R33 Gtr Gearbox Issues

[tommis85]

Hi All,

Thought I'd write up my gearbox issue on here with the hope that someone else has had similar problems....it goes a little something like this:

A couple months ago I had a "new" second hand gearbox put in after having cooked my old one thanks to the wrong oil and amounts having been put in. Now, ever since I've had the new one you'd feel a slight catch when you shift from 2nd to 3rd...as if a gear tooth is getting nicked just before disengagement/engagement. It only happens under sat, 3000rpm and shifts smoothly above that. Too avoid the little crunch I shift up slower in sync with the feedback felt through the gear stick.

I switched to Redline's lightweight oil when I got the box which made things a bit better and also enabled it to shift into 1st while rolling - something it didn't do before that.

I'm thinking it would have something to do with the synchros, maybe heavy duty clutch adjustment/travel, and maybe the oil, or all of the above.

If someone could get back to me on what they think might be going on here.....that would be fantastic!

Cheers,

Tom

[AngryRB]

im no expert, but with my car it was a bit like that when i bought it, when cold it would actually kind of seize up and crunch in second if the shift was too slow

I think its important to not overfill it, i found mine was almost a litre overfull and when i put new oil in, ( just a nulon synthetic) i used some engine oil to thin it down( mobil1 0-40) and played round with it till i got up to about 700ml which got rid of the crunching and notches, alot of people think this is a joke or rediculous but i was told to do that by a gearbox mechanic and so far my box is still going strong.

i think its a combination of having the right amount of oil , right viscosity and how bad the synchro's are and how fast your trying to throw the gear in, maybe on a gtr it needs more revs? im not sure.

Edited March 4, 2012 by SliverS2

[tommis85]

That's an interesting thing you're doing there but luckily I do have my old box to compare to which ran perfectly till I cooked it. No matter what temp, oil or RPM that old box shifted flawlessly so I dare say it might be the synchros.

So how much oil are you running in your GTST? I'm running around the 3.8L mark with a little bit taken out when I put the additive in.

I should also add that she'll not "catch/notch" at the RPM where it does it if you shift fast ;-) But I just want to be able to shift normally.

[Birds]

It's a worn synchro on 3rd gear. These boxes tend to respond best to a 75w90 or 80w90 mineral oil. Redline won't fix the issue, but it can mask it. It will come back worse than before. The only real fix is to pull the box apart and replace the third gear synchro. Problem with second hand boxes...sometimes they last 100,000km, others will get you around the corner before you realise someone passed their problem onto you.

[TM7GTR]

I switched to Redline's lightweight oil when I got the box which made things a bit better and also enabled it to shift into 1st while rolling - something it didn't do before that.

Why on earth would you wanna shift into 1st while rolling 1st gear is for moving off from a stand still

[Hadouken]

My gearbox was kind of like that after the oil was replaced. But after a couple 100 km's the oil must have moved its way around all the synchros and just bedded in.

Box feels great now. Still doesn't like it when it's cold but a couple minutes of driving and there are no problems.

Do you sense a difference between cold and hot? As in after driving a whole it shifts better?

[tommis85]

My gearbox was kind of like that after the oil was replaced. But after a couple 100 km's the oil must have moved its way around all the synchros and just bedded in.

Box feels great now. Still doesn't like it when it's cold but a couple minutes of driving and there are no problems.

Do you sense a difference between cold and hot? As in after driving a whole it shifts better?

I see, may I ask what oil you were using? I'm happy to try a couple different ones to see if they make a difference. I've heard a lot of good but also a bit of bad news about the Redline range etc. And yep, sometimes the box feels like it shifts better at warmer temps but it will still do it's little "catch" thing at around 3000-3500rpm shifts.

[tommis85]

It's a worn synchro on 3rd gear. These boxes tend to respond best to a 75w90 or 80w90 mineral oil. Redline won't fix the issue, but it can mask it. It will come back worse than before. The only real fix is to pull the box apart and replace the third gear synchro. Problem with second hand boxes...sometimes they last 100,000km, others will get you around the corner before you realise someone passed their problem onto you.

Hi Birds,

Yep that's what I'm thinking but was also seeing of it's an oil issue....but then, it ran flawlessly no matter what oil I was running....so yes, must be mechanical as you say. Yep that's what I have heard other's say too - that it simply masks the problem. You use lightweight to mask small problems and heavy weight to mask bigger problems

The sad thing is that I did ask them to inspect the box before hand but they said that "she'll be fine" (because they got it from someone they "trusted") Argh! As for the 75w90, I ran that in my old box and in my GTST box...ran flawlessly

Guess I'll be getting onto my mechanic and seeing what they can do for me. More $$$

[Hadouken]

vmx80 is what i got

[tommis85]

vmx80 is what i got

Ok, I might have a look at what I can do there. Thanks for your input!

[tricstar]

The sad thing is that I did ask them to inspect the box before hand but they said that "she'll be fine" (because they got it from someone they "trusted") Argh! As for the 75w90, I ran that in my old box and in my GTST box...ran flawlessly

The problem there is, if you don't have someone who does these boxes all the time, it can cost as much if not more than the box cost to get it striped and inspected, so it really is a lucky dip, generally cheaper to get the old one rebuilt, depending whats broken..

