually the syncro ring.
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Old 03-16-2016, 08:29 AM   #3
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Yes, it's not an actual synchronizing ring that is welded. The ring could be called a stop ring.

This topic was once covered in a Swedish Bilsport car magazine. The original article was in Swedish, but here's a translation of that in English:



M90 with a bad third gear?


To choose a gearbox to a car is always difficult a task. Or, excuse us, to put it in other words, to brake a transmission is not too hard because modern manual trannies are not designed to be very strong. If one does not have the means to use a specially manufactured racing transmission, which in our case would've cost as much as our entire budget raised to the second power, a good choice would be to use an automatic transmission like in so many other "tough guy cars" you see on the strip. In a turbocharged car this would be even more ideal because when using one the engine will not come off boost during gear changes and it works better than a manual on take-off too. Besides, an automatic is more gentle to the rest of the driveline and to the tires too. So an automatic would be a winner choice in our situation then. But, does anyone know of a strong automatic transmission that fits a volvo directly and easily? That's right, there are no such things. So that was that.

We did not have the time to modify an amerikanski-automatic to fit our car so we decided to use Volvo's M90 transmission instead. "But the third gear breaks down on those all the time" they say. And they are right. We have a lot of M90-trannies in our garage with a broken third gear. However there is a solution to that problem which at least might save an already broken down transmission in some cases. The reason for the disaster is a too fast of a gear change from the second gear to the third. In such a case the synchronising ring (synkring?) gets an impact from the synchronising hub (synknav?) and it comes off from its place and hits the gear. Just one missed gear change might be enough for this.

Do you think that you have it in you to dismantle a transmission? Do you think that you can put it back together after dismantling? Good. Then all you need is a M90 tranny and start to work.

CAPTIONS:

Open sesame

Once we have taken the transmission apart enough we concentrate on the middle axle. It is on this axle where the synchronising hub (synknav?) is situated. Fiddling around with a tranny is not as hard as it might seem to be. However you should install every part you remove to the same place and position where you took it away from. The bearing on this axle has to be removed when we start to weld to the gear because it is made of plastic and it would melt if not removed. It might seem impossible at first to remove the bearing but there actually is an opening in the bearing as shown in the picture. You just need to twist it out!

OUT OF ORDER

When looking at the gear you should see a machined groove in it. That is where the synchronising ring (synkring?) should be. The teeth in the gear underneath it are in bad shape. That has happened because of a missed gear during gear change. Synchronising ring descends too low and gets in touch with the gear and makes correct functioning impossible. Note the bearing groove above the gear. That is where the plastic bearing is supposed to be.

WELDING

Here the ring is back in its place. We shall now weld that ring to the gear from every tooth with a mig-welder. It sounds a bit rugged as a fix but it does work. Keep the old oil in the tranny, preferably fill it up. That way the welding sparks will not get attached to wrong places and besides the oil cools the parts down. And no, the oil shall not burst into flames even though welding sparks shall drop in there. Weld one of the teeth to the ring and then turn the axle 180 degrees. Weld again and now turn 90 degrees and after welding that turn again 180 degrees and weld and so on. Weld every tooth to the ring and weld with enough current to get good welds. With any luck you have just saved a broken down m90 transmission or fortified one to take the forthcoming abuse.



I'll try to find the article and the pictures in it later.
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Last edited by Wagner; 03-16-2016 at 08:37 AM..
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Old 03-16-2016, 09:10 AM   #4
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OK, that's great, thanks. But I am still unclear what the "gear" is that has had the ring welded to it, nor what the ring is for. What does / did that gear with the knackered teeth engage with, and how come it's now acceptable to leave it in that state? Is this mod anything at all to do with the synchro rings or synchro hubs?
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Old 03-16-2016, 09:16 AM   #5
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The ring that is welded holds things in a correct position. A miss-shift can and does cause the ring to dislodge from it's position, and that causes the transmission to not work as intended. The method of failure is described in the article. Once you open the transmission it will make more sense.

In those pictures stuff has already been removed from the shaft where the ring is.


Here is the original page from the magazine article:
http://www.pukema.com/bilsport/container13-3.jpg

EDIT: i have a whole lot of pictures of this process, but i don't have them online it seems. I have posted them here long ago, so they could probably be found somewhere in this forum.

Last edited by Wagner; 03-16-2016 at 09:26 AM..
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Old 03-16-2016, 09:33 AM   #6
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Hi, I have searched hard, but they seem to have disappeared, if you still have them would it be a total PITA to re-post them, or send them direct to me at chris@chriswilson.tv? I do a few of the Toyota Supra twin turbo six speed manual Getrag rebuilds and they are not an easy box to strip as you need 2 bespoke pullers. Is the M90 a relatively simple box to tear down and build back up? Cheers.
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Old 03-16-2016, 09:43 AM   #7
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please post the Images here or make a thread on welding the stop rings.
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Old 03-16-2016, 09:51 AM   #8
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Quote:
Originally Posted by Chris Wilson View Post
Is the M90 a relatively simple box to tear down and build back up? Cheers.
Yes it is. Normal hand tools and a generic puller are all that is needed. And keeping track of what was where, and putting it back together the way it was.

