http://www.streetfire.net/v...el-noise_2370933.htm

I believe and am hoping the problem with this transmission is tied into the troubles that brought about the immediate changes in the second year GM application of the F40.

I’m going to assume without any research that the failed part is a synchro/blocker ring combination. I may have to redo the video once I get my hands on an editor or can get my old laptop working again if it does not show, but in it you can see that the ring below the damaged brass bushing moves up and down, you can see this demonstrated in a couple of pictures below that I’ll point out.

My theories are as follow:
The side impact in the accident it was involved in may have damaged or weakened the part by a resulting slide hammer like effect. That small rotating assembly felt like it weighed at least 25 lbs.

Since this tranny along with many others in stock applications had an occasional difficulty with shifting into 1st gear particularly when cold, the damaged part may have been a contributor, or damaged as a result of excessive force used to shift into 1st as the bushing is pushed up.

I noticed some drag on some of the gears on the damaged assembly that didn’t appear to have anything to do with debris as they turned smoothly. I suspected long ago that possibly temperature related drag might be involved with the difficult cold shifting in the event the drag felt is abnormal and caused continued gear movement at times where they shouldn’t be moving.

Then there’s the possibility that it was caused by torque since the first sign of a problem beyond shifting difficulty occurred after a boosted run through 3rd gear which caused a lower volume sound of the whine you can hear in the video and was then duplicated on a second boosted run before realizing the whine was not cupped tire noise when it got louder.

[This message has been edited by Joseph Upson (edited 03-15-2012).]

The scrapes here give some idea of how the Vss was damaged confirming that there was an internal tranny problem. The speedometer stopped working minutes before the tranny noise started.

[This message has been edited by Joseph Upson (edited 02-05-2012).]

Good info, thanks for posting.

Jack

It looks like a pretty strong tranny. If not for the syncros & rings, it looks like the weak link would be the input shaft. Haven't heard of one of those breaking yet? Do you think the newer F40 syrcros & rings would fit the older version?

You probably have this already... https://www.fiero.nl/forum/Forum2/HTML/113638.html

quote Originally posted by 1fatcat: It looks like a pretty strong tranny. If not for the syncros & rings, it looks like the weak link would be the input shaft. Haven't heard of one of those breaking yet? Do you think the newer F40 syrcros & rings would fit the older version? You probably have this already... https://www.fiero.nl/forum/Forum2/HTML/113638.html

Given the speed at which GM made the upgrades I'd be surprised if the parts were not interchangeable. It appears the problem is with 6th gear which is interesting because for quite some time I had not been able to shift into 6th gear at elevated rpm without a gear scrape.

Thanks for posting this. I can't get my head around why the dog teeth would ever snap off of the 6th gear assembly. It's a low stress part compared to most of the other parts. I doubt it's failure was a result of anything a driver could do to it, or for that matter, raw power. Interesting indeed.

quote Originally posted by Fierobsessed: Thanks for posting this. I can't get my head around why the dog teeth would ever snap off of the 6th gear assembly. It's a low stress part compared to most of the other parts. I doubt it's failure was a result of anything a driver could do to it, or for that matter, raw power. Interesting indeed.

That's why I mentioned the possibility of a slide hammer effect during the accident it was involved in possibly being a source of the damage, as I mentioned earlier shifting into 6th gear at elevated rpm (as it's coming down from the previous gear) has been a slight problem for a while and during the minutes preceeding the onset of the critical symptoms I noticed that even during light load and low rpm the gear scraping during 5-6 shift became more pronounced, so much so that I began to think something was going wrong. A few minutes after that the whine heard in the video appeared only it was about three or four times louder and could be heard on decel and cruise in 1st and 2nd gear.

Although 6th gear is involved with the actual failed part, there is something about 1st and 2nd gear that aggravates it so I can't say that it's not torque related as the couple of boosted runs days earlier brought about the first sign there was a problem when the Vss was knocked out and a faint whine could be heard.

Then again, it could be related to the forced 1st gear shifts against resistance that did it over time.