I had a box inspected thru a reputable workshop (in perth) and with new seals etc cost me $1100 to tell me it was all good (smashed it 3 weeks later anyway),, send them over east now and get broken boxes rebuilt for about $800.

my gearbox guy also says to use 75-80, 75-90, anybrand, but with quite a bit of track work, change regularly

ps this is in a GTR also.

[tricstar]

Why on earth would you wanna shift into 1st while rolling 1st gear is for moving off from a stand still

why not theres plenty of times I do due events, at a tight hair-pin or shiccane, or rolling up to a "give way", don't usually have any issues..

[tommis85]

why not theres plenty of times I do due events, at a tight hair-pin or shiccane, or rolling up to a "give way", don't usually have any issues..

That's right...a box with good synchro's shouldn't have any issues with this. If I do it I usually ease it in gently so the cluister can be bought up to matching speed etc

[tommis85]

Have been doing some reading in some other forums about the Redline Lightweight Shockproof I'm running in the box and as always some people rave on about it and others are quite scared of it!

At the mo I'mn suspecting either the syncho as per previous posts or the oil. Here's a little exert aboit the oil..

"Do yourself a favour and get rid of that Redline light weight. You will find in a GTR that the Motul gear oil will create a nicer shift. The Redline stuff gums up the sychros and makes it hard to change gears.

This was a recommendation from Terry at Award Diff and Gearbox when i had trouble with my gearbox. It wouldnt change nicely so i drained the box, ran some crappy oil for a few hundred klms to wash out the Redline and re filled it with a quality Motul gear oil and the gearbox is much nicer.

The Redline is great for dog boxes but there is better out there for synchro boxes"

What do you reckon? Should I maybe try some Motul oil in the weights recommended by tricstar??

[Birds]

You can try it but I wouldn't expect a change - Redline is the miracle worker / bandaid. If it does make a difference, it's still just masking an issue because these boxes should be able to run on a mineral 75w90 with no issues. You have a worn synchro and there is no real fix for this other than to change it. The good news is that GTR boxes are dirt cheap compared to GTS-T boxes, the bad news is that another second hand one might also be fked. Go get it reconditioned IMO.

Second hand gearboxes - there's usually a reason they came out of the car in the first place...either had issues or someone upgraded it, in which case the box has probably had a hard life. The only good boxes seem to come out of parted cars or people converting to auto.

[AngryRB]

That's an interesting thing you're doing there but luckily I do have my old box to compare to which ran perfectly till I cooked it. No matter what temp, oil or RPM that old box shifted flawlessly so I dare say it might be the synchros.

So how much oil are you running in your GTST? I'm running around the 3.8L mark with a little bit taken out when I put the additive in.

I should also add that she'll not "catch/notch" at the RPM where it does it if you shift fast ;-) But I just want to be able to shift normally.

when i first drained the oil there was about 3Litres in it, when i filled it up it overflowed at about 2.2Litres so i think the extra oil in there was creating drag maybe,is your car completely level when you fill it?

I think if the gearbox is that bad and its looking like a rebuild time, then as a last resort you could try thinning it down alot, for example i must have about 1.2litres of nulon gearbox oil and about 1litres of Mobil Gold 0-40 so overall it must be about 60w.

It took a few hundred km's to really get better too, its not an instant fix. Used to own a Mazda eunos and the synchros were worn out big time, the dealer said to put automatic fluid in which is very thin, it solved the crunching issues, box felt ok too, just saying as a last resort to try before rebuilding.

[tricstar]

when i first drained the oil there was about 3Litres in it, when i filled it up it overflowed at about 2.2Litres so i think the extra oil in there was creating drag maybe,is your car completely level when you fill it?

I think if the gearbox is that bad and its looking like a rebuild time, then as a last resort you could try thinning it down alot, for example i must have about 1.2litres of nulon gearbox oil and about 1litres of Mobil Gold 0-40 so overall it must be about 60w.

It took a few hundred km's to really get better too, its not an instant fix. Used to own a Mazda eunos and the synchros were worn out big time, the dealer said to put automatic fluid in which is very thin, it solved the crunching issues, box felt ok too, just saying as a last resort to try before rebuilding.

So does the GTS box take that much less than the GTR? I thought they were similar just without the Transfer case at the back. cause the GTR box takes 4L, some times when filling the box when its in the car I can't quite get 4L in but when ever its out I always get 4L in...

when I've had sluggish syncros the shockproof has helped,

[tommis85]

Tricstar, yeh the GTS boxes take a fair bit less from memory...but you'd probably want to confirm the exact amount. I'll have to measure how much i got in mine although I dount it would make much of a difference to the synchros.

I had a brief chat to my mechanic about the synchros and exactly when they *notch* and he insists that IF they are broke, they should be notching on fast shifts the most. (mine notches at regular shift speed and is fine on a slow shift and a fast shift etc)

Yeh the lightweight does work wonders! However, I'd much rather a healthy box and run normal good quality gear oil in it rather than something as controvercial (so many "claimed" pro's and con's) as the Redline range.