The technician I spoke with today does a mini refresh, like I am doing, at 20 hours run time to replace the forward gear and often the crown wheel. He said that at 20 hours, there are sometimes extensive damage to the forward gear, sometimes minor.
@davidf, wow, I am surprised there is that much wear in 20 hours. 😳
20 hours is not great!! Although I have seen a forward gear starting to wear after only a few hours. I guess once the metal is in the oil it probably speeds up the wear process, plus once the case hardening has gone it will rapidly wear anyway. Super finishing all the gears (or at least all the loaded gears) should help, along with using good oil and regular oil changes. An in-line filter is also not a bad idea. Again it’s definitely not a fix, there’s only so much you can do with the products available.
Fortunately I did not see much damage elsewhere. I will look into super finishing -- thank you for the tip.
I found a tiny bit of steel on the bottom outlet fitting magnet, and similar amount on the level plug magnet.
I plan to remove the GDU every 20 hours to inspect and replace pitted gears and bearings as needed. It is not difficult once you have done the procedure once, and I did not even need to remove the oil pump or breather plate to maneuver it out. I ended up disassembling the GDU by myself which is also not hard, but a little messy and tedious to clean everything well.
This time I will only replace the forward gear and the paper gasket, and five drive pegs. Drive pegs and gaskets are pretty inexpensive; not so for the other parts.
@charleyhradicalsportscarregistry-com ... refer my earlier post with video... I've got what looks to be the start of that wear pattern on almost all 24 teeth of the forward drive gear after only 6 hours... mine will definitely be worse than David's at 20 hours!
... I still suspect (strongly) that the difference in what people are experiencing is because some cooling pumps prime themselves after a re-fill, and some don't.
Hi All,
Just a bit more of an update on this topic.. I feel like I'm starting to understand what's required here.
I now own three of these GDU's (one in the older RSX I have, a brand new one in the XX delivered earlier this year... and the 'spare' I purchased before deciding to buy a new car)
What triggers this post is something I found in the newest XXR Owners Manual... seems Radical have been reading our posts.. or maybe (finally) realising there are some GDU's that never 'self-prime'
They are also fitting a 'rock catcher' on the GDU drain fitting that filters the oil to the GDU pump and oil cooler circuit...
My new XX delivered to Australia in March doesn't have this 'Earls Filter' fitted, so suspect it's on all new XXR's?
As written here on a previous post I now check my GDU is primed before each race weekend - takes about 5 minutes... it's my theory that they can lose their prime if they sit in the garage too long between events... and I have proven that by finding no prime until I use the syringe (I use that instead of a vacuum pump described by someone else on this thread). Since taking this approach my forward drive gear wear has noticeably slowed down (checked using a video borescope after every second event). I'm using Neo-Synth RHD oil.
I also now use a RaceTech temp strip on the outside of my GDU case to try and get a handle on GDU temps.
I've only just started this and tried a temp strip with a range of 71C - 110C. We had 5 races in total, but the first 4 heats were only over 5 laps (plus 2 lap warm-up) of a 2.5km long circuit - the temp strips showed a max temp of 93C after each of those. The final race was held over 10 laps (plus 2 again) but this time the temp strips showed a temp of over 110C ... probably a bit hotter than I expected. These strips obviously measure the gear case temp and I expect the oil might be at least 10-15C hotter than that.. although not sure.
For the next event I have installed a new strip with a temp range of 116C - 154C and I'm hoping it doesn't register too far up on that!
I'd be keen to hear if anyone has similar experience or data... or even an opinion on how hot we should expect these to run.
The oil removed after the last event still looks fine, and there was very little metal debris on the Magnom magnet filter I've installed on the oil feed line to the pump.
In the meantime, I've prepared the spare GDU for when it's needed... micro-polished the gearsets and vapour blasted the GDU casings to tidy them up
vs brand new...
@rjbender That’s really interesting 👍 It sounds like Radical have ditched the oil cooler and replaced it with a heat exchanger for the XXR? Not sure about the 1st gear at idle part of the manual, I’d have thought the pump would be turning too slowly. I normally use a higher gear for that job.
Not a huge fan of the “rock catcher” oil filter. They are fitted to the gearbox oil system on SR8’s. Problem with them is the filter is flat, so it could potentially block completely, which I have seen a few times on SR8’s, and causes more harm than good. Although the blockage is normally caused by sealant, so less likely to happen on a gdu.
Your spare gdu looks absolutely awesome, great job on that. I’d like to think the polished gears will make a difference to the wear, it certainly has on a customer car of mine. I particularly like the threaded holes on some of the billet parts on the casing, so you can remove them easily, very cool 👌
@alex-heavens -G'day Alex, You noticed the threaded holes - Well spotted!... yes, will help get it apart without causing damage to the mating faces.
I agree with your comment about first gear at idle normally being to slow... but I wonder if that's because all of our pumps lose prime to some extent and that requires the pump to be driven faster to get enough suction to re-establish full prime. If they have just (fully) primed the pump with a syringe I think 1st gear might work? My concern is always that the pumps lose prime.... and on my RSX that definitely happens over a month or more between events.
Yep - also agree about the rock catcher... also interesting to see that they have machined the hex head of the Earls filter to get it to clear the chassis rail.... its a tight spot.
I've put a MagNom filter in my pump suction line - best upgrade so far to the GDU. Easy to clean and will definitely catch any steel particles before they get to the pump