I'll post the pictures tonight.
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Old 03-16-2016, 11:00 AM   #9
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Quote:
Originally Posted by Chris Wilson View Post
But I am still unclear what the "gear" is that has had the ring welded to it, nor what the ring is for. What does / did that gear with the knackered teeth engage with, and how come it's now acceptable to leave it in that state?
I think the 'gear' is in-fact just a left over from the machining process. i.e. there needs to be a 'stop' there and it is not possible to machine the teeth on the gear below it without cutting teeth on the 'stop' too. The 'ring' is added to the resulting bastard child of a gear to make sure it functions as a stop. Welding them together is simply making the whole lot more permanent.

Yes, dismantling the M90 is relatively easy. I did it with a puller last used on my lawnmower. As mentioned in the article above there doesn't seem to be much need to take the whole thing apart. Just remove enough to get to the gear in question and take any plastic bits out of harms way. Then blast it with the MIG and make sure to drain the oil after it's been put back together.
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Old 03-16-2016, 12:07 PM   #10
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crogthomas: Many thanks, that all makes a lot more sense now, I realise all the gears are permanently in mesh and "grinding the he ears" as in a mis-shift is really the synchro teeth grinding as they try to synchronise gear speeds on the shaft(s). So seeing that gear not in mesh with another was very confusing. asd you state it's an "orphan" gear things become a lot clearer and more sensible ;) Thanks!!


Wagner:
If you can post the photos my self and at least one other member will be most appreciative. Photos speak a thousand words in all languages! Cheers.
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Old 03-16-2016, 05:24 PM   #11
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I did mine mine way-back-when and back then i did not know better. There is no need to disassemble the whole transmission for this job. Like the picture shown above, and like the one in the Bilsport article shows, all you need to do is remove enough to get access to the ring.

Be that as it may, here are the pictures. You can see pretty well what you have there and what you need to do:





























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Old 03-17-2016, 07:10 AM   #12
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Superb, sincere thanks for taking the time and trouble to upload those photos, very helpful indeed!
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Old 03-17-2016, 07:18 AM   #13
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May I just ask whether the twin roller bearing outlined in red is caged in plastic? I guess if it is that's one of the main reasons to fill the case with oil to absorb welding heat? A full strip sounds far more sensible, for heat issues, access issues, and the ability to properly clean before welding. Thanks again.

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Old 03-17-2016, 07:35 AM   #14
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Quote:
Originally Posted by Chris Wilson View Post
May I just ask whether the twin roller bearing outlined in red is caged in plastic? I guess if it is that's one of the main reasons to fill the case with oil to absorb welding heat? A full strip sounds far more sensible, for heat issues, access issues, and the ability to properly clean before welding. Thanks again.

Yes it is indeed plastic. But it is easily removable, as there is a split in it. You simply take it away from the axle, as mentioned in the article. No special tools needed, just pry it off.

The gear rolls freely around that bearing. The stop ring, which is to be welded, is right below that bearing.

It really will make a whole lot more sense when you open the transmission.

Last edited by Wagner; 03-17-2016 at 07:41 AM..
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Old 03-17-2016, 07:51 AM   #15
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OK, that's clear now, too. Thanks for your patience!
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Old 03-17-2016, 04:02 PM   #16
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a picture of why the ring needs to be welded. It should just rest against that edge, but the teeth break off when you get a little violent when changing into third. Later model m90's (1997 and 1998) have a slightly different ring, with an extra ridge like the one seen in the pictures above. These transmissions also have three piece synchros and can handle a little more brutality before they let go.
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Old 03-19-2016, 10:30 AM   #17
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Since I have one M90 and another (hopefully) on the way, I'd like to know what component(s) break due to these missed 3rd shifts..... the bastard child "half gear" adjacent to the stop ring, the ring itself, or both? If folks who have the broken remains will post up, that would help those of us who have not yet walked this road...... It is apparent that welding these items together will stabilize that failure point. Is this pretty much THE achilles in the M90, nothing else?

Since more and more of these M90's are finding there way to the States, we eventually will need a "How to overhaul your M90" thread. Are the wearing bits (synchros, thrust bearings, etc) available in the aftermarket?
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Old 03-21-2016, 07:48 PM   #18
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Well for the most part the answer is "no" but the thing was designed by Getrag as far as I've heard, so there should be some sort of cross reference somehow.

