Getrag 440/446 parts.

[Bret Brinkmann]

Synchro rings do not transfer power. Gears, shafts, and dog teeth do. No one needs a high horse power synchro ring. The rings synchronize the speed of the gear and the speed of the shaft. That is it. Makeing sure the clutch isn't dragging and that you have a good gear oil are the things to do. Oh yeah don't mis-shift either. The forks only break because synchronization does not occur but you try to change gears any way (forceing it into gear in other words). You want to change gears and the gear don't want to, so some thing has to break. The weakest link breaks and that is the fork. Better than striping the dog teeth off the gear and having to buy a new gear. If the gear oil is good, the clutch isn't draging, and you don't mis-shift then will not be a problem.

The forks will break along the casting lines. If one were to grind down the casting lines the strength of the fork would be increased. Sharpe angles will all ways be weak spots.

SkortchGT - Just look at just about every thread I have posted in about drive trains. There is tons of info I have posted.

Oh yeah, what does every one think about the Supra, 911, and Skyline? Pretty awsome cars huh? They have Getrag drive trains also. (This statement is just for everyone who refers to Getrag as "Getrash".) At least we don't shatter gears like the Nissians and Subarus. Or turn our half shafts into quarter shafts like the Vipers and Hondas. (Yes I compaired the Viper to a Honda.)

[RobBeck]

I agree with all that... thats why I thought it was a waste to make a super heavy duty synchro. I dont think that a billet aluminum shift fork would cause any troubles tho.... perhaps even help with positive shifting, and maybe a cheaper alternative to buying new (just a thought). Other than that I feel if the tranny is well maintained and continues to shift positive it should last a really long time, when the positive shifting begins to deplete it would be a good idea to get to the root cause and eliminate it. Eventually a synchro will wear or burn out from just age or from a high RPM blocked shift, but I would rather keep that as a fuse to protect everything else anyhow... if we can keep synchros in stock, maintain well, and shift positively our trannies will stay in good shape for many years to come. I am pretty sure the 6 speed setup at least has been proven to withstand a massive amount of power. Missing gears while shifting/grinding, running low or have worn oil, poor clutch engagement, etc. are things that will put this tranny in the grave. Monetarily speaking, my worst fear with this trans would be the worn dogteeth from missed shifts/grinding.

Rob

Originally Posted by Bret Brinkmann

Synchro rings do not transfer power. Gears, shafts, and dog teeth do. No one needs a high horse power synchro ring. The rings synchronize the speed of the gear and the speed of the shaft. That is it. Makeing sure the clutch isn't dragging and that you have a good gear oil are the things to do. Oh yeah don't mis-shift either. The forks only break because synchronization does not occur but you try to change gears any way (forceing it into gear in other words). You want to change gears and the gear don't want to, so some thing has to break. The weakest link breaks and that is the fork. Better than striping the dog teeth off the gear and having to buy a new gear. If the gear oil is good, the clutch isn't draging, and you don't mis-shift then will not be a problem.

The forks will break along the casting lines. If one were to grind down the casting lines the strength of the fork would be increased. Sharpe angles will all ways be weak spots.

SkortchGT - Just look at just about every thread I have posted in about drive trains. There is tons of info I have posted.

Oh yeah, what does every one think about the Supra, 911, and Skyline? Pretty awsome cars huh? They have Getrag drive trains also. (This statement is just for everyone who refers to Getrag as "Getrash".) At least we don't shatter gears like the Nissians and Subarus. Or turn our half shafts into quarter shafts like the Vipers and Hondas. (Yes I compaired the Viper to a Honda.)

[SkortchGT]

Bret- I'll be sure to check out your previous posts. Let us know when you have heard something about a parts supplier or if there is anything I can do to help.

[Gatecrasher]

Oh yeah, what does every one think about the Supra, 911, and Skyline? Pretty awsome cars huh? They have Getrag drive trains also.

Not to take this too far off topic, but the only Skyline with a Getrag gearbox is the 6 speed R34 GTR. The 5-speed R32 and 33 were Nissan transmissions, and they have major issues with shattering the entire 3rd gear. The 6sp in the 34 is not very well regarded among Japanese tuners due to the thinner gears and, I belive, syncro problems


The only reason you never hear people bitch about Skyline transmissions is because they have at least 4 complete gearbox replacments available.

The Supra guys can't get syncros either (at least, not easily), but apparently theirs are designed better in the first place.

As for the Porsches, how many are modified for significant additional power compared to ours? How many are owned by old, retired doctors that only take them out on Sunday and never get above 65 mph?

[Bret Brinkmann]

In most cases custom makeing parts like a billet fork would significantly increase the cost of the item. Plus, if it was stronger, it would then reveal the next weakest link in a forced shift. Possibley the dog teeth? I don't know...

If only we lived in Japan. This thread wouldn't have even started. They get all the cool cars plus part to fix them and then some. I'm so jealous.

