Shane's 1985 Pulsar ET - 13.3 and 116mph..

Wes · Post by **Wes** » Tue Oct 10, 2006 2:26 pm

Hey guys
Ben and i have spent most of the morning working out specs and trying to get a solution for the high revving n13 box (in 5th gear, namely 3200rpm @ 100kph)

So...
Heres what we've nutted out:

You must get the N13 box, and your n12 ET box in front of you....

Pull the guts out of each, and have a fresh start (im drawing a mental picture only for this example!) now, get the casing you want to use. Right, now thats in front of you.
You must then use the N13 mainshaft as its pinion gear MUST be mated with the n13 crown wheel. You CAN NOT transpose crown wheels (final drive gears) without its pinion gear mate which is part of the main shaft....

I have to do things this way (reason is explained below, so i will be talking this bit through for anyone in the same boat as me....)
Here goes:

Pull the 4th and 5th gears off the N12ET mainshaft and swap it for the n13's 5th gear. Right, that the n13 and n12ET mainshaft part out of the way. The rest of the gearing matches the n12ET anyway. So unless the n13's gearset is damaged, leave it as is.

The next step is to pull out the entire input shaft of the n13 and put in the n12ET's main shaft to now match the ET gear set. You cant have one without the other. The only reason i personally will be swapping 4th and 5th on my n13 gearset as opposed to putting in an entire ET set in a straigth swap is that i had mine full rebuilt, and want to make use of the new bearings.

NOW, saying all this.... again, you NEED the n13 mainshaft and final drive (crown wheel). You can either swap ALL the n12ET gears over to the n13 mainshaft or just the 4th and 5th which are the only different ratio'd gears compared to the other.

BUT, to make the n12 gearset mesh, which will now be on the n13 mainshaft, you MUST use the n12ET Input shaft as the gearing on them (which is fixed and cannot be removed like the gears on the mainshaft can be) is mated for that n12 gearset, which now has the normal N12ET ratio 4th and 5th.

So, in a nutshell.... to make it painfully easy....
All gearing from the N12ET will now be on the n13 Mainshaft. The N12ET input shaft is also retained and used to mate with the n12ET gearset.
You then have all that driving through to the n13 pinion of the mainshaft, which then meshes with the n13 crown wheel (higher ratio 4.167) which takes the load off the gearbox and reduces the original spec n13 "3200rpm@100kph" down by around *ONLY GUESSING- 200-300rpm, making it roughly 2900-3000rpm*

THis is the conclusion Ben and i came to. Ben had a LOT of input into this and explained a lot to get me back up to speed. There is no way in hell im taking all the credit for this. And if for some weird reason it doesnt work, then it WAS all Bens idea... His number is 04.......
heeheh

Im getting this done very soon, so is Ben, and we'll take pics and update everyone on how it goes.

Wes

Ben Hewitson · Post by **Ben Hewitson** » Tue Oct 10, 2006 2:37 pm

nice work Wes and as you say, i've send off my diff this morning and wll get into the rebuild soon. i'll take pics and write a decent tech article too. i'll be using the N13 final drive (crown and pinion gear+shaft) and the rest wil be N12.

stay tuned.

Wes · Post by **Wes** » Tue Oct 10, 2006 2:44 pm

Was good workin this out with ya mate, and it makes perfect sense and perfect sense that it will work
I'll post this in tech articles too and when Ben and i have finished them we should get Renegade to Sticky it for everyone

And on another note.....
*in soft TV ad voice*

"Donations to the 'Build a Gbox Foundation' can be sent to Ben And Wes and are fully tax deductable.

Ben and Wes..... helping out our fellow ET owners in our community"

lol

Wes

Post by **shanec86** » Tue Oct 10, 2006 4:29 pm

Lol you only just worked that out? and it took 5 pages of text? hahaha

i had it up in my original post..

