Grinding Noise When Selecting 4Th Gear?

[Country Cruzin]

when i go to select 4th gear bout 3/4 of the time time it grinds/crunches going in, all other gears are fine. would seem to me like a synchro, but i dont understand a whole lot bout gear boxes..

anyone else had this problem?? if so how did u fix it, an how much? anyhelp would be appreaciated thanks

[GTSBoy]

Synchro more than likely, but also possible to be wear on a number of other parts associate with shifting the cogs back and forth. Bandaid fix is to use Redline Shockproof oil. Proper fix is strip down & rebuild at cost between several hundred and 2 grand.

[Country Cruzin]

would that sorta price include labour? an wot do u get with a rebuild? car has done 150k so the gears are probably getting worn to, but i guess a whole new box would be expensive

[GTSBoy]

Several hundred is a personal strip down and replacement of barest essentials. 2 grand is paying someone to do it and replacing the bare essentials and a few other bits and pieces that you'd feel bad putting back into a "rebuilt" gearbag.

[Country Cruzin]

hmm i wonder how hard it is to fit an r34 box into a r34 gtr, they'd all be a fair bit newer, heard of one bloke doin it

[10 4]

Do redline shockproof... once that starts grinding after you have that in it THEN its really time for a rebuild/replacement

[dark.sky]

My RB25 box was crunching 4th, I took the gearbox out and took it to a local gearbox specialist. He fitted a brand new syncro to 4th, and a better condition, but second hand syncro to 3rd. Price was $350 parts and labour.

[Carbon 34]

Do redline shockproof... once that starts grinding after you have that in it THEN its really time for a rebuild/replacement

Do not put shockproof in a 5 spd box , redline MTL or 90w only

Its not a bandaid it does what the factory oil failed to do !! but don't expect a miracle if the sychronos or bearings are screwed , it will make the box smoother in all gears and could save it from rebuild for a long time ( my rx7 box had second failing at 47,000miles -usa it had redline then never played up again ,sold the car with 497,000 on it 11yrs later and it was flogged hard on the track!!)

Shockproof is too slick and will make sychros grind , they need to mesh , redline tech will tell you that ( its a major cause of gearbox failures on skylines and any normal 5spd boxes )

Dog boxes /straight cut gears are another story

[noone]

Shockproof is too slick and will make sychros grind , they need to mesh , redline tech will tell you that ( its a major cause of gearbox failures on skylines and any normal 5spd boxes )

Dog boxes /straight cut gears are another story

the recomendation on the redline site for a R32-34 skyline states

Nissan 5 spd use 'Lightweight Shockproof', Getrag in R34 use 'Superlight Shockproof'. @ see handbook for Litres

[Duncan]

honestly mate, the best thing you can do for crunchy gears is shift a bit slower. Stop for a fraction in the centre of the gate before selecting the gear and it will pop straight in no crunch

changing to another oil (I used redline for years) can reduce the symptom but increases the issue over time, and the only real fix is a gearbox reco at $1k-$2k.

[noone]

changing to another oil (I used redline for years) can reduce the symptom but increases the issue over time, and the only real fix is a gearbox reco at $1k-$2k.

When you say Redline do you mean Lightweight shockproof or MTL or Heavyweight shock proof or MT90?

Depending on who you ask I have seen all recommended

trying to save myself from a rebuild/replace straight away scenario especially as i am dealing with expensive freight costs either way!!

Its probably unavoidable in the long term but for what $150 in oil I reckon probably worth a try?

Edited January 2, 2013 by noone

[GTSBoy]

Lightweight Shockproof is the usual choice for crunchy synchros in Nissan boxes.

[Carbon 34]

honestly mate, the best thing you can do for crunchy gears is shift a bit slower. Stop for a fraction in the centre of the gate before selecting the gear and it will pop straight in no crunch

changing to another oil (I used redline for years) can reduce the symptom but increases the issue over time, and the only real fix is a gearbox reco at $1k-$2k.

Been using redline for longer then a few sau posters have been alive lol

mtl is 5 spd , getrags use shockproof , call redline tech in australia !!

unless your ham fisting the box then of course shockproof is the go , its notorious for gear clashes on street cars if driven mild

Bit like duncan says that gear set is not the one that fails normally unless thrashed

And no oil will fix a damaged box get it rebuilt or swap out of a wrecked one ?

[dark.sky]

Has no one read what I've said? Take your box to a specialist and get them to fix exactly what is causing the crunching, nothing more, nothing less. Why do a 1-2k gearbox rebuild when you could spend $350 like I did and the box is as good as new... When it starts whining and carrying on, then I'll get a rebuild.

[Duncan]

Has no one read what I've said? Take your box to a specialist and get them to fix exactly what is causing the crunching, nothing more, nothing less. Why do a 1-2k gearbox rebuild when you could spend $350 like I did and the box is as good as new... When it starts whining and carrying on, then I'll get a rebuild.

It's good advice...but if you have to pay to remove and replace the gearbox as well it will cost $500-$1000 to do so, and your car is off the road.

Worn synchros are very common in a 15-20yo gear box, can be reasonably confidently diagnosed based on symptoms, and there is a cheap band-aid (ie specific oils) that can mask it for years before a full build is required.

[Cadmoon]

Mine was crunching quite badly into 2nd and 3rd no matter how slowly I shifted. I chucked some shockproof in and it make it a lot better, still nicks slightly when I shift fast and crunches when I slam it in but overall made it much nicer to drive.

[noone]

Just wish there was someone local who was familiar with these box's

freight is as always the killer for me

Edited January 3, 2013 by noone

[Htowngodzilla]

I had same issue with 4-5  on 6speed r34 gtr changed few gears and syncros on there, problem is I never got to use the car cuz was in a build been over a year and now drink the car it make weird shine  noise some time and on road don't shift nice some gears grinds.  I was advised to use the Supra gearbox oil  but I don't know why the noise  and grind is it the oil or bad build.