I have quite a few neighbors who own Porsches varying from the boxster to the 911 turbo and it seems that the faster the Porsche is the harder it is driven. I don't think those two guys with the 911 turbos even knows that you don't have to go WOT all the time. EVERY TIME I see them they are getting on it. Same with the C2s and C4s for the most part. However I have only seen a boxster getting driven hard once. But only for a second though. Have I mentioned the 911 turbos I see in my town get driven hard ALL THE TIME? I just wanted to stress that part. I also want to know why they never get pulled. Another reason for Bret to be jealous.

[RobBeck]

Cost for a custom fork all pends on who is making them. I happen to have a pretty good relationship with a machinist who can work with me from time to time. I havent seen the forks on this car yet... but if they are as simplex as other trannies I have rebuilt then I dont see them as TOO much of a problem to fabricate. I still do not know what our cost will end up being on them if we can even get them, but if it is anything like the synchros then it very well could be a couple hundred bones ... time will tell hopefully. As for making the forks stronger all I could see that doing is provide less undesirable flex (if the factory one even presents a problem in this area ). The only thing this would do is a more precise shift... no slop when banging gears. Adjustable positive stops on the shifter mechanism (if not already equipped) would also be a nice upgrade, these can prevent overshifting and unnecessary stress on the forks and the synchros. The weakest link is always going to be the synchros, as it should. If they are upgraded to not wear... then you are going to wear something else which will likely cost even more to replace (or not be replaceable at all!). Synchros are like brake pads, they wear out eventually then you throw them in the gutter and go buy some others. It is just a fact of life, it will happen eventually... you should consider them as a fuse or a pawn..... but if the tranny has been shifted properly (no missed gears) along with good maintenance they should last quite a few thousand miles.

Rob

Originally Posted by Bret Brinkmann

In most cases custom makeing parts like a billet fork would significantly increase the cost of the item. Plus, if it was stronger, it would then reveal the next weakest link in a forced shift. Possibley the dog teeth? I don't know...

[devilmanVISA]

There is an insane amount of material removal involved with making shift forks from billet. Unless you can clamp the material in 4-6 different places while its cut or else it will warp. That is where the expense comes in. Using something like ductile iron can negate some of the expense of the machine work but with an increase in material cost.

I don't think the design of the shift fork should be changed at all. I just think that the material needs to be changed to prevent them from warping and cracking and breaking etc. Something with a little bit more rigidity that can withstand a little bit more force.

[RobBeck]

Originally Posted by devilmanVISA

There is an insane amount of material removal involved with making shift forks from billet.

So I guess you have seen them on this trans... got any pics? I know other trans shift forks I have seen are 100% doable.

Originally Posted by devilmanVISA

Unless you can clamp the material in 4-6 different places while its cut or else it will warp. That is where the expense comes in. Using something like ductile iron can negate some of the expense of the machine work but with an increase in material cost.

T6061 is fairly cheap (and has got to be WAY stronger than cast), the mills run thru it like it is butter... and yes nice fixtures will have to be made to do them..... get me some pics and relative dimensions and I will determine if it would be expensive or not The 1/2 and 3/4 shift forks are all I am concerned with.

Originally Posted by devilmanVISA

I don't think the design of the shift fork should be changed at all. I just think that the material needs to be changed to prevent them from warping and cracking and breaking etc. Something with a little bit more rigidity that can withstand a little bit more force.

No one said anything about changing the shift fork design... that would be silly. Making an exact replica out of billet T6061 is what I am referring to.

Rob

[Bret Brinkmann]

It is my understanding that cast has less flex than forged materials. That really surprised me when I read it but I guess it makes sense. The forged materials take more force to break because they flex. The cast materials don't flex so they break sooner. So with less flex the cast fork would be better. Also, do to the design of the shift select lever it is impossible to over shift.

The forks wouldn't be an issue in the first place if the transaxle woud shift into gear. The transaxle would shift into gear if the maintenance was kept up with and clutch didn't drag. In other words, there isn't any point in makeing a billet fork.

[Boostaddict]

Actually, thats not quite it. All things being equal, the elastic modulus will determine the amount of "flex" before breaking. Nothing to do with forging at all. Forged alloys are typically very different than casting alloys (due to cost) so you can't compare apples to apples. A suitable forged alloy should always out perform a comparable cast alloy, depending on how it was subsequently heat treated (don't want to anneal it obviously, or you wouldn't used a forging material). Anyway, back to the 60k maintenance

Wayne

Originally Posted by Bret Brinkmann

It is my understanding that cast has less flex than forged materials. That really surprised me when I read it but I guess it makes sense. The forged materials take more force to break because they flex. The cast materials don't flex so they break sooner. So with less flex the cast fork would be better. Also, do to the design of the shift select lever it is impossible to over shift.

The forks wouldn't be an issue in the first place if the transaxle woud shift into gear. The transaxle would shift into gear if the maintenance was kept up with and clutch didn't drag. In other words, there isn't any point in makeing a billet fork.