GU Nissan Patrol gearbox

Submitted: Thursday, Jan 17, 2019 at 13:22
ThreadID: 137688 Views:2410 Replies:1 FollowUps:9
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G'day all,
I have a 2001 GU 4.2TD Nissan Patrol. It is the model that has trouble with the shaft on the 5th gear at around 120,000 Km, it has now done 120k. The car has been used mainly as a tow vehicle, probably 90% of it's life. I tow in 4th gear. So the question is will the 5th gear shaft be worn by not using 5th gear, or will it be worn regardless.
Thanks in advance, Cheers Pete.
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Reply By: Member Kerry W (WA) - Sunday, Jan 20, 2019 at 10:29

Sunday, Jan 20, 2019 at 10:29
Is it noisy? Should be the first sign of wear. Otherwise turn up the stereo and keep driving!
Kerry W (Qld)
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Follow Up By: Peter B89 - Sunday, Jan 20, 2019 at 11:10

Sunday, Jan 20, 2019 at 11:10
Thanks for the reply, no not noisy. Apparently the spline on the shaft that the 5th gear runs on was not up to scratch on some of the 2000 to 2001 manual gear box's, the spline wears down and 5th gear just lets go.
Cheers Pete.
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Follow Up By: Member Kerry W (WA) - Sunday, Jan 20, 2019 at 19:52

Sunday, Jan 20, 2019 at 19:52
Peter, Have an earlier GQ Patrol with 350k on the clock. 5th is starting to be noisy for different reasons to yours, but like you, I only use 4th - as running 33” tyres. I have considered a rebuild - Plenty of reconditioning kits around for Patrol gearboxes but I’m confident that short of bearing failure, my gearbox will get me home. Don’t know about yours though - do you say they go without warning?
Kerry W (Qld)
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Follow Up By: Peter B89 - Sunday, Jan 20, 2019 at 20:15

Sunday, Jan 20, 2019 at 20:15
Kerry, as I understand it on 2000 to 2001 GU Patrols the shaft that the 5th gear runs on had an undersized spline . It is common for 5th to fail around 120000km. The other 4 gears should still operate. what I was asking is if anyone knew whether the 5th gear shaft would last longer if I was not actually using 5th gear .
Cheers Pete.
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FollowupID: 896482

Follow Up By: Shaker - Sunday, Jan 20, 2019 at 20:42

Sunday, Jan 20, 2019 at 20:42
The spline is too short, a GQ shaft will rectify any issues. Look for discoloured oil as it’s a clear indicator of impending doom!
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Follow Up By: Peter B89 - Sunday, Jan 20, 2019 at 21:02

Sunday, Jan 20, 2019 at 21:02
Yes .. spline is too short, I think Nissan has an upgraded replacement shaft for when it goes. The gear box oil has never been all that clean at any of it's 40,000km changes, although no dreaded reddish tinge, so I guess the 5th gear shaft spins all the time and is going to wear out whether I use 5th gear or not.
Cheers Pete.
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FollowupID: 896486

Follow Up By: RMD - Monday, Jan 21, 2019 at 13:58

Monday, Jan 21, 2019 at 13:58
All the shafts run all the time. What you are asking is, will, NOT directing torque through 5th gear lengthen it's life. Yes. No work no wear.
The shaft splines inside the gear are not full depth and so radially fail because they wear away, causing no drive in 5th. If it is happening the oil will contain metallic particles and lots of fuzz on the drain magnet. Can't see any reason the oil would be significantly changed in colour if good lube is used.
Using a small amount of Nulon G 70 Teflon will lengthen gbox life.
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FollowupID: 896504

Follow Up By: Peter B89 - Monday, Jan 21, 2019 at 16:06

Monday, Jan 21, 2019 at 16:06
Thanks for that information, it has been helpful. I will take note of the Nulon G 70 Teflon.
Cheers Pete.
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FollowupID: 896506

Follow Up By: Guy G - Monday, Jan 21, 2019 at 18:34

Monday, Jan 21, 2019 at 18:34
As stated, no work = less wear. Any abnormal metallic deposits on the drain plug magnet are your best guide and consider using a fully synthetic oil as they are much less prone to oxidation from heat. Also do not be alarmed by any black stained oil which can often be left on the gears after heat treatment and not removed during assembly at the factory. If the oil has been changed a few times this should no longer be a problem.
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Follow Up By: Peter B89 - Tuesday, Jan 22, 2019 at 08:03

Tuesday, Jan 22, 2019 at 08:03
Thanks for the reply, much appreciated.

Cheers Pete.
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FollowupID: 896520

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