N12 gears, n13 main shaft, n12 input shaft, n12 diff hemisphere, n13 crown wheel.

whack it all together, and you get 5th gear 100km/h @ 2700rpm

simple

Panda_ET · Post by **Panda_ET** » Tue Oct 10, 2006 4:37 pm

whoa wes u lost me but it sounds good lol

Wes · Post by **Wes** » Tue Oct 10, 2006 4:39 pm

Geezz man, coulda jumped in ANY time here and told us that!

We obv never saw it, nor did anyone else
Are you serious? It drops to 2700?? that seems far far too low to me

I dont see how it can only go up by 200rpm and come down by 500rpm when the biggest factor in increasing the revs is the final drive gear. Thats the most influencial part of this whole setup
Going from 3.550 to 4.167 is huge

Ben Hewitson · Post by **Ben Hewitson** » Tue Oct 10, 2006 4:42 pm

we have to take into account that its not 3.55:1 versus 4.1:1 only. its also a different ratio 5th gear. so its actually a little more than half way. so yeah. 2700 sounds reasonable. and very very good to me.

Wes · Post by **Wes** » Tue Oct 10, 2006 4:44 pm

Yeah, that will be great to me too
Just depends what sized rims he has etc
I have 15's so mines gonna be the same as stock ET height meaning my speedo will be accurate still

Post by **shanec86** » Tue Oct 10, 2006 11:49 pm

http://www.f-body.org/gears/

put all the crap in that. and look what comes out the other end... geez its accurate

Wes · Post by **Wes** » Wed Oct 11, 2006 2:11 am

Man hahaha thats not accurate at all
Its already saying that i'll be doing 3000RPM @ 60mph in 5th
Its already 200rpm out....

And yeah, i put in the details of the setup im trying to achieve and it said 2700.... so, considering the first value was 200rpm UNDER what mine actually does on the road... im gonna take it that the second value of 2700 is ALSO 200rpm lower than it will be on the road, which equates closer to Ben and my own guestimate of around 2900-3000rpm

Will have to see how it goes though. How accurates your tacho?
Ive got an Autometer which is more accurate than stock....infact my stock one reads around or just under 100rpm more than what the Autometer reads....

Ben Hewitson · Post by **Ben Hewitson** » Wed Oct 11, 2006 8:54 am

hey i'll take what i can get. if it turns out anywhere i'll be happy.

for the record , i checked this morning, i can do 2300-2400 in 5th at 100km/h.. thats with my 195/55/15's on. i dare say thats it a little different for every car.

i'll wait to see what i can get out of it. but 2700 sounds great. if thats what your getting on the track Shane, i'll be happy with that.

Wes · Post by **Wes** » Wed Oct 11, 2006 11:29 am

Oh yeah, i agree. The lower the better in top gear for fuel economy.
The freeways the obvious main link to most places in perth...cuts right down the middle of nearly everything, so more often than not im sitting at 100kph. Its amazing how much and extra 200rpm makes so even to drop that much would be great, but if it IS 500rpm.... even better!

Wes

Post by **shanec86** » Wed Oct 11, 2006 5:57 pm

60mph is actually 96km/h so look at the 62mph column... theres your lost 200rpm

and i have an autometer tacho which reads exactly the same as stock

Wes · Post by **Wes** » Wed Oct 11, 2006 6:11 pm

its only 100rpm

ANYway, im HOPING youre right, and that actual bum in seat testing will have a lower rpm, im just doubting it (for my setup anyway) but will let you all know

Got the inlet manifold today, it looks hot, just polished it, looks even hotter now!
Just waiting till monday now when the guy can swap the bearings over for me and the 4th and 5th gears so i can put the box back in

Wes

Ben Hewitson · Post by **Ben Hewitson** » Fri Oct 13, 2006 4:52 pm

well. not to ALL.. CA18DE boxes with the hydro clutch (all of them) DO NOT FIT INTO AN N12.!!!! ok. dont ask me again. the CA18DE gearbox has a 10 bolt crown wheel and the N12 diff centre has 8.. so its CA16DE or 1.8L LE or Q model N13 pulsar that are needed to find.

cheers.

N12 Turbo Forums

Shane's 1985 Pulsar ET - 13.3 and 116mph..

Worked out a way of dropping 5th gear high rpm in N13 BOX