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The Big Fist

Gearbox not selecting 5th/6th at high rpm

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Hi guys,

I've got a problem in my s15 that has slowly been developing over the last few track days I've done.

Basically it has been struggling to select 5th, almost like the gear isnt there.

Once in it peforms no problem, It's just hard to select.

Then by my second session I can't select it all.

I am changing between 6500 and 7000rpm.

Once I got back to the pits I still couldn't select the gear or when stationary.

 

Once cooled down and I head off home I can select it and drive no problem.

 

Could it be heat related ? The car has the stock turbo about 190rwkw and I believe I am mechanically sympathetic and not smashing gears.

 

Any ideas ?

 

Cheers

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Similar symtoms to my other post in the next gearbox thread. Mine died all of a sudden without being able to select 5th, 6th or reverse. Prior to that, when selecting 6th gear, the reverse bridge would engage and it ins't meant to.

 

Don't bother with this box. Save for another box and use Penrite Pro Gear 75W-85 wiith a grippy organic clutch.

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Why are you changing gears at 6500-7000rpm for with that amount of power and turbo? Power would start to drop off by about 6200, so you'd be better off changing then.

 

Change at peak power, don't rev it out because you can.

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Thanks guys,

So is it a symptom of the box dying ?

Can I prolong it by using a different oil ?

 

Fine to say change at 6200rpm but with no shift light and speeds on the track I tend to miss when to shift I am sorry !

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Just a quick glance at the tacho will do. Or I've gotten used to the sound of my car and can remember when to change.

 

Do you know what oil is in it now? I use Motul 75W90, can't fault it. Box always feels smooth even after a lot of abuse at the track.

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using average oil in your gearbox will have some effect on shifting, specially at track days when they get really hot, as you mentioned when it cools down you can select gears again.

 

service the gearbox with good oil. track rated / high temp rated stuff.

 

if its a stock clutch get a heavy duty or similar that can handle a bit more abuse. dont get an overkill clutch setup, thats how you blow up boxes, but thats also when you have a lot of power.

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Thanks guys, I would say that it is stock oil as I haven't touched it and the guy who had it before me didn't do any racing.

The clutch is also stock. Would you guys recommend the Motul 75W90 over the Redline ?

 

My other problem is smoking brakes, I cooked the fronts. I might as well ask in this thread as well. Would upgrading the pads only be wise or should I get a new set of rotors to go with them ? Car does very minimal street driving. QF1ARM and new rotors a decent upgrade ?

 

Many thanks !!

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I managed to cook my qfms on the street, with new rotors and motul dot 5.1, so I'd suggest something else. Not sure why they get such raving reviews...

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I wouldn't trust the shock proof shit. Heard too many bad stories. Motul, Penrite, even some people like Castrol gear oil.

 

As for a brake setup, stock callipers with new/slotted rotors, braided brake lines, brake master stopper and Ferodo (DS?)2500 pads. Those Ferodos are a great street/track pad.

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You will also get longer life out of a suitable quality pad set, there are better options out there than the QFMs. I changed from the QFMs to Project Mu Club Racers due to the high wear rates on the QFMs. Endless are also worth considering.

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Thanks guys, I would say that it is stock oil as I haven't touched it and the guy who had it before me didn't do any racing.

The clutch is also stock. Would you guys recommend the Motul 75W90 over the Redline ?

 

My other problem is smoking brakes, I cooked the fronts. I might as well ask in this thread as well. Would upgrading the pads only be wise or should I get a new set of rotors to go with them ? Car does very minimal street driving. QF1ARM and new rotors a decent upgrade ?

 

Many thanks !!

 

 

Penrite Progear 75W-85 for the box, I used to use redline lightweight shockproof and didn't have any problems. A little notchy on cold days until it was warm then I couldn't fault it. I think Penrite is just as good as Motul and Castrol though. A reputable tuner and other performance places I know love Penrite.

