gearbox question

[ydragu]

will a 97 rsb gearbox have the same ratio as the old shape bc chassis i think it is

its a single turbo facelift old shape 1993

[greatdanz]

The BC ratio should be 4.11 and the RSB would be a 4.44, make sure you use the matching diff with the RSB gearbox if you plan to fit it to the the RS, and it will work

[Joker]

for those that don\'t know about stuff like this (ie me) is it easier to switch the REAR or CENTER diff to make them match?

I assume center/back of the Gearbox one

[Guest]

Two things missing from this thread that are mildly important. Heres a little clue - GEARBOX NUMBERS.

[greatdanz]

 JoKer said:

for those that dont know about stuff like this (ie me) is it easier to switch the REAR or CENTER diff to make thme match?

I assume center/back of the Gearbox one

its alot easier to replace the rear IMO anyway

[funkytown]

 JoKer said:

for those that dont know about stuff like this (ie me) is it easier to switch the REAR or CENTER diff to make thme match?

I assume center/back of the Gearbox one

center is irrelevant (where the center is 1:1 (for completeness)). its the front and rear that need to match. your question swapped with "front" as the front is the one that also comes in your subaru 4wd box is the harder to change. The rear being the easiest to make it all match.

And to clints point - dont guess. Use the gearbox numbers and the gearbox charts in the sticky to confirm what you have / need.

[Joker]

told you I didn\'t know

and doubt and RSB.BG/BD will be anything other than a 4.44, the BC also will almost always (room for error) 4.11 no?

but yes : numbers will reveal all

[funkytown]

no joker. USE THE CHART!

auto and manual with in a model year can differ, and cross model year also different and non logical pattern in diff choice

[ydragu]

just found a leggy with a buggered box and im wrecking a twin turbo one hence no gearbox numbers so the crown wheel and pinion will go straight into the bc diff case or can i just swap the whole diff

thanks heaps for the help guys and the quick response

[funkytown]

Count the crown wheel teeth. Will tell you what ratio it is.

The tt will have gearbox numbers on the chassis tag. As will the bc tbh

[Joker]

 funkytown said:

no joker. USE THE CHART!

auto and manual with in a model year can differ, and cross model year also different and non logical pattern in diff choice

see that\'s the kinda info we needed in this thread : like pulling teeth hahahhah

[greatdanz]

Haha

[ydragu]

havmt bought the car yet might just take a punt should be able to make it work i guess

cheers guys

[CUDDAS]

My bc \'gt\' autos were 4.444 and bc \'rs\' manuals. were 4.111 rears were viscous lsd

so could cover both

[Koom]

Also with the age of the majority of the cars on here, it\'s not unreasonable to think that the gearbox has been swapped at some time in the past and could now contain anything. I don\'t even trust the numbers on the box as the internals can be swapped (rare cases).

(Also another rare case is where a 1.1:1 centre diff is used and then you end up with 4.444 at one end and 4.111 at the other. I had that on a TY755* box I put in my RS)

ydragu, just swap the whole rear diff, checking that the axles are correct or swap them too as the inner cv\'s are different between some models. I\'d only swap the crown/pinion inside the diff housing if I didn\'t have the axles to fit into the replacement diff.

[Eight_dollar]

centre diff can only be 1:1

Even if the output gearset in the back of the gearbox worked at a 1.1:1 ratio - there isnt a front and rear diff ratio that would work to give even front and rear diff output speeds

(sits back and waits to be corrected)

[Koom]

According to my notes that I made when I split it to figure out what it was (there was no info on the net for a TY755VN5AA), the front diff had 40:9 teeth i.e. 4.444:1

The centre diff had 40:37 teeth so was actually 1:1.081

If you divide 4.444/1.081 you get 4.111 and my rear diff has 37:9 teeth i.e. 4.111:1

So it all works out. I think it would be for a mechanical torque split but I\'m too jetlagged currently to figure if it gives a slight torque advantage to the rear or if it all works out to be equal and in that case there must have been some other reason to put in a centre diff that wasn\'t a plain old 1:1 ratio?

[Eight_dollar]

ahhh 1.081:1 that works

its the final drive gears in the box that give the ratio - The centre diff gears wont move unless there is slip at either end of the car