Professional analysis and pictures of our 6MT internals
01-29-2007 | 06:16 AM
#21
Nice work with the pictures, and I for one can appreciate the Maxima gear comparison - having stripped those gears clean of their teeth many times in the past. I assume the Maxima gears were from Neal's transmission?
Sounds like the Z trannies have a good foundation - hopefully TRE can provide the few little fixes necessary to keep people on the road.
Sounds like the Z trannies have a good foundation - hopefully TRE can provide the few little fixes necessary to keep people on the road.
01-29-2007 | 06:57 AM
#22
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Joined: Oct 2002
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From: West suburbs of Chi-town
Originally Posted by jcn30127
.....as I am about to ask Nissan to put #5 !!! in my -Z-.
It has always been a 5th synchro problem for me.
Can you tell us why the 6MT is (sometimes) very notchy in the shifting department. Pics?
It has always been a 5th synchro problem for me.
Can you tell us why the 6MT is (sometimes) very notchy in the shifting department. Pics?
The synchro issue really isn't our focus area with this build-up as I've had zero shifting issues with this trans over the past 40K miles.
As for notchy, I can't answer that. Notchy to one person is a good positive engagement to another. I've never driven a 350Z with a trasmission that I felt was "notchy". Very positive engagement yes...but I like that.
Sorry you've had such bad luck...it took me 2 replacements to get a good one back in the day. I think I got my 008 trans that I have now in early 2004.
Originally Posted by Hal@IP
Nice work with the pictures, and I for one can appreciate the Maxima gear comparison - having stripped those gears clean of their teeth many times in the past. I assume the Maxima gears were from Neal's transmission?
Sounds like the Z trannies have a good foundation - hopefully TRE can provide the few little fixes necessary to keep people on the road.
Sounds like the Z trannies have a good foundation - hopefully TRE can provide the few little fixes necessary to keep people on the road.
Last edited by BriGuyMax; 01-29-2007 at 07:00 AM.
01-29-2007 | 07:08 AM
#23
Brian, the issue I see with the trans, is the VERY sluggish shifting under heavy load...550whp+, and 7000rpm+. Can you ask your trans guy, if this issue can be fixed? This is what seperates the Supra and Viper transmissions from the 350z, IMHO. Strength and size of gears is one piece of the puzzle, but the shift forks, synchros and blocking plates are another piece I would like to understand. How can we make our trans shift better without locking out, or grinding under very heavy load. In 4th gear, I cannot shift to 5th at 7500rpm....just wont go into gear, so I am forced to shift into 5th at about 7000rpm max.
01-29-2007 | 07:19 AM
#24
Originally Posted by BriGuyMax
I think I got my 008 trans that I have now in early 2004.
01-29-2007 | 07:21 AM
#25
My cd008 got switched out after 7k miles for 5th gear grindout. Im on the cd009 and is just grinded twice in 5th last week. Im not sure if its driving method, or if its the sycnrhos themselves.
01-29-2007 | 07:26 AM
#26
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Joined: Oct 2002
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From: West suburbs of Chi-town
Originally Posted by Sharif@Forged
Brian, the issue I see with the trans, is the VERY sluggish shifting under heavy load...550whp+, and 7000rpm+. Can you ask your trans guy, if this issue can be fixed? This is what seperates the Supra and Viper transmissions from the 350z, IMHO. Strength and size of gears is one piece of the puzzle, but the shift forks, synchros and blocking plates are another piece I would like to understand. How can we make our trans shift better without locking out, or grinding under very heavy load. In 4th gear, I cannot shift to 5th at 7500rpm....just wont go into gear, so I am forced to shift into 5th at about 7000rpm max.
That's actually one of the things that he'll be working on. He asked me how far I planned on revving the car out, and I hadn't really thought about it. He can definitely modify things to help it shift much better at higher RPM. It's one of the many things he does with the DSM transmissions, as they are really bad with high RPM lockout. I really wasn't sure if people had issues shifting at higher RPM and I will definitely bring it up with him now. Thanks for the info.
01-29-2007 | 08:17 AM
#27
Very good info. Brian, thanks for sharing. This place is only 2 hours from me! I had the same problem with so called "high rpm lockout" and also was told my sycros and shift forks needed replaced. Once you find out what mods can be done, If they'll work on it, I'll consider shipping them my tranny while my motor is out being built.
01-29-2007 | 08:42 AM
#28
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From: Boston, MA
Originally Posted by BriGuyMax
While that definitely could be the case, the dimensions of the gears seems to be in line with other very beefy transmissions. The strenth is supported by the fact that only a very small handful of people have even broken this trans. Furthmore, the people whom have broken them typically haven't torn them down to do a failure analysis. So we really don't even know what exactly broke.
EDIT: Typically the gear design is the primary determining factor in failure threshold, rather than an insufficiently prepared gear steel.
EDIT: Typically the gear design is the primary determining factor in failure threshold, rather than an insufficiently prepared gear steel.
You are right, gear design is the most important factor, but simple over looked material traits can casue a lot of issues like crack propagation, thermal expansion... Material properties can be changed during the machinging and postprocessing of the gears as well. Small changes in the stress-strain curve can quickly go against the engineered intent when used past the factor of safety.
