Thread: Gearbox issues!

Originally Posted by Deaf Ender

Hi Chris078,

I've changed the oil to 15w40 mineral oil and added a tube of Nulon G70 and yes, there is a significant improvement. I am now able to make the change from 2nd to 3rd on the first attempt, 95% of the time and she feels much slicker. I'm now encouraged to keep this gearbox as is, rather than overhauling it just yet, as there is no adverse noise from it. I did however find a couple of small metal chips in the oil, one looked like the corner of a gear tooth about an 1/8th inch square and the other looked like a flake about a 1/4 of an inch long and very thin, similar to a sheath from a grain of oats. I asked a gearbox overhauler in Ballarat about adding Nulon G70 and he reckons its safe to use, but advised against synthetic oil as it "gunks up" some of the more porus components.

Deaf Ender.

Glad you had a good result! From what I have read, the gearbox action may continue to improve over time as the additive works it's way into the roller bearings and other parts.

This gearbox is notorious for keeping on going way past when other gearboxes would simply give up.
Drive as smoothly as possible, change the oil regularly, adding the G70 and you'll probably get a surprising number of km out of it before you have to rebuild it.

Enjoy your smooth(er) shift action!

Originally Posted by Bearman

G'day Deaf Ender,
Just be wary of getting a s/h box and putting it in as it may be worse than yours and it's a pain if you have to pull it out and then reco it or your original box, which is probably the best way to go. And you would have to make sure it has the tapered roller intermediate shaft assembly in it - in other words it would have to come from another ex army Perentie with the same transfer ratio. Range rover boxes are different. A rattling noise without the clutch pushed in is normal for these boxes behind the Isuzu donk. Have you checked that the clutch is disengaging properly first. The symptoms you describe could indicate a dragging clutch. What about 1st and 4th gear, are they hard to engage/disengage. Try gear changing with the engine stopped and then with it running and see if there is any difference. If the clutch is not disengaging properly it will be hard to get into/out of gear when running and relatively easy when stopped. With regards to oil, use the same as the engine (15W/40 diesel engine oil). Apart from the disengaging problems, are there any other noises in the box/transfer? I do a few of these boxes and could do it for you if you want to send it to me but I am pretty flat out at the moment and it would probably be 3-4 weeks before I could do it. Try what I have suggested and get back to me....Brian

Hi Brian,


You've just described the exact symptoms my Perentie has started to show over the past few days. I couldn't get it out of 1st this morning with the engine running. Turned it off and I could easily go through the gears. My clutch peddle started to get really soft a bout 3 days ago and I have to have my foot hard to the floor to change gear. Some have suggested a new slave cylinder. Would this seem right to most people?
Many thanks
Shaun