Rb25Det Gearbox Fluid For Motorsport And Replacement Intervals

[Littlehorn]

So i broke my last gearbox (running Castrol Syntrax 75w90) and replacement parts seem to no longer be produced for what i needed. So i ended up buying a second hand reconditioned box for an arm and a leg.

After doing a bit of reading I decided to go with Redline shock proof heavy.

I have run this for the last few track days it would be hopeless for road driving as it seems to take quite a while to warm up so shifting is very careful for the first 15 mins or so.

It seems to run alright but i still get a bit of grating going into 4th and 5th when driving hard on race track (not silly quick shifting just careful shifting but at 6500-7000 rpm)

So what do other people use in dedicated race cars?

My second question is how often do you replace the fluid in your gearbox? It seems most other fluids are every 2-3 track days.

[Victory]

I run Shockproof Heavy in my diffs and Shockproof Light in my gearboxes.

I would suggest that Shockproof Heavy would be too thick for a R33 gearbox.

[Littlehorn]

Had been thinking about trying the lightweight might give that a try next.

[sweefu]

I'm a bit unsure about the lightweight shockproof gear oil

Can anyone confirm if it's a GL4 or GL5 specification lube?

I've been told GL5 oils are bad for RB25 (or similar) gearboxes because GL5 additives are bad for the brass synchro's, it can cause the teeth to wear prematurely

I don't know how much truth there is in this, but I've switched from the LWSP to MT-90 (GL4) to see if there is any difference.

I ran LWSP in two of my previous gearboxes, my most recent gearbox was an RB25 and the dog teeth/synchro teeth wore before anything else, that box had LWSP in it (previous owner and I both used LWSP in it)

Anyway, can anyone else shed some light on this?

[Dale FZ1]

GL4 specification oils are the go.

GL5 gives nicer shifts for road use only, and also result in problems when shafts/gears are spinning faster and the shifts tend to be hurried.

After that it becomes a bit of trial/error to find what brand oil you best like in your car.

[dan.1337]

I'm running Royal Purple Gearmax 75W-90 (Shockproof light wasn't available from my supplier when I needed to change) in a nearly exclusively track car.

Has been pretty good on cold mornings and at the track. Have noticed a slight crunch from 4-5 once in a while, but that could be me not depressing the clutch fully too.

Will probably try Shockproof light next time.

[Russman]

I'm using Redline Shockproof lightweight in mine. I have blown a box before but that's unlikely to be related to oil due to how they failed. Many years of track days and no excessive wear on components. I'll stick with it.

[ssxRicho]

I've killed 3 boxes now. The last one was re-conditioned and did 3yrs of track work.

Bottom line, the synchro clips fall off most of the gears over time. Then the teeth start to catch and you get that crunching sound. Then eventually the fork or the synchro blasts itself to pieces.

I replace mine every 7-10 track days depending on heat.

[34GeeTeeTee]

I've killed 3 boxes now. The last one was re-conditioned and did 3yrs of track work.

Bottom line, the synchro clips fall off most of the gears over time. Then the teeth start to catch and you get that crunching sound. Then eventually the fork or the synchro blasts itself to pieces.

I replace mine every 7-10 track days depending on heat.

Gearbox or oil?

I was running redline and it was getting noisy and crunchy, switched to Nulon and it went quiet..... But 2 track days later that box finally retired 3rd gear.....

New box is running Royal Purple and so far so good, one thing i noticed is with the new box its not pumping oil out the breather like the last one was which is a bonus!

[Littlehorn]

I will be giving lightweight a go. Interesting 7-10 track days, i have only done 4 on the shockproof heavy and it seems to be starting to crunch a little.

I had the same thing with my last gearbox running Castrol Syntrax the synchro clips came off then it stopped holding in gear so off throttle it would just pop out. The fork was fine but i had done damage to 3rd gear and a few other parts, some of which are no longer available so the only way to fix would be to get the parts machined.

Cheers for the advice.

[iruvyouskyrine]

Have heard so many mixed reports about Redline Shockproof lightweight. Its a 50/50 split of people saying it destroys synchros and the other half act as if it is a gift from god.

sweefu asked a good question, does anyone have any info about it rating as a GL4/GL5 oil?

[PN-Mad]

Double post

[PN-Mad]

Edit, I think it's GL5, but the specs on the site don't actually say.

I think one of the issues is that it's super sticky. I changed a box out, put some conventional coloured oil back in it.

Serviced that and the bloody stuff came out blue as. I had the tranny serviced with some synchros changed, and fresh bearings. The recommendation for oils for me was the royal purple synchro max ( RPs version on ATF for manual boxes), simple dextron III ATF, or shockproof.

I went with ATF, this was for a S14 box.

[iruvyouskyrine]

I will be having the same problem. I have already used the smurfs blood in the box and was told i would have trouble flushing it out. I'm going to go out on a limb and guess that mixing oild would be bad, so i may just stick to using the lightweight shockproof.

[PN-Mad]

If you can get the car up in the air easy, you could try just buying some cheap as fk 20-50w motor oil, drop the redline, fill it up and run it through the gears to flush it round. Try to get some heat into it using the rear brakes. Repeat, then fill with your preferred oil. $15 for some dirt cheap mineral oil. You just wouldn't want to leave it in the box for permanent use.

[sweefu]

I've read on forums that the LWSP has GL-5 additives but as above, I can't confirm.

I used LWSP previously but switched to Redline MT90 (GL-4), I've drained the box and refilled it and it looks like a mix of LWSP and MT90

Next change I'll probably switch back to something simple like Castrol VMX 80 and see how much better/worse the box seems with a cheap oil.

I'm unconvinced the Redline oils make enough difference to justify the cost at this stage, although I might change my tune after using a cheap oil again.

[CEF33Y]

I use castrol vmx 80 with my current rb25 gearbox. Car is used as a daily, and also drifting.

I change it at a 12 month service, which would be 3-6 track days and about 20 thousand km.

Box was second hand when I bought it, almost 3 years ago.

Previous cefiro had a stuffed second gear syncro, i.e wouldnt go it gear over 3500 rpm, changed to redline lightweight shockproof and it near on fixed my issue, couldnt notice the syncro issue driving normally.

On the flip side, had a mate (still rb25 gearbox) with a notchy second gear syncro, he changed to redline LWSP and it made the issue worse.

So I dunno, I run the cheap stuff, and if (when) my box has issues i'll try a redline oil again.

[scotty nm35]

Don't bother trying the lightweight smurfs blood, it seems to melt into sludge under the syncro rings requiring a teardown to get rid of it. Plain light gearbox oil for me.

[boostn0199]

My experiences I have been running redline lightweight when the car was a daily and still used it when became track car havent had a problem with it for years. I only change the oil when I blow the box lol which only happened last month after 7 years.