Also, improper transmission level design like tolerance stack-ups and lubrication and especially IMPROPER USE can produce wear that induces premature failure.
01-29-2007 | 09:07 AM
#29
Good job Bri. A quick question and I am by no means trying to cast doubt on the shop here. I have a few friends with 3000GTs and from what I heard that is the biggest problem with them. The trans that is. They are from what I told fairly weak. Is this trans you were comparing a stock trans or aftermarket... Is the 3000GT trans really good contrary to what I'm hearing? just curious. Like I said I'm not doubting and by no means am I a trans expert.
01-29-2007 | 09:26 AM
#31
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Joined: Oct 2002
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From: West suburbs of Chi-town
Originally Posted by Muzlimchu
You are right, gear design is the most important factor, but simple over looked material traits can casue a lot of issues like crack propagation, thermal expansion... Material properties can be changed during the machinging and postprocessing of the gears as well. Small changes in the stress-strain curve can quickly go against the engineered intent when used past the factor of safety.
Also, improper transmission level design like tolerance stack-ups and lubrication and especially IMPROPER USE can produce wear that induces premature failure.
Also, improper transmission level design like tolerance stack-ups and lubrication and especially IMPROPER USE can produce wear that induces premature failure.
All correct, and that's precisely why my gears will be magnafluxed (sp?) to see if they've developed any microscopic cracks. More info to follow.
01-29-2007 | 09:27 AM
#32
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Joined: Oct 2002
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From: West suburbs of Chi-town
Originally Posted by MIAPLAYA
Good job Bri. A quick question and I am by no means trying to cast doubt on the shop here. I have a few friends with 3000GTs and from what I heard that is the biggest problem with them. The trans that is. They are from what I told fairly weak. Is this trans you were comparing a stock trans or aftermarket... Is the 3000GT trans really good contrary to what I'm hearing? just curious. Like I said I'm not doubting and by no means am I a trans expert.
Maybe they're talking about the FWD 3000GTs. This was a stock GETRAG trans out of a VR-4 and from what John has seen the VR-4 transmissions are very stout.
01-29-2007 | 09:34 AM
#35
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Joined: Oct 2002
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From: West suburbs of Chi-town
Originally Posted by rocks
Are you going to check into cryo treating the trans gears? That could possibly help.
Cryo treating as well as shot peening will be methods that we will be considering. Both methods usefulness depends on the alloy composition of the gears though.
01-29-2007 | 09:36 AM
#36
Originally Posted by BriGuyMax
Maybe they're talking about the FWD 3000GTs. This was a stock GETRAG trans out of a VR-4 and from what John has seen the VR-4 transmissions are very stout.
01-29-2007 | 09:39 AM
#37
Originally Posted by MIAPLAYA
Maybe but I seem to remember them having VR4s. IDK maybe I'm way off base. Again I am no trans expert and have never really been into the DSM scene. Just what I heard from a couple buddies who had them. I'll see if I can dig anything up on the interweb.
01-29-2007 | 09:50 AM
#40
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Joined: Oct 2002
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From: West suburbs of Chi-town
Originally Posted by MIAPLAYA
Thats a good question. I don't know. I'm scouring the interweb now.
Wiki article exerpt taken from 3si.org
It is a common misconception that the 3000GT was equipped with a very weak transmission (which is technically a transaxle due to placement). Some even accuse it of being fabricated entirely of aluminum, which is quite ridiculous. This may stem from the fact that the external casing of the W5MG1 transmission was made of aluminum. The transmissions do have a tendency to fail, however this was not due to weakness or poor design. Rather this can be blamed on Mitsubishi's poor deal with Getrag, the transmission manufacturer. In the agreement, Mitsubishi agreed to consider the transmissions "non-serviceable," and instruct all their dealers to simply replace the entire transmission if there was ever a problem. Indeed, the factory service manual has a single page devoted to the Getrag transmission, saying exactly this. This of course generated significant increase in sales for Getrag, at the expense of the loyal owners one might add. The major problem with the transmission was the synchronizers (notably 1-2 and 2-3), coupled with the fact that Mitsubishi specified the wrong viscosity fluid for the transmission. Some even speculate that this fluid is the major reason for said failures. As a result, many 3000GTs have developed grinding synchronizers that sound terrible and cause mis-shifts. In some cases, switching to a modern synthetic like "synchromesh" or a combination of Redline fluids, has been known to cure the problem entirely, or at least ameliorate it significantly. The fluids also go a long way to preventing new transmissions from developing this problem. Unfortunately, Mitsubishi technicians and dealers either do not know this or do not tell their customers this. Instead they [correctly] suspect bad synchronizers, and the only course of action is to replace the entire transmission. Getrag also refused to offer parts to any transmission mechanics who tried to fix the problem. As a result, many a VR4 owner has had to replace their transmission, and the car has developed a bad reputation for such, however it is unfair to accuse the transmission of being weak. Until recently there were absolutely no internal modifications for the transmissions, which clearly means that all the 700 and 800 horsepower VR4s out there run with perfectly stock transmissions. Though output shafts breaking is a common occurrence at that level of power (as it is for all AWD cars with that kind of power), internal failure is virtually unheard of.
Last edited by BriGuyMax; 01-29-2007 at 09:55 AM.