M32 Trans Teardown

[rcmn0022]

As a retrofit, can't we just have the brass made to slip over then be held in place by a spring pin.

It shouldn't fall off and we should eliminate the slop in the transmission. At that point we can mash the gears and should be grind free.

 

[Preloader]

I don't see why not. I could provide a shift fork for R&D. Now I just need one of you to help me find a reliable source to produce the retro and a short turnaround.

Any ideas of who?

 

[Swordsmith]

Hello All,

I can reach out to my internal resources. Please clarify if I am misunderstanding your concern. You guys are experiencing a grind noise with the third gear.

Erica Tiffany
Chevrolet Customer Care

I had a transmission go bad because (like the one Preloader is working on in this thread) it started popping out of third gear, and eventually refused to stay in third at all, ever.

The replacement transmission immediately started grinding going from third to second, and soon also going into fifth from any gear, and a problem going into reverse.

After a great deal of runaround, the dealer acknowledged that there was a problem with the second transmission but claimed that it is simply typical of econoboxes and that there's nothing that can be done. They taught me a workaround trick for reverse and sent me, unhappily, on my way.

I know that it is not true that all Sonic 6 speeds have this grinding issue, because my first transmission did not have it at all.

It isn't occurring only in third, in fact second is the most frequently reported gear, but I've seen reports of it in second, third, and fifth, and there may be others. Since it turns out the problem is a materials issue, it's quite logical to think that the same cause is working in each of these similar but differing cases.

Now, Preloader has done the tear down work that I feel Chevy "skunk works" guys should have done when these problems first showed up, maybe you can get them to issue a service bulletin and either (current policy) replace the whole transmission, or (more sensibly) finally give Chevy service departments permission to go in and do the repair, which sounds like a lot of hours of work, and then a few pennies on parts.

More importantly, redesigning the transmission going forward, in 2015+ Sonics, stop saving a few pennies by using plastic internals when it's going to cost you hundreds of dollars in repair hours, per car.

The Sonic is among the best cars GM has ever produced, it's sad to see that it may end up on the junk heap of history because bean counters decided plastic would do where something stronger would have cost only slightly more and vastly increased the reliability and useable life of the car.

 

[Chevrolet Customer Care]

Hello all,

Its almost the end of my shift. I have not heard back from our internal resources yet. They may have left for the day. I will check back tomorrow.

Erica Tiffany
Chevrolet Customer Care

 

[Preloader]

Hello all,

Its almost the end of my shift. I have not heard back from our internal resources yet. They may have left for the day. I will check back tomorrow.

Erica Tiffany
Chevrolet Customer Care

You have my permission to show them my pics and the explanation and likely source of the problem.

PLASTIC shift fork tips. Causing too much play in the Synch Baulks when they get hot.

Pic showing said plastic tip:

Pic showing plastic tip failure/demise which resulted in damaged 3rd gear synch teeth and ultimately an unusable "hardly used" transmission:

 

[Preloader]

Found it!!!!

59T 3rd gear.

3rd Gear with 59 Teeth - M20 & M32 6 Speed Manual Gearbox-Genuine OE Part | eBay

 

[theenico]

Take a further back photo and maybe insert an arrow pointing to third gear.

I ask because I think the mainshaft (driving) gear for 3rd also drives 5th. If so, ratio swapping may have gotten more complicated. Basically, I don't think you can throw a 56 tooth gear in place of the 59 tooth.

In a normal setup with two shafts, you always replace gears in pairs (driving and driven). In the M32, it may end having to be sets of 3.

I just went back to the stickied ratio thread and there appears to be a pattern developing that may confirm my theory. All M32s with the 1.30 3rd also have a 0.74 5th. All the M32s with a 1.48 3rd have a 0.88 5th.

 

[$ub$onic]

Found it!!!!

59T 3rd gear.

3rd Gear with 59 Teeth - M20 & M32 6 Speed Manual Gearbox-Genuine OE Part | eBay

So the unserviceable transmission is getting serviced ?

 

[Preloader]

Take a further back photo and maybe insert an arrow pointing to third gear.

In a normal setup with two shafts, you always replace gears in pairs (driving and driven). In the M32, it may end having to be sets of 3.

