Mav Gearbox Problem

[rookie]

Hello everyone and thanks for letting me join your forum.

I've got an "L" reg Mav which has developed a G/Box fault.
It's always had a noise (whine) from the gearbox since I bought it 6 months ago. However, yesterday i was towing a horse box (30 miles), got it home no probs and reversed it up my drive (steep slope).

When I went out int e cat later, it drove fine for about 5 miles but then I found if I tries to select 2nd gear it was making a terrible grating sound and would not go in unless I stopped the car.

This morning I have found that I also cannot select reverse, no grating on reverse it just physically will not go in.

Ran through the usual things like selecting 4L, deselecting and reversing to disengage. Selecting gears whilst in diff neutral, pumping the clutch etc, but to no avail.

G/Box oil appears to be up to level.If I select 2nd from stationary, it will go into gear but with a clunk and the car seems to jump forward a very slight amount, when i then try to drive away it judders slightly but does pull away (though it just doesn't feel like it should).

Sorry for the long post but thought it best to supply as much info as I had on the problem.

Thanks in advance guys.

 

[96terrano]

hello and welcome:thumb2

well, the noise is bearings as mine used to do that, also sounds like damaged synchro rings if it wont go in when moving so the Gearbox defiantly needs replaced i'd say

temporally, have you tried to double de-clutch to get it in to gear? that might work

 

[Fez_uk]

can you confirm are you running it in 2 wheel drive only?

 

[rookie]

Hi

Yes, I was trying it in 2wd only, though I did try it in the other options as well.

I have ow started stripping it down. Drained oil, two lumps of steel attached to sump plug about the size of a currant and a fair bit of brass shavings in the oil.

Have been offered a second hand one with a guarantee that it is ok for £300. In the meantime I intend to strip this one and see if there is anything inside which is repairable/replaceable. Is that possible ?

cheers guys

 

[96terrano]

very easy to strip down, here's one i did, they are long buggers :lol


http://www.nissan4x4ownersclub.com/forum/showthread.php?t=15210&highlight=gearbox+autopsy

 

[rookie]

Brill photo's mate, that helps a lot.
Now for the 10 million $ question, are the interior parts available anywhere ?

I have seen the overhaul kits on line which include bearings and gasket, for £98, however, I don't know if that covers all of the bearings in the box. Also, as I have already seen evidence of Brass in the oil, would those gears be available from somewhere ?

I don't mind stripping it down if there is some point to it, but if the parts are not available then there seems little point. However, having said that, if companies are advertising these boxes as reconditioned, then you would have to assume that all parts are available.

Afraid I wouldn't know where to start looking for those parts so I am hoping someone could point me in the right direction :lol

I am a bit loathe to get the second hand unit for £300, even though the guy is guaranteeing it, it's a lot of work if it is no good just to get it off again and then I am back to square one because as far as I can determine there is not another one available in Cornwall.

So my preference, assuming the interior parts are available, is to repair mine. By the way, the gearbox oil that i took out was very thin (ran almost like water) and it was red in colour (though more black than red), does that sound like the correct grade for these boxes ?

Thanks in advance guys.

 

[briggie]

Brill photo's mate, that helps a lot.
Now for the 10 million $ question, are the interior parts available anywhere ?

I have seen the overhaul kits on line which include bearings and gasket, for £98, however, I don't know if that covers all of the bearings in the box. Also, as I have already seen evidence of Brass in the oil, would those gears be available from somewhere ?

I don't mind stripping it down if there is some point to it, but if the parts are not available then there seems little point. However, having said that, if companies are advertising these boxes as reconditioned, then you would have to assume that all parts are available.

Afraid I wouldn't know where to start looking for those parts so I am hoping someone could point me in the right direction :lol

I am a bit loathe to get the second hand unit for £300, even though the guy is guaranteeing it, it's a lot of work if it is no good just to get it off again and then I am back to square one because as far as I can determine there is not another one available in Cornwall.

So my preference, assuming the interior parts are available, is to repair mine. By the way, the gearbox oil that i took out was very thin (ran almost like water) and it was red in colour (though more black than red), does that sound like the correct grade for these boxes ?

Thanks in advance guys.

red ??? , you sure its not atf that's in it ? :nenau

 

[solarman216]

bearings and seals available from loads of places, new gears will be Nissan only £££££££££££, box rebuilders usually have several other oldboxes they can rob from, and they know the gears that always fail and so get pattern parts machined up, but mostly inferior quality, having said that most likely will out last a 16 year old truck anyway, personally I would go with the £300 used box with a warranty, Rick

 

[96terrano]

bearings and seals available from loads of places, new gears will be Nissan only £££££££££££, box rebuilders usually have several other oldboxes they can rob from, and they know the gears that always fail and so get pattern parts machined up, but mostly inferior quality, having said that most likely will out last a 16 year old truck anyway, personally I would go with the £300 used box with a warranty, Rick

shame the gearboxes aren't still being manufactured

 

[solarman216]

shame the gearboxes aren't still being manufactured

everything today has a planned life span, most are shorter than you think, Rick

 

[96terrano]

everything today has a planned life span, most are shorter than you think, Rick

yes, i heard car manufactures are almost building use by dates into new vehicles so they'll last for so long then you'll have to buy another as it'll start to go wrong.....not being built to as a high quality as they could be......more money for the vehicle manufacturer when you buy another car

 

[rookie]

Thanks for the replies chaps. Just to confirm, YES, the gear oil was/is RED. The joints between the gearbox and the bellhousing have been sealed with a white silicon substance and even the bell housing to engine surface was coated with silicon as was the starter flange.