 

As for brakes, get slotted only rotors which may go burn through pads more but are effective on track. Avoid drilled as they crack and warp easier than slotted. If you can, try to get a Skyline GT-T conversion done or better yet GTR Brembo or any other Brembo kit for the right price. It's definitely cheaper to get the R34 GT-T conversion done, even GTS would help from the R33. There is a larger rotor area which will aid with calipers gripping the rotors and the rear rotors are usually thicker for heat dissipation. Don't try to get a larger rotor with the same sized calipers, it's useless in the sense the caliper can over cover a certain area of the rotor, not the entire side of the rotor!

 

EBC and Ferodo brakes are always great but more expensive than A1RM. But usually, you get what you pay for.

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I track my s15. Qfm are a waste of money. Ferrodo 2500s work well n I'm currently trying pmu hc+.. Standard rotors are fine. Once they wear out upgrade to pmu or if your baller something different. I find dba rotors worse than standard Nissan rotors. Run brake ducting to your rotor centres is most important. As for gear oil. Ya box sounds like it hasn't been looked after, run light weight shockproof. Been running it forever and can make a crappy box feel great. I've never heard horror stories of redline uses.

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Hey to The Big Fist,

 

I developed the same problem at Wanneroo raceway on my last track day, I'm hoping some fresh gearbox oil and a nismo coppermix clutch do the trick in fixing the issue (currently I'm running a stock clutch with the same power as you with old gbox & clutch fluid).

 

In regards to your brake dilemma, I was running R33 GTS-T front brakes with dba 4000s + PMU club racers and stock S15 rear brakes with dba 4000s + QFM a1rs at the same track day which performed amazingly till towards the end of the day when the QFMs backing plate started to melt, pad material turned white and the rear rotors were scorched... I'm now in the process of installing skyline 2 pots on the rear with the PMU club racers which should be much better to cope with the heat since they are larger and also vented unlike the S15's small solid rear rotors.

 

Also what do you think of the MCA reds on the track?

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Hey to The Big Fist,

 

I developed the same problem at Wanneroo raceway on my last track day, I'm hoping some fresh gearbox oil and a nismo coppermix clutch do the trick in fixing the issue (currently I'm running a stock clutch with the same power as you with old gbox & clutch fluid).

 

In regards to your brake dilemma, I was running R33 GTS-T front brakes with dba 4000s + PMU club racers and stock S15 rear brakes with dba 4000s + QFM a1rs at the same track day which performed amazingly till towards the end of the day when the QFMs backing plate started to melt, pad material turned white and the rear rotors were scorched... I'm now in the process of installing skyline 2 pots on the rear with the PMU club racers which should be much better to cope with the heat since they are larger and also vented unlike the S15's small solid rear rotors.

 

Also what do you think of the MCA reds on the track?

what other pads have you tried? I run stock s15 rears and they work a treat for me with ds 2500s. interested about the club racers as ive heard some really positive reviews on them. I have a mate with an s2k and he had this problem with 6 after his last day. apparently its common on his car and you have to jam it in and out of gear when cold because a small burr is developed and wont alow it to go in to 6th. he did that and through some redline at it and now its a lot better!

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What other pads have I tried? That was my first track orientated brake setup, before that my car had bendix ultimates which the previous owner installed so I can't comment on the ds 2500s. As for the club racers I love them, once they wear out i'll be replacing them with the same thing. The main race track we have here in W.A is really hard on brakes, so I always knew I was taking a chance with the s15 rears, I just couldn't be bothered at the time messing around with the skyline drum handbrakes and bmc.. Lesson learnt, I should of done it properly the first time.

 

I'll be replacing my fluid with redlines lightweight shockproof for my next track event which is next Friday, i'll update this thread afterwards in regards to if it resolved my gearbox issues.

Edited by GENES15

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martini ls 75w90 good oil and not expensive.

As for how high your revving it shouldn't really matter with circuit racing as some times you need to hold a certain gear a little bit longer to maintain a speed desired

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Thanks for all the information guys. It is a great help. I've got another track day (well night) next thursday so will change the oil and see how I get on.

I impulse bought some qfm's before the bad reviews started and was too embarassed to admit it ! So now I am stuck with whether to whack them on (fronts only) or run stock brakes for the night and sell these off.

 

Genes15, I still haven't fitted the reds, pretty embarassing but they've been sitting here boxed up since May !

 

Cheers,

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They will be better than stock. Just use em n then you'll appreciate a better quality pad :)

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BIt of an update !

