TD42 fourth gear synchro problem

Hi all, I have just had the oil in my gearbox changed/replaced and now I have difficulty changing from fifth to fourth gear. I have checked that the oil the mechanic used was the right one, (Penrite 80 90) Pro gear. Also for the first 1000 KlM's it would not go into fourth gear without "snicking" but that seems to have fixed itself. The gearbox was fine before the oil change and I am confused as to why only an oil change can have such an effect on synchro and gear changing. My question is will it rectify itself or am I looking at a re-con gearbox down the road. the gearbox has about 320000 KLM's on it, any advice would be greatly appreciated.

patrols use a GL4 oil, but GL5 is more common . if you read the labels some GL5 oils say they are compatible with GL4 but some people have had issues with there gear boxes when they used them . nissan specifies GL4 . some that have used GL5 say it's ok , but others that have used it have had problems which went away when they went back to a GL4 oil . i have recently changed the gearbox oil on my patrol , i used synthetic nulon w75/85 GL4 . iv'e had the car from new and the gears were always notchy but now is mutch smoother

Without looking I'm sure the oil is a 75/85, slightly lighter than the 80/90 used. My gearbox have done near 500k and I used a 75/85 plus the Nulon smooth gear change additive, which helps. But I know its only a matter of time for this old box...

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Originally Posted by nipagu7

patrols use a GL4 oil, but GL5 is more common . if you read the labels some GL5 oils say they are compatible with GL4 but some people have had issues with there gear boxes when they used them . nissan specifies GL4 . some that have used GL5 say it's ok , but others that have used it have had problems which went away when they went back to a GL4 oil . i have recently changed the gearbox oil on my patrol , i used synthetic nulon w75/85 GL4 . iv'e had the car from new and the gears were always notchy but now is mutch smoother

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Yep, I used a GL5 oil thinking it would be better, & changes were horrible until the car was properly warmed up. When I tried a GL4 oil changes were like it had been when warmed up ….from cold. I believe GL5 does nasty things to Patrol synchros.

Think I might have to look at what the oil I used was. My gearbox is very notchy particularly when under the loud pedal going from 3rd to 4th. Might have to give it a change anyway.

FWIW the GL5 gearbox oil I had been running was Nulon 75w/90 semi synthetic + Nulon G70 PTFE additive.

The GL4 gearbox oil I changed to (with a big improvement) is Penrite Pro Gear 75w 85 full synthetic.

GL4 is what I've been using all the time.
That Nulon additive Mudski told me about made considerable difference ,especially during colder months.

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