Haven't managed to work out how to separate the bell from the box. Have just loosened the whole lump off and it is now sitting on the front and rear cross members (still trying to work out how to get it down in one lump without doing any damage)

Too dark to carry on tonight and I've had a couple of cans chilling in the fridge all day.

Ah well, tomorrows another day:thumb2

 

[solarman216]

Thanks for the replies chaps. Just to confirm, YES, the gear oil was/is RED. The joints between the gearbox and the bellhousing have been sealed with a white silicon substance and even the bell housing to engine surface was coated with silicon as was the starter flange.

Haven't managed to work out how to separate the bell from the box. Have just loosened the whole lump off and it is now sitting on the front and rear cross members (still trying to work out how to get it down in one lump without doing any damage)

Too dark to carry on tonight and I've had a couple of cans chilling in the fridge all day.

Ah well, tomorrows another day:thumb2

Oh right you have a pig of a job on your hands, to get it out you have to remove the front torsion bars and then the X member that they tie into and then some serious muscle to support it down, a good trolly jack helps but it is very un ballanced so wants to fall to one side you can remove the transfer box to reduce the weight (recomended) but still a barstuard to do, torsion bars are in the down loads, good luck, Rick

 

[briggie]

im still confused that the g/box oil is red ......sounds like atf to me .... but in a manual box ??? :nenau...... of course I may be wrong .

 

[rayf3262]

im still confused that the g/box oil is red ......sounds like atf to me .... but in a manual box ??? :nenau...... of course I may be wrong .

Some manual gearboxes like the LT77 do use ATF, but the Terrano/Mav box is not one of them..

 

[briggie]

Some manual gearboxes like the LT77 do use ATF, but the Terrano/Mav box is not one of them..

I wonder if this is the problem with his g/box ? ...... but I know nuffin

 

[briggie]

of course it may not be atf that's in it ..... but I cant think of any other g/box oil that's red .

 

[rookie]

Hi Buddy, all I can tell you is that it was red, it smelled like gearoil but looked exactly like ATF.

Stripped the front off the box today and found a loose roller from a bearing and quite a bit of brass scrapings. Still haven't worked out how to free the selectors (which are in excellent condition visually) from the section of the box that holds the gearstick.

I am assuming that I have to remove the bearings on the end of each selector shaft and then all of the multitude of gears from the two shafts.

I did note that every joint surface in the gearbox had been siliconed together, the box itself had "Diesel" written on it with a paint marker and the rear box had "Auto" written on it the same way, so I assume the original box was actually a second hand one from a scrappy

Tried to separate the whole gearbox before lowering to the ground but found it impossible so it all came down in one lump.

Which leads me to the next question...........does anyone know how to reset the torsion bars on rebuild ?

About to go and collect the new second hand box tomorrow so may have to put my old one to the back of the workshop until I get time to look at it.

cheers lads

 

[96terrano]

Hi Buddy, all I can tell you is that it was red, it smelled like gearoil but looked exactly like ATF.

Stripped the front off the box today and found a loose roller from a bearing and quite a bit of brass scrapings. Still haven't worked out how to free the selectors (which are in excellent condition visually) from the section of the box that holds the gearstick.

I am assuming that I have to remove the bearings on the end of each selector shaft and then all of the multitude of gears from the two shafts.

I did note that every joint surface in the gearbox had been siliconed together, the box itself had "Diesel" written on it with a paint marker and the rear box had "Auto" written on it the same way, so I assume the original box was actually a second hand one from a scrappy

Tried to separate the whole gearbox before lowering to the ground but found it impossible so it all came down in one lump.

Which leads me to the next question...........does anyone know how to reset the torsion bars on rebuild ?

About to go and collect the new second hand box tomorrow so may have to put my old one to the back of the workshop until I get time to look at it.

cheers lads

on the selector folks, their were pins that were holding the folks to the rods, you have to know these securing pins out, they are in tight

 

[rookie]

Hi 96terrano

Yes, I did knock them out and the forks are now free, do I have to remove the first two bearings on the end of the shaft and then strip all of the selector gears off to be able to split the two halves of the box .
Or do the 3 carriers rods slide out of the patch plate between the boxes?

I can see that the gear stick yoke is held on by a 10mm bolt but there is no way to access it without splitting the two halves is there?

cheers