Nissan Tranny is Theh Suked..

 

You mean like you do to mine??
Im making a comment, the Nissan tranny is not very good or at least some components of it are VERY prone to failure.. i would either go Auto or a SMT Dog Box.

 

Not to be a pain, but why go auto..? i know a few auto guys that have engines able to push over 600 that can't get the Z auto tranny to hold. They are either replacing it with some type of after market tranny (eg: TH400) or making the drastic move to a 6mt.
Do you think a car with over 600 -> 800+whp should be using the auto or the 6mt tranny? Lets say this is for a daily street driven car, not a purpose built drag or circuit race car. I am very interested in your thoughts on this.
If you do not feel it should be in this thread, please PM me with your thoughts/expereince in this.
Thanks.
--B

 

I was reffering to a TH400 not the Nissan Auto. The TH400 has been put in hundreds of thousands of American production street cars and has proved to be a true workhorse as far as transmissions go. It has proven to be streetable and race track reliable tenfold over the Nissan 6MT, which is a relatively new transmission for Nissan and their engineers. The TH400 is a very drivable tranny contrary to what the naysayers feel..If your drag racing, you can set it up with a manual valvebody, where you have to shift into each gear, so its not as simple as step on the gas and go straight, contrary to Albertos beliefs..
If you truely prefer the feel of shifting with a clutch, then look into a Domestic 4 or 5 speed, which would handle the HP and cost 1/3 rd of what a JDM company would rape us Import guys for..For example, you could build a TH400 to handle 1000whp for about $2000 USD, where as a comparable 6mt Dog box style tranny would cost in upwards of $6800 plus install..
We have found a partial problem with the 6MT that we feel contributes to its failure, and it has nothing to do with the Synchros,but relates to the clutch engagement and release. On a side note the 6MT internals may be similar to the R-34 6mt or the Toyota Supra 6MT..So that may be another route to take.
I would say if Nissan engineers have not yet fixed the issues 100% with the 6MT, then I would highly doubt there will be an affordable aftermarket fix in the near future, but I might be wrong.

 

Thanks for the information. I will have to do a bit more research then.
The problem with the TH400 in my opinion, is that I have never driven a auto that shifted crispy, cleaning and applied the power instantly when I wanted it.
I have never driven a race prepared car, but I can't imagine it would apply the power like a standard does.
Anyway, thanks again for the info as I know it will be useful for me and others in the future.
--B

 

You can arrange the TH400 to shift VERY hard if you wish..The main thing for me going TH400 was only having to shift 2 times from 0-170mph.

 

th350 will always shift harder than th400.

You could get a dogcut gear box for a Borgwarner t5 for 2500$, on adapting it too the vq35 i have no idea
http://www.gforcetransmissions.com/tran_gt-5.asp

 

BTW ---Not to **** off BriGuy ---But the 400 is great -------BUT if u want to strickly drag ----Why the HELL not go with the Cast Iron Power Glide ????

 

I'm not knocking the TH400...I'm just saying it's not the topic of this thread.

 

Perhaps you open your eyes and apply some of the tecnology the Domestic guys have been using for year witout failure. Keep in mind, Nissan set out to bring back the Z car with a $29,000 price tag goal. There are some parts on the Z that can be improved upon vastly, namely the transmission. The way I look at it, you can sink lots of money and time developing your own fix, or you can adapt and overcome using proven technology. I personally am sure The tranny problems are not with the internals of the tranny's themselves, but partialy Driver and partially clutch engagement and release issues. This is what is breaking transmissions, from what we have experienced. This is where we get "locked out" of gear when shifting from 2-3rd often and after a few good bad shifts, you break the synchros and grind gears.This is caused by the clutch not fully disengaging or sticking and dragging. From what we have found, frequent clutch pedal adjustments help alot.
A straight cut gear will help out, and a DOG ring syle gear box would be killer for drag racing,however for most the Dog box is out of reach.

 

Most 350Z owners are not looking to build specific drag cars, but balanced cars for track day lapping, drag racing, and daily-drive thrashing. A domestic auto trans is not the solution for those people.

I am interested to see what develops on the 6MT modification scene. Supras and Vipers are running sub 10's with their 6MT's just fine.

And as a side note, straight cut gears (affectionally called dog boxes) are horrible for a street car. They whine like crazy (think of the reverse gear on an old Honda...and the familiar whine as you backup at higher speeds), and if the trans lasts 20K miles, you should consider yourself lucky. They are designed for racing only, and you better get really good at rev matching and double clutching on downshifts.

 

AH yes ---Like the old Muncie Rock Crushers as they were called, Indestructable. I luved them.

NOW ---There would be an excuse to light up a million rants, like------My trans grinds 1-2 2-3 3-4 4-5 and 5-6 also 6-5 5-4 4-3 3-2 2-1 and sometimes Reverse, is this covered under warrenty ????

 

One could always opt for the old T-56 6 Speed used by GM in the Corvettes and other street rods. There are several companies making them with upgraded gears for 900+whp applications. And you can choose your gear ratio to suite your needs. There are also plenty og 9-10 second GM's running these trannies, and they perform well on the street and road coarse. No double clutching or rev matching with them. With an adaptor plate these could be made to work theoredically.
or at least reverse engineer one of these to see what they do to make them so strong.

 

And I think in the 2000.00 range or less

 

Posts moved to clean up the sticky thread.

 

Sharif, straight cut doesnt equal "dog box". The term dog refers to dog ear engagment. You can have straight cut gears in a syncromesh transmissions. Both will wine though. The dog ear engagment allows the driver to not use the clutch when shifting, just lift off the throttle a bit and push into the next gear. Just like power shiftig but its made to do this, where as syncromesh will not take this abuse for long.

 

yup exactly,


also brent, my tranny shifts perfectly (th400) it bangs gears hard as hell if i want it to or it can be smooth if i shift it slower, it being all mechanical you can really tell the difference if you slam it or take it easy...


i will be putting on my stock 6 speed for the next month or two, then i plan on throwing on the Th400 again for fun!!

 

Too add my 2 cents, The nissan Tranny has its weakpoints. My thought is if we can improve the gearing in this car for FI that would be a great solution. I find myself when driving fast abusing 1st, 2nd, and 3rd just to go. The car revs so fast it is hard to keep up. I am tossing around the idea of a turbo 400 as I am not a die hard dragger but I like being able to jump in the car and go. If you break a turbo 400 your doing something very wrong (if the trans is built right) And lets face it I live in South Florida where all the roads are straight so gear rowing is not that important. It is not a easy choice as I have talked with so many people about this and still not sure. But if the car is street driven with a turbo 400 you can get a gearvendors overdrive to aid in fuel mileage. That is what some Supra guys are doing.

Looking forward to the feedback from everyone.

Ryan

 

Thanks for the information.
This thread (and the original it spawned off from) have really helped in my understanding of our tranny and general principals of its operation. Based on what I have been reading here, I guess I should be doing some more research on some beefed up tranny's.
--B

 

So has anyone attempted, or have feedback on, a tranny swap for something other than a TH400? All this talk about Getrags, dog boxes, T56, etc. but has anyone actually done it? Somehow, based on my experience with modding this car so far, it's just not that easy.