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Can You Put A Rb26 Gearbox On An Rb20

Viper_r32

By Viper_r32,
in Australian Capital Territory

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Viper_r32 Community Regular

Viper_r32

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hey, due to all my turbo probs lately I've decided that I'm going to swap out my engine. I'm just going to replace it with a second hand one for the moment and slowly rebuild my current engine with much stronger gear. thinking an RB26 crank and con rods forged pistons bigger cams etc. i know i could just drop a 26 in but its more about the experience of building something up. i know it would cost around the same if not more in the long run but after allot of though it's what i want to do.

my only question is the gear box. i'm interested if an RB26 gearbox can bolt to an RB20 engine. as i want a box that could handle a bit more punishment. Plus something with a different gear ratio to the standard RB20 box. any one know if one will bolt up or not?

Bluprint Veteran

Bluprint

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The RB26 box is not of any use to you because of the 4WD transfer case hanging off the side of it.

An RB25DET gearbox is the same but without the 4WD gear, and yes they bolt on.

Oh yeah, you'll need to have a custom tailshaft made up because the 25 gearbox is bigger.

I'd just leave the box you have until you have the power to require changing to a stronger box.

Edited by Bluprint
Viper_r32 Community Regular

Viper_r32

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The RB26 box is not of any use to you because of the 4WD transfer case hanging off the side of it.

An RB25DET gearbox is the same but without the 4WD gear, and yes they bolt on.

Oh yeah, you'll need to have a custom tailshaft made up because the 25 gearbox is bigger.

I'd just leave the box you have until you have the power to require changing to a stronger box.

I'll be ordering my replacement engine soon, and i just figured i was better off to get the gearbox at the same time!

although i would be interested to know if the rb25 gearbox has sincro in 1st as the rb20 gearbox doesn't and it really ticks me off sometimes.

Edited by Viper_r32
mjfawke Collaborator

mjfawke

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I'll be ordering my replacement engine soon, and i just figured i was better off to get the gearbox at the same time!

although i would be interested to know if the rb25 gearbox has sincro in 1st as the rb20 gearbox doesn't and it really ticks me off sometimes.

All Nissan boxes since at least the 60's have had synchromesh on all forward gears.

Edited by mjfawke
Viper_r32 Community Regular

Viper_r32

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All Nissan boxes since at least the 60's have had synchromesh on all forward gears.

not true as all s13, boxes and rb20 boxes do not contain sincro in first gear,

this is why when you slow down at a set of light and just as your about to stop the lights turn green so you go to stick the gear in first but the box wont let you. this is because 1st dose not contain sincro!

infamous_t Veteran

infamous_t

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not true as all s13, boxes and rb20 boxes do not contain sincro in first gear,

this is why when you slow down at a set of light and just as your about to stop the lights turn green so you go to stick the gear in first but the box wont let you. this is because 1st dose not contain sincro!

+1 for GTR boxes not having first gear syncro

datto260Z Experienced

datto260Z

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Im pretty sure the first 5 speed GTRs had the same 5 speed thats used behind the RB25, in fact arn't they rated as a stronger box than the 6 speed anyways? Just going off rumours etc but i know the 25 box is strong as anyways and bolts on, so it would probly be your best bet. Cheaper too maybe?

Viper_r32 Community Regular

Viper_r32

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geese when did this turn into a debate, i hate debates :)

cant we all just get along :(

anyway i know my gearbox and the one my mate has in his s15 do not have sincro in first, so would prefer one that dose. so maybe a 25 box is the go, I'll see what the price difference is when i order my replacement RB20.

decided that I'm just getting a replacement RB20 for now. but im going to replace the watter and oil pump for N1 stuff. and put one of those new stronger collars on the pump as i believe thats what has caused the prob in my existing engine.

so wile I'm getting that done i'm going ahead with a short shifter kit, and replacing my Cusco coil overs for some Tien Super Street ones. as the Cusco are just to stiff for a daily driver. I'm getting new bucket seats. a clear camgear cover and to top it all off a new shift knob

so about $5000, later but that's the price you pay for high performance cars!

and ill just keep my existing engine and slowly rebuild it over time, possibly a full Tomei RB22 or 24 kit. well see........

Edited by Viper_r32
mjfawke Collaborator

mjfawke

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I'm going to say this slowly again, one more time : All... Nissan... boxes... since... at... least... the... 60's... have... had... synchromesh... on... all... forward... gears. For good measure, the GTR also has it on reverse.

BNR32t Proficient

BNR32t

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I dont know enough about other box's, only have rb25 and rb26 gear box exp,

But from my exp with older box's the synchro will start to fail will age and with a FULL gearbox rebuild will be back to new. HOWEVER, this is with older cars that are 40years old :( Not 20year old nissens.

I dont see why the synchro would fail in a 20 year old car unless its been pushed hard.

Edited by BNR32t
Viper_r32 Community Regular

Viper_r32

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I'm going to say this slowly again, one more time : All... Nissan... boxes... since... at... least... the... 60's... have... had... synchromesh... on... all... forward... gears. For good measure, the GTR also has it on reverse.

ok, im not disagreing with you, and i'm not saying you are wrong. you are probably correct. all i'm trying to say is that i don't have syncro in first.

one of my close mates who has been into imports long before me, and has driven an s15 for like the last 7 years told me that allot of Nissan boxes don't have syncro in first. maybe he was wrong i am just trying to work out what box i want to go to and whether or not i will buy a 25 box or go for another 20 box. I'm not trying to say you are wrong in any way I'm just trying to get an idea of what most people think i should do? i didn't mean to offend you so if i did i apologize.

Viper_r32 Community Regular

Viper_r32

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I dont know enough about other box's, only have rb25 and rb26 gear box exp,

But from my exp with older box's the synchro will start to fail will age and with a FULL gearbox rebuild will be back to new. HOWEVER, this is with older cars that are 40years old :( Not 20year old nissens.

I dont see why the synchro would fail in a 20 year old car unless its been pushed hard.

i actually believe the gear box and engine have been pushed hard, as i believe one of the previous owners in japan used to race it on the track. but have to say it is interesting that despite being pushed so hard the engine still has full compression even at 190,000ks

infamous_t Veteran

infamous_t

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And if you have a look at page CH-31 of the GTR service manual, you will find a 1'st gear synchro baulk ring.

I stand corrected, still, yet to drive a GTR that 'feels' like it has a first gear syncro :)

For good measure, the GTR also has it on reverse.

You learn something new everyday :(

Edited by infamous_t

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