[This message has been edited by Joseph Upson (edited 02-06-2012).]

quote Originally posted by Joseph Upson: ... It appears the problem is with 6th gear which is interesting because for quite some time I had not been able to shift into 6th gear at elevated rpm without a gear scrape.

What you call elevated RPM in 6th gear? Lke you were doing 130MPH++ to do a 5-6 change? I don't get that one.

Probably means, ring it out in 3rd and skip shift to 6th...?

quote Originally posted by 1fatcat: Probably means, ring it out in 3rd and skip shift to 6th...?

Not quite "ringing it out" but skip shifting yes, not aggressively however, it would do it in sequential shifting also and seemed almost unavoidable with time. I had a 5 spd Getrag that did that over nearly every gear, sold the car before destroying behind the V8 it was attached to. That tranny had the problem when I purchased it though.

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UPDATE

With only a description of the engine, the symptoms and the pictures, no tranny combo information, the Saab tranny builder said the following;

Running a solid hub clutch and no dual mass flywheel?
Seems to be a fatigue sort of failure.

He is correct, I have a solid flywheel and near solid clutch hub, it has tiny springs that were designed to reduce chatter from the transmission in conjunction with the dualmass.


He also mentioned a light weight flywheel (<~14lbs> ) as a possible contributor as well. I'm close on that one.

He is also familiar with the difficutly shifting sometimes and stated that the factory fix was to lower the tranny fluid to about 1.5L from 3.1L. He runs redline MT85 in his gearbox but i'm not encouraging this.

[This message has been edited by Joseph Upson (edited 02-21-2012).]

How many miles you had on that one? I have over 10k mi with a solid hub SPEC and my car does put over 400lbtq (364rw). Trany still shifts lke butter. I have a spare just in case.

quote Originally posted by Alex4mula: How many miles you had on that one? I have over 10k mi with a solid hub SPEC and my car does put over 400lbtq (364rw). Trany still shifts lke butter. I have a spare just in case.

I don't know the history behind the tranny, only that it was salvaged from a wrecked vehicle. I put about 10k on it tops. If you have wheel spin that might put your torque load down some from mine as I have none with the 245 on the rear. The car just squats and goes. Time will tell, I didn't abuse the tranny that's for sure. It does appear that a solid disc combined with a solid light weight flywheel and high output suggests impending doom at some point.

If the builder wasn't so accurate in describing my clutch and flywheel arrangement without a hint in advance after looking at the pictures, I might not be as concerned. The guy that built my clutch didn't have the materials available to build me a sprung, Kevlar puck, and I wasn't about to go with the ceramic version and end up having to replace it in likely 30k miles, that's about how long the dual friction clutch disc lasted.

quote Originally posted by Joseph Upson: He is also familiar with the difficutly shifting sometimes and stated that the factory fix was to lower the tranny fluid to about 1.5L from the 2L. He runs redline MT85 in his gearbox but i'm not encouraging this.

According to the G6 guys, the "official" fluid capacity for the F40 was 3.1L, right? So the fix is to run it half-empty?

quote Originally posted by raccoons: According to the G6 guys, the "official" fluid capacity for the F40 was 3.1L, right? So the fix is to run it half-empty?

If I recall correctly I filled the tranny with at least 3 qts of synchromesh (wrong fluid of course) and had the problem and I imagine the cars drove off the lot with ~3qts or L as well and still had trouble. I'm not going to argue with either side, especially not a builder who can look at my pictures and tell me what kind of flywheel and clutch disc I'm running without any hints. The builder runs 2L of Redline MT85 in his, I'l start with 2L and see what happens.

That quantity is nothing new, GM powertrain is probably where they got that spec from.

[This message has been edited by Joseph Upson (edited 02-21-2012).]

quote Originally posted by Joseph Upson: That quantity is nothing new, GM powertrain is probably where they got that spec from.

Mitchell On Demand says 3.1 Qts also.

quote Originally posted by 1fatcat: Mitchell On Demand says 3.1 Qts also.

3 qts installed and the ocassional shifting difficulty on cold start is present in the new tranny although not as bad. I'm not going to waste my time cracking open the 4th qt just to add .1 because I doubt that's going to make a difference. Perhaps the builder is correctly stating the fix as running a lower than capacity fluid level.

hey! at least it is back together. keep us updated!!!

