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Cold Shifting

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Recently put a rebuilt S14 5 speed into my S15 and filled it with Redline MT-90 75W90 full synth, however when the oil is cold it's quite hard to shift from 1st into 2nd. It feels quite notchy and will occasionally grind unless I shift it really slowly (shift into neutral gate, then into 2nd). All other gears feel pretty good and 1st to 2nd feels smooth once the oil has warmed up. There's no issue shifting from 3rd to 2nd when cold. I'm pretty sure the clutch is disengaging correctly. Is this normal for these gearboxes?

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Redline oil made my gearbox noisy as f**k and difficult to shift.

 

Nulon gearbox oil + PTFE additive and the noise is gone and feels 1000x better on shifting. can still be tricky using reverse occasionally but hard shifting is no longer an issue.

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Redline works really well with dog boxes, drain the oil and replace it with mxv80.

If it's still notchy then call the box shop that rebuilt it because no sr boxes shift very smooth all the time.

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Make sure your master and slave are properly bled, and if you haven't already done so change the fluid and make sure you get all of the old fluid out.

I was having similar issues and my slave was seeping so I had to replace anyway. I bled mine from under the car but I found the only way to get all the air out of the master was to jack the front of the car slightly and a quick bleed from the master nipple as well.

I was told never do this. I still don't know why? Was the one thing that made the biggest difference to my overall shift quality but particularly between 1st and 2nd.

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I have the exact same problem with MT90, going to dump it and replace it with a lighter weight oil. Hard to shift to 2nd when cold, take a while to warm up and is OK after that

 

Never had the issue until MT90 went in

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Which oil did you have in it previously junkie? Was thinking I might give the OEM stuff a go...

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Shift issues can be caused by so many things, but I agree with the MT90 or Redline in general creating / making issues worse. Yet to meet someone (in person) that has actually used it and was satisfied. Motul gear 300 soooooo much better.

Even Nulon with the n70 additive is much better than Redline. I'm sure Redline is good for something, just not sure what.

Just make sure you're dealing with the root cause instead of just trying to compensate for it. In my case: slave>fluid>bleed from the lower nipple>bleed from master. Fixed.

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I'm guessing it was OEM or similar, it was the first box change I did myself. Did have the clutch fluid replaced and bled properly too, didn't make any improvement. I would imagine issues with clutch would be constant and wouldn't go away once the box is warm

 

Going to go try Castrol VMX I think, probably closest to OEM

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^^Yeah that's what I (and the two workshops I went to) thought as well, must be an issue with the gearbox or wrong fluid. Wasn't the clutch itself as it was new and bled as per the workshop manual.

Different gearbox oil did make slight differences but never fixed the issue, Motul being the best, Redline being the worst and Nulon with n70 being very close to Motul.

When cold was a notchy, crunchy bitch particularly between 1st and 2nd and sometimes trying to get reverse, which improved dramatically when warm or if the ambient temp was high.

Bleeding the master (and changing slave) was a revelation in gearbox operation, but only after jacking the front of the car for a while to allow any air to flow to that end of the master.

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I have redline gear oil and have very hard shifts when box is cold. Warm/hot shifts are so-so, still not amazing. I have probably bled the slave 5 or more times. I think the redline stuff is such high viscosity that it might only be useful on track or very high temp situations.

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It's the Redline LWSP oil that causes problems, the MT-90 is OK, I think.

 

I was using LWSP for a few years and read about people having problems, I've had lots of gearbox problems but I can't be sure if they are related or not.

 

The most suspicious case was an RB25 box, only ran on LWSP for as long as I've known (old owner plus me) and the brass synchros wore out before anything else at all. Whole box was neat, synchros were ruined.

 

I then switched to MT90 and it's been OK, the last lot I had in my current box (Z32) came out a dark grey colour, it seemed like it had been burnt. It had been in the car for a tarmac rally and 3 drift events though, plus about 20,000km or so of street driving - far too long to leave it in there.

 

Having said that, I'm tempted to try Castrol again, I agree with someone saying the VMX or would be close to OEM or similar to it.

 

It's a pity there's no objective arguments out there, or conclusive testing... For me at least, I stay away from GL-5 spec. oils as Nissan use/recommend a GL-4 from factory. That knocks out a lot of the modern oils from Supercheap Auto etc like the synthetic Nulon and Penrite (although I am a big fan of Nulon, I haven't tried the 'smooth shift' synthetic gear oil because it is GL-5, as it their gearbox additive).

 

Keen to hear more thoughts on this!

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fark... can't remember if I'm running lightweight shockproof or MT90. No real change in how the box feels though and 1st syncro is still as rubbish as when I bought it.

 

Then again, an old, worn out box will usually feel the same 3 years on. Not that I'd know from experience...

 

Anyway, you might be on to something there sweefu...

 

Wikipedia reckons this

 

GL-5 is not necessarily backward-compatible in synchro-mesh transmissions which are designed for a GL-4 oil: GL-5 has a lower coefficient of friction due to the higher concentration of EP additives over GL-4, and thus synchros can not engage as effectively. Also, transmissions which explicitly call for GL-4 oil may have been designed around this lower concentration of EP additives and thus may contain yellow metal parts which GL-5 will corrode.

 

Reading some other sites, seems that the GL-5 additives will prolong life of gears and shafts but will wear out synchros.

Edited by Skepticism

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I am using Nulon 75W-80 smooth shift GL4 premium mineral with half a tube of the g70 goop. Cold is workable but could still be better, but quickly warms up and is very smooth (although can crunch 1st to 2nd and 2nd to 3rd if you shift too fast or too slow).

 

Would try the 75W-85 synthetic GL4 next time.

 

If somebody made a 65W-90 GL4 oil I recon that would be the perfect oil. Thin enough when cold not to baulk, and thick enough when hot not to crunch.

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You can't throw a blanket over redline oil and say it makes things worse. What type of redline oil are you talking about? I personally tryed mt-90 after having redline shockproof in it n it made my box feel knotchy. Went back to redline shock proof and its a smooth as silk.

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If your in brissi I have some shock proof you can use.

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Ran Redline LWSP in my rex for 5 years and it was great, now running the same in my stock 6 speed S15 box for the last 2 years and is fine.

Being notchy on cold is pretty normal with the blue goop but when warmed up it's fine.

 

Just my 2 cents

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all these guys with gears shifting notchy or crunchy not as good as youd like?

i have a z32 in my 180sx wouldn't shift into 1st directly at a stop. had to go into other gear then back into 1st. also 5th on the freeway was crunching 3-4times out of ten times. then i was told about mbl8 an aussie sold product that i am now a distributor for. my gearbox feels very much like new. also fixed my mates gq patrol box and made his missus xr5 shift much smoother. oil doesnt matter just use this stuff pm me if your keen its cheap and works 100%. been on here for years so not a scammer just found something that works want to pass it along. cheers

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