diff upgrade/swap

[David Cullen]

just a thought bouncing around in my head, has anyone swapped or upgraded their diff?
from reading up on it the only bolt on option is from the E30 - 318i
has anyone done this and was there any great difference? thanks
Dave

 

[zedonist]

Hi Dave,

I have been looking for one, you can work out the difference in speed, but what you gain in acceleration, you lose in top end and motorway cruising will be a pain, so it's only for lane screaming.

 

[oldcarman]

Hi Dave,

I have been looking for one, you can work out the difference in speed, but what you gain in acceleration, you lose in top end and motorway cruising will be a pain, so it's only for lane screaming.

Are there not different ratios offered to suit different conditions dependant upon the users end use?

 

[zedonist]

There are a number of ratios on the small case diffs, but only the e30 one gives the right gearing for better acceleration on the Z3. Whn I get chance I will find out the info and post.

 

[oldcarman]

There are a number of ratios on the small case diffs, but only the e30 one gives the right gearing for better acceleration on the Z3. Whn I get chance I will find out the info and post.

Hi Rich, in my case I find acceleration is fine for the type of roads and traffic I have around here but I'd like to see a gear ratio that would drop my top gear revs down as almost 95% or more of my driving is hiway! JIM

 

[David Cullen]

thanks Zed, yes i know i cant have one without the other in this case and to be honest i like take off speed more than top end speed as at the moment i use too much top end speed and am going to get myself in some serious trouble some day so would like to divert my attention towards the 0 to 100mph if i dont like it i can always change back anyway, thus the drop in method rather than change things and then find i dont like ratios etc

 

[Kevin Cartwright]

I swapped my Small case 4.44 for a medium case 3.73lsd from an 88 e30 325. I had to use the small case axle flanges. I simply installed them into the medium case diff. Kept the stock axles. I used a Finned cover from a z3m to help cool the gear oil. Pretty much a plug and play option. with the 3.73 i cruise at 80mph at 4,000ish revs and top speed is around 127 at redline in 5th. Hit a local pull apart yard for the $60 diff and a $100 cover from a forum member. All in all $200 for a finned lsd with new fluid installed.

 

[oldcarman]

Very nice! @zedonist was going to go the same route. Do you know if anyone has successfully put a six speed trans behind a 1.9 M44? I think a double overdrive would be nice to have as 99% of my driving is highway because I live about 100 mi from the closest big city. Would be nice to push the MPG up with both a trans and diff change! Did you take any pics so you could do a write up article? How can I determine my diff ratio? Are the gear ratios the same for all years with 1.9 engines? JIM

 

[Kevin Cartwright]

I looked into the 6 speed swap but it's to much custom work. Driveshaft, shift linkage, mount, clutch disk, slave cylinder. All of those things would need to be sourced custom or from another model but it would be so much trial and error. Diff ratio is written on a small metal tag attached to one of the diff cover bolts. its about 1/2" by 3" tag with the ratio and if it has Clutch packs (LsD) or not Mine reads S3.73 for limited slip 3.73 ratio. ill grab a picture later if i can. I can throw together a write up if anyone is interested.

 

[t-tony]

I would think that a write up would be of interest to many on our side of the Atlantic Kevin when you consider the prices we pay for fuel back home, as @oldcarman remarked re the MPG.

Tony.