Questions about Gearboxes

Post by **MyGQ** » Thu Jul 26, 2007 6:41 pm

Hi Fellas, need a bit of the golden info that OL always provides me.

OK i have a GU Turbo 4.2L that has the dodgy 5th gear in it. as you can probably guess, its shat that gear.

I have the ability to get a 4.2L GQ petrol gear box for nothing, now i know that the GU and GQ put their gear shifters in different spots, was wondering if you replaced the top cover off the GU gearbox onto the GQ is that would work to make the shifters fit in the same place?

If that isn't possible, i understand the 5th gear sits in the extension housing on the GQ/CU gear boxes, in that event, could you use the extension housing off the GQ and put it onto the back of the GU box to give it 5th gear again? or won't that work either.

If the answer is no to my questions above, is there an aftermarket gear that you can get for this to give it 5th again or i sit just a upgraded gear from Nissan you need to get? if there is an aftermarket one, can someone please tell me who to call and where to get it?

Post by **Clanky** » Sat Jul 28, 2007 11:46 am

Why not look at the Marks adaptors 5 gear reduction replacment?
Might solve your troubles and suit big tyres too

Post by **Clanky** » Sat Jul 28, 2007 11:51 am

Here's the link

http://www.marks4wd.com/products/gearma ... -gears.htm

Post by **turps** » Sat Jul 28, 2007 12:15 pm

Clanky wrote:Why not look at the Marks adaptors 5 gear reduction replacment?
Might solve your troubles and suit big tyres too

Nah it will make big tyres worse. Ok this is just guessing as I cant find where I put and excel sheet that works out such things.
But example- If running 35s and in current 5th gear at 100km/r (by GPS not dash) and it revs to 2300. If you fit a lower O/D gear and make it 10-15%lower (ie .84 or .91 :1 changed to .74:1). Then engine revs will drop to 2070rpm for the same speed.
Now depending on the motor. This may take it out of its optimum power range. If there is now a big arse motor in there. Then it may have the torque down lower and be fine. But with the factory motors I would think it would labour abit and actually put more load on the engine and use more fuel.

Post by **chimpboy** » Sat Jul 28, 2007 12:28 pm

turps wrote:
Clanky wrote:Why not look at the Marks adaptors 5 gear reduction replacment?
Might solve your troubles and suit big tyres too
Nah it will make big tyres worse. Ok this is just guessing as I cant find where I put and excel sheet that works out such things.
But example- If running 35s and in current 5th gear at 100km/r (by GPS not dash) and it revs to 2300. If you fit a lower O/D gear and make it 10-15%lower (ie .84 or .91 :1 changed to .74:1). Then engine revs will drop to 2070rpm for the same speed.
Now depending on the motor. This may take it out of its optimum power range. If there is now a big arse motor in there. Then it may have the torque down lower and be fine. But with the factory motors I would think it would labour abit and actually put more load on the engine and use more fuel.

I agree... anyone know how much the Nissan replacement 5th gear costs?

Post by **Clanky** » Sat Jul 28, 2007 12:52 pm

Ooops!
Sorry, I was working it out on my 4.625:1 diff gears
Agree, it wont help much with stock gears.

Post by **raptorthumper** » Sat Jul 28, 2007 2:16 pm

Have a read of my thread. I dont know if you can simply put the GU shifter cover on the GQ. Why dont you try it. It's pretty quick to remove it.

To answer your question about swapping extension housings, you cant just fit the rear extension housing from GQ to GU as it is the mainshaft that gets stripped as well as 5th gear. Also the gear ratio's in the GQ are slightly different to the GU's so the gears wont simply replace.

http://www.outerlimits4x4.com/phpBB2/vi ... hp?t=22988

Grant.

Post by **sudso** » Sun Jul 29, 2007 4:54 pm

GQ TD42 and TB42 5 speeds are the same box too.

Post by **MyGQ** » Sun Jul 29, 2007 8:53 pm

ok well we had a look at the top covers, they don't interchange

next thing we are going to do is strip out the 2 boxes (GU and GQ) and put the gears and shit out of the GQ box (all the goodies) into the GU box. Hopefully this will work

Post by **benhl** » Sat Aug 02, 2008 3:27 pm

MyGQ wrote:Hopefully this will work

Did it?

Post by **MyGQ** » Sat Aug 02, 2008 4:19 pm

Yes but you need to do a bit of machining.

The GU selectors are allow where the GQ are metal, the GU ones are slightly thicker and need a tiny bit taken off them to make them fit with the GQ syncro's we did it, thanks to a mates help it cost us all up $400, we stripped the gears out of the GQ box and gave it to mate to put into GU box. wasn't too bad

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Questions about Gearboxes

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