Trying to understand what the ratios are for the IRS Gearboxes for T1 & T3 are.
Do they all have the same final drive ratio?

I have a IRS box with a yellow paint mark on it, Does this give some info about what ratios it has inside?

What is the tallest final drive ratio available, that would fit inside this box?

Thanx

I found this web site http://www.albinsgear.com.au  they may be able to help?

Hi

Type 1 box are 4.125 R&P with double side plate, single side plates have 3.88. All type 3 boxes had 4.125 final drive, wether they were double or single side plate. The 3.88 box uses a .93 4th, the 4.125 box uses a .88 4th. This works out that they both have about the same KPH per RPM in 4th gear. The 3.88 box ends up having 3rd & 4th close because of this. Type 3 boxes dont use engine mounts under the bellhousing so the holes have alloy blanking slugs in them which can be punched out.

Steve

...and the gear selector rod has its grub-screw hole on the underside of the rod for Type 3, rather than on top.

I didn't know that about 4th gear ratios - thanks Steve!

Thanks

Forgot about the grub screw

so a twin plate box with a 3.88 r&p and heavy side plates would be better cruising at 110km ie lower rpms

it might happen ive got a spare at the moment besides i need to fit a heavy duty side plate due to the extremely heavy right foot and a t4 in a bug :duh

I dont know about that barls, I've got a ssp 3.88 box in my 1303 (fattest of all bugs), only mod is a superdiff and my 1835 would be maybe 80hp and I drive it pretty harsh sometimes - I was never suggested to do anythign about the sideplate.

Are the dsp sideplates weaker or something ?

the side plates are the same strenght but the single has one on the right and the case on the left which is good cause when you put the power down the strain is put on the case not the left side plate which flex and eventually leak on a twin plate box. this is why the 1303 box is so good for modifed engines

Makes sense - the alloy casting would be much stiffer than a pressed steel plate.

yeah it makes a lot of sense when you start seeing the flex marks. sorry for hijacking back to the original question

So a 3.88 final drive with a 0.88 4th would be the best combo for tallest final drive.

Reason I ask is that the 6cyl 911 motor in the T34 is revving at 3k at 100ks. Want to knock about 500 revs of that for more relaxed cruising. And probably better fuel economy.
Power is not a problem so raising all gear ratios would have very little effect.

You could get Albins to supply a 0.77 4th gear set, and with a 3.88 R&P would give about 2500RPM. Tyre size will play a bit of a role with exact RPMs.

Or

Custom and Speed Parts sell a 3.44 R&P,

then all your gears could be taller.

Justs checked out the custom & speed parts web site. Nice gear but oh so exy. 600 euros for the 3.44 R & P.

Abins might be a better bet. Cant quite work out that gear calculator.

"Final Drive Ratio X Constant Ratio X Gear Ratio = Overall Ratio"

whats the Constant Ratio ???

If you give me your ratios and tyre size I can graph it and send/post it as a .jpg file.

Cheers Astro.

Wheel size overall (height) = 61cm
Final drive = 3.88
4th gear ratio = 0.88

Post it would be good mate. Might be usefull for others too.

Dean, I need your aspect ratio, width and wheel size

ie 195/60/15
etc

I'll post the pic when it's done
:thumb

[Edited on 9-6-2005 by 56astro]

here ya go astro

205/60/15

here she is, changing gear @ 4000RPM



[Edited on 9-6-2005 by 56astro]

Thanks mate. Can you do one for me with 0.77 4th?

Much appreciated :beer

hmmm looks like the 3.88 is the go for chaos then

With a 7200 redline on this 911 motor I can now see how 0 to 100ks in 6 secs is possible. Only one gear change.

Thanks Astro, that looks a lot better.
The 277ks at 7000 would be interesting too???:thumb
salt flats here we come!!

Hey Grey 57, just wondering which 911 motor you have?
ie. is it a 'T' 'E' or 'S' ?
Reason I ask is because each has a different powerband therefore requiring different gearing. The 'T' was the mild one and 'S' was the screamer with 'E' somewhere in between.

Gracey, mine is a 2.4 MFI out of a 72 911T. The mild one. 157 SAE horses (or 140 DIN hp)

No probs mate. 277km/h - wahooooooo

BTW
your sig line needs fixin.
I think you have to put a [img] before the http,
and a [/img] after the .gif
Delete the stuff in front.

Hi

The 3.88 box comes with an extremley fine tooth 4th gears, they are very weak in HP applications, so its a good move to fit some Albins gears, or you can do a freeway flyer with the .88 from the earlier box.

The gear calculator at this site is very basic but easy to use http://www.vw-store.com/Engine%20Calc.htm 

Steve


Steve