5th heating up. GU

[gu town]

My 5th gear heats the gearstick and box up fairly quick.

I hadn't changed the gear oil for a long time and on one trip it started to make a very slight whining noise, so I didnt use it until i got home and changed it with the best oil I could get at the time. Penrite semi synthetic 85/90 or something like that. About 20,000 km later it's not making the noise but heats up noticibly after about 10mins in 5th at 100-120kmh.

The car in question is a 2000 gu ute with a td42 on 35's with 350,000km I rarely tow and never in 5th although It has been on 35's for over 100,000km.


I am thinking of changing the oil to a full synthetic and changing every 15-20,000 km to prolong the enivitable busted 5th.

Am I right in doing this? Is there anything else I can do?

[forkcy]

hey mate

i ran royal purple in a gq patrol for a while and i'm about to go back to it as it seems to be the best of all the oils i have run.
but i can't help you with the 5th gear problem.

Luke

[GUtripper]

Iirc most people reported dirty burnt oil before 5th let go.....
It may be the heat is a warning sign.

Nissan have got the double sided flange fifth gear and longer shaft as a retrofit kit for the earlier gearboxes.... Dunno cost though.

I towed all the time in my 2005 gu... Never a sign of issues.

[love ke70]

Not sure how similar GQ and GU boxes are, but mine has run so hot you cant touch the steel of the shifter, floor pan or PTO control box cause it will burn you, for hours on end, and not had an issue.
my exhaust dumps behind the gearbox crossmember, so that may not help either.
20K on gear oil on 35s is due a change anyway, so change it and see if the problem goes away...

[MikeH]

I race a GQ and found the heat coming through the floor immense, the whole transmission tunnel is so hot water steams instantly.
I changed to redline synthetic gear oil and put a temp gauge in the PTO cover at the same time, the gearbox gets to just over 100 degrees but it feels noticeably cooler in the cab, I do wonder how hot it was getting. It myst have been up around 140 degrees before.

[love ke70]

isnt the redline bad for synchro boxes?

[MikeH]

It's fine if you buy the right one there are a couple of different types. You need a GL-4 oil in a patrol box, not a GL-5.
AFAIK its the sulphur compounds in the GL-5 oils which stuff the brass synchros. It takes a while to react as well, so people don't realise its the oil thats buggering their gearbox.
A LOT of auto-parts shops will happily sell you the wrong oil claiming that the GL-5 is a higher spec equivalent, it isn't.

Will cost you about $300 for redline for the box and transfer.

[turps]

My GQ used to get the gear stick hot enough that you coulndt hold a hand on it. Never seemed to cause any issues.

[gu town]

thanks fellas.

oil choice is not huge here in katherine but ill chase up a gl-4 oil and change it.

[love ke70]

truck places should have a suitable castrol product which I have found to work well, something like vmx 80

[gu town]

ended up with a 75-85 penrite fully synthetic. did gearbox and transfer.

First 100km no heat whatsoever.

The next 500km I think there was more heat in 4th but less heat overall.

This was loaded with a tinnie on the roof on 35's @ 110-120km/h

[love ke70]

Just see how your shift quality goes, I moved away from penrite oils after I thought my box was shagged, changed to castrol and the shift quality was perfect again. YMMV.

Cheers, Andy

[gu town]

shifting is perfect for the moment.

cheers all.

[GUtripper]

I used nothing but Penrite in mine, despite everyone saying how Castrol VMX was the ONLY oil to use.

Others who drove it said it had the best feeling shift of any GU /GQ they'd ever driven.

YMMV