transmission grinds when shifting to 5th

[KornFlakeZ]

Ever since i had the car it grinded when upshifting to 5th gear but i wasnt anywhere as bad as it is now. Basically i have tried shifting at lower RPMs (2k,2.5k) and higher RPMs (5k and up), Shifting a little bit more slower and faster and it still grinds... Any ideas on what could be the cause? I have a 90 NA by the way.

[zcar93na]

All Z's that are 5 speed start to do that after the transmissions are abused and pounded through the gears. Most start to grind in 2nd and 4th, I know mine has since I got it.

[Ace2cool]

Synchros. It's a known issue that they finally fixed with the '99 spec trans. You can replace the synchros with a kit.

[zcar93na]

Synchros. It's a known issue that they finally fixed with the '99 spec trans. You can replace the synchros with a kit.

Would you have a link to that kit? I've looked for it but can only find the US spec

[Ace2cool]

The US spec is the one you need. They don't really make the JDM kits, because they don't fail. They don't swap either, TMK.

[Shoey2]

The US spec is the one you need. They don't really make the JDM kits, because they don't fail. They don't swap either, TMK.

do you mean my jdm trans wont use the same synchros, or the '99 spec wont trans wont fit on my 90 tt?

[Oh Em Zee]

Just wait until you try to downshift from 5th to 4th, high rpm. >_<
DAT GRIND!

[zcar93na]

do you mean my jdm trans wont use the same synchros, or the '99 spec wont trans wont fit on my 90 tt?

Your transmission is the same as a US trans. In 98, when nissan made a few changes to the 300z, one was they upgraded the transmission. It'll bolt up to our engine, the thing that is different is stronger synchronizers.

[Shoey2]

do you mean my jdm trans wont use the same synchros, or the '99 spec wont trans wont fit on my 90 tt?

Your transmission is the same as a US trans. In 98, when nissan made a few changes to the 300z, one was they upgraded the transmission. It'll bolt up to our engine, the thing that is different is stronger synchronizers.

ok good, thats what i was hoping. im gonna make sure that $1700 quote i got at work is still the same for the later model trans.

[KornFlakeZ]

Sry i havent replied lately, works been a lil rough lately. Anyway, do you guys think that by changing oil it could ease the grind? I REAAALLY dont want to lower the transmission after the car was stopped for like 3+ months after some engine problems... But i am conscious it will eventually have to be done, so when the day comes, what rebuild kit do you guys recommend?

[Shoey2]

https://specialtyz.com/shop/lubro-moly- ... r-oil.html

this might be what we are looking for. has any one here used this yet or something similar?

[Ace2cool]

Oil change just prolongs the inevitable. It CAN work, doesn't mean it WILL work. And zcar93na has it right. they only changed the internal stuff. It'll mate up and all the dimensions are the same.

[KornFlakeZ]

Well i guess ill put some of that redline stuff in the transmission until i locate a rebuild kit... sigh, if this was any other car i would sold it already because working on it is such a PAIN! But its a Z so any pain its worth it

[Shoey2]

i just put in BG synthetic like what SZ sells. helped my 90 TT with 135,000 kms.
id say a 20% improvement but you know its still just a bandaid. i just dont rev it over 5k and shift slower, use more torque then boost.
but i mostly drive 80% in town, 20% highway. so i can use the lower gears more. 5th is not really used most of the time for me.
i have had sucess with lucas stuff in old customer cars, but i dont know if it is good for our 5 speeds.

[KornFlakeZ]

yeah, ive heard that the syncros in our 5spds are made with softer metals so you just cant put any oil in there or it will just eat the syncros

[zcar93na]

Here's a full rebuild kit, or you can just buy new sychronizers
http://www.drivetrain.com/parts_catalog ... l_kit.html
From what I've read, Nissan pickups used the same transmissions, but I'd still order the 300z kit to make sure it has everything you need.

EDIT: I think the synrchos for the pickups are the only thing different. That was kind of a random fact but I've thought about putting a VG in 4x4 hardbody pickup, so disregard what I said, just get the kit for a 300zx. If all that it does is a light grind, then I would just replace the synchros

[ThisIsSparTTa]

I don't know if it adds a ton of value to the thread, but my transmission, which theoritically has 165k on it, grinds on hard shifts from 3rd to 4th when really going at it. I've tried a little rev matching or double clutching, but haven't had much luck...also, I'm not running it that hard very often either. Anyways, the synopsis seems to be that (as expected) the synchros on these guys go out over time, but at least it doesn't seem to be a common problem on any 1 gear. I haven't looked as much at the Z transmission, but when I was looking at RX-7s which have 1 that always fails, it was described as not too bad to replace the synchros...if you had a transmission lift, and a gear puller.

[KornFlakeZ]

I don't know if it adds a ton of value to the thread, but my transmission, which theoritically has 165k on it, grinds on hard shifts from 3rd to 4th when really going at it. I've tried a little rev matching or double clutching, but haven't had much luck...also, I'm not running it that hard very often either. Anyways, the synopsis seems to be that (as expected) the synchros on these guys go out over time, but at least it doesn't seem to be a common problem on any 1 gear. I haven't looked as much at the Z transmission, but when I was looking at RX-7s which have 1 that always fails, it was described as not too bad to replace the synchros...if you had a transmission lift, and a gear puller.

Thats problem... i dont have any of those two. And if i did, lowering the transmission on these cars is such a PITA!

[Ace2cool]

In what universe? The hardest part is getting the top bolts out. Other than that, it's easy. You don't even need a transmission lift. Put the car on jack stands, and balance the transmission on a floor jack.

And gear pullers are anywhere from $15 to $55

[Shoey2]

i agree with ace. pulling the trans on these cars in a easy as pie i dont see what all the fuss is about. exhaust, driveshaft, bell housing bolts, trans mount out, pull and done. just get long extentions with a swivel. comes out with hand tools.

[KornFlakeZ]

i agree with ace. pulling the trans on these cars in a easy as pie i dont see what all the fuss is about. exhaust, driveshaft, bell housing bolts, trans mount out, pull and done. just get long extentions with a swivel. comes out with hand tools.

Problem is that the bolts connecting the exhaust are welded from all the rust and corrosion ( not to mention the heat from the exhaust ) and if i cant get the bolts out i have no other than to cut the exhaust and weld it back in once im done. Whats the easiest way to remove the upper transmission bolts? I already deleted the EGR so i have a bit more room to work in.

[Shoey2]

all you need is a torch, the tank with the trigger on top, and some good sockets. just get exhaust gaskets, they are cheap. and go to town. maybe some penetrating fluid on them the night before to soak in...rust is easy to deal with once its stripped then your gonna be cursing