318i diff

[jamesh1977]

hi my wee brother just had his 318i rear ended.. so will be lookin to put a car on the road for him but only one i got that he can insure is my 316i but it needs a diff. will the 318i diff be the same ratio as the 316i? if not will it make much diffrence? also how big a job changing one? never changed a diff on one before so not %100 sure cheers james

[kevo]

hiya james,
depends on what years etc as to wether the ratios will be the same but i'm pretty sure they'll be identical as long as they are both M40 engines or both M10 engines if you se what i mean. (btw if they are different ratios the diff will still go on anyhow).

as for changing the diff, depends on your mechanical ability, do you own ....

8mm allen key,
17/19/13mm spanners/sockets,
axle stands
jack

if you do you probably have some idea in which case it's easy enough, all you do is...
1. jack the thing up
2. chuck your axle stands under (wherever you feel comfy with them),
3. take the wheels off (makes it easier to see)
4. undo the drive shafts on either side of the diff (8mm allen key or you'd be better off using a socket type one)
5. undo the prop from the diff 4x 13mm bolts
6. undo 3 of the 4 19/17mm (can't remember which) bolts on top of the diff and the one holding onto the bush on the pass side of the car
7. now put your jack back under to take the weight of the diff.
8. undo the 4th bolt on top of the diff and lower it down (it's not mental heavy just awkward really).
9. now go have a cuppa and reverse to fit. oh and remmber to copperslip everything makes it easier next time.

if you're stuck give us a shout.
Kevo

[eko]

James look here to confirm final drive ratios -
http://www.unixnerd.demon.co.uk/e30.html

PS did you get the aeriel?

[jamesh1977]

cheers kevo seems straight forward enuff just wasnt sure as the last diff i changed was a live axle on a mk2 escort.
was under looking earlier and should really have had a light with me as it was gettin dark and looked as if there was more to it. have you ever changed a fuel tank on one? would it be easier to do while ive got the diff off? i done the filler neck on my own car but been told this ones needing the tank. hoping it will only be the filler but again hard to say till im under it in the light. i bought it a couple of weeks ago in a deal but hadnt even looked at it intill tonight after my wee brother was in his bump. so went up and drove this one home in the cover of darkness. all seems ok with it considering its been layed up since march drove ok bar the diff noise (turned the radio up didint hear it so much!! but not ideal for my wee bro to run about in)


ariel arrived yestarday mate safe and sound

[jamesh1977]

looking at that link the now and being honest i never understand these numbers its telling me the 316i has a 4.27 and the 318i has a 4.10 so anyone want to explain what diffrence it will make?

[Brian28]

The higher the big number is to :1, the lower the diff ratio is. A lower diff ratio will give better accelleration but the car will be revving higher at motorway speeds. A higher diff ratio will have worse acceleration but better fuel economy and more relaxed on a run. Most cars are too low ratio from the factory to give more impressive 0-60 figures when first launched. If you swap as above your car will be slightly taller geared, will be fine and unlikely that you will notice unless specifically checking for revs against speed.