Dropped the gearbox oil which looked a tad milky and rather gold speckly. The specs were not magnetic.

Replaced with Motul 300 75w90race or something like that. Fitted the QFM's and hit the track tonight.

Well......hit the track, first lap 5th gear, wouldn't go in. Much swearing. 2 more laps and it would not go in, all other gears no problem.

Driving home on the freeway, normal driving even midrange rpm it will shift fine. I think the synchros must be shot ?

Nice waste of the oil and a track entry.

So seen as the car is 199,900km old I think I might just rebuild the box for now as the car is only pushing maybe 195-200rwkw according to virtual dyno.

Has anyone got any good links for parts ?

 

Thanks,

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Did you try redline shockproof? Going to a track day with previous problems isn't really good. Track days will bring out all your weaknesses in your vehicle.

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I thought the issue was heat related as the previous track day I was running for longer periods. The one last night was limited to 4 or 5 laps per group.

The other gears are all fine so I wouldn't have thought the oil would have been the culprit ?

 

Cheers,

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doubt it's the synchro it never is they don't wear. it will either be the clutch rings or dogs on the baulk ring, the dogs on 5th gear or the hub ring for 5th and reverse not an expensive fix.

Edited by - Donny -

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It would not be directly the oil. Just thought redline may make it work somewhat. But as donny said get it looked at n fixed.

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doubt it's the synchro it never is they don't wear. it will either be the clutch rings or dogs on the baulk ring, the dogs on 5th gear or the hub ring for 5th and reverse not an expensive fix.

 

Thanks Donny, It did say in the service book that if it was not selecting gears to first look at oil and second the baulk ring. I just thought the synchros as the old oil had a lot of gold flecks in it and reverse can be hard to select / want to pop out sometimes.

If anyone's interested I got some pricing from Australian Transmission Components.

$330+ for bearing kit

Approx $90+ per synchro.

 

Cheers,

 

Stuss15, I got a little concerned with the redline as some people had some negative things to say whereas the motul seemed to get good reviews.

I really didn't like the thick consistency of it and in a mates 32 gtr he's always blowing it out the breather, but that's probably because of some other issue !

 

Cheers,

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Myself and mates use it n makes shitty boxes usually feel a lot better. A lot of tyre kickers comment on it without using it or blame the oil for a simply old worn box. Thanks for the info on those parts too! Always good to know.

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Big fist if you want better pricing we stock most of genuine Nissan gearbox parts. by the way the baulk rings are the gold things that you think are called synchronizer. The synchro are actually the splined shift that the hub ring slides on to synchronize the baulk ring with the dog gears on the gear your trying to select. everybody thinks the synchro are the baulk rings

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Big fist if you want better pricing we stock most of genuine Nissan gearbox parts. by the way the baulk rings are the gold things that you think are called synchronizer. The synchro are actually the splined shift that the hub ring slides on to synchronize the baulk ring with the dog gears on the gear your trying to select. everybody thinks the synchro are the baulk rings

 

Thanks Donny,

Hopefully get it out next week and pull it apart. Thanks for the explanation, I found some pics which show it pretty well with the baulk ring and the 2 synchro cones. Found a nice picture showing the teeth on the baulk ring being worn and also on the outer part of the synchro cone.

Sounds like a bit of a paint to pull the box out to be honest !

 

Cheers,

Peter

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Just a quick update.

Box is all undone and ready to be pulled out tomorrow !

While it's out, is it worth changing the clutch, pretty sure it is the stock unit.

Are the extreme clutches worth getting as I can get one for next to nothing.

 

Lastly, solid gearbox mount. Is it worth putting one in or just get the Nismo one ?

 

Not sure if I mentioned in the previous posts that when I said it won't go into 5th, it doesnt crunch, it literally just doesnt go in like the shifter is hitting a stop.

Some internerds are saying it's clutch drag or mounts and that if it was synchros it would crunch ?

 

Thanks,

Peter

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Yeah its a good idea to change clutch while it's all out but go npc not extreme.

and dude if you haven't done boxes before I don't recommend trying on a 6 speed first they can be a real pain and you generally need a lot of custom tools pulleys and dollies to do them.

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