As for the bearings, the tapered roller bearings will undoubtedly be a standard size and probably have a part number right on them. If not, measuring them will allow a suitable replacement. Not sure if we will be able to find a source for the plastic caged roller bearings, but again, measuring them should allow us to find a suitable replacement.

I was undecided but after this thread I'm definitely tearing down my M90 to weld 3rd gear, I'll try to research whatever I can on the synchros.
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Old 03-21-2016, 08:15 PM   #19
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My experience of OE manual box bearings suggests they tend to use "bastard" size bearings, in that the OD, ID, width or snap ring grooves makes replacements often only available, if available at all, from the car's manufacturer. In some way auto box parts are more freely available from the after market.
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Old 03-21-2016, 10:07 PM   #20
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All this M90 chatter has me wondering if I'm heading in the right direction with my build. I've not put a build thread up here as I just can't spare the time right now - but my 122 currently sports a Toyota IRS and a Corvette C4 (modified) front suspension and I'm prepping an RN whiteblock for this thing. The plan was originally to hit 250 hp and that has now moved up just a little with me eyeing up a BW EFR turbo.

So for a transmission (I'm literally weeks away from this mock up) I was going to use a beefed up T5 with A-Five gears from Astro with their race 5th gear for a 2.93 first and 0.79 or whatever OD - my rear end ratio is 3.91. With the Canadian peso now in the tank we're paying 35 - 40 % more for USD these days. So that fancy bomb-proof T5 just became a $2500 USD rebuild. Damn near at the price of a TKO at that price point. If I can get a more modern 3 shaft M90 that would hold the power, would that be the better bet? The clutch is easier for the T5 as lots of options exist and I've got a 850 flat flywheel. Not sure about the M90 other than I've heard the 850 T5R and a race PP (707) is the way to go.

Welding stop rings is no concern for me. Just need some opinions.
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Old 03-21-2016, 10:32 PM   #21
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Well you've seen the Whiteblock M90 thread in the FS section, and I'm sure you realize that those boxes are rare as hen's teeth in North America. However if you can source one (as Homer did) the rest of the bits appear to be pretty straight forward. The M90's (as far as I know) are all configured for the external hydraulic slave, and they are reputed to work well. I think for your application the question is, will you plan to bang shift the hell out of it (get the T5 and easy replacement/rebuild), or if you intend to drive it "sensibly" then the M90 might be for you. Gearing for a Whiteblock should have that 3.50 first, and a couple choices for 5th OD. From a true performance standpoint, I doubt you can do better than the T5 2.9 first gear, 0.79 5th to match your 3.91 final or even a 4.10 final. Build yourself an Excel spreadsheet, or just use the online calculators to find your RPM drop between gears. I'd opine that a complete M90 kit will be a simpler solution, but the T5 more of an optimum solution......just my $0.02.
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Old 03-22-2016, 07:07 AM   #22
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Quote:
Originally Posted by DET17 View Post
I'd opine that a complete M90 kit will be a simpler solution, but the T5 more of an optimum solution......just my $0.02.
Agreed.
The big attraction (in the UK at least) is that the M90 is cheap, strong and easy to fit.
Not all of that may apply to you.
If you have to import one, it's not so cheap.
If you have to convert to hydraulic clutch actuation, not so easy.

Remember that the whiteblock and redblock M90s are different and not interchangeable due to the integral bellhousing.

The downside of the M90 is the first and second gear ratios, which are, odd. They're both very low, I assume for pulling caravans.

The M90 is rumoured to have the same internals as the M56 850 gearbox, so there may be some scope for spare parts to be acquired that way.

This is why the 850 clutch is suitable, it has the correct number of splines to fit the M90.

DET17: eabras' photo shows the typical failure mode. Teeth breaking off the non-gear.
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Old 03-22-2016, 08:01 AM   #23
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I just wish I could swap the ratios between first (3.91:1) and reverse (3.00:1) on my M90 saloon.
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Old 03-22-2016, 10:18 AM   #24
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I just wish I could swap the ratios between first (3.91:1) and reverse (3.00:1) on my M90 saloon.
Ratios, as you know, from the WIKI summary:

The M90 gearbox is available with different gear ratios
G M90H1 M90H2 M90L1 M90L2
1 3.54:1 3.54:1 3.91:1 3.91:1
2 2.05:1 2.05:1 2.20:1 2.20:1
3 1.38:1 1.38:1 1.38:1 1.38:1
4 1.00:1 1.00:1 1.00:1 1.00:1
5 0.81:1 0.70:1 0.81:1 0.70:1
R 3.00:1 3.00:1 3.00:1 3.00:1

That 1-2 transition doesn't really lend itself to performance, does it?
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Old 03-22-2016, 02:12 PM   #25
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About the only time I am happy with first is when crawling up a wicked hill in traffic lol.
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