Update Joseph? Get this ironed out?

quote Originally posted by mptighe: Update Joseph? Get this ironed out?

It could have been weakened by the accident it was involved in before I purchased it along with the unknown used history, or overwhelmed by the torque loads combined with the side effects of a lighter non dualmass flywheel and unsprung clutch hub as the Saab tranny builder suggested-- fatigue related failure, or all of the above.

Hello everyone!, this is actually my first post here. I have a used F40 that I bought cheap because the previous owner said it lost 5th gear, but the other 5 gears worked fine.

I don't know much about its history, other than it came out of an otherwise healthy looking G6. He was a young guy, tinted tails, so based on just that, I assume he didn't granny his tranny. It came out of a 2006 G6 with about 100k km, or about 62k miles.

I recently opened it up to get a brief look at the condition of the gears and found this:
Look familiar?

quote Originally posted by Cabernut: Hello everyone!, this is actually my first post here. I have a used F40 that I bought cheap because the previous owner said it lost 5th gear, but the other 5 gears worked fine. I don't know much about its history, other than it came out of an otherwise healthy looking G6. He was a young guy, tinted tails, so based on just that, I assume he didn't granny his tranny. It came out of a 2006 G6 with about 100k km, or about 62k miles. I recently opened it up to get a brief look at the condition of the gears and found this: Look familiar?

I believe this is why GM dumped the first year F40 and upgraded the second year. The changes they made to this tranny in just one years time is a strong indicator that there was a problem and they were aware of it.

Probably wouldn't be a bad idea to go ahead and buy a backup tranny now.

[This message has been edited by Joseph Upson (edited 08-25-2012).]

quote Originally posted by Joseph Upson: I believe this is why GM dumped the first year F40 and upgraded the second year. The changes they made to this tranny in just one years time is a strong indicator that there was a problem and they were aware of it.

The F40-MT2 was used for several years before they put it in the G6, in the Saab 9-3, since 2003. The main things they changed in the 07+ MU9 version is the gear ratios (to seem more sporty for appealing to the US market), and the detent on the shift sleeve so shifting will be faster, and to help with the shifter vibration complaints. I doubt any of those changes are related to people breaking anything in the transmission, as it's not really a common occurrence.

quote Originally posted by dobey: The F40-MT2 was used for several years before they put it in the G6, in the Saab 9-3, since 2003. The main things they changed in the 07+ MU9 version is the gear ratios (to seem more sporty for appealing to the US market), and the detent on the shift sleeve so shifting will be faster, and to help with the shifter vibration complaints. I doubt any of those changes are related to people breaking anything in the transmission, as it's not really a common occurrence.

I'll be building a frankenstein F40 using the 3.91 final and 0.62 sixth from an '04 Saab trans in an '07 G6 transmission. I may be able to see the differences between some of the components.

[This message has been edited by Will (edited 08-25-2012).]

It still really annoys me to see that it broke. It wasn't the synchro, it was the darn dog tooth ring. I'm somewhat unfamiliar with the design on triple cone or double cone Synchros, but I do know that the dog teeth are still supposed to be fused to, or be one continuous part with the shaft that the gear is driven/driving from. I have NEVER seen a dog tooth ring break off, because it just can't happen, at least on all models that the Fiero came with. It looks like it's a completely separate ring from the driven shaft in this design for some reason. I don't even see how it was attached, but the bent synchro is blocking the view of the mounting surface.

quote Originally posted by dobey: The F40-MT2 was used for several years before they put it in the G6, in the Saab 9-3, since 2003. The main things they changed in the 07+ MU9 version is the gear ratios (to seem more sporty for appealing to the US market), and the detent on the shift sleeve so shifting will be faster, and to help with the shifter vibration complaints. I doubt any of those changes are related to people breaking anything in the transmission, as it's not really a common occurrence.