I just went back to the stickied ratio thread and there appears to be a pattern developing that may confirm my theory. All M32s with the 1.30 3rd also have a 0.74 5th. All the M32s with a 1.48 3rd have a 0.88 5th.

Makes sense. IIRC, it's 1/2, 3/4/R and 5/6 per shaft. I'll take appropriate pic tmw. Arrows included if I make strong enough coffee.

Hell, I'll take some video of the shift action too.

 

[theenico]

The input/mainshaft cluster drives all gears (R,1,2,3,4,5,6). The two output shafts have the driven gears. One output/pinion shaft carries 2, 5 and 6. The other output handles R, 1, 3, and 4.

That's why I was saying that there may be one or more input/cluster/driving gears that mate with 2 different out put gears.

For example: One of the gears on the input shaft may mate with a gear on each of the output shafts. Basically, one input drives 2 different outputs.

I really wish I had one of these to take apart myself.

 

[Stew]

Very good thread. I like the more technical nature and group input of threads like this.

 

[Preloader]

The input/mainshaft cluster drives all gears (R,1,2,3,4,5,6). The two output shafts have the driven gears. One output/pinion shaft carries 2, 5 and 6. The other output handles R, 1, 3, and 4.

That's why I was saying that there may be one or more input/cluster/driving gears that mate with 2 different out put gears.

For example: One of the gears on the input shaft may mate with a gear on each of the output shafts. Basically, one input drives 2 different outputs.

I really wish I had one of these to take apart myself.

Facepalm on my part. I wasn't considering that the input mainshaft had all the drive gears. I'll break it all down with pics, so everyone can get a visual these fundamentals.

 

[theenico]

That's alright. There is an illustrated power-flow diagram somewhere on the web, but it sucks. A real picture with labels/arrows is always better.

 

[Stanley]

Very excited to see you doing this. I've got the 1.8 5sp. I noticed the 2nd grind shortly after getting it, but had it going in 3 and 5 too. Dealer wasn't able to "replicate" and sent me off until I can reproduce it, telling me not to baby it because if it gets worse can reproduce it they can get it fixed. Now at nearly 5k miles, its mainly going into 3rd, sometimes 5th. Would love to see some action on this from GM. I'm unmodded and a basic commuter driver. I honestly think its funny, yet a bit sad with all these grinding posts on here, the GM CSR seems not to have noticed this issue before. Looking forward to continued updates. opcorn:

 

[Preloader]

Admitting they are aware is like accepting responsibility. They prolly won't readily do that because re$pon$ibility co$t$ money.

We'll have to corner them. Looks like Klyston has a pending lawsuit. Maybe he's got the right idea. I just don't have that kind of energy.

 

[rodslinger]

Admitting they are aware is like accepting responsibility. They prolly won't readily do that because re$pon$ibility co$t$ money.

We'll have to corner them. Looks like Klyston has a pending lawsuit. Maybe he's got the right idea. I just don't have that kind of energy.

Thanks for the write-up. I always like seeing someone tackle something head on. I did miss the back story. I recall you had grinding issues and popping out of 3rd. Was GM refusing to fix this/out of warranty or did you just want to dive in and see what the real issue was and try to fix it permanently?

 

[Preloader]

Those are the issues, but no, I never actually tried to have GM do anything to my car. I had a spare trans and simply swapped back. And yes, I want to fix it myself, and with something more permanent.

HOWEVER, I do believe I can be of use to those that are getting nowhere with fighting GM on this specific grind issue. Any pics I post on this thread are welcome to be used by any one in your disputes.

I will try to dig deeper and get more pics today, but I woke up sicker than a dog this morning, so we'll see if a little soup can snap me out of it. Otherwise, it's gonna be a couple days.

 

[firstorbit84]

Incredible thread so far. Hope you feel better Pre, and thanks for all the effort on this.

It's issues like this that make me not want to keep my car past warranty or replace it with another Chevrolet small car

 

[Preloader]

Yeah, I'm officially full blown sick:

I'll try again tomorrow. I'm dying to get further in, so it won't be long. I promise.

 

[Chevrolet Customer Care]

Hello,

Still no word. I did provide my resource with the link here as well. I will give them to the end of the week before I reach out again.

Erica Tiffany
Chevrolet Customer Care