James R
Member
Registered: 4th Feb 03
Location: 205GTi16/306GTi16
User status: Offline
|
If you change the final drive ratio on your gearbox to mae the box shorter, it will boost acceleration but will cut potential top speed, I've just switch from a 3.74 final to a 4.18 final meaning a boost of 12% torque at the wheel in any given gear, on my engine with will limit me to 136mph@7.5krpm, but that's more than plenty for this country, and we'll see how it affects my acceleration in a few weeks.
The 4.18 final is found in the F13Wide box's fitted to early novas, happy hunting.
Have a look at this thread for the how to
http://www.migweb.co.uk/forums/showthread.php?t=131112
|
Adam
Member
Registered: 1st May 01
Location: Hurstbourne Tarrant
User status: Offline
|
Plagerised for CS
changed j1400's final drive from a 3.7 to a 4.18 so thought i'd do a thread on how its done, maybe it could go in the archives or something?
firstly, to check what final drive you have, look for this number, under a few layers of dirt, on the side and you'll see the f/d number there, yes it does exist! 
now, get the relevant final drive that you want, and yes you need both pinion and crown wheel
now, start by removing the turret
now remove all the thirteen mm headed bolts from the sandwhich plate, now you can lever the cluster out of the box
now remove the final drive pinion, by firstly removing the circlip and either levering or pulling of
at this point we had a bit of a mince
now you're ready for the diff removal, remove the diff plate, then undo the bolt on the retaining tag for the bearing carrier castellated nut, and mark its position so you get the bearing pre load right on reasssembly, now, using a flat bar or similar, undo the nut and remove, then remove the diff assembly
undo the nuts on the pinion and remove it form the diff, this may need a tap or two, for which you can use the box as a support!
now fit your new one, and do the bolts up to torque, thenease it back into the box
then refit the cluster, remembering to fit the thrust washer back on the reverse shaft, it only goes on one shaft, so its pretty obvious where it goes, use new gaskets, and do the bolts back up to torque and you're done!
so there you go, hopes this helps anyone thinking of tackling thsi job but thought it was too scary
*if you are using new beaings, you cannot simply do the casstleated nut up to where it was before, you must check the meshing of the pinion and crownwheel by the use of engineering blue on the teeth as desribed in the haynes guide*
|
James R
Member
Registered: 4th Feb 03
Location: 205GTi16/306GTi16
User status: Offline
|
Is this work archiving Adam??
|
J100RSA
Member
Registered: 4th Mar 01
Location: Thornhill, West Yorkshire
User status: Offline
|
bet your kitchen smells nice 
|
broster
Premium Member
Registered: 6th Dec 02
Location: Drives: E39
User status: Offline
|
gunna say i like your workshop mate! looks like a task i may undetake soon. what kinda difference do u get?
|
James R
Member
Registered: 4th Feb 03
Location: 205GTi16/306GTi16
User status: Offline
|
Not my Kitchen, that's Lee's place, but my car stinks of eggs now 
Broster, It should knock about 0.2 of my 0-60 and about 0.3/0.4 off a 1/4, it especially good if you have a raised rev limit and a cam'd engine.
|
broster
Premium Member
Registered: 6th Dec 02
Location: Drives: E39
User status: Offline
|
humm i have both the above may deffo get it done to mine then!
|
James R
Member
Registered: 4th Feb 03
Location: 205GTi16/306GTi16
User status: Offline
|
Just hard to find the buggers, if you take a hard wire brush with you and clean as in the pics at th etop you see the final ratio scribbed in to the box. Happy hunting.
|
broster
Premium Member
Registered: 6th Dec 02
Location: Drives: E39
User status: Offline
|
cheers matey, ill be down the scrappy soon, how much is the full gear box?
|
Kris TD
Member
Registered: 25th Mar 02
Location: Ware, Hertfordshire
User status: Offline
|
or use a diesel corsa box, thats the f13 wide ration.
|
James R
Member
Registered: 4th Feb 03
Location: 205GTi16/306GTi16
User status: Offline
|
You don't use th ebox, just pull the final out Kris 
|
Greg_M
Member
Registered: 2nd Sep 03
Location: Grantham, Lincolnshire
User status: Offline
|
bothered
|