I know all about it. The catch however is this; The F40 was not installed from the Saab series vehicles "As Is" into the G6. The bellhousing was changed and the gear ratios were changed and the problem may have been a result of those changes due to some oversight, or seemingly minor change to accomodate the modifications that resulted in the problems we are seeing. One things for sure, the F40 has been in play since about 2003, it didn't get dumped on the market and upgraded until it was put in the G6. Surely those issues didn't go ignored for all those years and I suspect they didn't exist before then.

The Saab turbo V6 produced more power and torque than the 3900 so we can't say it wasn't taxed either.

[This message has been edited by Joseph Upson (edited 08-25-2012).]

quote Originally posted by Joseph Upson: I know all about it. The catch however is this; The F40 was not installed from the Saab series vehicles "As Is" into the G6. The bellhousing was changed and the gear ratios were changed and the problem may have been a result of those changes due to some oversight, or seemingly minor change to accomodate the modifications that resulted in the problems we are seeing. One things for sure, the F40 has been in play since about 2003, it didn't get dumped on the market and upgraded until it was put in the G6. Surely those issues didn't go ignored for all those years and I suspect they didn't exist before then. The Saab turbo V6 produced more power and torque than the 3900 so we can't say it wasn't taxed either.

I'm pretty sure the only change to fit to the 3.9 was the bell housing, and removal of the AWD diff. The gear ratios for the F40 transmissions in the pre-07 Saab 9-3 that I've found, are the same as in the G6. I've seen no indication anywhere, that they are different. And from what I've seen, all post-08 F40 transmissions in all GM cars where offered, have the same gear and FD ratios; regardless of AWD or not.

quote Originally posted by dobey: I'm pretty sure the only change to fit to the 3.9 was the bell housing, and removal of the AWD diff. The gear ratios for the F40 transmissions in the pre-07 Saab 9-3 that I've found, are the same as in the G6. I've seen no indication anywhere, that they are different. And from what I've seen, all post-08 F40 transmissions in all GM cars where offered, have the same gear and FD ratios; regardless of AWD or not.

Then it must be during the bellhousing swap or in the grade of parts. The AWD does have a difference as the MK6 vs. MU9. Different first and final drive gears in 09. I've seen the final drive version Will mentioned which I recall also had some differences but it has been a while since I saw it on GM Powertrain.

quote Originally posted by Will: I'll be building a frankenstein F40 using the 3.91 final and 0.62 sixth from an '04 Saab trans in an '07 G6 transmission. I may be able to see the differences between some of the components.

3.91 is a bit much with that first gear unless you plan on racing with a boat and trailer attached. Wouldn't the 3.76 FD from the 09 AWD be a better choice? Then again I guess you could skip first altogether with a 3.91 and end up with a better outcome only needing two shifts after launch in the 1/4 to have a gear combo suitable enough for a good elapsed time. For a turbo car or, any with good power output, 1st is to short and 2nd to steep to launch in so a timely shift into 4th is necessary as 3rd will not take you high enough above 100 mph unless your motor makes power all the way to 7k.

[This message has been edited by Joseph Upson (edited 08-26-2012).]

quote Originally posted by Joseph Upson: 3.91 is a bit much with that first gear unless you plan on racing with a boat and trailer attached. Wouldn't the 3.76 FD from the 09 AWD be a better choice? Then again I guess you could skip first altogether with a 3.91 and end up with a better outcome only needing two shifts after launch in the 1/4 to have a gear combo suitable enough for a good elapsed time. For a turbo car or, any with good power output, 1st is to short and 2nd to steep to launch in so a timely shift into 4th is necessary as 3rd will not take you high enough above 100 mph unless your motor makes power all the way to 7k.

The higher you rev, the more sense those ratios make. It's still useless in a road race or AutoX environment, but makes for a hell of a holeshot, and I'm only turning to 6400 right now. When I bump the limiter up to 7 or 7.5, the 3.79 first and 3.91 final should be monstrous on the strip. I'll be using the 0.62 sixth, so my top gear will be taller than 5th in the Isuzu 5 speed. With the 0.81 fifth in the '07 gearbox, I'll have a 5th gear that will be the best it can be for acceleration at the Texas Mile. I wouldn't want a 5th gear that short in a 5 speed.